Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

10 files changed, 2673 insertions, 0 deletions

diff --git a/gfx/wr/example-compositor/compositor-wayland/Cargo.toml b/gfx/wr/example-compositor/compositor-wayland/Cargo.toml
new file mode 100644
index 0000000000..0f5bba73b5
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-wayland/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "compositor-wayland"
+version = "0.1.0"
+authors = ["Glenn Watson <gw@intuitionlibrary.com>",
+           "Robert Mader <robert.mader@posteo.de>"]
+edition = "2018"
+license = "MPL-2.0"
+
+[build-dependencies]
+cc = "1.0"
+pkg-config = "^0.3.17"
diff --git a/gfx/wr/example-compositor/compositor-wayland/build.rs b/gfx/wr/example-compositor/compositor-wayland/build.rs
new file mode 100644
index 0000000000..ab418b94c7
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-wayland/build.rs
@@ -0,0 +1,63 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::process::Command;
+use std::env;
+use std::fs;
+
+extern crate pkg_config;
+
+fn main() {
+    let out_dir = env::var("OUT_DIR").unwrap();
+
+    fs::create_dir_all(&format!("{}/include", out_dir)).unwrap();
+    Command::new("wayland-scanner")
+        .args(&["client-header", "/usr/share/wayland-protocols/stable/viewporter/viewporter.xml"])
+        .arg(&format!("{}/include/viewporter-client-protocol.h", out_dir))
+        .status().unwrap();
+
+    Command::new("wayland-scanner")
+        .args(&["public-code", "/usr/share/wayland-protocols/stable/viewporter/viewporter.xml"])
+        .arg(&format!("{}/viewporter-protocol.c", out_dir))
+        .status().unwrap();
+
+    Command::new("wayland-scanner")
+        .args(&["client-header", "/usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml"])
+        .arg(&format!("{}/include/xdg-shell-client-protocol.h", out_dir))
+        .status().unwrap();
+
+    Command::new("wayland-scanner")
+        .args(&["public-code", "/usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml"])
+        .arg(&format!("{}/xdg-shell-protocol.c", out_dir))
+        .status().unwrap();
+
+    cc::Build::new()
+        .include(&format!("{}/include", out_dir))
+        .file("src/lib.cpp")
+        .file(&format!("{}/viewporter-protocol.c", out_dir))
+        .file(&format!("{}/xdg-shell-protocol.c", out_dir))
+        .compile("wayland");
+
+    println!("cargo:rustc-link-lib=dylib=stdc++");
+
+    pkg_config::Config::new()
+        .atleast_version("1")
+        .probe("egl")
+        .unwrap();
+    pkg_config::Config::new()
+        .atleast_version("1")
+        .probe("gl")
+        .unwrap();
+    pkg_config::Config::new()
+        .atleast_version("1")
+        .probe("wayland-client")
+        .unwrap();
+    pkg_config::Config::new()
+        .atleast_version("1")
+        .probe("wayland-egl")
+        .unwrap();
+
+    println!("cargo:rerun-if-changed=src/lib.rs");
+    println!("cargo:rerun-if-changed=src/lib.cpp");
+}
diff --git a/gfx/wr/example-compositor/compositor-wayland/src/lib.cpp b/gfx/wr/example-compositor/compositor-wayland/src/lib.cpp
new file mode 100644
index 0000000000..5529c987a9
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-wayland/src/lib.cpp
@@ -0,0 +1,772 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define UNICODE
+
+#include <algorithm>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <map>
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <unordered_map>
+#include <vector>
+
+#include <wayland-client.h>
+#include <wayland-egl.h>
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+#include <GL/gl.h>
+#include <GLES2/gl2.h>
+
+#include "viewporter-client-protocol.h"
+#include "xdg-shell-client-protocol.h"
+
+#define UNUSED(x) (void)(x)
+
+#define MIN(x, y) (((x) < (y)) ? (x) : (y))
+#define MAX(x, y) (((x) > (y)) ? (x) : (y))
+
+#define NUM_QUERIES 2
+
+#define VIRTUAL_OFFSET 512 * 1024
+
+enum SyncMode {
+  None_ = 0,
+  Swap = 1,
+  Commit = 2,
+  Flush = 3,
+  Query = 4,
+};
+
+// The OS compositor representation of a picture cache tile.
+struct Tile {
+  uint64_t surface_id;
+  int x;
+  int y;
+
+  struct wl_surface* surface;
+  struct wl_subsurface* subsurface;
+  struct wp_viewport* viewport;
+  struct wl_egl_window* egl_window;
+  EGLSurface egl_surface;
+  bool is_visible;
+
+  std::vector<EGLint> damage_rects;
+};
+
+struct TileKey {
+  int x;
+  int y;
+
+  TileKey(int ax, int ay) : x(ax), y(ay) {}
+};
+
+bool operator==(const TileKey& k0, const TileKey& k1) {
+  return k0.x == k1.x && k0.y == k1.y;
+}
+
+struct TileKeyHasher {
+  size_t operator()(const TileKey& key) const { return key.x ^ key.y; }
+};
+
+struct Surface {
+  uint64_t id;
+  int tile_width;
+  int tile_height;
+  bool is_opaque;
+  std::unordered_map<TileKey, Tile*, TileKeyHasher> tiles;
+};
+
+struct WLDisplay {
+  struct wl_display* display;
+  struct wl_registry* registry;
+  struct wl_compositor* compositor;
+  struct wl_subcompositor* subcompositor;
+  struct xdg_wm_base* wm_base;
+  struct wl_seat* seat;
+  struct wl_pointer* pointer;
+  struct wl_touch* touch;
+  struct wl_keyboard* keyboard;
+  struct wl_shm* shm;
+  struct wl_cursor_theme* cursor_theme;
+  struct wl_cursor* default_cursor;
+  struct wl_surface* cursor_surface;
+  struct wp_viewporter* viewporter;
+
+  PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC swap_buffers_with_damage;
+};
+
+struct WLGeometry {
+  int width, height;
+};
+
+struct WLWindow {
+  WLGeometry geometry;
+  bool enable_compositor;
+  SyncMode sync_mode;
+  bool closed;
+
+  WLDisplay* display;
+  struct wl_surface* surface;
+  struct xdg_surface* xdg_surface;
+  struct xdg_toplevel* xdg_toplevel;
+  struct wl_callback* callback;
+  struct wp_viewport* viewport;
+  bool wait_for_configure;
+
+  struct wl_egl_window* egl_window;
+  EGLSurface egl_surface;
+
+  EGLDeviceEXT eglDevice;
+  EGLDisplay eglDisplay;
+  EGLContext eglContext;
+  EGLConfig config;
+
+  // Maintain list of layer state between frames to avoid visual tree rebuild.
+  std::vector<uint64_t> currentLayers;
+  std::vector<uint64_t> prevLayers;
+
+  // Maps WR surface IDs to each OS surface
+  std::unordered_map<uint64_t, Surface> surfaces;
+  std::vector<Tile*> destroyedTiles;
+  std::vector<Tile*> hiddenTiles;
+};
+
+extern "C" {
+
+static void init_wl_registry(WLWindow* window);
+static void init_xdg_window(WLWindow* window);
+
+WLWindow* com_wl_create_window(int width, int height, bool enable_compositor,
+                               SyncMode sync_mode) {
+  WLDisplay* display = new WLDisplay;
+  WLWindow* window = new WLWindow;
+
+  window->display = display;
+  window->geometry.width = width;
+  window->geometry.height = height;
+  window->enable_compositor = enable_compositor;
+  window->sync_mode = sync_mode;
+  window->closed = false;
+
+  display->display = wl_display_connect(NULL);
+  assert(display->display);
+
+  init_wl_registry(window);
+  if (enable_compositor && !display->viewporter) {
+    fprintf(stderr, "Native compositor mode requires wp_viewporter support\n");
+    window->closed = true;
+  }
+
+  window->eglDisplay =
+      eglGetPlatformDisplay(EGL_PLATFORM_WAYLAND_KHR, display->display, NULL);
+
+  eglInitialize(window->eglDisplay, nullptr, nullptr);
+  eglBindAPI(EGL_OPENGL_API);
+
+  EGLint num_configs = 0;
+  EGLint cfg_attribs[] = {EGL_SURFACE_TYPE,
+                          EGL_WINDOW_BIT,
+                          EGL_RENDERABLE_TYPE,
+                          EGL_OPENGL_BIT,
+                          EGL_RED_SIZE,
+                          8,
+                          EGL_GREEN_SIZE,
+                          8,
+                          EGL_BLUE_SIZE,
+                          8,
+                          EGL_ALPHA_SIZE,
+                          8,
+                          EGL_DEPTH_SIZE,
+                          24,
+                          EGL_NONE};
+  EGLConfig configs[32];
+
+  eglChooseConfig(window->eglDisplay, cfg_attribs, configs,
+                  sizeof(configs) / sizeof(EGLConfig), &num_configs);
+  assert(num_configs > 0);
+  window->config = configs[0];
+
+  EGLint ctx_attribs[] = {EGL_CONTEXT_OPENGL_PROFILE_MASK,
+                          EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT,
+                          EGL_CONTEXT_MAJOR_VERSION,
+                          3,
+                          EGL_CONTEXT_MINOR_VERSION,
+                          2,
+                          EGL_NONE};
+
+  // Create an EGL context that can be used for drawing
+  window->eglContext = eglCreateContext(window->eglDisplay, window->config,
+                                        EGL_NO_CONTEXT, ctx_attribs);
+
+  window->surface = wl_compositor_create_surface(display->compositor);
+  init_xdg_window(window);
+
+  struct wl_region* region =
+      wl_compositor_create_region(window->display->compositor);
+  wl_region_add(region, 0, 0, INT32_MAX, INT32_MAX);
+  wl_surface_set_opaque_region(window->surface, region);
+  wl_region_destroy(region);
+
+  if (enable_compositor) {
+    xdg_toplevel_set_title(window->xdg_toplevel,
+                           "example-compositor (Wayland)");
+  } else {
+    xdg_toplevel_set_title(window->xdg_toplevel, "example-compositor (Simple)");
+  }
+
+  window->wait_for_configure = true;
+  wl_surface_commit(window->surface);
+
+  EGLBoolean ok = eglMakeCurrent(window->eglDisplay, EGL_NO_SURFACE,
+                                 EGL_NO_SURFACE, window->eglContext);
+  assert(ok);
+
+  display->swap_buffers_with_damage =
+      (PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC)eglGetProcAddress(
+          "eglSwapBuffersWithDamageKHR");
+
+  return window;
+}
+
+bool com_wl_tick(WLWindow* window) {
+  if (window->wait_for_configure) {
+    int ret = 0;
+    while (window->wait_for_configure && !window->closed && ret != -1) {
+      wl_display_dispatch(window->display->display);
+    }
+  } else {
+    wl_display_dispatch_pending(window->display->display);
+  }
+
+  return !window->closed;
+}
+
+static void unmap_hidden_tiles(WLWindow* window) {
+  for (Tile* tile : window->hiddenTiles) {
+    if (tile->subsurface) {
+      wl_subsurface_destroy(tile->subsurface);
+      tile->subsurface = nullptr;
+    }
+  }
+  window->hiddenTiles.clear();
+}
+
+static void clean_up_tiles(WLWindow* window) {
+  for (Tile* tile : window->destroyedTiles) {
+    eglDestroySurface(window->eglDisplay, tile->egl_surface);
+    wl_egl_window_destroy(tile->egl_window);
+    wp_viewport_destroy(tile->viewport);
+    wl_surface_destroy(tile->surface);
+    delete tile;
+  }
+  window->destroyedTiles.clear();
+}
+
+static void handle_callback(void* data, struct wl_callback* callback,
+                            uint32_t time) {
+  WLWindow* window = (WLWindow*)data;
+  UNUSED(time);
+
+  assert(window->callback == callback);
+
+  wl_callback_destroy(callback);
+  window->callback = nullptr;
+}
+
+static const struct wl_callback_listener frame_listener = {handle_callback};
+
+void com_wl_swap_buffers(WLWindow* window) {
+  if (window->enable_compositor) {
+    for (auto surface_it = window->surfaces.begin();
+         surface_it != window->surfaces.end(); ++surface_it) {
+      Surface* surface = &surface_it->second;
+
+      for (auto tile_it = surface->tiles.begin();
+           tile_it != surface->tiles.end(); ++tile_it) {
+        Tile* tile = tile_it->second;
+
+        if (!tile->damage_rects.empty() && tile->is_visible) {
+          eglMakeCurrent(window->eglDisplay, tile->egl_surface,
+                         tile->egl_surface, window->eglContext);
+          eglSwapInterval(window->eglDisplay, 0);
+
+          /* if (window->display->swap_buffers_with_damage) {
+            window->display->swap_buffers_with_damage(
+                window->eglDisplay, tile->egl_surface,
+                tile->damage_rects.data(), tile->damage_rects.size() / 4);
+          } else */
+          eglSwapBuffers(window->eglDisplay, tile->egl_surface);
+          tile->damage_rects.clear();
+
+          eglMakeCurrent(window->eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
+                         window->eglContext);
+        } else {
+          wl_surface_commit(tile->surface);
+        }
+      }
+    }
+    wl_surface_commit(window->surface);
+    unmap_hidden_tiles(window);
+    clean_up_tiles(window);
+
+    int ret = 0;
+    switch (window->sync_mode) {
+      case SyncMode::None_:
+        wl_display_roundtrip(window->display->display);
+        break;
+      case SyncMode::Swap:
+        window->callback = wl_surface_frame(window->surface);
+        wl_callback_add_listener(window->callback, &frame_listener, window);
+        wl_surface_commit(window->surface);
+
+        while (window->callback && !window->closed && ret != -1) {
+          ret = wl_display_dispatch(window->display->display);
+        }
+        break;
+      default:
+        assert(false);
+        break;
+    }
+  } else {
+    // If not using native mode, then do a normal EGL swap buffers.
