Bug 2056581 - Have autoscroll take DPI into account. r=botond

Differential Revision: https://phabricator.services.mozilla.com/D317166

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -275,6 +275,7 @@ class MOZ_RAII AutoFocusSequenceNumberSetter {
 };
 
 APZCTreeManager::APZCTreeManager(LayersId aRootLayersId,
+                                 CSSToLayoutDeviceScale aWidgetScale,
                                  UniquePtr<IAPZHitTester> aHitTester)
     : mTestSampleTime(Nothing(), "APZCTreeManager::mTestSampleTime"),
       mInputQueue(new InputQueue()),
@@ -290,6 +291,7 @@ APZCTreeManager::APZCTreeManager(LayersId aRootLayersId,
       mApzcTreeLog("apzctree"),
       mTestDataLock("APZTestDataLock"),
       mDPI(160.0),
+      mWidgetScale(aWidgetScale),
       mHitTester(std::move(aHitTester)),
       mScrollGenerationLock("APZScrollGenerationLock"),
       mInteractiveWidget(
@@ -315,9 +317,10 @@ void APZCTreeManager::Init() {
 }
 
 already_AddRefed<APZCTreeManager> APZCTreeManager::Create(
-    LayersId aRootLayersId, UniquePtr<IAPZHitTester> aHitTester) {
+    LayersId aRootLayersId, CSSToLayoutDeviceScale aWidgetScale,
+    UniquePtr<IAPZHitTester> aHitTester) {
   RefPtr<APZCTreeManager> manager =
-      new APZCTreeManager(aRootLayersId, std::move(aHitTester));
+      new APZCTreeManager(aRootLayersId, aWidgetScale, std::move(aHitTester));
   manager->Init();
   return manager.forget();
 }
@@ -4079,6 +4082,10 @@ float APZCTreeManager::GetDPI() const {
   return mDPI;
 }
 
+CSSToLayoutDeviceScale APZCTreeManager::GetWidgetScale() const {
+  return mWidgetScale;
+}
+
 void APZCTreeManager::EndWheelTransaction(
     PWebRenderBridgeParent::EndWheelTransactionResolver&& aResolver) {
   RefPtr<nsISerialEventTarget> controllerThread =

gfx/layers/apz/src/APZCTreeManager.h

@@ -10,6 +10,7 @@
 #include "FocusState.h"          // for FocusState
 #include "HitTestingTreeNode.h"  // for HitTestingTreeNodeAutoLock
 #include "IAPZHitTester.h"       // for IAPZHitTester::HitTestResult
+#include "Units.h"
 #include "VsyncSource.h"
 #include "gfxPoint.h"                // for gfxPoint
 #include "mozilla/Assertions.h"      // for MOZ_ASSERT_HELPER2
@@ -137,7 +138,8 @@ class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
   static mozilla::LazyLogModule sLog;
 
   static already_AddRefed<APZCTreeManager> Create(
-      LayersId aRootLayersId, UniquePtr<IAPZHitTester> aHitTester = nullptr);
+      LayersId aRootLayersId, CSSToLayoutDeviceScale aWidgetScale = {},
+      UniquePtr<IAPZHitTester> aHitTester = nullptr);
   void SetSampler(APZSampler* aSampler);
   void SetUpdater(APZUpdater* aUpdater);
 
@@ -290,6 +292,11 @@ class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
    */
   float GetDPI() const;
 
+  /**
+   * Returns the Widget scale value in use.
+   */
+  CSSToLayoutDeviceScale GetWidgetScale() const;
+
   /**
    * Find the hit testing node for the scrollbar thumb that matches these
    * drag metrics. Initializes aOutThumbNode with the node, if there is one.
@@ -532,7 +539,8 @@ class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
   already_AddRefed<wr::WebRenderAPI> GetWebRenderAPI() const;
 
  protected:
-  APZCTreeManager(LayersId aRootLayersId, UniquePtr<IAPZHitTester> aHitTester);
+  APZCTreeManager(LayersId aRootLayersId, CSSToLayoutDeviceScale aScale,
+                  UniquePtr<IAPZHitTester> aHitTester);
 
   void Init();
 
@@ -1164,6 +1172,8 @@ class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
   // This must only be touched on the controller thread.
   float mDPI;
 
