exo: Fix multi-display hardware cursor

components/exo/pointer.cc

Index: components/exo/pointer.cc
diff --git a/components/exo/pointer.cc b/components/exo/pointer.cc
index 273a74208214f2b2ab82ffb7c1ed1a3cc69cc6cb..7f1d352bd13f2bbd033db9fde2afaf30d1d60eb6 100644
--- a/components/exo/pointer.cc
+++ b/components/exo/pointer.cc
@@ -16,6 +16,7 @@
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
+#include "ui/base/cursor/cursor_util.h"
 #include "ui/display/manager/display_manager.h"
 #include "ui/display/manager/managed_display_info.h"
 #include "ui/display/screen.h"
@@ -34,7 +35,16 @@
 namespace exo {
 namespace {
 
+// TODO(oshima): Some accessibility features, including large cursors, disable
+// hardware cursors. Ash does not support compositing for custom cursors, so it
+// replaces them with the default cursor. As a result, this scale has no effect
+// for now. See crbug.com/708378.
 const float kLargeCursorScale = 2.8f;
+
+// Scale at which cursor snapshot is captured. The resulting bitmap is scaled on
+// displays whose DSF does not match this scale.
+const float kCursorCaptureScale = 2.0f;
+
 const double kLocatedEventEpsilonSquared = 1.0 / (2000.0 * 2000.0);
 
 // Synthesized events typically lack floating point precision so to avoid
@@ -113,17 +123,14 @@ void Pointer::SetCursor(Surface* surface, const gfx::Point& hotspot) {
       // snapshot. Where in the tree is not important but we might as well use
       // the cursor container.
       WMHelper::GetInstance()
-          ->GetContainer(ash::kShellWindowId_MouseCursorContainer)
+          ->GetPrimaryDisplayContainer(ash::kShellWindowId_MouseCursorContainer)
           ->AddChild(surface_->window());
     }
     cursor_changed = true;
   }
 
-  // Update hotspot.
-  if (hotspot != hotspot_) {
-    hotspot_ = hotspot;
+  if (hotspot != hotspot_)
     cursor_changed = true;
-  }
 
   // Early out if cursor did not change.
   if (!cursor_changed)
@@ -132,10 +139,10 @@ void Pointer::SetCursor(Surface* surface, const gfx::Point& hotspot) {
   // If |surface_| is set then asynchronously capture a snapshot of cursor,
   // otherwise cancel pending capture and immediately set the cursor to "none".
   if (surface_) {
-    CaptureCursor();
+    CaptureCursor(hotspot);
   } else {
+    cursor_bitmap_.reset();
     cursor_capture_weak_ptr_factory_.InvalidateWeakPtrs();
-    cursor_ = ui::CursorType::kNone;
     UpdateCursor();
   }
 }
@@ -251,7 +258,6 @@ void Pointer::OnMouseEvent(ui::MouseEvent* event) {
   }
 
   last_event_type_ = event->type();
-  UpdateCursorScale();
 }
 
 void Pointer::OnScrollEvent(ui::ScrollEvent* event) {
@@ -263,7 +269,12 @@ void Pointer::OnScrollEvent(ui::ScrollEvent* event) {
 
 void Pointer::OnCursorSetChanged(ui::CursorSetType cursor_set) {
   if (focus_)
-    UpdateCursorScale();
+    UpdateCursor();
+}
+
+void Pointer::OnCursorDisplayChanged(const display::Display& display) {
+  if (focus_)
+    UpdateCursor();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -275,7 +286,7 @@ void Pointer::OnSurfaceCommit() {
 
   // Capture new cursor to reflect result of commit.
   if (focus_)
-    CaptureCursor();
+    CaptureCursor(hotspot_);
 }
 
 bool Pointer::IsSurfaceSynchronized() const {
@@ -307,62 +318,25 @@ Surface* Pointer::GetEffectiveTargetForEvent(ui::Event* event) const {
   return delegate_->CanAcceptPointerEventsForSurface(target) ? target : nullptr;
 }
 
-void Pointer::UpdateCursorScale() {
-  DCHECK(focus_);
-
-  display::Screen* screen = display::Screen::GetScreen();
-  WMHelper* helper = WMHelper::GetInstance();
-
-  // Update cursor scale if the effective UI scale has changed.
-  display::Display display = screen->GetDisplayNearestWindow(focus_->window());
-  float scale = helper->GetDisplayInfo(display.id()).GetEffectiveUIScale();
-
-  if (display::Display::HasInternalDisplay()) {
-    float primary_device_scale_factor =
-        screen->GetPrimaryDisplay().device_scale_factor();
-    // The size of the cursor surface is the quotient of its physical size and
-    // the DSF of the primary display. The physical size is proportional to the
-    // DSF of the internal display. For external displays (and the internal
-    // display when secondary to a display with a different DSF), scale the
-    // cursor so its physical size matches with the single display case.
-    if (!display.IsInternal() ||
-        display.device_scale_factor() != primary_device_scale_factor) {
-      scale *= primary_device_scale_factor /
-               helper->GetDisplayInfo(display::Display::InternalDisplayId())
-                   .device_scale_factor();
-    }
-  }
-
-  if (helper->GetCursorSet() == ui::CURSOR_SET_LARGE)
-    scale *= kLargeCursorScale;
-
-  if (scale != cursor_scale_) {
-    cursor_scale_ = scale;
-    if (surface_)
-      CaptureCursor();
-  }
-}
-
-void Pointer::CaptureCursor() {
+void Pointer::CaptureCursor(const gfx::Point& hotspot) {
   DCHECK(surface_);
   DCHECK(focus_);
 
-  // Set UI scale before submitting capture request.
-  surface_->window()->layer()->SetTransform(
-      gfx::GetScaleTransform(gfx::Point(), cursor_scale_));
-
-  float primary_device_scale_factor =
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor();
+  // Surface size is in DIPs, while layer size is in pseudo-DIP units that
+  // depend on the DSF of the display mode. Scale the layer to capture the
+  // surface at a constant pixel size, regardless of the primary display's
+  // UI scale and display mode DSF.
+  display::Display display = display::Screen::GetScreen()->GetPrimaryDisplay();
+  auto* helper = WMHelper::GetInstance();
+  float scale = helper->GetDisplayInfo(display.id()).GetEffectiveUIScale() *
+                kCursorCaptureScale / display.device_scale_factor();
+  surface_->window()->SetTransform(gfx::GetScaleTransform(gfx::Point(), scale));
 
   std::unique_ptr<cc::CopyOutputRequest> request =
       cc::CopyOutputRequest::CreateBitmapRequest(
           base::Bind(&Pointer::OnCursorCaptured,
-                     cursor_capture_weak_ptr_factory_.GetWeakPtr(),
-                     gfx::ScaleToFlooredPoint(
-                         hotspot_,
-                         // |hotspot_| is in surface coordinate space so apply
-                         // both device scale and UI scale.
-                         cursor_scale_ * primary_device_scale_factor)));
+                     cursor_capture_weak_ptr_factory_.GetWeakPtr(), hotspot));
+
   request->set_source(cursor_capture_source_id_);
   surface_->window()->layer()->RequestCopyOfOutput(std::move(request));
 }
@@ -372,19 +346,46 @@ void Pointer::OnCursorCaptured(const gfx::Point& hotspot,
   if (!focus_)
     return;
 
-  cursor_ = ui::CursorType::kNone;
-  if (!result->IsEmpty()) {
+  if (result->IsEmpty()) {
+    cursor_bitmap_.reset();
+  } else {
     DCHECK(result->HasBitmap());
-    std::unique_ptr<SkBitmap> bitmap = result->TakeBitmap();
+    cursor_bitmap_ = *result->TakeBitmap();
+    hotspot_ = hotspot;
+  }
+
+  UpdateCursor();
+}
+
+void Pointer::UpdateCursor() {
+  DCHECK(focus_);
+
+  if (cursor_bitmap_.drawsNothing()) {
+    cursor_ = ui::CursorType::kNone;
+  } else {
+    SkBitmap bitmap = cursor_bitmap_;
+    gfx::Point hotspot =
+        gfx::ScaleToFlooredPoint(hotspot_, kCursorCaptureScale);
+
+    auto* helper = WMHelper::GetInstance();
+    const display::Display& display = helper->GetCursorDisplay();
+    float scale = helper->GetDisplayInfo(display.id()).device_scale_factor() /
+                  kCursorCaptureScale;
+
+    if (helper->GetCursorSet() == ui::CURSOR_SET_LARGE)
+      scale *= kLargeCursorScale;
+
+    ui::ScaleAndRotateCursorBitmapAndHotpoint(scale, display.rotation(),
+                                              &bitmap, &hotspot);
 
     ui::PlatformCursor platform_cursor;
 #if defined(USE_OZONE)
     // TODO(reveman): Add interface for creating cursors from GpuMemoryBuffers
     // and use that here instead of the current bitmap API. crbug.com/686600
     platform_cursor = ui::CursorFactoryOzone::GetInstance()->CreateImageCursor(
-        *bitmap.get(), hotspot, cursor_scale_);
+        bitmap, hotspot, 0);
 #elif defined(USE_X11)
-    XcursorImage* image = ui::SkBitmapToXcursorImage(bitmap.get(), hotspot);
+    XcursorImage* image = ui::SkBitmapToXcursorImage(&bitmap, hotspot);
     platform_cursor = ui::CreateReffedCustomXCursor(image);
 #endif
     cursor_ = ui::CursorType::kCustom;
@@ -396,12 +397,6 @@ void Pointer::OnCursorCaptured(const gfx::Point& hotspot,
 #endif
   }
 
-  UpdateCursor();
-}
-
-void Pointer::UpdateCursor() {
-  DCHECK(focus_);
-
   aura::Window* root_window = focus_->window()->GetRootWindow();
   if (!root_window)
     return;