Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

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

1 files changed, 632 insertions, 0 deletions

diff --git a/dom/canvas/WebGLContextValidate.cpp b/dom/canvas/WebGLContextValidate.cpp
new file mode 100644
index 0000000000..f01ed06a36
--- /dev/null
+++ b/dom/canvas/WebGLContextValidate.cpp
@@ -0,0 +1,632 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "WebGLContext.h"
+
+#include <algorithm>
+#include "GLSLANG/ShaderLang.h"
+#include "CanvasUtils.h"
+#include "gfxEnv.h"
+#include "GLContext.h"
+#include "jsfriendapi.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_webgl.h"
+#include "nsPrintfCString.h"
+#include "WebGLBuffer.h"
+#include "WebGLContextUtils.h"
+#include "WebGLFramebuffer.h"
+#include "WebGLProgram.h"
+#include "WebGLRenderbuffer.h"
+#include "WebGLSampler.h"
+#include "WebGLShader.h"
+#include "WebGLTexture.h"
+#include "WebGLValidateStrings.h"
+#include "WebGLVertexArray.h"
+
+#if defined(MOZ_WIDGET_COCOA)
+#  include "nsCocoaFeatures.h"
+#endif
+
+////////////////////
+// Minimum value constants defined in GLES 2.0.25 $6.2 "State Tables":
+const uint32_t kMinMaxVertexAttribs = 8;            // Page 164
+const uint32_t kMinMaxVertexUniformVectors = 128;   // Page 164
+const uint32_t kMinMaxFragmentUniformVectors = 16;  // Page 164
+const uint32_t kMinMaxVaryingVectors = 8;           // Page 164
+
+const uint32_t kMinMaxVertexTextureImageUnits = 0;    // Page 164
+const uint32_t kMinMaxFragmentTextureImageUnits = 8;  // Page 164
+const uint32_t kMinMaxCombinedTextureImageUnits = 8;  // Page 164
+
+const uint32_t kMinMaxDrawBuffers = 4;
+
+// These few deviate from the spec: (The minimum values in the spec are
+// ridiculously low)
+const uint32_t kMinMaxTextureSize = 1024;        // ES2 spec says `64` (p162)
+const uint32_t kMinMaxCubeMapTextureSize = 512;  // ES2 spec says `16` (p162)
+const uint32_t kMinMaxRenderbufferSize = 1024;   // ES2 spec says `1` (p164)
+
+// Minimum value constants defined in GLES 3.0.4 $6.2 "State Tables":
+const uint32_t kMinMax3DTextureSize = 256;
+const uint32_t kMinMaxArrayTextureLayers = 256;
+
+////////////////////
+// "Common" but usable values to avoid WebGL fingerprinting:
+const uint32_t kCommonMaxTextureSize = 2048;
+const uint32_t kCommonMaxCubeMapTextureSize = 2048;
+const uint32_t kCommonMaxRenderbufferSize = 2048;
+
+const uint32_t kCommonMaxVertexTextureImageUnits = 8;
+const uint32_t kCommonMaxFragmentTextureImageUnits = 8;
+const uint32_t kCommonMaxCombinedTextureImageUnits = 16;
+
+const uint32_t kCommonMaxVertexAttribs = 16;
+const uint32_t kCommonMaxVertexUniformVectors = 256;
+const uint32_t kCommonMaxFragmentUniformVectors = 224;
+const uint32_t kCommonMaxVaryingVectors = 8;
+
+const uint32_t kCommonMaxViewportDims = 4096;
+
+// The following ranges came from a 2013 Moto E and an old macbook.
+const float kCommonAliasedPointSizeRangeMin = 1;
+const float kCommonAliasedPointSizeRangeMax = 63;
+const float kCommonAliasedLineWidthRangeMin = 1;
+const float kCommonAliasedLineWidthRangeMax = 1;
+
+template <class T>
+static bool RestrictCap(T* const cap, const T restrictedVal) {
+  if (*cap < restrictedVal) {
+    return false;  // already too low!
+  }
+
+  *cap = restrictedVal;
+  return true;
+}
+
+////////////////////
+
+namespace mozilla {
+
+bool WebGLContext::ValidateBlendEquationEnum(GLenum mode, const char* info) {
+  switch (mode) {
+    case LOCAL_GL_FUNC_ADD:
+    case LOCAL_GL_FUNC_SUBTRACT:
+    case LOCAL_GL_FUNC_REVERSE_SUBTRACT:
+      return true;
+
+    case LOCAL_GL_MIN:
+    case LOCAL_GL_MAX:
+      if (IsWebGL2() ||
+          IsExtensionEnabled(WebGLExtensionID::EXT_blend_minmax)) {
+        return true;
+      }
+
+      break;
+
+    default:
+      break;
+  }
+
+  ErrorInvalidEnumInfo(info, mode);
+  return false;
+}
+
+bool WebGLContext::ValidateBlendFuncEnumsCompatibility(GLenum sfactor,
+                                                       GLenum dfactor,
+                                                       const char* info) {
+  bool sfactorIsConstantColor = sfactor == LOCAL_GL_CONSTANT_COLOR ||
+                                sfactor == LOCAL_GL_ONE_MINUS_CONSTANT_COLOR;
+  bool sfactorIsConstantAlpha = sfactor == LOCAL_GL_CONSTANT_ALPHA ||
+                                sfactor == LOCAL_GL_ONE_MINUS_CONSTANT_ALPHA;
+  bool dfactorIsConstantColor = dfactor == LOCAL_GL_CONSTANT_COLOR ||
+                                dfactor == LOCAL_GL_ONE_MINUS_CONSTANT_COLOR;
+  bool dfactorIsConstantAlpha = dfactor == LOCAL_GL_CONSTANT_ALPHA ||
+                                dfactor == LOCAL_GL_ONE_MINUS_CONSTANT_ALPHA;
+  if ((sfactorIsConstantColor && dfactorIsConstantAlpha) ||
+      (dfactorIsConstantColor && sfactorIsConstantAlpha)) {
+    ErrorInvalidOperation(
+        "%s are mutually incompatible, see section 6.8 in"
+        " the WebGL 1.0 spec",
+        info);
+    return false;
+  }
+
+  return true;
+}
+
+bool WebGLContext::ValidateStencilOpEnum(GLenum action, const char* info) {
+  switch (action) {
+    case LOCAL_GL_KEEP:
+    case LOCAL_GL_ZERO:
+    case LOCAL_GL_REPLACE:
+    case LOCAL_GL_INCR:
+    case LOCAL_GL_INCR_WRAP:
+    case LOCAL_GL_DECR:
+    case LOCAL_GL_DECR_WRAP:
+    case LOCAL_GL_INVERT:
+      return true;
+
+    default:
+      ErrorInvalidEnumInfo(info, action);
+      return false;
+  }
+}
+
+bool WebGLContext::ValidateFaceEnum(const GLenum face) {
+  switch (face) {
+    case LOCAL_GL_FRONT:
+    case LOCAL_GL_BACK:
+    case LOCAL_GL_FRONT_AND_BACK:
+      return true;
+
+    default:
+      ErrorInvalidEnumInfo("face", face);
+      return false;
+  }
+}
+
+bool WebGLContext::ValidateAttribArraySetter(uint32_t setterElemSize,
+                                             uint32_t arrayLength) {
+  if (IsContextLost()) return false;
+
+  if (arrayLength < setterElemSize) {
+    ErrorInvalidValue("Array must have >= %d elements.", setterElemSize);
+    return false;
+  }
+
+  return true;
+}
+
+// ---------------------
+
+static webgl::Limits MakeLimits(const WebGLContext& webgl) {
+  webgl::Limits limits;
+
+  gl::GLContext& gl = *webgl.GL();
+
+  // -
+
+  for (const auto i : IntegerRange(UnderlyingValue(WebGLExtensionID::Max))) {
+    const auto ext = WebGLExtensionID(i);
+    limits.supportedExtensions[ext] = webgl.IsExtensionSupported(ext);
+  }
+
+  // -
+  // WebGL 1
+
+  // Note: GL_MAX_TEXTURE_UNITS is fixed at 4 for most desktop hardware,
+  // even though the hardware supports much more.  The
+  // GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS value is the accurate value.