+    switch (window->sync_mode) {
+      case SyncMode::None_:
+        eglSwapInterval(window->eglDisplay, 0);
+        break;
+      case SyncMode::Swap:
+        eglSwapInterval(window->eglDisplay, 1);
+        break;
+      default:
+        assert(false);
+        break;
+    }
+    eglSwapBuffers(window->eglDisplay, window->egl_surface);
+  }
+}
+
+// Create a new native surface
+void com_wl_create_surface(WLWindow* window, uint64_t surface_id,
+                           int tile_width, int tile_height, bool is_opaque) {
+  assert(window->surfaces.count(surface_id) == 0);
+
+  Surface surface;
+  surface.id = surface_id;
+  surface.tile_width = tile_width;
+  surface.tile_height = tile_height;
+  surface.is_opaque = is_opaque;
+
+  window->surfaces.emplace(surface_id, surface);
+}
+
+void com_wl_create_tile(WLWindow* window, uint64_t surface_id, int x, int y) {
+  WLDisplay* display = window->display;
+
+  assert(window->surfaces.count(surface_id) == 1);
+  Surface* surface = &window->surfaces.at(surface_id);
+
+  TileKey key(x, y);
+  assert(surface->tiles.count(key) == 0);
+
+  Tile* tile = new Tile;
+  tile->surface_id = surface_id;
+  tile->x = x;
+  tile->y = y;
+  tile->is_visible = false;
+
+  tile->surface = wl_compositor_create_surface(display->compositor);
+  tile->viewport =
+      wp_viewporter_get_viewport(display->viewporter, tile->surface);
+
+  if (surface->is_opaque) {
+    struct wl_region* region =
+        wl_compositor_create_region(window->display->compositor);
+    wl_region_add(region, 0, 0, INT32_MAX, INT32_MAX);
+    wl_surface_set_opaque_region(tile->surface, region);
+    wl_region_destroy(region);
+  }
+
+  tile->egl_window = wl_egl_window_create(tile->surface, surface->tile_width,
+                                          surface->tile_height);
+  tile->egl_surface = eglCreateWindowSurface(window->eglDisplay, window->config,
+                                             tile->egl_window, NULL);
+  assert(tile->egl_surface != EGL_NO_SURFACE);
+
+  surface->tiles.emplace(key, tile);
+}
+
+static void show_tile(WLWindow* window, Tile* tile) {
+  if (tile->is_visible) {
+    assert(tile->subsurface);
+    return;
+  }
+
+  tile->subsurface = wl_subcompositor_get_subsurface(
+      window->display->subcompositor, tile->surface, window->surface);
+
+  /* This is not comprehensive yet, see hide_tile() */
+  Surface* surface = &window->surfaces.at(tile->surface_id);
+  for (auto tile_it = surface->tiles.begin(); tile_it != surface->tiles.end();
+       ++tile_it) {
+    Tile* other_tile = tile_it->second;
+
+    if (other_tile->is_visible) {
+      wl_subsurface_place_above(tile->subsurface, other_tile->surface);
+    }
+  }
+
+  tile->is_visible = true;
+}
+
+static void hide_tile(WLWindow* window, Tile* tile) {
+  if (!tile->is_visible) {
+    return;
+  }
+
+  /*
+   * This is a workaround for missing API on the egl-wayland platform. We
+   * likely want to replace it a solution that detaches the buffer from
+   * the surface, which would require us to manage buffers manually.
+   */
+  wl_subsurface_set_position(tile->subsurface, window->geometry.width / 2,
+                             window->geometry.height / 2);
+  wp_viewport_set_source(tile->viewport, wl_fixed_from_int(0),
+                         wl_fixed_from_int(0), wl_fixed_from_int(1),
+                         wl_fixed_from_int(1));
+  wl_subsurface_place_below(tile->subsurface, window->surface);
+  tile->is_visible = false;
+  window->hiddenTiles.push_back(tile);
+}
+
+void com_wl_destroy_tile(WLWindow* window, uint64_t surface_id, int x, int y) {
+  assert(window->surfaces.count(surface_id) == 1);
+
+  Surface* surface = &window->surfaces.at(surface_id);
+  TileKey key(x, y);
+  assert(surface->tiles.count(key) == 1);
+  Tile* tile = surface->tiles[key];
+
+  hide_tile(window, tile);
+  wl_surface_commit(tile->surface);
+
+  window->destroyedTiles.push_back(tile);
+  surface->tiles.erase(key);
+}
+
+void com_wl_destroy_surface(WLWindow* window, uint64_t surface_id) {
+  assert(window->surfaces.count(surface_id) == 1);
+
+  Surface* surface = &window->surfaces.at(surface_id);
+  for (auto tile_it = surface->tiles.begin(); tile_it != surface->tiles.end();
+       tile_it = surface->tiles.begin()) {
+    Tile* tile = tile_it->second;
+
+    com_wl_destroy_tile(window, surface_id, tile->x, tile->y);
+  }
+
+  window->surfaces.erase(surface_id);
+}
+
+void com_wl_destroy_window(WLWindow* window) {
+  for (auto surface_it = window->surfaces.begin();
+       surface_it != window->surfaces.end(); ++surface_it) {
+    Surface& surface = surface_it->second;
+
+    com_wl_destroy_surface(window, surface.id);
+  }
+
+  if (window->egl_surface != EGL_NO_SURFACE) {
+    eglDestroySurface(window->eglDisplay, window->egl_surface);
+  }
+  eglDestroyContext(window->eglDisplay, window->eglContext);
+  eglTerminate(window->eglDisplay);
+
+  delete window;
+}
+
+// Bind a native surface to allow issuing GL commands to it
+GLuint com_wl_bind_surface(WLWindow* window, uint64_t surface_id, int tile_x,
+                           int tile_y, int* x_offset, int* y_offset,
+                           int dirty_x0, int dirty_y0, int dirty_width,
+                           int dirty_height) {
+  *x_offset = 0;
+  *y_offset = 0;
+
+  assert(window->surfaces.count(surface_id) == 1);
+  Surface* surface = &window->surfaces[surface_id];
+
+  TileKey key(tile_x, tile_y);
+  assert(surface->tiles.count(key) == 1);
+  Tile* tile = surface->tiles[key];
+
+  tile->damage_rects.push_back(dirty_x0);
+  tile->damage_rects.push_back(dirty_y0);
+  tile->damage_rects.push_back(dirty_width);
+  tile->damage_rects.push_back(dirty_height);
+
+  EGLBoolean ok = eglMakeCurrent(window->eglDisplay, tile->egl_surface,
+                                 tile->egl_surface, window->eglContext);
+  assert(ok);
+
+  return 0;
+}
+
+// Unbind a currently bound native surface
+void com_wl_unbind_surface(WLWindow* window) {
+  eglMakeCurrent(window->eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE,
+                 window->eglContext);
+}
+
+void com_wl_begin_transaction(WLWindow*) {}
+
+// Add a native surface to the visual tree. Called per-frame to build the
+// composition.
