Primary display change notifications.

services/ui/display/platform_screen_ozone.cc

Index: services/ui/display/platform_screen_ozone.cc
diff --git a/services/ui/display/platform_screen_ozone.cc b/services/ui/display/platform_screen_ozone.cc
index 127fcd8f90ff2b9eb9f541e49c1b074d00587fb7..c03e92c911b5654adc39de01ad52e31e4a257732 100644
--- a/services/ui/display/platform_screen_ozone.cc
+++ b/services/ui/display/platform_screen_ozone.cc
@@ -164,7 +164,7 @@ void PlatformScreenOzone::SwapPrimaryDisplay() {
     primary_display_id_ = cached_displays_[primary_display_index + 1].id;
   }
 
-  // TODO(kylechar): Update ws::DisplayManager.
+  delegate_->OnPrimaryDisplayChanged(primary_display_id_);
 }
 
 void PlatformScreenOzone::SetDisplayWorkArea(int64_t display_id,
@@ -210,16 +210,6 @@ void PlatformScreenOzone::ProcessRemovedDisplays(
         primary_display_id_ = Display::kInvalidDisplayID;
     }
   }
-
-  // If the primary display was removed find a new primary display id.
-  if (primary_display_id_ == Display::kInvalidDisplayID) {
-    for (const DisplayInfo& display : cached_displays_) {
-      if (!display.removed) {
-        primary_display_id_ = display.id;
-        break;
-      }
-    }
-  }
 }
 
 void PlatformScreenOzone::ProcessModifiedDisplays(
@@ -279,10 +269,6 @@ void PlatformScreenOzone::AddNewDisplays(
     if (GetCachedDisplayIterator(id) != cached_displays_.end())
       continue;
 
-    // If we have no primary display then this one should be it.
-    if (primary_display_id_ == Display::kInvalidDisplayID)
-      primary_display_id_ = id;
-
     DisplayInfo display_info;
     display_info.id = snapshot->display_id();
     display_info.metrics = MetricsFromSnapshot(*snapshot, next_display_origin_);
@@ -299,6 +285,12 @@ void PlatformScreenOzone::AddNewDisplays(
 
     cached_displays_.push_back(display_info);
     delegate_->OnDisplayAdded(display_info.id, display_info.metrics);
+
+    // If we have no primary display then this one should be it.
+    if (primary_display_id_ == Display::kInvalidDisplayID) {
+      primary_display_id_ = id;
+      delegate_->OnPrimaryDisplayChanged(primary_display_id_);
+    }
   }
 }
 
@@ -331,10 +323,27 @@ ViewportMetrics PlatformScreenOzone::MetricsFromSnapshot(
 
 void PlatformScreenOzone::OnDisplayModeChanged(
     const ui::DisplayConfigurator::DisplayStateList& displays) {
+  int64_t old_primary_display_id = primary_display_id_;
+
   ProcessRemovedDisplays(displays);
   ProcessModifiedDisplays(displays);
+
+  // If the primary display was removed try to find a new primary display.
+  if (primary_display_id_ == Display::kInvalidDisplayID) {
+    for (const DisplayInfo& display : cached_displays_) {

[sky, 2016/10/28 17:08:47]

Do you need to handle the case of no more displays here? That is, should this
set primary_display_id_ to invalid before the for loop?

[kylechar, 2016/10/28 19:40:36]

That's handled when the last primary display is marked removed,
primary_display_id_ will have been set to kInvalidDisplayID. If there is no
other displays it will stay as kInvalidDisplayID. 

I've changed this not to call OnPrimaryDisplayChanged() for kInvalidDisplayID
though as per your other comments.

+      if (!display.removed) {
+        primary_display_id_ = display.id;
+        break;
+      }
+    }
+  }
+
+  if (old_primary_display_id != primary_display_id_)
+    delegate_->OnPrimaryDisplayChanged(primary_display_id_);
+
   UpdateCachedDisplays();
   AddNewDisplays(displays);
+
   wait_for_display_config_update_ = false;
 }