+  gl.GetUIntegerv(LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS,
+                  &limits.maxTexUnits);
+  limits.maxTexUnits = std::min(
+      limits.maxTexUnits, uint32_t{UINT8_MAX});  // We want to use uint8_t.
+
+  gl.GetUIntegerv(LOCAL_GL_MAX_TEXTURE_SIZE, &limits.maxTex2dSize);
+  gl.GetUIntegerv(LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE, &limits.maxTexCubeSize);
+  gl.GetUIntegerv(LOCAL_GL_MAX_VERTEX_ATTRIBS, &limits.maxVertexAttribs);
+
+  auto dims = std::array<uint32_t, 2>{};
+  gl.GetUIntegerv(LOCAL_GL_MAX_VIEWPORT_DIMS, dims.data());
+  limits.maxViewportDim = std::min(dims[0], dims[1]);
+
+  if (!gl.IsCoreProfile()) {
+    gl.fGetFloatv(LOCAL_GL_ALIASED_LINE_WIDTH_RANGE,
+                  limits.lineWidthRange.data());
+  }
+
+  {
+    const GLenum driverPName = gl.IsCoreProfile()
+                                   ? LOCAL_GL_POINT_SIZE_RANGE
+                                   : LOCAL_GL_ALIASED_POINT_SIZE_RANGE;
+    gl.fGetFloatv(driverPName, limits.pointSizeRange.data());
+  }
+
+  if (webgl.IsWebGL2()) {
+    gl.GetUIntegerv(LOCAL_GL_MAX_ARRAY_TEXTURE_LAYERS,
+                    &limits.maxTexArrayLayers);
+    gl.GetUIntegerv(LOCAL_GL_MAX_3D_TEXTURE_SIZE, &limits.maxTex3dSize);
+    gl.GetUIntegerv(LOCAL_GL_MAX_UNIFORM_BUFFER_BINDINGS,
+                    &limits.maxUniformBufferBindings);
+    gl.GetUIntegerv(LOCAL_GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT,
+                    &limits.uniformBufferOffsetAlignment);
+  }
+
+  if (limits.supportedExtensions
+          [WebGLExtensionID::WEBGL_compressed_texture_astc]) {
+    limits.astcHdr = gl.IsExtensionSupported(
+        gl::GLContext::KHR_texture_compression_astc_hdr);
+  }
+
+  if (webgl.IsWebGL2() ||
+      limits.supportedExtensions[WebGLExtensionID::WEBGL_draw_buffers]) {
+    gl.GetUIntegerv(LOCAL_GL_MAX_DRAW_BUFFERS, &limits.maxColorDrawBuffers);
+  }
+
+  if (limits.supportedExtensions[WebGLExtensionID::EXT_disjoint_timer_query]) {
+    gl.fGetQueryiv(LOCAL_GL_TIME_ELAPSED_EXT, LOCAL_GL_QUERY_COUNTER_BITS,
+                   (int32_t*)&limits.queryCounterBitsTimeElapsed);
+    gl.fGetQueryiv(LOCAL_GL_TIMESTAMP_EXT, LOCAL_GL_QUERY_COUNTER_BITS,
+                   (int32_t*)&limits.queryCounterBitsTimestamp);
+  }
+
+  if (limits.supportedExtensions[WebGLExtensionID::OVR_multiview2]) {
+    gl.GetUIntegerv(LOCAL_GL_MAX_VIEWS_OVR, &limits.maxMultiviewLayers);
+  }
+
+  return limits;
+}
+
+bool WebGLContext::InitAndValidateGL(FailureReason* const out_failReason) {
+  MOZ_RELEASE_ASSERT(gl, "GFX: GL not initialized");
+
+  // Unconditionally create a new format usage authority. This is
+  // important when restoring contexts and extensions need to add
+  // formats back into the authority.
+  mFormatUsage = CreateFormatUsage(gl);
+  if (!mFormatUsage) {
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_FORMAT",
+                       "Failed to create mFormatUsage."};
+    return false;
+  }
+
+  GLenum error = gl->fGetError();
+  if (error != LOCAL_GL_NO_ERROR) {
+    const nsPrintfCString reason(
+        "GL error 0x%x occurred during OpenGL context"
+        " initialization, before WebGL initialization!",
+        error);
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_GLERR_1", reason};
+    return false;
+  }
+
+  mLoseContextOnMemoryPressure =
+      StaticPrefs::webgl_lose_context_on_memory_pressure();
+  mCanLoseContextInForeground =
+      StaticPrefs::webgl_can_lose_context_in_foreground();
+
+  /*
+  // Technically, we should be setting mStencil[...] values to
+  // `allOnes`, but either ANGLE breaks or the SGX540s on Try break.
+  GLuint stencilBits = 0;
+  gl->GetUIntegerv(LOCAL_GL_STENCIL_BITS, &stencilBits);
+  GLuint allOnes = ~(UINT32_MAX << stencilBits);
+  mStencilValueMaskFront = allOnes;
+  mStencilValueMaskBack  = allOnes;
+  mStencilWriteMaskFront = allOnes;
+  mStencilWriteMaskBack  = allOnes;
+  */
+
+  gl->GetUIntegerv(LOCAL_GL_STENCIL_VALUE_MASK, &mStencilValueMaskFront);
+  gl->GetUIntegerv(LOCAL_GL_STENCIL_BACK_VALUE_MASK, &mStencilValueMaskBack);
+  gl->GetUIntegerv(LOCAL_GL_STENCIL_WRITEMASK, &mStencilWriteMaskFront);
+  gl->GetUIntegerv(LOCAL_GL_STENCIL_BACK_WRITEMASK, &mStencilWriteMaskBack);
+
+  AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_VALUE_MASK,
+                         mStencilValueMaskFront);
+  AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_BACK_VALUE_MASK,
+                         mStencilValueMaskBack);
+  AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_WRITEMASK,
+                         mStencilWriteMaskFront);
+  AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_BACK_WRITEMASK,
+                         mStencilWriteMaskBack);
+
+  // Bindings, etc.
+
+  mBound2DTextures.Clear();
+  mBoundCubeMapTextures.Clear();
+  mBound3DTextures.Clear();
+  mBound2DArrayTextures.Clear();
+  mBoundSamplers.Clear();
+
+  mBoundArrayBuffer = nullptr;
+  mCurrentProgram = nullptr;
+
+  mBoundDrawFramebuffer = nullptr;
+  mBoundReadFramebuffer = nullptr;
+
+  // -----------------------
+
+  auto limits = MakeLimits(*this);
+
+  // -
+
+  if (limits.maxVertexAttribs < 8) {
+    const nsPrintfCString reason("GL_MAX_VERTEX_ATTRIBS: %d is < 8!",
+                                 limits.maxVertexAttribs);
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_V_ATRB", reason};
+    return false;
+  }
+
+  if (limits.maxTexUnits < 8) {
+    const nsPrintfCString reason(
+        "GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS: %u is < 8!", limits.maxTexUnits);
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_T_UNIT", reason};
+    return false;
+  }
+
+  mBound2DTextures.SetLength(limits.maxTexUnits);
+  mBoundCubeMapTextures.SetLength(limits.maxTexUnits);
+  mBound3DTextures.SetLength(limits.maxTexUnits);
+  mBound2DArrayTextures.SetLength(limits.maxTexUnits);
+  mBoundSamplers.SetLength(limits.maxTexUnits);
+
+  ////////////////
+
+  gl->GetUIntegerv(LOCAL_GL_MAX_RENDERBUFFER_SIZE, &mGLMaxRenderbufferSize);
+  gl->GetUIntegerv(LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS,
+                   &mGLMaxFragmentTextureImageUnits);
+  gl->GetUIntegerv(LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS,
+                   &mGLMaxVertexTextureImageUnits);
+
+  ////////////////
+
+  if (gl->IsGLES()) {
+    mGLMaxFragmentUniformVectors =
+        gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS);
+    mGLMaxVertexUniformVectors =
+        gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS);
+    if (gl->Version() >= 300) {
+      mGLMaxVertexOutputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VERTEX_OUTPUT_COMPONENTS) / 4;
+      mGLMaxFragmentInputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_FRAGMENT_INPUT_COMPONENTS) / 4;
+    } else {
+      mGLMaxFragmentInputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VARYING_VECTORS);
+      mGLMaxVertexOutputVectors = mGLMaxFragmentInputVectors;
+    }
+  } else {
+    mGLMaxFragmentUniformVectors =
+        gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS) / 4;
+    mGLMaxVertexUniformVectors =
+        gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VERTEX_UNIFORM_COMPONENTS) / 4;
+
+    if (gl->Version() >= 320) {
+      mGLMaxVertexOutputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VERTEX_OUTPUT_COMPONENTS) / 4;
+      mGLMaxFragmentInputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_FRAGMENT_INPUT_COMPONENTS) / 4;
+    } else {
+      // Same enum val as GL2's GL_MAX_VARYING_FLOATS.
