Process DisplaySnapshots in PlatformScreen.

services/ui/display/platform_screen_impl_ozone.h

Index: services/ui/display/platform_screen_impl_ozone.h
diff --git a/services/ui/display/platform_screen_impl_ozone.h b/services/ui/display/platform_screen_impl_ozone.h
index d7282df3bcce91440d9d324d84057ffe994bd51d..b8856b629a7b60331e0cd4157c7bb4637a8b5aec 100644
--- a/services/ui/display/platform_screen_impl_ozone.h
+++ b/services/ui/display/platform_screen_impl_ozone.h
@@ -23,14 +23,50 @@ namespace display {
 class PlatformScreenImplOzone : public PlatformScreen,
                                 public ui::DisplayConfigurator::Observer {
  public:
+  // TODO(kylechar): This struct is just temporary until we migrate
+  // DisplayManager code out of ash so it can be used here.
+  struct DisplayInfo {

[sky, 2016/09/01 19:25:08]

Does this need to be public?

[kylechar, 2016/09/02 15:18:34]

Not anymore (it did at a previous revision). Move to private.

+    DisplayInfo(int64_t new_id, gfx::Rect new_bounds)

[sky, 2016/09/01 19:25:08]

const gfx::rect&

[kylechar, 2016/09/02 15:18:34]

Done.

+        : id(new_id), bounds(new_bounds), known_bounds(new_bounds) {}
+
+    int64_t id;
+    // The display bounds.
+    gfx::Rect bounds;
+    // The display bounds that the delegate knows about.

[sky, 2016/09/01 19:25:08]

clarify what 'knows about' means here.
That said, why do you need this? It seems like in the one place you use this you
could copy the bounds to a local before updating the bounds and then compare the
two there.

[kylechar, 2016/09/02 15:18:34]

Clarified comment. As to why, the bounds can get changed in both
ProcessModifiedDisplays() and UpdateCachedDisplays() so a local won't work. If
either are different then I call OnDisplayModified(). I'm doing it this way so
that DisplayManager gets the absolutely minimum number of updates.

[sky, 2016/09/02 16:03:21]

I'm likely missing something. See my other comment.

+    gfx::Rect known_bounds;
+    bool removed = false;
+  };
+
   PlatformScreenImplOzone();
   ~PlatformScreenImplOzone() override;
 
- private:
   // PlatformScreen:
   void Init(PlatformScreenDelegate* delegate) override;
   int64_t GetPrimaryDisplayId() const override;
 
+ private:
+  // Process display snapshots and mark removed displays as removed. Does not

[sky, 2016/09/01 19:25:08]

Document what 'process' means here. I'm suggesting something like "Sets
|removed| on any displays that have been removed. Updates |primary_display_id_|
if the primary display was removed.

[kylechar, 2016/09/02 15:18:34]

Done.

+  // call delegate.
+  void ProcessRemovedDisplays(
+      const ui::DisplayConfigurator::DisplayStateList& snapshots);
+
+  // Processes display snapshots and updates the bounds of an existing displays.

[sky, 2016/09/01 19:25:08]

remove 'an'

[kylechar, 2016/09/02 15:18:34]

Done. I've updated the method descriptions to be more explanatory in general.

+  // Does not call delegate.
+  void ProcessModifiedDisplays(
+      const ui::DisplayConfigurator::DisplayStateList& snapshots);
+
+  // Examines list of cached displays and checks for modified or removed
+  // displays. Also updates display bounds in response to modified or removed
+  // displays. Calls OnDisplayModified() or OnDisplayRemoved() on the delegate
+  // when appropriate, at most once per display.
+  //
+  // Usually used after ProcessRemovedDisplays() and ProcessModifiedDisplays().
+  void UpdateCachedDisplays();
+
+  // Adds any new displays in the list of cached displays and calls delegate.
+  void AddNewDisplays(
+      const ui::DisplayConfigurator::DisplayStateList& snapshots);
+
   // ui::DisplayConfigurator::Observer:
   void OnDisplayModeChanged(
       const ui::DisplayConfigurator::DisplayStateList& displays) override;
@@ -43,7 +79,7 @@ class PlatformScreenImplOzone : public PlatformScreen,
 
   // TODO(kylechar): These values can/should be replaced by DisplayLayout.
   int64_t primary_display_id_ = display::Display::kInvalidDisplayID;
-  std::set<uint64_t> displays_;
+  std::vector<DisplayInfo> cached_displays_;
   gfx::Point next_display_origin_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformScreenImplOzone);