exo: Fix cursor jitter and cursor scale.

This removes jitter in cursor events by ignoring the floating
point precision of synthesized events.

This also makes sure any UI scale currently used is compensated
for as that should not effect the size of the cursor.

BUG=b/27827591, 549781

Review-Url: https://codereview.chromium.org/2022553003
Cr-Commit-Position: refs/heads/master@{#396611}

components/exo/pointer.cc

@@ -4,22 +4,41 @@
 
 #include "components/exo/pointer.h"
 
+#include "ash/display/display_info.h"
+#include "ash/display/display_manager.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "components/exo/pointer_delegate.h"
 #include "components/exo/surface.h"
+#include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/events/event.h"
 #include "ui/gfx/geometry/vector2d_conversions.h"
 #include "ui/views/widget/widget.h"
 
 namespace exo {
+namespace {
+
+// Synthesized events typically lack floating point precision so to avoid
+// generating mouse event jitter we consider the location of these events
+// to be the same as |location| if floored values match.
+bool SameLocation(const ui::LocatedEvent* event, const gfx::PointF& location) {
+  if (event->flags() & ui::EF_IS_SYNTHESIZED)
+    return event->location() == gfx::ToFlooredPoint(location);
+
+  return event->location_f() == location;
+}
+
+}  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // Pointer, public:
 
 Pointer::Pointer(PointerDelegate* delegate)
-    : delegate_(delegate), surface_(nullptr), focus_(nullptr) {
+    : delegate_(delegate),
+      surface_(nullptr),
+      focus_(nullptr),
+      cursor_scale_(1.0f) {
   ash::Shell::GetInstance()->AddPreTargetHandler(this);
 }
 
@@ -112,7 +131,7 @@ void Pointer::OnMouseEvent(ui::MouseEvent* event) {
       // here as mouse movement can generate both "moved" and "entered" events
       // but OnPointerMotion should only be called if location changed since
       // OnPointerEnter was called.
-      if (focus_ && event->location_f() != location_) {
+      if (focus_ && !SameLocation(event, location_)) {
         delegate_->OnPointerMotion(event->time_stamp(), event->location_f());
         delegate_->OnPointerFrame();
         location_ = event->location_f();
@@ -161,10 +180,31 @@ void Pointer::OnMouseEvent(ui::MouseEvent* event) {
   if (focus_) {
     if (!widget_)
       CreatePointerWidget();
-    widget_->SetBounds(
-        gfx::Rect(focus_->GetBoundsInScreen().origin() +
-                      gfx::ToRoundedVector2d(location_.OffsetFromOrigin()),
-                  gfx::Size(1, 1)));
+
+    // Update cursor location if mouse event caused it to change.
+    gfx::Point mouse_location = aura::Env::GetInstance()->last_mouse_location();
+    if (mouse_location != widget_->GetNativeWindow()->bounds().origin()) {
+      gfx::Rect bounds = widget_->GetNativeWindow()->bounds();
+      bounds.set_origin(mouse_location);
+      widget_->GetNativeWindow()->SetBounds(bounds);
+    }
+
+    // Update cursor scale if the effective UI scale has changed since last
+    // mouse event.
+    display::Display display =
+        display::Screen::GetScreen()->GetDisplayNearestWindow(
+            widget_->GetNativeWindow());
+    float ui_scale = ash::Shell::GetInstance()
+                         ->display_manager()
+                         ->GetDisplayInfo(display.id())
+                         .GetEffectiveUIScale();
+    if (ui_scale != cursor_scale_) {
+      gfx::Transform transform;
+      transform.Scale(ui_scale, ui_scale);
+      widget_->GetNativeWindow()->SetTransform(transform);
+      cursor_scale_ = ui_scale;
+    }
+
     if (!widget_->IsVisible())
       widget_->Show();
   } else {

components/exo/pointer.h

@@ -77,6 +77,9 @@ class Pointer : public ui::EventHandler,
   // The location of the pointer in the current focus surface.
   gfx::PointF location_;
 
+  // The scale applied to the cursor to compensate for the UI scale.
+  float cursor_scale_;
+
   // The position of the pointer surface relative to the pointer location.
   gfx::Point hotspot_;