+      mGLMaxFragmentInputVectors =
+          gl->GetIntAs<uint32_t>(LOCAL_GL_MAX_VARYING_COMPONENTS) / 4;
+      mGLMaxVertexOutputVectors = mGLMaxFragmentInputVectors;
+    }
+  }
+
+  ////////////////
+
+  if (StaticPrefs::webgl_min_capability_mode()) {
+    bool ok = true;
+
+    ok &= RestrictCap(&mGLMaxVertexTextureImageUnits,
+                      kMinMaxVertexTextureImageUnits);
+    ok &= RestrictCap(&mGLMaxFragmentTextureImageUnits,
+                      kMinMaxFragmentTextureImageUnits);
+    ok &= RestrictCap(&limits.maxTexUnits, kMinMaxCombinedTextureImageUnits);
+
+    ok &= RestrictCap(&limits.maxVertexAttribs, kMinMaxVertexAttribs);
+    ok &= RestrictCap(&mGLMaxVertexUniformVectors, kMinMaxVertexUniformVectors);
+    ok &= RestrictCap(&mGLMaxFragmentUniformVectors,
+                      kMinMaxFragmentUniformVectors);
+    ok &= RestrictCap(&mGLMaxVertexOutputVectors, kMinMaxVaryingVectors);
+    ok &= RestrictCap(&mGLMaxFragmentInputVectors, kMinMaxVaryingVectors);
+
+    ok &= RestrictCap(&limits.maxColorDrawBuffers, kMinMaxDrawBuffers);
+
+    ok &= RestrictCap(&limits.maxTex2dSize, kMinMaxTextureSize);
+    ok &= RestrictCap(&limits.maxTexCubeSize, kMinMaxCubeMapTextureSize);
+    ok &= RestrictCap(&limits.maxTex3dSize, kMinMax3DTextureSize);
+
+    ok &= RestrictCap(&limits.maxTexArrayLayers, kMinMaxArrayTextureLayers);
+    ok &= RestrictCap(&mGLMaxRenderbufferSize, kMinMaxRenderbufferSize);
+
+    if (!ok) {
+      GenerateWarning("Unable to restrict WebGL limits to minimums.");
+      return false;
+    }
+
+    mDisableFragHighP = true;
+  } else if (mResistFingerprinting) {
+    bool ok = true;
+
+    ok &= RestrictCap(&limits.maxTex2dSize, kCommonMaxTextureSize);
+    ok &= RestrictCap(&limits.maxTexCubeSize, kCommonMaxCubeMapTextureSize);
+    ok &= RestrictCap(&mGLMaxRenderbufferSize, kCommonMaxRenderbufferSize);
+
+    ok &= RestrictCap(&mGLMaxVertexTextureImageUnits,
+                      kCommonMaxVertexTextureImageUnits);
+    ok &= RestrictCap(&mGLMaxFragmentTextureImageUnits,
+                      kCommonMaxFragmentTextureImageUnits);
+    ok &= RestrictCap(&limits.maxTexUnits, kCommonMaxCombinedTextureImageUnits);
+
+    ok &= RestrictCap(&limits.maxVertexAttribs, kCommonMaxVertexAttribs);
+    ok &= RestrictCap(&mGLMaxVertexUniformVectors,
+                      kCommonMaxVertexUniformVectors);
+    ok &= RestrictCap(&mGLMaxFragmentUniformVectors,
+                      kCommonMaxFragmentUniformVectors);
+    ok &= RestrictCap(&mGLMaxVertexOutputVectors, kCommonMaxVaryingVectors);
+    ok &= RestrictCap(&mGLMaxFragmentInputVectors, kCommonMaxVaryingVectors);
