1 files changed, 178 insertions, 0 deletions
diff --git a/gfx/layers/apz/util/ActiveElementManager.cpp b/gfx/layers/apz/util/ActiveElementManager.cpp
new file mode 100644
index 0000000000..8da36bb2c0
--- /dev/null
+++ b/gfx/layers/apz/util/ActiveElementManager.cpp
@@ -0,0 +1,178 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "ActiveElementManager.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Document.h"
+
+static mozilla::LazyLogModule sApzAemLog("apz.activeelement");
+#define AEM_LOG(...) MOZ_LOG(sApzAemLog, LogLevel::Debug, (__VA_ARGS__))
+
+namespace mozilla {
+namespace layers {
+
+ActiveElementManager::ActiveElementManager()
+    : mCanBePan(false), mCanBePanSet(false), mSetActiveTask(nullptr) {}
+
+ActiveElementManager::~ActiveElementManager() = default;
+
+void ActiveElementManager::SetTargetElement(dom::EventTarget* aTarget) {
+  if (mTarget) {
+    // Multiple fingers on screen (since HandleTouchEnd clears mTarget).
+    AEM_LOG("Multiple fingers on-screen, clearing target element\n");
+    CancelTask();
+    ResetActive();
+    ResetTouchBlockState();
+    return;
+  }
+
+  mTarget = dom::Element::FromEventTargetOrNull(aTarget);
+  AEM_LOG("Setting target element to %p\n", mTarget.get());
+  TriggerElementActivation();
+}
+
+void ActiveElementManager::HandleTouchStart(bool aCanBePan) {
+  AEM_LOG("Touch start, aCanBePan: %d\n", aCanBePan);
+  if (mCanBePanSet) {
+    // Multiple fingers on screen (since HandleTouchEnd clears mCanBePanSet).
+    AEM_LOG("Multiple fingers on-screen, clearing touch block state\n");
+    CancelTask();
+    ResetActive();
+    ResetTouchBlockState();
+    return;
+  }
+
+  mCanBePan = aCanBePan;
+  mCanBePanSet = true;
+  TriggerElementActivation();
+}
+
+void ActiveElementManager::TriggerElementActivation() {
+  // Both HandleTouchStart() and SetTargetElement() call this. They can be
+  // called in either order. One will set mCanBePanSet, and the other, mTarget.
+  // We want to actually trigger the activation once both are set.
+  if (!(mTarget && mCanBePanSet)) {
+    return;
+  }
+
+  // If the touch cannot be a pan, make mTarget :active right away.
+  // Otherwise, wait a bit to see if the user will pan or not.
+  if (!mCanBePan) {
+    SetActive(mTarget);
+  } else {
+    CancelTask();  // this is only needed because of bug 1169802. Fixing that
+                   // bug properly should make this unnecessary.
+    MOZ_ASSERT(mSetActiveTask == nullptr);
+
+    RefPtr<CancelableRunnable> task =
+        NewCancelableRunnableMethod<nsCOMPtr<dom::Element>>(
+            "layers::ActiveElementManager::SetActiveTask", this,
+            &ActiveElementManager::SetActiveTask, mTarget);
+    mSetActiveTask = task;
+    NS_GetCurrentThread()->DelayedDispatch(
+        task.forget(), StaticPrefs::ui_touch_activation_delay_ms());
+    AEM_LOG("Scheduling mSetActiveTask %p\n", mSetActiveTask.get());
+  }
+}
+
+void ActiveElementManager::ClearActivation() {
+  AEM_LOG("Clearing element activation\n");
+  CancelTask();
+  ResetActive();
+}
+
+void ActiveElementManager::HandleTouchEndEvent(bool aWasClick) {
+  AEM_LOG("Touch end event, aWasClick: %d\n", aWasClick);
+
+  // If the touch was a click, make mTarget :active right away.
+  // nsEventStateManager will reset the active element when processing
+  // the mouse-down event generated by the click.
+  CancelTask();
+  if (aWasClick) {
+    // Scrollbar thumbs use a different mechanism for their active
+    // highlight (the "active" attribute), so don't set the active state
+    // on them because nothing will clear it.
+    if (!(mTarget && mTarget->IsXULElement(nsGkAtoms::thumb))) {
+      SetActive(mTarget);
+    }
+  } else {
+    // We might reach here if mCanBePan was false on touch-start and
+    // so we set the element active right away. Now it turns out the
+    // action was not a click so we need to reset the active element.
+    ResetActive();
+  }
+
+  ResetTouchBlockState();
+}
+
+void ActiveElementManager::HandleTouchEnd() {
+  AEM_LOG("Touch end, clearing pan state\n");
+  mCanBePanSet = false;
+}
+
+static nsPresContext* GetPresContextFor(nsIContent* aContent) {
+  if (!aContent) {
+    return nullptr;
+  }
+  PresShell* presShell = aContent->OwnerDoc()->GetPresShell();
+  if (!presShell) {
+    return nullptr;
+  }
+  return presShell->GetPresContext();
+}
+
+void ActiveElementManager::SetActive(dom::Element* aTarget) {
+  AEM_LOG("Setting active %p\n", aTarget);
+
+  if (nsPresContext* pc = GetPresContextFor(aTarget)) {
+    pc->EventStateManager()->SetContentState(aTarget,
+                                             dom::ElementState::ACTIVE);
+  }
+}
+
+void ActiveElementManager::ResetActive() {
+  AEM_LOG("Resetting active from %p\n", mTarget.get());
+
+  // Clear the :active flag from mTarget by setting it on the document root.
+  if (mTarget) {
+    dom::Element* root = mTarget->OwnerDoc()->GetDocumentElement();
+    if (root) {
+      AEM_LOG("Found root %p, making active\n", root);
+      SetActive(root);
+    }
+  }
+}
+
+void ActiveElementManager::ResetTouchBlockState() {
+  mTarget = nullptr;
+  mCanBePanSet = false;
+}
+
+void ActiveElementManager::SetActiveTask(
+    const nsCOMPtr<dom::Element>& aTarget) {
+  AEM_LOG("mSetActiveTask %p running\n", mSetActiveTask.get());
+
+  // This gets called from mSetActiveTask's Run() method. The message loop
+  // deletes the task right after running it, so we need to null out
+  // mSetActiveTask to make sure we're not left with a dangling pointer.
+  mSetActiveTask = nullptr;
+  SetActive(aTarget);
+}
+
+void ActiveElementManager::CancelTask() {
+  AEM_LOG("Cancelling task %p\n", mSetActiveTask.get());
+
+  if (mSetActiveTask) {
+    mSetActiveTask->Cancel();
+    mSetActiveTask = nullptr;
+  }
+}
+
+}  // namespace layers
+}  // namespace mozilla