exo: Implement lazy cursor changes.

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index b8080fe1c40fa4a086a7516f55bea19e027afe90..ee5c7e10122a7b80ee173bd91864fcc97ae40cdd 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -78,7 +78,10 @@ class CustomWindowDelegate : public aura::WindowDelegate {
   void OnBoundsChanged(const gfx::Rect& old_bounds,
                        const gfx::Rect& new_bounds) override {}
   gfx::NativeCursor GetCursor(const gfx::Point& point) override {
-    return ui::kCursorNone;
+    // If surface has a cursor provider then return 'none' as cursor providers
+    // are responsible for drawing cursors. Use default cursor if no cursor
+    // provider is registered.
+    return surface_->HasCursorProvider() ? ui::kCursorNone : ui::kCursorNull;

[Daniele Castagna, 2016/05/31 19:32:03]

I understand that when kCursorNull is returns the default cursor is used, but
something like kCursorDefault would make this like more readable.

   }
   int GetNonClientComponent(const gfx::Point& point) const override {
     return HTNOWHERE;
@@ -740,6 +743,18 @@ gfx::Rect Surface::GetNonTransparentBounds() const {
   return non_transparent_bounds;
 }
 
+void Surface::RegisterCursorProvider(Pointer* provider) {
+  cursor_providers_.insert(provider);
+}
+
+void Surface::UnregisterCursorProvider(Pointer* provider) {
+  cursor_providers_.erase(provider);
+}
+
+bool Surface::HasCursorProvider() const {
+  return !cursor_providers_.empty();
+}
+
 void Surface::SetSurfaceDelegate(SurfaceDelegate* delegate) {
   DCHECK(!delegate_ || !delegate);
   delegate_ = delegate;