+void com_wl_add_surface(WLWindow* window, uint64_t surface_id, int offset_x,
+                        int offset_y, int clip_x, int clip_y, int clip_w,
+                        int clip_h) {
+  Surface* surface = &window->surfaces[surface_id];
+  window->currentLayers.push_back(surface_id);
+
+  for (auto tile_it = surface->tiles.begin(); tile_it != surface->tiles.end();
+       ++tile_it) {
+    Tile* tile = tile_it->second;
+
+    int pos_x = MAX((tile->x * surface->tile_width) + offset_x, clip_x);
+    int pos_y = MAX((tile->y * surface->tile_height) + offset_y, clip_y);
+
+    float view_x = MAX((clip_x - offset_x) - tile->x * surface->tile_width, 0);
+    float view_y = MAX((clip_y - offset_y) - tile->y * surface->tile_height, 0);
+
+    float view_w = MIN(surface->tile_width - view_x, (clip_x + clip_w) - pos_x);
+    float view_h =
+        MIN(surface->tile_height - view_y, (clip_y + clip_h) - pos_y);
+    view_w = MIN(window->geometry.width - pos_x, view_w);
+    view_h = MIN(window->geometry.height - pos_y, view_h);
+
+    if (view_w > 0 && view_h > 0) {
+      show_tile(window, tile);
+
+      wl_surface_set_buffer_transform(tile->surface,
+                                      WL_OUTPUT_TRANSFORM_FLIPPED_180);
+      wl_subsurface_set_position(tile->subsurface, pos_x, pos_y);
+      wp_viewport_set_source(tile->viewport, wl_fixed_from_double(view_x),
+                             wl_fixed_from_double(view_y),
+                             wl_fixed_from_double(view_w),
+                             wl_fixed_from_double(view_h));
+    } else {
+      hide_tile(window, tile);
+    }
+  }
+}
+
+void com_wl_end_transaction(WLWindow* window) {
+  bool same = window->prevLayers == window->currentLayers;
+  if (!same) {
+    struct wl_surface* prev_surface = window->surface;
+
+    for (auto it = window->currentLayers.begin();
+         it != window->currentLayers.end(); ++it) {
+      Surface* surface = &window->surfaces[*it];
+
+      struct wl_surface* next_surface = nullptr;
+      for (auto tile_it = surface->tiles.begin();
+           tile_it != surface->tiles.end(); ++tile_it) {
+        Tile* tile = tile_it->second;
+
+        if (tile->is_visible) {
+          wl_subsurface_place_above(tile->subsurface, prev_surface);
+
+          if (!next_surface) {
+            next_surface = tile->surface;
+          }
+        }
+      }
+      prev_surface = next_surface;
+    }
+  }
+
+  window->prevLayers.swap(window->currentLayers);
+  window->currentLayers.clear();
+}
+
+void glInvalidateFramebuffer(GLenum target, GLsizei numAttachments,
+                             const GLenum* attachments) {
+  UNUSED(target);
+  UNUSED(numAttachments);
+  UNUSED(attachments);
+}
+
+// Get a pointer to an EGL symbol
+void* com_wl_get_proc_address(const char* name) {
+  /* Disable glInvalidateFramebuffer for now as it triggers errors.
+   * This is likely due to the egl-wayland platform, which we may want to
+   * replace with a custom implementation in order to have more control
+   * over the low-lever bits.
+   */
+  if (strcmp(name, "glInvalidateFramebuffer") == 0) {
+    return (void*)glInvalidateFramebuffer;
+  }
+
+  return (void*)eglGetProcAddress(name);
+}
+
+void com_wl_deinit(WLWindow* window) { UNUSED(window); }
+
+static void handle_xdg_surface_configure(void* data,
+                                         struct xdg_surface* surface,
+                                         uint32_t serial) {
+  WLWindow* window = (WLWindow*)data;
+
+  xdg_surface_ack_configure(surface, serial);
+
+  if (window->wait_for_configure) {
+    if (window->enable_compositor) {
+      int width = window->geometry.width;
+      int height = window->geometry.height;
+
+      window->egl_window = wl_egl_window_create(window->surface, 1, 1);
+      window->egl_surface = eglCreateWindowSurface(
+          window->eglDisplay, window->config, window->egl_window, NULL);
+      assert(window->egl_surface != EGL_NO_SURFACE);
+
+      EGLBoolean ok = eglMakeCurrent(window->eglDisplay, window->egl_surface,
+                                     window->egl_surface, window->eglContext);
+      assert(ok);
+
+      glClearColor(1.0, 1.0, 1.0, 1.0);
+      glClear(GL_COLOR_BUFFER_BIT);
+
+      window->viewport = wp_viewporter_get_viewport(window->display->viewporter,
+                                                    window->surface);
+      wp_viewport_set_destination(window->viewport, width, height);
+
+      eglSwapBuffers(window->eglDisplay, window->egl_surface);
+    } else {
+      window->egl_window = wl_egl_window_create(
+          window->surface, window->geometry.width, window->geometry.height);
+      window->egl_surface = eglCreateWindowSurface(
+          window->eglDisplay, window->config, window->egl_window, NULL);
+      assert(window->egl_surface != EGL_NO_SURFACE);
+
+      EGLBoolean ok = eglMakeCurrent(window->eglDisplay, window->egl_surface,
+                                     window->egl_surface, window->eglContext);
+      assert(ok);
+    }
+  }
+
+  window->wait_for_configure = false;
+}
+
+static const struct xdg_surface_listener xdg_surface_listener = {
+    handle_xdg_surface_configure};
+
+static void handle_xdg_toplevel_configure(void* data,
+                                          struct xdg_toplevel* toplevel,
+                                          int32_t width, int32_t height,
+                                          struct wl_array* states) {
+  WLWindow* window = (WLWindow*)data;
+  UNUSED(toplevel);
+  UNUSED(states);
+
+  if (width > 0 && height > 0) {
+    window->geometry.width = width;
+    window->geometry.height = height;
+
+    if (!window->wait_for_configure) {
+      if (window->enable_compositor) {
+        wp_viewport_set_destination(window->viewport, window->geometry.width,
+                                    window->geometry.height);
+      } else {
+        wl_egl_window_resize(window->egl_window, window->geometry.width,
+                             window->geometry.height, 0, 0);
+      }
+    }
+  }
+}
+
+static void handle_xdg_toplevel_close(void* data,
+                                      struct xdg_toplevel* toplevel) {
+  UNUSED(toplevel);
+  WLWindow* window = (WLWindow*)data;
+  window->closed = true;
+}
+
+static const struct xdg_toplevel_listener xdg_toplevel_listener = {
+    handle_xdg_toplevel_configure,
+    handle_xdg_toplevel_close,
+};
+
+static void xdg_wm_base_ping(void* data, struct xdg_wm_base* shell,
+                             uint32_t serial) {
+  UNUSED(data);
+  xdg_wm_base_pong(shell, serial);
+}
+
+static const struct xdg_wm_base_listener wm_base_listener = {
+    xdg_wm_base_ping,
+};
+
+static void registry_handle_global(void* data, struct wl_registry* registry,
+                                   uint32_t name, const char* interface,
+                                   uint32_t version) {
+  WLDisplay* d = (WLDisplay*)data;
+
+  if (strcmp(interface, "wl_compositor") == 0) {
+    d->compositor = (struct wl_compositor*)wl_registry_bind(
+        registry, name, &wl_compositor_interface, MIN(version, 4));
+  } else if (strcmp(interface, "wp_viewporter") == 0) {
+    d->viewporter = (struct wp_viewporter*)wl_registry_bind(
+        registry, name, &wp_viewporter_interface, 1);
+  } else if (strcmp(interface, "xdg_wm_base") == 0) {
+    d->wm_base = (struct xdg_wm_base*)wl_registry_bind(
+        registry, name, &xdg_wm_base_interface, 1);
+    xdg_wm_base_add_listener(d->wm_base, &wm_base_listener, NULL);
+  } else if (strcmp(interface, "wl_subcompositor") == 0) {
+    d->subcompositor = (struct wl_subcompositor*)wl_registry_bind(
+        registry, name, &wl_subcompositor_interface, 1);
+  }
+}
+
+static void registry_handle_global_remove(void* data,
+                                          struct wl_registry* registry,
+                                          uint32_t name) {
+  UNUSED(data);
+  UNUSED(registry);
+  UNUSED(name);
+}
+
+static const struct wl_registry_listener registry_listener = {
+    registry_handle_global, registry_handle_global_remove};
+
+static void init_wl_registry(WLWindow* window) {
+  WLDisplay* display = window->display;
+
+  display->registry = wl_display_get_registry(display->display);
+  wl_registry_add_listener(display->registry, &registry_listener, display);
+
+  wl_display_roundtrip(display->display);
+
+  assert(display->compositor);
+  assert(display->wm_base);
+  assert(display->subcompositor);
+}
+
+static void init_xdg_window(WLWindow* window) {
+  window->xdg_surface =
+      xdg_wm_base_get_xdg_surface(window->display->wm_base, window->surface);
+  assert(window->xdg_surface);
+  xdg_surface_add_listener(window->xdg_surface, &xdg_surface_listener, window);
+
+  window->xdg_toplevel = xdg_surface_get_toplevel(window->xdg_surface);
+  xdg_toplevel_add_listener(window->xdg_toplevel, &xdg_toplevel_listener,
+                            window);
+  assert(window->xdg_toplevel);
+}
+}
diff --git a/gfx/wr/example-compositor/compositor-wayland/src/lib.rs b/gfx/wr/example-compositor/compositor-wayland/src/lib.rs
new file mode 100644
index 0000000000..daddbb6495
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-wayland/src/lib.rs
@@ -0,0 +1,269 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::os::raw::{c_void, c_char};
+
+/*
+
+  This is a very simple (and unsafe!) rust wrapper for the Wayland / EGL
+  implementation in lib.cpp.
+
+  It just proxies the calls from the Compositor impl to the C99 code. This is very
+  hacky and not suitable for production!
