[Compositor threaded scrollbar scrolling] Option + click for Mac.

Mac uses Option + click instead of Shift + click (on Windows/Linux).

Bug: 1016955
Change-Id: I49c54fb8773c68d37d4bc0b7fc677f259767967b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1885975
Commit-Queue: Rahul Arakeri <arakeri@microsoft.com>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714864}

cc/input/input_handler.h

@@ -198,6 +198,8 @@ class CC_EXPORT InputHandler {
 
   virtual InputHandlerPointerResult MouseMoveAt(
       const gfx::Point& mouse_position) = 0;
+  // TODO(arakeri): Pass in the modifier instead of a bool once the refactor
+  // (crbug.com/1022097) is done. For details, see crbug.com/1016955.
   virtual InputHandlerPointerResult MouseDown(const gfx::PointF& mouse_position,
                                               bool shift_modifier) = 0;
   virtual InputHandlerPointerResult MouseUp(

cc/input/scrollbar_controller.cc

@@ -201,7 +201,7 @@ ui::input_types::ScrollGranularity ScrollbarController::Granularity(
   return ui::input_types::ScrollGranularity::kScrollByPixel;
 }
 
-float ScrollbarController::GetScrollDeltaForShiftClick(
+float ScrollbarController::GetScrollDeltaForAbsoluteJump(
     const ScrollbarLayerImplBase* scrollbar) {
   layer_tree_host_impl_->active_tree()->UpdateScrollbarGeometries();
 
@@ -605,7 +605,7 @@ int ScrollbarController::GetScrollDeltaForScrollbarPart(
     case ScrollbarPart::BACK_TRACK:
     case ScrollbarPart::FORWARD_TRACK:
       if (shift_modifier) {
-        scroll_delta = GetScrollDeltaForShiftClick(scrollbar);
+        scroll_delta = GetScrollDeltaForAbsoluteJump(scrollbar);
         break;
       }
       owner_scroll_layer =

cc/input/scrollbar_controller.h

@@ -125,8 +125,9 @@ class CC_EXPORT ScrollbarController {
   void RecomputeAutoscrollStateIfNeeded();
   void ResetState();
 
-  // Shift + click is expected to do a non-animated jump to a certain offset.
-  float GetScrollDeltaForShiftClick(const ScrollbarLayerImplBase* scrollbar);
+  // Shift (or "Option" in case of Mac) + click is expected to do a non-animated
+  // jump to a certain offset.
+  float GetScrollDeltaForAbsoluteJump(const ScrollbarLayerImplBase* scrollbar);
 
   // Determines if the delta needs to be animated.
   ui::input_types::ScrollGranularity Granularity(

third_party/blink/web_tests/TestExpectations

@@ -2649,13 +2649,6 @@ crbug.com/953847 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling/fast/sc
 # 1px scroll offset difference for compositor threaded scrollbar scrolling on Linux.
 crbug.com/1009892 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling_hidpi/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
 
-# TODO (arakeri): Mac uses the "Option" modifier instead of "Shift" to do the non-animated jump. This hasn't been implemented yet.
-crbug.com/1016955 [ Mac ] fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-crbug.com/1016955 [ Mac ] virtual/threaded-prefer-compositing/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-crbug.com/1016955 [ Mac ] virtual/scroll_customization/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-crbug.com/1016955 [ Mac ] virtual/hidpi/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-crbug.com/1016955 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-
 # Some control characters still not visible
 crbug.com/893490 [ Mac ] external/wpt/css/css-text/white-space/control-chars-001.html [ Failure ]
 crbug.com/893490 [ Mac ] external/wpt/css/css-text/white-space/control-chars-002.html [ Failure ]

third_party/blink/web_tests/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html

@@ -102,14 +102,23 @@ window.onload = () => {
   promise_test (async (test) => {
     resetScrollOffset(standardDivFast);
 
-    // Testing forward scroll on vertical scrollbar.
-    await mouseClickOn(SCROLLBAR_BUTTON_FWD.x, standardRectFast.top + 50, /*left_click*/0, /*modifier*/ "Shift");
+    // Testing forward scroll on vertical scrollbar. Mac uses "Option" key
+    // instead of "Shift". The Option key is mapped to "Alt" in GPUbenchmarking.
+    await mouseClickOn(SCROLLBAR_BUTTON_FWD.x, standardRectFast.top + 50,
+    /*left_click*/0, /*modifier*/ onMacPlatform ? "Alt" : "Shift");
+    if (onMacPlatform) {
+      // TODO(arakeri): crbug.com/1019076 Option + click is off by 3-4 px.
+      assert_approx_equals(standardDivFast.scrollTop, 549, 3,
+      "Option + click forward didn't scroll.");
+    } else {
       let expected_offset = 0;
       if (onLinuxPlatform)
         expected_offset = window.devicePixelRatio == 1 ? 695 : 606;
       else
         expected_offset = window.devicePixelRatio == 1 ? 626 : 579.5;
-    assert_equals(standardDivFast.scrollTop, expected_offset, "Shift + click forward didn't scroll.");
-  }, "Test shift + click on non-custom composited scrollbars.");
+        assert_equals(standardDivFast.scrollTop, expected_offset,
+        "Shift + click forward didn't scroll.");
+    }
+  }, "Test non-animated click scroll on non-custom composited scrollbars.");
 }
 </script>

ui/events/blink/input_handler_proxy.cc

@@ -20,6 +20,7 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/default_tick_clock.h"
 #include "base/trace_event/trace_event.h"
+#include "build/build_config.h"
 #include "cc/input/main_thread_scrolling_reason.h"
 #include "third_party/blink/public/platform/web_input_event.h"
 #include "third_party/blink/public/platform/web_mouse_wheel_event.h"
@@ -445,6 +446,15 @@ void InputHandlerProxy::InjectScrollbarGestureScroll(
     input_handler_->SetNeedsAnimateInput();
 }
 
+bool HasModifier(const WebInputEvent& event) {
+#if defined(OS_MACOSX)
+  // Mac uses the "Option" key (which is mapped to the enum "kAltKey").
+  return event.GetModifiers() & WebInputEvent::kAltKey;
+#else
+  return event.GetModifiers() & WebInputEvent::kShiftKey;
+#endif
+}
+
 InputHandlerProxy::EventDisposition
 InputHandlerProxy::RouteToTypeSpecificHandler(
     const WebInputEvent& event,
@@ -519,10 +529,13 @@ InputHandlerProxy::RouteToTypeSpecificHandler(
 
       if (mouse_event.button == blink::WebMouseEvent::Button::kLeft) {
         CHECK(input_handler_);
+        // TODO(arakeri): Pass in the modifier instead of a bool once the
+        // refactor (crbug.com/1022097) is done. For details, see
+        // crbug.com/1016955.
         cc::InputHandlerPointerResult pointer_result =
             input_handler_->MouseDown(
                 gfx::PointF(mouse_event.PositionInWidget()),
-                event.GetModifiers() & WebInputEvent::kShiftKey);
+                HasModifier(event));
         if (pointer_result.type == cc::PointerResultType::kScrollbarScroll) {
           // Generate GSB and GSU events and add them to the
           // CompositorThreadEventQueue.