+  CSSToLayoutDeviceScale mWidgetScale;
+
   friend class IAPZHitTester;
   UniquePtr<IAPZHitTester> mHitTester;
 

gfx/layers/apz/src/AutoscrollAnimation.cpp

@@ -10,22 +10,26 @@
 #include "APZCTreeManager.h"
 #include "AsyncPanZoomController.h"
 #include "FrameMetrics.h"
+#include "Units.h"
 #include "mozilla/StaticPrefs_general.h"
 
 namespace mozilla {
 namespace layers {
 
 // Helper function for AutoscrollAnimation::DoSample().
-// Basically copied as-is from toolkit/actors/AutoScrollChild.sys.mjs.
-static float Accelerate(ScreenCoord curr, ScreenCoord start) {
+// Basically copied as-is from toolkit/actors/AutoScrollChild.sys.mjs, the only
+// addition is adjusting for DPI.
+static float Accelerate(ScreenCoord curr, ScreenCoord start,
+                        const CSSToLayoutDeviceScale& widgetScale) {
   // |speed| is the divisor in |val| below, so a higher multiplier must make
   // |speed| smaller to produce a faster autoscroll. The multiplier is a
   // percentage (100 = default). Clamp to avoid a zero divisor.
-  static const float baseSpeed = 12.0f;
+  constexpr float baseSpeed = 12.0f;
+
   int multiplier =
       std::max(1, int(StaticPrefs::general_autoscroll_speed_multiplier()));
   float speed = std::max(1.0f, baseSpeed * 100 / multiplier);
-  float val = (curr - start) / speed;
+  float val = (curr - start) / (speed * widgetScale.scale);
   if (val > 1) {
     return val * sqrtf(val) - 1;
   }
@@ -48,6 +52,9 @@ bool AutoscrollAnimation::DoSample(FrameMetrics& aFrameMetrics,
 
   ScreenPoint mouseLocation = treeManager->GetCurrentMousePosition();
 
+  // Get the dpi so accelerate can scale to screen dpi.
+  const auto widgetScale = treeManager->GetWidgetScale();
+
   // The implementation of this function closely mirrors that of its main-
   // thread equivalent, the autoscrollLoop() function in
   // toolkit/actors/AutoScrollChild.sys.mjs.
@@ -69,8 +76,10 @@ bool AutoscrollAnimation::DoSample(FrameMetrics& aFrameMetrics,
   //     its output is interpreted as CSS coordinates. This is intentional,
   //     insofar as autoscrollLoop() does the same thing.
   CSSPoint scrollDelta{
-      Accelerate(mouseLocation.x, mAnchorLocation.x) * timeCompensation,
-      Accelerate(mouseLocation.y, mAnchorLocation.y) * timeCompensation};
+      Accelerate(mouseLocation.x, mAnchorLocation.x, widgetScale) *
+          timeCompensation,
+      Accelerate(mouseLocation.y, mAnchorLocation.y, widgetScale) *
+          timeCompensation};
 
   mApzc.ScrollByAndClamp(scrollDelta);
 

gfx/layers/apz/test/gtest/APZTestCommon.h

@@ -237,7 +237,9 @@ class TestAPZCTreeManager : public APZCTreeManager {
  public:
   explicit TestAPZCTreeManager(MockContentControllerDelayed* aMcc,
                                UniquePtr<IAPZHitTester> aHitTester = nullptr)
-      : APZCTreeManager(LayersId{0}, std::move(aHitTester)), mcc(aMcc) {
+      : APZCTreeManager(LayersId{0}, CSSToLayoutDeviceScale{1},
+                        std::move(aHitTester)),
+        mcc(aMcc) {
     Init();
   }
 

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -274,7 +274,7 @@ void CompositorBridgeParent::Initialize() {
     MOZ_ASSERT(!mApzcTreeManager);
     MOZ_ASSERT(!mApzSampler);
     MOZ_ASSERT(!mApzUpdater);
-    mApzcTreeManager = APZCTreeManager::Create(mRootLayerTreeID);
+    mApzcTreeManager = APZCTreeManager::Create(mRootLayerTreeID, mScale);
     mApzSampler = new APZSampler(mApzcTreeManager, true);
     mApzUpdater = new APZUpdater(mApzcTreeManager, true);
   }