Automatically set the overscan insets if the output has the flag and no preference is set.

ash/display/display_manager.cc

Index: ash/display/display_manager.cc
diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 476815b2e2b54d0a2e1f19f23344ce24f4ce7221..9e577a1ab98ad624ff086b4df027b8720baa9a8e 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -72,6 +72,13 @@ int64 GetDisplayIdForOutput(XID output) {
 }
 #endif
 
+gfx::Insets GetDefaultDisplayOverscan(const gfx::Display& display) {
+  // Currently we assume 5% for each edge.
+  int width = display.bounds().width() / 20;
+  int height = display.bounds().height() / 20;
+  return gfx::Insets(height, width, height, width);

[oshima, 2013/01/12 02:06:38]

Is 5% good assumption?

Isn't it better to just let a user to set overscan if overscan info wasn't
found?

[Jun Mukai, 2013/01/14 18:18:51]

No info, there's only a bool flag and marcheu suggested 5% of overscan.  see
https://code.google.com/p/chromium/issues/detail?id=139419#c3

But I'm afraid I made mistake, 5% overscan means 2.5% for each edge.

+}
+
 }  // namespace
 
 using aura::RootWindow;
@@ -146,6 +153,7 @@ const gfx::Display& DisplayManager::FindDisplayContainingPoint(
 void DisplayManager::SetOverscanInsets(int64 display_id,
                                        const gfx::Insets& insets_in_dip) {
   display_info_[display_id].overscan_insets_in_dip = insets_in_dip;
+  display_info_[display_id].overscan_insets_specified = true;
 
   // Copies the |displays_| because UpdateDisplays() compares the passed
   // displays and its internal |displays_|.
@@ -201,12 +209,16 @@ void DisplayManager::OnNativeDisplaysChanged(
     new_displays = updated_displays;
   }
 
+  RefreshDisplayInfo();
+
   for (DisplayList::const_iterator iter = new_displays.begin();
        iter != new_displays.end(); ++iter) {
     std::map<int64, DisplayInfo>::iterator info =
         display_info_.find(iter->id());
     if (info != display_info_.end()) {
       info->second.original_bounds_in_pixel = iter->bounds_in_pixel();
+      if (info->second.overscan && !info->second.overscan_insets_specified)
+        info->second.overscan_insets_in_dip = GetDefaultDisplayOverscan(*iter);
     } else {
       display_info_[iter->id()].original_bounds_in_pixel =
           iter->bounds_in_pixel();
@@ -214,7 +226,6 @@ void DisplayManager::OnNativeDisplaysChanged(
   }
 
   UpdateDisplays(new_displays);
-  RefreshDisplayNames();
 }
 
 void DisplayManager::UpdateDisplays(
@@ -420,7 +431,7 @@ void DisplayManager::Init() {
   }
 #endif
 
-  RefreshDisplayNames();
+  RefreshDisplayInfo();
 
 #if defined(OS_WIN)
   if (base::win::GetVersion() >= base::win::VERSION_WIN8)
@@ -546,7 +557,11 @@ void DisplayManager::EnsurePointerInDisplays() {
   root_window->MoveCursorTo(target_location);
 }
 
-void DisplayManager::RefreshDisplayNames() {
+DisplayManager::DisplayInfo::DisplayInfo()
+  : overscan(false), overscan_insets_specified(false) {

[oshima, 2013/01/12 02:06:38]

one argument per line (I think)

[Jun Mukai, 2013/01/14 18:18:51]

Done.

+}
+
+void DisplayManager::RefreshDisplayInfo() {
 #if defined(OS_CHROMEOS)
   if (!base::chromeos::IsRunningOnChromeOS())
     return;
@@ -570,6 +585,11 @@ void DisplayManager::RefreshDisplayNames() {
     } else if (!name.empty()) {
       display_info_[id].name = name;
     }
+
+    bool overscan = false;
+    if (ui::GetOutputOverscanFlag(outputs[i], &overscan)) {
+      display_info_[id].overscan = true;
+    }

[oshima, 2013/01/12 02:06:38]

the code looks a bit odd. Won't 

ui::GetOutputOverscanFlag(outputs[i], &display_info_[id].overscan);

Work? (the comment of the function says it won't touch the flag when not found)

and nuke {}

[Jun Mukai, 2013/01/14 18:18:51]

Done.

   }
 #endif
 }