+
+ */
+
+// Opaque wrapper for the Window type in lib.cpp
+#[repr(C)]
+pub struct Window {
+    _unused: [u8; 0]
+}
+
+// C99 functions that do the compositor work
+extern {
+    fn com_wl_create_window(
+        width: i32,
+        height: i32,
+        enable_compositor: bool,
+        sync_mode: i32,
+    ) -> *mut Window;
+    fn com_wl_destroy_window(window: *mut Window);
+    fn com_wl_tick(window: *mut Window) -> bool;
+    fn com_wl_get_proc_address(name: *const c_char) -> *const c_void;
+    fn com_wl_swap_buffers(window: *mut Window);
+
+    fn com_wl_create_surface(
+        window: *mut Window,
+        id: u64,
+        tile_width: i32,
+        tile_height: i32,
+        is_opaque: bool,
+    );
+
+    fn com_wl_create_tile(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+    );
+
+    fn com_wl_destroy_tile(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+    );
+
+    fn com_wl_destroy_surface(
+        window: *mut Window,
+        id: u64,
+    );
+
+    fn com_wl_bind_surface(
+        window: *mut Window,
+        surface_id: u64,
+        tile_x: i32,
+        tile_y: i32,
+        x_offset: &mut i32,
+        y_offset: &mut i32,
+        dirty_x0: i32,
+        dirty_y0: i32,
+        dirty_width: i32,
+        dirty_height: i32,
+    ) -> u32;
+    fn com_wl_unbind_surface(window: *mut Window);
+
+    fn com_wl_begin_transaction(window: *mut Window);
+
+    fn com_wl_add_surface(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+        clip_x: i32,
+        clip_y: i32,
+        clip_w: i32,
+        clip_h: i32,
+    );
+
+    fn com_wl_end_transaction(window: *mut Window);
+
+    fn com_wl_deinit(window: *mut Window);
+}
+
+pub fn create_window(
+    width: i32,
+    height: i32,
+    enable_compositor: bool,
+    sync_mode: i32,
+) -> *mut Window {
+    unsafe {
+        com_wl_create_window(width, height, enable_compositor, sync_mode)
+    }
+}
+
+pub fn destroy_window(window: *mut Window) {
+    unsafe {
+        com_wl_destroy_window(window);
+    }
+}
+
+pub fn tick(window: *mut Window) -> bool {
+    unsafe {
+        com_wl_tick(window)
+    }
+}
+
+pub fn get_proc_address(name: *const c_char) -> *const c_void {
+    unsafe {
+        com_wl_get_proc_address(name)
+    }
+}
+
+pub fn create_surface(
+    window: *mut Window,
+    id: u64,
+    tile_width: i32,
+    tile_height: i32,
+    is_opaque: bool,
+) {
+    unsafe {
+        com_wl_create_surface(
+            window,
+            id,
+            tile_width,
+            tile_height,
+            is_opaque,
+        )
+    }
+}
+
+pub fn create_tile(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+) {
+    unsafe {
+        com_wl_create_tile(
+            window,
+            id,
+            x,
+            y,
+        )
+    }
+}
+
+pub fn destroy_tile(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+) {
+    unsafe {
+        com_wl_destroy_tile(
+            window,
+            id,
+            x,
+            y,
+        )
+    }
+}
+
+pub fn destroy_surface(
+    window: *mut Window,
+    id: u64,
+) {
+    unsafe {
+        com_wl_destroy_surface(
+            window,
+            id,
+        )
+    }
+}
+
+pub fn bind_surface(
+    window: *mut Window,
+    surface_id: u64,
+    tile_x: i32,
+    tile_y: i32,
+    dirty_x0: i32,
+    dirty_y0: i32,
+    dirty_width: i32,
+    dirty_height: i32,
+) -> (u32, i32, i32) {
+    unsafe {
+        let mut x_offset = 0;
+        let mut y_offset = 0;
+
+        let fbo_id = com_wl_bind_surface(
+            window,
+            surface_id,
+            tile_x,
+            tile_y,
+            &mut x_offset,
+            &mut y_offset,
+            dirty_x0,
+            dirty_y0,
+            dirty_width,
+            dirty_height,
+        );
+
+        (fbo_id, x_offset, y_offset)
+    }
+}
+
+pub fn add_surface(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+    clip_x: i32,
+    clip_y: i32,
+    clip_w: i32,
+    clip_h: i32,
+) {
+    unsafe {
+        com_wl_add_surface(
+            window,
+            id,
+            x,
+            y,
+            clip_x,
+            clip_y,
+            clip_w,
+            clip_h,
+        )
+    }
+}
+
+pub fn begin_transaction(window: *mut Window) {
+    unsafe {
+        com_wl_begin_transaction(window)
+    }
+}
+
+pub fn unbind_surface(window: *mut Window) {
+    unsafe {
+        com_wl_unbind_surface(window)
+    }
+}
+
+pub fn end_transaction(window: *mut Window) {
+    unsafe {
+        com_wl_end_transaction(window)
+    }
+}
+
+pub fn swap_buffers(window: *mut Window) {
+    unsafe {
+        com_wl_swap_buffers(window);
+    }
+}
+
+pub fn deinit(window: *mut Window) {
+    unsafe {
+        com_wl_deinit(window);
+    }
+}
diff --git a/gfx/wr/example-compositor/compositor-windows/Cargo.toml b/gfx/wr/example-compositor/compositor-windows/Cargo.toml
new file mode 100644
index 0000000000..b191626a69
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-windows/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "compositor-windows"
+version = "0.1.0"
+authors = ["Glenn Watson <gw@intuitionlibrary.com>"]
+edition = "2018"
+license = "MPL-2.0"
+
+[build-dependencies]
+cc = "1.0"
diff --git a/gfx/wr/example-compositor/compositor-windows/build.rs b/gfx/wr/example-compositor/compositor-windows/build.rs
new file mode 100644
index 0000000000..dc7358aa6a
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-windows/build.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+fn main() {
+    // HACK - This build script relies on Gecko having been built, so that the ANGLE libraries
+    //        have already been compiled. It also assumes they are being built with an in-tree
+    //        x86_64 object directory.
+
+    cc::Build::new()
+        .file("src/lib.cpp")
+        .include("../../../angle/checkout/include")
+        .compile("windows");
+
+    // Set up linker paths for ANGLE that is built by Gecko
+    println!("cargo:rustc-link-search=../../obj-x86_64-pc-mingw32/gfx/angle/targets/libEGL");
+    println!("cargo:rustc-link-search=../../obj-x86_64-pc-mingw32/gfx/angle/targets/libGLESv2");
+
+    // Link to libEGL and libGLESv2 (ANGLE) and D3D11 + DirectComposition
+    println!("cargo:rustc-link-lib=libEGL");
+    println!("cargo:rustc-link-lib=libGLESv2");
+    println!("cargo:rustc-link-lib=dcomp");
+    println!("cargo:rustc-link-lib=d3d11");
+    println!("cargo:rustc-link-lib=dwmapi");
+}
diff --git a/gfx/wr/example-compositor/compositor-windows/src/lib.cpp b/gfx/wr/example-compositor/compositor-windows/src/lib.cpp
new file mode 100644
index 0000000000..d39726ea0a
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-windows/src/lib.cpp
@@ -0,0 +1,694 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define UNICODE
+
+#include <windows.h>
+#include <math.h>
+#include <dcomp.h>
+#include <d3d11.h>
+#include <assert.h>
+#include <map>
+#include <vector>
+#include <dwmapi.h>
+#include <unordered_map>
+
+#define EGL_EGL_PROTOTYPES 1
+#define EGL_EGLEXT_PROTOTYPES 1
+#define GL_GLEXT_PROTOTYPES 1
+#include "EGL/egl.h"
+#include "EGL/eglext.h"
+#include "EGL/eglext_angle.h"
+#include "GL/gl.h"
+#include "GLES/gl.h"
+#include "GLES/glext.h"
+#include "GLES3/gl3.h"
+
+#define NUM_QUERIES 2
+
+#define USE_VIRTUAL_SURFACES
+#define VIRTUAL_OFFSET 512 * 1024
+
+enum SyncMode {
+  None = 0,
+  Swap = 1,
+  Commit = 2,
+  Flush = 3,
+  Query = 4,
+};
+
+// The OS compositor representation of a picture cache tile.
+struct Tile {
+#ifndef USE_VIRTUAL_SURFACES
+  // Represents the underlying DirectComposition surface texture that gets drawn
+  // into.
+  IDCompositionSurface* pSurface;
+  // Represents the node in the visual tree that defines the properties of this
+  // tile (clip, position etc).
+  IDCompositionVisual2* pVisual;
+#endif
+};
+
+struct TileKey {
+  int x;
+  int y;
+
+  TileKey(int ax, int ay) : x(ax), y(ay) {}
+};
+
+bool operator==(const TileKey& k0, const TileKey& k1) {
+  return k0.x == k1.x && k0.y == k1.y;
+}
+
+struct TileKeyHasher {
+  size_t operator()(const TileKey& key) const { return key.x ^ key.y; }
+};
+
+struct Surface {
+  int tile_width;
+  int tile_height;
+  bool is_opaque;
+  std::unordered_map<TileKey, Tile, TileKeyHasher> tiles;
+  IDCompositionVisual2* pVisual;
+#ifdef USE_VIRTUAL_SURFACES
+  IDCompositionVirtualSurface* pVirtualSurface;
+#endif
+};
+
+struct CachedFrameBuffer {
+  int width;
+  int height;
+  GLuint fboId;
+  GLuint depthRboId;
+};
+
+struct Window {
+  // Win32 window details
+  HWND hWnd;
+  HINSTANCE hInstance;
+  bool enable_compositor;
+  RECT client_rect;
+  SyncMode sync_mode;
+
+  // Main interfaces to D3D11 and DirectComposition
+  ID3D11Device* pD3D11Device;
+  IDCompositionDesktopDevice* pDCompDevice;
+  IDCompositionTarget* pDCompTarget;
+  IDXGIDevice* pDXGIDevice;
+  ID3D11Query* pQueries[NUM_QUERIES];
+  int current_query;
+
+  // ANGLE interfaces that wrap the D3D device
+  EGLDeviceEXT EGLDevice;
+  EGLDisplay EGLDisplay;
+  EGLContext EGLContext;
+  EGLConfig config;
+  // Framebuffer surface for debug mode when we are not using DC
+  EGLSurface fb_surface;
+
+  // The currently bound surface, valid during bind() and unbind()
+  IDCompositionSurface* pCurrentSurface;
+  EGLImage mEGLImage;
+  GLuint mColorRBO;
+
+  // The root of the DC visual tree. Nothing is drawn on this, but
+  // all child tiles are parented to here.
+  IDCompositionVisual2* pRoot;
+  IDCompositionVisualDebug* pVisualDebug;
+  std::vector<CachedFrameBuffer> mFrameBuffers;
+
+  // Maintain list of layer state between frames to avoid visual tree rebuild.
+  std::vector<uint64_t> mCurrentLayers;
+  std::vector<uint64_t> mPrevLayers;
+
+  // Maps WR surface IDs to each OS surface
+  std::unordered_map<uint64_t, Surface> surfaces;
+};
+
+static const wchar_t* CLASS_NAME = L"WR DirectComposite";
+
+static GLuint GetOrCreateFbo(Window* window, int aWidth, int aHeight) {
+  GLuint fboId = 0;
+
+  // Check if we have a cached FBO with matching dimensions
+  for (auto it = window->mFrameBuffers.begin();
+       it != window->mFrameBuffers.end(); ++it) {
+    if (it->width == aWidth && it->height == aHeight) {
+      fboId = it->fboId;
+      break;
+    }
+  }
+
+  // If not, create a new FBO with attached depth buffer
+  if (fboId == 0) {
+    // Create the depth buffer
+    GLuint depthRboId;
+    glGenRenderbuffers(1, &depthRboId);
+    glBindRenderbuffer(GL_RENDERBUFFER, depthRboId);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, aWidth,
+                          aHeight);
+
+    // Create the framebuffer and attach the depth buffer to it
+    glGenFramebuffers(1, &fboId);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboId);
+    glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
+                              GL_RENDERBUFFER, depthRboId);
+
+    // Store this in the cache for future calls.