+
+    if (limits.lineWidthRange[0] <= kCommonAliasedLineWidthRangeMin) {
+      limits.lineWidthRange[0] = kCommonAliasedLineWidthRangeMin;
+    } else {
+      ok = false;
+    }
+    if (limits.pointSizeRange[0] <= kCommonAliasedPointSizeRangeMin) {
+      limits.pointSizeRange[0] = kCommonAliasedPointSizeRangeMin;
+    } else {
+      ok = false;
+    }
+
+    ok &=
+        RestrictCap(&limits.lineWidthRange[1], kCommonAliasedLineWidthRangeMax);
+    ok &=
+        RestrictCap(&limits.pointSizeRange[1], kCommonAliasedPointSizeRangeMax);
+    ok &= RestrictCap(&limits.maxViewportDim, kCommonMaxViewportDims);
+
+    if (!ok) {
+      GenerateWarning(
+          "Unable to restrict WebGL limits in order to resist fingerprinting");
+      return false;
+    }
+  }
+
+  mLimits = Some(limits);
+
+  ////////////////
+
+  if (gl->IsCompatibilityProfile()) {
+    gl->fEnable(LOCAL_GL_POINT_SPRITE);
+  }
+
+  if (!gl->IsGLES()) {
+    gl->fEnable(LOCAL_GL_PROGRAM_POINT_SIZE);
+  }
+
+#ifdef XP_MACOSX
+  if (gl->WorkAroundDriverBugs() && gl->Vendor() == gl::GLVendor::ATI &&
+      !nsCocoaFeatures::IsAtLeastVersion(10, 9)) {
+    // The Mac ATI driver, in all known OSX version up to and including
+    // 10.8, renders points sprites upside-down. (Apple bug 11778921)
+    gl->fPointParameterf(LOCAL_GL_POINT_SPRITE_COORD_ORIGIN,
+                         LOCAL_GL_LOWER_LEFT);
+  }
+#endif
+
+  if (gl->IsSupported(gl::GLFeature::seamless_cube_map_opt_in)) {
+    gl->fEnable(LOCAL_GL_TEXTURE_CUBE_MAP_SEAMLESS);
+  }
+
+  // initialize shader translator
+  if (!sh::Initialize()) {
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_GLSL",
+                       "GLSL translator initialization failed!"};
+    return false;
+  }
+
+  // Mesa can only be detected with the GL_VERSION string, of the form
+  // "2.1 Mesa 7.11.0"
+  const char* versionStr = (const char*)(gl->fGetString(LOCAL_GL_VERSION));
+  mIsMesa = strstr(versionStr, "Mesa");
+
+  // Notice that the point of calling fGetError here is not only to check for
+  // errors, but also to reset the error flags so that a subsequent WebGL
+  // getError call will give the correct result.
+  error = gl->fGetError();
+  if (error != LOCAL_GL_NO_ERROR) {
+    const nsPrintfCString reason(
+        "GL error 0x%x occurred during WebGL context"
+        " initialization!",
+        error);
+    *out_failReason = {"FEATURE_FAILURE_WEBGL_GLERR_2", reason};
+    return false;
+  }
+
+  if (IsWebGL2() && !InitWebGL2(out_failReason)) {
+    // Todo: Bug 898404: Only allow WebGL2 on GL>=3.0 on desktop GL.
