exo: Select cursor capture scale at run time

components/exo/pointer.cc

Index: components/exo/pointer.cc
diff --git a/components/exo/pointer.cc b/components/exo/pointer.cc
index 2271212085be6ee4ae72f40f096ca8100cd30ceb..23f99aa17ccf0e925901f62f9f20bcf0b48e9585 100644
--- a/components/exo/pointer.cc
+++ b/components/exo/pointer.cc
@@ -4,6 +4,7 @@
 
 #include "components/exo/pointer.h"
 
+#include <algorithm>

[reveman, 2017/06/22 21:24:01]

nit: remove if not needed

[Dominik Laskowski, 2017/06/22 22:31:14]

Removed along with std::max.

 #include <utility>
 
 #include "ash/public/cpp/shell_window_ids.h"
@@ -41,10 +42,6 @@ namespace {
 // 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
@@ -79,6 +76,8 @@ Pointer::Pointer(PointerDelegate* delegate)
   helper->AddPreTargetHandler(this);
   helper->AddCursorObserver(this);
   helper->AddDisplayConfigurationObserver(this);
+
+  OnDisplayConfigurationChanged();

[reveman, 2017/06/22 21:24:01]

nit: don't call this here. see comment below

[Dominik Laskowski, 2017/06/22 22:31:14]

Done.

 }
 
 Pointer::~Pointer() {
@@ -270,6 +269,12 @@ void Pointer::OnCursorDisplayChanged(const display::Display& display) {
 
 void Pointer::OnDisplayConfigurationChanged() {
   UpdatePointerSurface(surface_);
+
+  capture_scale_ = 1.0f;
+  for (const auto& display : display::Screen::GetScreen()->GetAllDisplays()) {
+    const auto& info = WMHelper::GetInstance()->GetDisplayInfo(display.id());
+    capture_scale_ = std::max(capture_scale_, info.device_scale_factor());
+  }

[reveman, 2017/06/22 21:24:01]

nit: please move this logic into a GetCaptureScale() helper function in
anonymous namespace so you can do capture_scale_(GetCaptureScale()) in ctor
initialization list instead of calling OnDisplayConfigurationChanged from there

[Dominik Laskowski, 2017/06/22 22:31:14]

Done.

 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -345,7 +350,7 @@ void Pointer::CaptureCursor(const gfx::Point& hotspot) {
   display::Display display = display::Screen::GetScreen()->GetPrimaryDisplay();
   auto* helper = WMHelper::GetInstance();
   float scale = helper->GetDisplayInfo(display.id()).GetEffectiveUIScale() *
-                kCursorCaptureScale / display.device_scale_factor();
+                capture_scale_ / display.device_scale_factor();
   surface_->window()->SetTransform(gfx::GetScaleTransform(gfx::Point(), scale));
 
   std::unique_ptr<cc::CopyOutputRequest> request =
@@ -380,13 +385,12 @@ void Pointer::UpdateCursor() {
     cursor_ = ui::CursorType::kNone;
   } else {
     SkBitmap bitmap = cursor_bitmap_;
-    gfx::Point hotspot =
-        gfx::ScaleToFlooredPoint(hotspot_, kCursorCaptureScale);
+    gfx::Point hotspot = gfx::ScaleToFlooredPoint(hotspot_, capture_scale_);
 
     auto* helper = WMHelper::GetInstance();
     const display::Display& display = helper->GetCursorDisplay();
     float scale = helper->GetDisplayInfo(display.id()).device_scale_factor() /
-                  kCursorCaptureScale;
+                  capture_scale_;
 
     if (helper->GetCursorSet() == ui::CURSOR_SET_LARGE)
       scale *= kLargeCursorScale;