+    CachedFrameBuffer frame_buffer_info;
+    frame_buffer_info.width = aWidth;
+    frame_buffer_info.height = aHeight;
+    frame_buffer_info.fboId = fboId;
+    frame_buffer_info.depthRboId = depthRboId;
+    window->mFrameBuffers.push_back(frame_buffer_info);
+  }
+
+  return fboId;
+}
+
+static LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam,
+                                LPARAM lParam) {
+  switch (message) {
+    case WM_DESTROY:
+      PostQuitMessage(0);
+      return 1;
+  }
+
+  return DefWindowProc(hwnd, message, wParam, lParam);
+}
+
+extern "C" {
+Window* com_dc_create_window(int width, int height, bool enable_compositor,
+                             SyncMode sync_mode) {
+  // Create a simple Win32 window
+  Window* window = new Window;
+  window->hInstance = GetModuleHandle(NULL);
+  window->enable_compositor = enable_compositor;
+  window->mEGLImage = EGL_NO_IMAGE;
+  window->sync_mode = sync_mode;
+
+  WNDCLASSEX wcex = {sizeof(WNDCLASSEX)};
+  wcex.style = CS_HREDRAW | CS_VREDRAW;
+  wcex.lpfnWndProc = WndProc;
+  wcex.cbClsExtra = 0;
+  wcex.cbWndExtra = 0;
+  wcex.hInstance = window->hInstance;
+  wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
+  ;
+  wcex.lpszMenuName = nullptr;
+  wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
+  wcex.lpszClassName = CLASS_NAME;
+  RegisterClassEx(&wcex);
+
+  int dpiX = 0;
+  int dpiY = 0;
+  HDC hdc = GetDC(NULL);
+  if (hdc) {
+    dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
+    dpiY = GetDeviceCaps(hdc, LOGPIXELSY);
+    ReleaseDC(NULL, hdc);
+  }
+
+  RECT window_rect = {0, 0, width, height};
+  AdjustWindowRect(&window_rect, WS_OVERLAPPEDWINDOW, FALSE);
+  UINT window_width = static_cast<UINT>(
+      ceil(float(window_rect.right - window_rect.left) * dpiX / 96.f));
+  UINT window_height = static_cast<UINT>(
+      ceil(float(window_rect.bottom - window_rect.top) * dpiY / 96.f));
+
+  LPCWSTR name;
+  DWORD style;
+  if (enable_compositor) {
+    name = L"example-compositor (DirectComposition)";
+    style = WS_EX_NOREDIRECTIONBITMAP;
+  } else {
+    name = L"example-compositor (Simple)";
+    style = 0;
+  }
+
+  window->hWnd =
+      CreateWindowEx(style, CLASS_NAME, name, WS_OVERLAPPEDWINDOW,
+                     CW_USEDEFAULT, CW_USEDEFAULT, window_width, window_height,
+                     NULL, NULL, window->hInstance, NULL);
+
+  ShowWindow(window->hWnd, SW_SHOWNORMAL);
+  UpdateWindow(window->hWnd);
+  GetClientRect(window->hWnd, &window->client_rect);
+
+  // Create a D3D11 device
+  D3D_FEATURE_LEVEL featureLevelSupported;
+  HRESULT hr = D3D11CreateDevice(nullptr, D3D_DRIVER_TYPE_HARDWARE, NULL,
+                                 D3D11_CREATE_DEVICE_BGRA_SUPPORT, NULL, 0,
+                                 D3D11_SDK_VERSION, &window->pD3D11Device,
+                                 &featureLevelSupported, nullptr);
+  assert(SUCCEEDED(hr));
+
+  D3D11_QUERY_DESC query_desc;
+  memset(&query_desc, 0, sizeof(query_desc));
+  query_desc.Query = D3D11_QUERY_EVENT;
+  for (int i = 0; i < NUM_QUERIES; ++i) {
+    hr = window->pD3D11Device->CreateQuery(&query_desc, &window->pQueries[i]);
+    assert(SUCCEEDED(hr));
+  }
+  window->current_query = 0;
+
+  hr = window->pD3D11Device->QueryInterface(&window->pDXGIDevice);
+  assert(SUCCEEDED(hr));
+
+  // Create a DirectComposition device
+  hr = DCompositionCreateDevice2(window->pDXGIDevice,
+                                 __uuidof(IDCompositionDesktopDevice),
+                                 (void**)&window->pDCompDevice);
+  assert(SUCCEEDED(hr));
+
+  // Create a DirectComposition target for a Win32 window handle
+  hr = window->pDCompDevice->CreateTargetForHwnd(window->hWnd, TRUE,
+                                                 &window->pDCompTarget);
+  assert(SUCCEEDED(hr));
+
+  // Create an ANGLE EGL device that wraps D3D11
+  window->EGLDevice = eglCreateDeviceANGLE(EGL_D3D11_DEVICE_ANGLE,
+                                           window->pD3D11Device, nullptr);
+
+  EGLint display_attribs[] = {EGL_NONE};
+
+  window->EGLDisplay = eglGetPlatformDisplayEXT(
+      EGL_PLATFORM_DEVICE_EXT, window->EGLDevice, display_attribs);
+
+  eglInitialize(window->EGLDisplay, nullptr, nullptr);
+
+  EGLint num_configs = 0;
+  EGLint cfg_attribs[] = {EGL_SURFACE_TYPE,
+                          EGL_WINDOW_BIT,
+                          EGL_RENDERABLE_TYPE,
+                          EGL_OPENGL_ES2_BIT,
+                          EGL_RED_SIZE,
+                          8,
+                          EGL_GREEN_SIZE,
+                          8,
+                          EGL_BLUE_SIZE,
+                          8,
+                          EGL_ALPHA_SIZE,
+                          8,
+                          EGL_DEPTH_SIZE,
+                          24,
+                          EGL_NONE};
+  EGLConfig configs[32];
+
+  eglChooseConfig(window->EGLDisplay, cfg_attribs, configs,
+                  sizeof(configs) / sizeof(EGLConfig), &num_configs);
+  assert(num_configs > 0);
+  window->config = configs[0];
+
+  if (window->enable_compositor) {
+    window->fb_surface = EGL_NO_SURFACE;
+  } else {
+    window->fb_surface = eglCreateWindowSurface(
+        window->EGLDisplay, window->config, window->hWnd, NULL);
+    assert(window->fb_surface != EGL_NO_SURFACE);
+  }
+
+  EGLint ctx_attribs[] = {EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE};
+
+  // Create an EGL context that can be used for drawing
+  window->EGLContext = eglCreateContext(window->EGLDisplay, window->config,
+                                        EGL_NO_CONTEXT, ctx_attribs);
+
+  // Create the root of the DirectComposition visual tree
+  hr = window->pDCompDevice->CreateVisual(&window->pRoot);
+  assert(SUCCEEDED(hr));
+  hr = window->pDCompTarget->SetRoot(window->pRoot);
+  assert(SUCCEEDED(hr));
+
+  hr = window->pRoot->QueryInterface(__uuidof(IDCompositionVisualDebug),
+                                     (void**)&window->pVisualDebug);
+  assert(SUCCEEDED(hr));
+
+  // Uncomment this to see redraw regions during composite
+  // window->pVisualDebug->EnableRedrawRegions();
+
+  EGLBoolean ok = eglMakeCurrent(window->EGLDisplay, window->fb_surface,
+                                 window->fb_surface, window->EGLContext);
+  assert(ok);
+
+  return window;
+}
+
+void com_dc_destroy_window(Window* window) {
+  for (auto surface_it = window->surfaces.begin();
+       surface_it != window->surfaces.end(); ++surface_it) {
+    Surface& surface = surface_it->second;
+
+#ifndef USE_VIRTUAL_SURFACES
+    for (auto tile_it = surface.tiles.begin(); tile_it != surface.tiles.end();
+         ++tile_it) {
+      tile_it->second.pSurface->Release();
+      tile_it->second.pVisual->Release();
+    }
+#endif
+
+    surface.pVisual->Release();
+  }
+
+  if (window->fb_surface != EGL_NO_SURFACE) {
+    eglDestroySurface(window->EGLDisplay, window->fb_surface);
+  }
+  eglDestroyContext(window->EGLDisplay, window->EGLContext);
+  eglTerminate(window->EGLDisplay);
+  eglReleaseDeviceANGLE(window->EGLDevice);
+
+  for (int i = 0; i < NUM_QUERIES; ++i) {
+    window->pQueries[i]->Release();
+  }
+  window->pRoot->Release();
+  window->pVisualDebug->Release();
+  window->pD3D11Device->Release();
+  window->pDXGIDevice->Release();
+  window->pDCompDevice->Release();
+  window->pDCompTarget->Release();
+
+  CloseWindow(window->hWnd);
+  UnregisterClass(CLASS_NAME, window->hInstance);
+
+  delete window;
+}
+
+bool com_dc_tick(Window*) {
+  // Check and dispatch the windows event loop
+  MSG msg;
+  while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
+    if (msg.message == WM_QUIT) {
+      return false;
+    }
+
+    TranslateMessage(&msg);
+    DispatchMessage(&msg);
+  }
+
+  return true;
+}
+
+void com_dc_swap_buffers(Window* window) {
+  // If not using DC mode, then do a normal EGL swap buffers.
+  if (window->fb_surface != EGL_NO_SURFACE) {
+    switch (window->sync_mode) {
+      case SyncMode::None:
+        eglSwapInterval(window->EGLDisplay, 0);
+        break;
+      case SyncMode::Swap:
+        eglSwapInterval(window->EGLDisplay, 1);
+        break;
+      default:
+        assert(false);  // unexpected vsync mode for simple compositor.
+        break;
+    }
+
+    eglSwapBuffers(window->EGLDisplay, window->fb_surface);
+  } else {
+    switch (window->sync_mode) {
+      case SyncMode::None:
+        break;
+      case SyncMode::Commit:
+        window->pDCompDevice->WaitForCommitCompletion();
+        break;
+      case SyncMode::Flush:
+        DwmFlush();
+        break;
+      case SyncMode::Query:
+        // todo!!!!
+        break;
+      default:
+        assert(false);  // unexpected vsync mode for native compositor
+        break;
+    }
+  }
+}
+
+// Create a new DC surface
+void com_dc_create_surface(Window* window, uint64_t id, int tile_width,
+                           int tile_height, bool is_opaque) {
+  assert(window->surfaces.count(id) == 0);
+
+  Surface surface;
+  surface.tile_width = tile_width;
+  surface.tile_height = tile_height;
+  surface.is_opaque = is_opaque;
+
+  // Create the visual node in the DC tree that stores properties
+  HRESULT hr = window->pDCompDevice->CreateVisual(&surface.pVisual);
+  assert(SUCCEEDED(hr));
+
+#ifdef USE_VIRTUAL_SURFACES
+  DXGI_ALPHA_MODE alpha_mode = surface.is_opaque
+                                   ? DXGI_ALPHA_MODE_IGNORE
+                                   : DXGI_ALPHA_MODE_PREMULTIPLIED;
+
+  hr = window->pDCompDevice->CreateVirtualSurface(
+      VIRTUAL_OFFSET * 2, VIRTUAL_OFFSET * 2, DXGI_FORMAT_B8G8R8A8_UNORM,
+      alpha_mode, &surface.pVirtualSurface);
+  assert(SUCCEEDED(hr));
+
+  // Bind the surface memory to this visual
+  hr = surface.pVisual->SetContent(surface.pVirtualSurface);
+  assert(SUCCEEDED(hr));
+#endif
+
+  window->surfaces[id] = surface;
+}
+
+void com_dc_create_tile(Window* window, uint64_t id, int x, int y) {
+  assert(window->surfaces.count(id) == 1);
+  Surface& surface = window->surfaces[id];
+
+  TileKey key(x, y);
+  assert(surface.tiles.count(key) == 0);
+
+  Tile tile;
+
+#ifndef USE_VIRTUAL_SURFACES
+  // Create the video memory surface.
+  DXGI_ALPHA_MODE alpha_mode = surface.is_opaque
+                                   ? DXGI_ALPHA_MODE_IGNORE
+                                   : DXGI_ALPHA_MODE_PREMULTIPLIED;
+  HRESULT hr = window->pDCompDevice->CreateSurface(
+      surface.tile_width, surface.tile_height, DXGI_FORMAT_B8G8R8A8_UNORM,
+      alpha_mode, &tile.pSurface);
+  assert(SUCCEEDED(hr));
+
+  // Create the visual node in the DC tree that stores properties
+  hr = window->pDCompDevice->CreateVisual(&tile.pVisual);
+  assert(SUCCEEDED(hr));
+
+  // Bind the surface memory to this visual
+  hr = tile.pVisual->SetContent(tile.pSurface);
+  assert(SUCCEEDED(hr));
+
+  // Place the visual in local-space of this surface
+  float offset_x = (float)(x * surface.tile_width);
+  float offset_y = (float)(y * surface.tile_height);
+  tile.pVisual->SetOffsetX(offset_x);
+  tile.pVisual->SetOffsetY(offset_y);
+
+  surface.pVisual->AddVisual(tile.pVisual, FALSE, NULL);
+#endif
+
+  surface.tiles[key] = tile;
+}
+
+void com_dc_destroy_tile(Window* window, uint64_t id, int x, int y) {
+  assert(window->surfaces.count(id) == 1);
+  Surface& surface = window->surfaces[id];
+
+  TileKey key(x, y);
+  assert(surface.tiles.count(key) == 1);
+  Tile& tile = surface.tiles[key];
+
+#ifndef USE_VIRTUAL_SURFACES
+  surface.pVisual->RemoveVisual(tile.pVisual);
+
+  tile.pVisual->Release();
+  tile.pSurface->Release();
+#endif
+
+  surface.tiles.erase(key);
+}
+
+void com_dc_destroy_surface(Window* window, uint64_t id) {
+  assert(window->surfaces.count(id) == 1);
+  Surface& surface = window->surfaces[id];
+
+  window->pRoot->RemoveVisual(surface.pVisual);
+
+#ifdef USE_VIRTUAL_SURFACES
+  surface.pVirtualSurface->Release();
+#else
+  // Release the video memory and visual in the tree
+  for (auto tile_it = surface.tiles.begin(); tile_it != surface.tiles.end();
+       ++tile_it) {
+    tile_it->second.pSurface->Release();
+    tile_it->second.pVisual->Release();
+  }
+#endif
+
+  surface.pVisual->Release();
+  window->surfaces.erase(id);
+}
+
+// Bind a DC surface to allow issuing GL commands to it
+GLuint com_dc_bind_surface(Window* window, uint64_t surface_id, int tile_x,
+                           int tile_y, int* x_offset, int* y_offset,
+                           int dirty_x0, int dirty_y0, int dirty_width,
+                           int dirty_height) {
+  assert(window->surfaces.count(surface_id) == 1);
+  Surface& surface = window->surfaces[surface_id];
+
+  TileKey key(tile_x, tile_y);
+  assert(surface.tiles.count(key) == 1);
+  Tile& tile = surface.tiles[key];
+
+  // Inform DC that we want to draw on this surface. DC uses texture
+  // atlases when the tiles are small. It returns an offset where the
+  // client code must draw into this surface when this happens.
+  RECT update_rect;
+  update_rect.left = dirty_x0;
+  update_rect.top = dirty_y0;
+  update_rect.right = dirty_x0 + dirty_width;
+  update_rect.bottom = dirty_y0 + dirty_height;
+  POINT offset;
+  D3D11_TEXTURE2D_DESC desc;
+  ID3D11Texture2D* pTexture;
+  HRESULT hr;
+
+  // Store the current surface for unbinding later
+#ifdef USE_VIRTUAL_SURFACES
+  LONG tile_offset_x = VIRTUAL_OFFSET + tile_x * surface.tile_width;
+  LONG tile_offset_y = VIRTUAL_OFFSET + tile_y * surface.tile_height;
+
+  update_rect.left += tile_offset_x;
+  update_rect.top += tile_offset_y;
+  update_rect.right += tile_offset_x;
+  update_rect.bottom += tile_offset_y;
+
+  hr = surface.pVirtualSurface->BeginDraw(
+      &update_rect, __uuidof(ID3D11Texture2D), (void**)&pTexture, &offset);
+  window->pCurrentSurface = surface.pVirtualSurface;
+#else
+  hr = tile.pSurface->BeginDraw(&update_rect, __uuidof(ID3D11Texture2D),
+                                (void**)&pTexture, &offset);
+  window->pCurrentSurface = tile.pSurface;
+#endif
+
+  // DC includes the origin of the dirty / update rect in the draw offset,
+  // undo that here since WR expects it to be an absolute offset.
+  assert(SUCCEEDED(hr));
+  offset.x -= dirty_x0;
+  offset.y -= dirty_y0;
+  pTexture->GetDesc(&desc);
+  *x_offset = offset.x;
+  *y_offset = offset.y;
+
+  // Construct an EGLImage wrapper around the D3D texture for ANGLE.
+  const EGLAttrib attribs[] = {EGL_NONE};
+  window->mEGLImage = eglCreateImage(
+      window->EGLDisplay, EGL_NO_CONTEXT, EGL_D3D11_TEXTURE_ANGLE,
+      static_cast<EGLClientBuffer>(pTexture), attribs);
+
+  // Get the current FBO and RBO id, so we can restore them later
+  GLint currentFboId, currentRboId;
+  glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &currentFboId);
+  glGetIntegerv(GL_RENDERBUFFER_BINDING, &currentRboId);
+
+  // Create a render buffer object that is backed by the EGL image.
+  glGenRenderbuffers(1, &window->mColorRBO);
+  glBindRenderbuffer(GL_RENDERBUFFER, window->mColorRBO);
+  glEGLImageTargetRenderbufferStorageOES(GL_RENDERBUFFER, window->mEGLImage);
+
+  // Get or create an FBO for the specified dimensions
+  GLuint fboId = GetOrCreateFbo(window, desc.Width, desc.Height);
+
+  // Attach the new renderbuffer to the FBO
+  glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboId);
+  glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                            GL_RENDERBUFFER, window->mColorRBO);
+
+  // Restore previous FBO and RBO bindings
+  glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentFboId);
+  glBindRenderbuffer(GL_RENDERBUFFER, currentRboId);
+
+  return fboId;
+}
+
+// Unbind a currently bound DC surface
+void com_dc_unbind_surface(Window* window) {
+  HRESULT hr = window->pCurrentSurface->EndDraw();
+  assert(SUCCEEDED(hr));
+
+  glDeleteRenderbuffers(1, &window->mColorRBO);
+  window->mColorRBO = 0;
+
+  eglDestroyImage(window->EGLDisplay, window->mEGLImage);
+  window->mEGLImage = EGL_NO_IMAGE;
+}
+
+void com_dc_begin_transaction(Window*) {}
+
+// Add a DC surface to the visual tree. Called per-frame to build the
+// composition.
+void com_dc_add_surface(Window* window, uint64_t id, int x, int y, int clip_x,
+                        int clip_y, int clip_w, int clip_h) {
+  Surface surface = window->surfaces[id];
+  window->mCurrentLayers.push_back(id);
+
+  // Place the visual - this changes frame to frame based on scroll position
+  // of the slice.
+  float offset_x = (float)(x + window->client_rect.left);
+  float offset_y = (float)(y + window->client_rect.top);
+#ifdef USE_VIRTUAL_SURFACES
+  offset_x -= VIRTUAL_OFFSET;
+  offset_y -= VIRTUAL_OFFSET;
+#endif
+  surface.pVisual->SetOffsetX(offset_x);
+  surface.pVisual->SetOffsetY(offset_y);
+
+  // Set the clip rect - converting from world space to the pre-offset space
+  // that DC requires for rectangle clips.
+  D2D_RECT_F clip_rect;
+  clip_rect.left = clip_x - offset_x;
+  clip_rect.top = clip_y - offset_y;
+  clip_rect.right = clip_rect.left + clip_w;
+  clip_rect.bottom = clip_rect.top + clip_h;
+  surface.pVisual->SetClip(clip_rect);
+}
+
+// Finish the composition transaction, telling DC to composite
+void com_dc_end_transaction(Window* window) {
+  bool same = window->mPrevLayers == window->mCurrentLayers;
+
+  if (!same) {
+    HRESULT hr = window->pRoot->RemoveAllVisuals();
+    assert(SUCCEEDED(hr));
+
+    for (auto it = window->mCurrentLayers.begin();
+         it != window->mCurrentLayers.end(); ++it) {
+      Surface& surface = window->surfaces[*it];
+
+      // Add this visual as the last element in the visual tree (z-order is
+      // implicit, based on the order tiles are added).
+      hr = window->pRoot->AddVisual(surface.pVisual, FALSE, NULL);
+      assert(SUCCEEDED(hr));
+    }
+  }
+
+  window->mPrevLayers.swap(window->mCurrentLayers);
+  window->mCurrentLayers.clear();
+
+  HRESULT hr = window->pDCompDevice->Commit();
+  assert(SUCCEEDED(hr));
+}
+
+// Get a pointer to an EGL symbol
+void* com_dc_get_proc_address(const char* name) {
+  return eglGetProcAddress(name);
+}
+}
diff --git a/gfx/wr/example-compositor/compositor-windows/src/lib.rs b/gfx/wr/example-compositor/compositor-windows/src/lib.rs
new file mode 100644
index 0000000000..f0e5fa5b9c
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor-windows/src/lib.rs
@@ -0,0 +1,265 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::os::raw::{c_void, c_char};
+
+/*
+
+  This is a very simple (and unsafe!) rust wrapper for the DirectComposite / D3D11 / ANGLE
+  implementation in lib.cpp.
+
+  It just proxies the calls from the Compositor impl to the C99 code. This is very
+  hacky and not suitable for production!
+
+ */
+
+// Opaque wrapper for the Window type in lib.cpp
+#[repr(C)]
+pub struct Window {
+    _unused: [u8; 0]
+}
+
+// C99 functions that do the compositor work
+extern {
+    fn com_dc_create_window(
+        width: i32,
+        height: i32,
+        enable_compositor: bool,
+        sync_mode: i32,
+    ) -> *mut Window;
+    fn com_dc_destroy_window(window: *mut Window);
+    fn com_dc_tick(window: *mut Window) -> bool;
+    fn com_dc_get_proc_address(name: *const c_char) -> *const c_void;
+    fn com_dc_swap_buffers(window: *mut Window);
+
+    fn com_dc_create_surface(
+        window: *mut Window,
+        id: u64,
+        tile_width: i32,
+        tile_height: i32,
+        is_opaque: bool,
+    );
+
+    fn com_dc_create_tile(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+    );
+
+    fn com_dc_destroy_tile(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+    );
+
+    fn com_dc_destroy_surface(
+        window: *mut Window,
+        id: u64,
+    );
+
+    fn com_dc_bind_surface(
+        window: *mut Window,
+        surface_id: u64,
+        tile_x: i32,
+        tile_y: i32,
+        x_offset: &mut i32,
+        y_offset: &mut i32,
+        dirty_x0: i32,
+        dirty_y0: i32,
+        dirty_width: i32,
+        dirty_height: i32,
+    ) -> u32;
+    fn com_dc_unbind_surface(window: *mut Window);
+
+    fn com_dc_begin_transaction(window: *mut Window);
+
+    fn com_dc_add_surface(
+        window: *mut Window,
+        id: u64,
+        x: i32,
+        y: i32,
+        clip_x: i32,
+        clip_y: i32,
+        clip_w: i32,
+        clip_h: i32,
+    );
+
+    fn com_dc_end_transaction(window: *mut Window);
+}
+
+pub fn create_window(
+    width: i32,
+    height: i32,
+    enable_compositor: bool,
+    sync_mode: i32,
+) -> *mut Window {
+    unsafe {
+        com_dc_create_window(width, height, enable_compositor, sync_mode)
+    }
+}
+
+pub fn destroy_window(window: *mut Window) {
+    unsafe {
+        com_dc_destroy_window(window);
+    }
+}
+
+pub fn tick(window: *mut Window) -> bool {
+    unsafe {
+        com_dc_tick(window)
+    }
+}
+
+pub fn get_proc_address(name: *const c_char) -> *const c_void {
+    unsafe {
+        com_dc_get_proc_address(name)
+    }
+}
+
+pub fn create_surface(
+    window: *mut Window,
+    id: u64,
+    tile_width: i32,
+    tile_height: i32,
+    is_opaque: bool,
+) {
+    unsafe {
+        com_dc_create_surface(
+            window,
+            id,
+            tile_width,
+            tile_height,
+            is_opaque,
+        )
+    }
+}
+
+pub fn create_tile(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+) {
+    unsafe {
+        com_dc_create_tile(
+            window,
+            id,
+            x,
+            y,
+        )
+    }
+}
+
+pub fn destroy_tile(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+) {
+    unsafe {
+        com_dc_destroy_tile(
+            window,
+            id,
+            x,
+            y,
+        )
+    }
+}
+
+pub fn destroy_surface(
+    window: *mut Window,
+    id: u64,
+) {
+    unsafe {
+        com_dc_destroy_surface(
+            window,
+            id,
+        )
+    }
+}
+
+pub fn bind_surface(
+    window: *mut Window,
+    surface_id: u64,
+    tile_x: i32,
+    tile_y: i32,
+    dirty_x0: i32,
+    dirty_y0: i32,
+    dirty_width: i32,
+    dirty_height: i32,
+) -> (u32, i32, i32) {
+    unsafe {
+        let mut x_offset = 0;
+        let mut y_offset = 0;
+
+        let fbo_id = com_dc_bind_surface(
+            window,
+            surface_id,
+            tile_x,
+            tile_y,
+            &mut x_offset,
+            &mut y_offset,
+            dirty_x0,
+            dirty_y0,
+            dirty_width,
+            dirty_height,
+        );
+
+        (fbo_id, x_offset, y_offset)
+    }
+}
+
+pub fn add_surface(
+    window: *mut Window,
+    id: u64,
+    x: i32,
+    y: i32,
+    clip_x: i32,
+    clip_y: i32,
+    clip_w: i32,
+    clip_h: i32,
+) {
+    unsafe {
+        com_dc_add_surface(
+            window,
+            id,
+            x,
+            y,
+            clip_x,
+            clip_y,
+            clip_w,
+            clip_h,
+        )
+    }
+}
+
+pub fn begin_transaction(window: *mut Window) {
+    unsafe {
+        com_dc_begin_transaction(window)
+    }
+}
+
+pub fn unbind_surface(window: *mut Window) {
+    unsafe {
+        com_dc_unbind_surface(window)
+    }
+}
+
+pub fn end_transaction(window: *mut Window) {
+    unsafe {
+        com_dc_end_transaction(window)
+    }
+}
+
+pub fn swap_buffers(window: *mut Window) {
+    unsafe {
+        com_dc_swap_buffers(window);
+    }
+}
+
+pub fn deinit(_window: *mut Window) {
+    todo!()
+}
diff --git a/gfx/wr/example-compositor/compositor/Cargo.toml b/gfx/wr/example-compositor/compositor/Cargo.toml
new file mode 100644
index 0000000000..02c6ebe0ce
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "compositor"
+version = "0.1.0"
+authors = ["Glenn Watson <gw@intuitionlibrary.com>"]
+edition = "2018"
+license = "MPL-2.0"
+
+[dependencies]
+webrender = { path = "../../webrender" }
+gleam = "0.15"
+
+[target.'cfg(windows)'.dependencies]
+compositor-windows = { path = "../compositor-windows" }
+
+[target.'cfg(target_os = "linux")'.dependencies]
+compositor-wayland = { path = "../compositor-wayland" }
diff --git a/gfx/wr/example-compositor/compositor/src/main.rs b/gfx/wr/example-compositor/compositor/src/main.rs
new file mode 100644
index 0000000000..0a0275fe3f
--- /dev/null
+++ b/gfx/wr/example-compositor/compositor/src/main.rs
@@ -0,0 +1,549 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+
+   An example of how to implement the Compositor trait that
+   allows picture caching surfaces to be composited by the operating
+   system.
+
+   The current example supports DirectComposite on Windows only.
+
+*/
+
+use euclid::Angle;
+use gleam::gl;
+use std::ffi::CString;
+use std::sync::mpsc;
+use webrender::{CompositorSurfaceTransform, Transaction, api::*};
+use webrender::api::units::*;
+use webrender::Device;
+#[cfg(target_os = "windows")]
+use compositor_windows as compositor;
+#[cfg(target_os = "linux")]
+use compositor_wayland as compositor;
+use std::{env, f32, process};
+
+// A very hacky integration with DirectComposite. It proxies calls from the compositor
+// interface to a simple C99 library which does the DirectComposition / D3D11 / ANGLE
+// interfacing. This is a very unsafe impl due to the way the window pointer is passed
+// around!
+struct DirectCompositeInterface {
+    window: *mut compositor::Window,
+}
+
+impl DirectCompositeInterface {
+    fn new(window: *mut compositor::Window) -> Self {
+        DirectCompositeInterface { window }
+    }
+}
+
+impl webrender::Compositor for DirectCompositeInterface {
+    fn create_surface(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeSurfaceId,
+        _virtual_offset: DeviceIntPoint,
+        tile_size: DeviceIntSize,
+        is_opaque: bool,
+    ) {
+        compositor::create_surface(
+            self.window,
+            id.0,
+            tile_size.width,
+            tile_size.height,
+            is_opaque,
+        );
+    }
+
+    fn destroy_surface(&mut self, _device: &mut Device, id: webrender::NativeSurfaceId) {
+        compositor::destroy_surface(self.window, id.0);
+    }
+
+    fn create_tile(&mut self, _device: &mut Device, id: webrender::NativeTileId) {
+        compositor::create_tile(self.window, id.surface_id.0, id.x, id.y);
+    }
+
+    fn destroy_tile(&mut self, _device: &mut Device, id: webrender::NativeTileId) {
+        compositor::destroy_tile(self.window, id.surface_id.0, id.x, id.y);
+    }
+
+    fn bind(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeTileId,
+        dirty_rect: DeviceIntRect,
+        _valid_rect: DeviceIntRect,
+    ) -> webrender::NativeSurfaceInfo {
+        let (fbo_id, x, y) = compositor::bind_surface(
+            self.window,
+            id.surface_id.0,
+            id.x,
+            id.y,
+            dirty_rect.min.x,
+            dirty_rect.min.y,
+            dirty_rect.width(),
+            dirty_rect.height(),
+        );
+
+        webrender::NativeSurfaceInfo {
+            origin: DeviceIntPoint::new(x, y),
+            fbo_id,
+        }
+    }
+
+    fn unbind(&mut self, _device: &mut Device) {
+        compositor::unbind_surface(self.window);
+    }
+
+    fn begin_frame(&mut self, _device: &mut Device) {
+        compositor::begin_transaction(self.window);
+    }
+
+    fn add_surface(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeSurfaceId,
+        transform: CompositorSurfaceTransform,
+        clip_rect: DeviceIntRect,
+        _image_rendering: ImageRendering,
+    ) {
+        compositor::add_surface(
+            self.window,
+            id.0,
+            transform.offset.x as i32,
+            transform.offset.y as i32,
+            clip_rect.min.x,
+            clip_rect.min.y,
+            clip_rect.width(),
+            clip_rect.height(),
+        );
+    }
+
+    fn end_frame(&mut self, _device: &mut Device) {
+        compositor::end_transaction(self.window);
+    }
+    fn create_external_surface(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _: bool,
+    ) {
+        todo!()
+    }
+
+    fn attach_external_image(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _external_image: ExternalImageId,
+    ) {
+        todo!()
+    }
+
+    fn enable_native_compositor(&mut self, _device: &mut Device, _enable: bool) {
+        todo!()
+    }
+
+    fn deinit(&mut self, _device: &mut Device) {
+        compositor::deinit(self.window);
+    }
+
+    fn get_capabilities(&self, _device: &mut Device) -> webrender::CompositorCapabilities {
+        webrender::CompositorCapabilities {
+            virtual_surface_size: 1024 * 1024,
+            ..Default::default()
+        }
+    }
+
+    fn invalidate_tile(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeTileId,
+        _valid_rect: DeviceIntRect,
+    ) {
+    }
+
+    fn start_compositing(
+        &mut self,
+        _device: &mut Device,
+        _color: webrender::webrender_api::ColorF,
+        _dirty_rects: &[DeviceIntRect],
+        _opaque_rects: &[DeviceIntRect],
+    ) {
+    }
+
+    fn create_backdrop_surface(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _color: webrender::webrender_api::ColorF,
+    ) {
+        todo!()
+    }
+
+    fn get_window_visibility(&self, _device: &mut Device) -> webrender::WindowVisibility {
+        todo!()
+    }
+}
+
+// Simplisitic implementation of the WR notifier interface to know when a frame
+// has been prepared and can be rendered.