+    return false;
+  }
+
+  // OpenGL core profiles remove the default VAO object from version
+  // 4.0.0. We create a default VAO for all core profiles,
+  // regardless of version.
+  //
+  // GL Spec 4.0.0:
+  // (https://www.opengl.org/registry/doc/glspec40.core.20100311.pdf)
+  // in Section E.2.2 "Removed Features", pg 397: "[...] The default
+  // vertex array object (the name zero) is also deprecated. [...]"
+  mDefaultVertexArray = WebGLVertexArray::Create(this);
+  mDefaultVertexArray->BindVertexArray();
+
+  mPrimRestartTypeBytes = 0;
+
+  // -
+
+  mGenericVertexAttribTypes.assign(limits.maxVertexAttribs,
+                                   webgl::AttribBaseType::Float);
+  mGenericVertexAttribTypeInvalidator.InvalidateCaches();
+
+  static const float kDefaultGenericVertexAttribData[4] = {0, 0, 0, 1};
+  memcpy(mGenericVertexAttrib0Data, kDefaultGenericVertexAttribData,
+         sizeof(mGenericVertexAttrib0Data));
+
+  mFakeVertexAttrib0BufferObject = 0;
+
+  mNeedsLegacyVertexAttrib0Handling = gl->IsCompatibilityProfile();
+  if (gl->WorkAroundDriverBugs() && kIsMacOS) {
+    // Failures in conformance/attribs/gl-disabled-vertex-attrib.
+    // Even in Core profiles on NV. Sigh.
+    mNeedsLegacyVertexAttrib0Handling |= (gl->Vendor() == gl::GLVendor::NVIDIA);
+
+    mBug_DrawArraysInstancedUserAttribFetchAffectedByFirst |=
+        (gl->Vendor() == gl::GLVendor::Intel);
+
+    // Failures for programs with no attribs:
+    // conformance/attribs/gl-vertex-attrib-unconsumed-out-of-bounds.html
+    mMaybeNeedsLegacyVertexAttrib0Handling = true;
+  }
+  mMaybeNeedsLegacyVertexAttrib0Handling |= mNeedsLegacyVertexAttrib0Handling;
+
+  if (const auto& env =
+          gfxEnv::MOZ_WEBGL_WORKAROUND_FIRST_AFFECTS_INSTANCE_ID()) {
+    const auto was = mBug_DrawArraysInstancedUserAttribFetchAffectedByFirst;
+    mBug_DrawArraysInstancedUserAttribFetchAffectedByFirst =
+        (env.as_str != "0");
+    printf_stderr(
+        "mBug_DrawArraysInstancedUserAttribFetchAffectedByFirst: %i -> %i\n",
+        int(was), int(mBug_DrawArraysInstancedUserAttribFetchAffectedByFirst));
+  }
+
+  // -
+
+  mNeedsIndexValidation =
+      !gl->IsSupported(gl::GLFeature::robust_buffer_access_behavior);
+  switch (StaticPrefs::webgl_force_index_validation()) {
+    case -1:
+      mNeedsIndexValidation = false;
+      break;
+    case 1:
+      mNeedsIndexValidation = true;
+      break;
+    default:
+      MOZ_ASSERT(StaticPrefs::webgl_force_index_validation() == 0);
+      break;
+  }
+
+  for (auto& cur : mExtensions) {
+    cur = {};
+  }
+
+  return true;
+}
+
+bool WebGLContext::ValidateFramebufferTarget(GLenum target) const {
+  bool isValid = true;
+  switch (target) {
+    case LOCAL_GL_FRAMEBUFFER:
+      break;
+
+    case LOCAL_GL_DRAW_FRAMEBUFFER:
+    case LOCAL_GL_READ_FRAMEBUFFER:
+      isValid = IsWebGL2();
+      break;
+
+    default:
+      isValid = false;
+      break;
+  }
+
+  if (MOZ_LIKELY(isValid)) {
+    return true;
+  }
+
+  ErrorInvalidEnumArg("target", target);
+  return false;
+}
+
+}  // namespace mozilla