+struct Notifier {
+    tx: mpsc::Sender<()>,
+}
+
+impl Notifier {
+    fn new(tx: mpsc::Sender<()>) -> Self {
+        Notifier { tx }
+    }
+}
+
+impl RenderNotifier for Notifier {
+    fn clone(&self) -> Box<dyn RenderNotifier> {
+        Box::new(Notifier {
+            tx: self.tx.clone(),
+        })
+    }
+
+    fn wake_up(&self, _composite_needed: bool) {}
+
+    fn new_frame_ready(&self, _: DocumentId, _scrolled: bool, _composite_needed: bool, _: FramePublishId) {
+        self.tx.send(()).ok();
+    }
+}
+
+fn push_rotated_rect(
+    builder: &mut DisplayListBuilder,
+    rect: LayoutRect,
+    color: ColorF,
+    spatial_id: SpatialId,
+    _root_pipeline_id: PipelineId,
+    angle: f32,
+    time: f32,
+    item_key: SpatialTreeItemKey,
+) {
+    let color = color.scale_rgb(time);
+    let rotation = LayoutTransform::rotation(
+        0.0,
+        0.0,
+        1.0,
+        Angle::radians(2.0 * std::f32::consts::PI * angle),
+    );
+    let center = rect.center();
+    let transform_origin = LayoutVector3D::new(center.x, center.y, 0.0);
+    let transform = rotation
+        .pre_translate(-transform_origin)
+        .then_translate(transform_origin);
+    let spatial_id = builder.push_reference_frame(
+        LayoutPoint::zero(),
+        spatial_id,
+        TransformStyle::Flat,
+        PropertyBinding::Value(transform),
+        ReferenceFrameKind::Transform {
+            is_2d_scale_translation: false,
+            should_snap: false,
+            paired_with_perspective: false,
+        },
+        item_key,
+    );
+    builder.push_rect(
+        &CommonItemProperties::new(
+            rect,
+            SpaceAndClipInfo {
+                spatial_id,
+                clip_chain_id: ClipChainId::INVALID,
+            },
+        ),
+        rect,
+        color,
+    );
+}
+
+fn build_display_list(
+    builder: &mut DisplayListBuilder,
+    scroll_id: ExternalScrollId,
+    root_pipeline_id: PipelineId,
+    layout_size: LayoutSize,
+    time: f32,
+    invalidations: Invalidations,
+) {
+    let size_factor = match invalidations {
+        Invalidations::Small => 0.1,
+        Invalidations::Large | Invalidations::Scrolling => 1.0,
+    };
+
+    let fixed_space_info = SpaceAndClipInfo {
+        spatial_id: SpatialId::root_scroll_node(root_pipeline_id),
+        clip_chain_id: ClipChainId::INVALID,
+    };
+
+    let scroll_spatial_id = builder.define_scroll_frame(
+        fixed_space_info.spatial_id,
+        scroll_id,
+        LayoutRect::from_size(layout_size),
+        LayoutRect::from_size(layout_size),
+        LayoutVector2D::zero(),
+        APZScrollGeneration::default(),
+        HasScrollLinkedEffect::No,
+        SpatialTreeItemKey::new(1, 0),
+    );
+
+    builder.push_rect(
+        &CommonItemProperties::new(
+            LayoutRect::from_size(layout_size).inflate(-10.0, -10.0),
+            fixed_space_info,
+        ),
+        LayoutRect::from_size(layout_size).inflate(-10.0, -10.0),
+        ColorF::new(0.8, 0.8, 0.8, 1.0),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(100.0, 100.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(1.0, 0.0, 0.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 1),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(800.0, 100.0),
+            LayoutSize::new(size_factor * 100.0, size_factor * 600.0),
+        ),
+        ColorF::new(0.0, 1.0, 0.0, 1.0),
+        fixed_space_info.spatial_id,
+        root_pipeline_id,
+        0.2,
+        time,
+        SpatialTreeItemKey::new(1, 2),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(700.0, 200.0),
+            LayoutSize::new(size_factor * 300.0, size_factor * 300.0),
+        ),
+        ColorF::new(0.0, 0.0, 1.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        0.1,
+        time,
+        SpatialTreeItemKey::new(1, 3),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(100.0, 600.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(1.0, 1.0, 0.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 4),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(700.0, 600.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(0.0, 1.0, 1.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 5),
+    );
+}
+
+#[derive(Debug, Copy, Clone)]
+enum Invalidations {
+    Large,
+    Small,
+    Scrolling,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+enum Sync {
+    None = 0,
+    Swap = 1,
+    Commit = 2,
+    Flush = 3,
+    Query = 4,
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 6 {
+        println!("USAGE: compositor [native|none] [small|large|scroll] [none|swap|commit|flush|query] width height");
+        process::exit(0);
+    }
+
+    let enable_compositor = match args[1].parse::<String>().unwrap().as_str() {
+        "native" => true,
+        "none" => false,
+        _ => panic!("invalid compositor [native, none]"),
+    };
+
+    let inv_mode = match args[2].parse::<String>().unwrap().as_str() {
+        "small" => Invalidations::Small,
+        "large" => Invalidations::Large,
+        "scroll" => Invalidations::Scrolling,
+        _ => panic!("invalid invalidations [small, large, scroll]"),
+    };
+
+    let sync_mode = match args[3].parse::<String>().unwrap().as_str() {
+        "none" => Sync::None,
+        "swap" => Sync::Swap,
+        "commit" => Sync::Commit,
+        "flush" => Sync::Flush,
+        "query" => Sync::Query,
+        _ => panic!("invalid sync mode [none, swap, commit, flush, query]"),
+    };
+
+    let width = args[4].parse().unwrap();
+    let height = args[5].parse().unwrap();
+    let device_size = DeviceIntSize::new(width, height);
+
+    // Load GL, construct WR and the native compositor interface.
+    let window = compositor::create_window(
+        device_size.width,
+        device_size.height,
+        enable_compositor,
+        sync_mode as i32,
+    );
+    let debug_flags = DebugFlags::empty();
+    let compositor_config = if enable_compositor {
+        webrender::CompositorConfig::Native {
+            compositor: Box::new(DirectCompositeInterface::new(window)),
+        }
+    } else {
+        webrender::CompositorConfig::Draw {
+            max_partial_present_rects: 0,
+            draw_previous_partial_present_regions: false,
+            partial_present: None,
+        }
+    };
+    let opts = webrender::WebRenderOptions {
+        clear_color: ColorF::new(1.0, 1.0, 1.0, 1.0),
+        debug_flags,
+        compositor_config,
+        surface_origin_is_top_left: false,
+        ..webrender::WebRenderOptions::default()
+    };
+    let (tx, rx) = mpsc::channel();
+    let notifier = Box::new(Notifier::new(tx));
+    let gl = unsafe {
+        gl::GlesFns::load_with(|symbol| {
+            let symbol = CString::new(symbol).unwrap();
+            let ptr = compositor::get_proc_address(symbol.as_ptr());
+            ptr
+        })
+    };
+    let (mut renderer, sender) =
+        webrender::create_webrender_instance(gl.clone(), notifier, opts, None).unwrap();
+    let mut api = sender.create_api();
+    let document_id = api.add_document(device_size);
+    let device_pixel_ratio = 1.0;
+    let mut current_epoch = Epoch(0);
+    let root_pipeline_id = PipelineId(0, 0);
+    let layout_size = device_size.to_f32() / euclid::Scale::new(device_pixel_ratio);
+    let mut time = 0.0;
+    let scroll_id = ExternalScrollId(3, root_pipeline_id);
+
+    // Kick off first transaction which will mean we get a notify below to build the DL and render.
+    let mut txn = Transaction::new();
+    txn.set_root_pipeline(root_pipeline_id);
+
+    if let Invalidations::Scrolling = inv_mode {
+        let mut root_builder = DisplayListBuilder::new(root_pipeline_id);
+        root_builder.begin();
+
+        build_display_list(
+            &mut root_builder,
+            scroll_id,
+            root_pipeline_id,
+            layout_size,
+            1.0,
+            inv_mode,
+        );
+
+        txn.set_display_list(current_epoch, root_builder.end());
+    }
+
+    txn.generate_frame(0, RenderReasons::empty());
+    api.send_transaction(document_id, txn);
+
+    // Tick the compositor (in this sample, we don't block on UI events)
+    while compositor::tick(window) {
+        // If there is a new frame ready to draw
+        if let Ok(..) = rx.try_recv() {
+            // Update and render. This will invoke the native compositor interface implemented above
+            // as required.
+            renderer.update();
+            renderer.render(device_size, 0).unwrap();
+            let _ = renderer.flush_pipeline_info();
+
+            // Construct a simple display list that can be drawn and composited by DC.
+            let mut txn = Transaction::new();
+
+            match inv_mode {
+                Invalidations::Small | Invalidations::Large => {
+                    let mut root_builder = DisplayListBuilder::new(root_pipeline_id);
+                    root_builder.begin();
+
+                    build_display_list(
+                        &mut root_builder,
+                        scroll_id,
+                        root_pipeline_id,
+                        layout_size,
+                        time,
+                        inv_mode,
+                    );
+
+                    txn.set_display_list(current_epoch, root_builder.end());
+                }
+                Invalidations::Scrolling => {
+                    let d = 0.5 - 0.5 * (2.0 * f32::consts::PI * 5.0 * time).cos();
+                    txn.set_scroll_offsets(
+                        scroll_id,
+                        vec![SampledScrollOffset {
+                            offset: LayoutVector2D::new(0.0, (d * 100.0).round()),
+                            generation: APZScrollGeneration::default(),
+                        }],
+                    );
+                }
+            }
+
+            txn.generate_frame(0, RenderReasons::empty());
+            api.send_transaction(document_id, txn);
+            current_epoch.0 += 1;
+            time += 0.001;
+            if time > 1.0 {
+                time = 0.0;
+            }
+
+            // This does nothing when native compositor is enabled
+            compositor::swap_buffers(window);
+        }
+    }
+
+    renderer.deinit();
+    compositor::destroy_window(window);
+}