[SystemInfo API] Implement DisplayInfoProvider::UpdateDisplayUnitInfoForPlatform for Linux GTK

chrome/browser/extensions/api/system_display/display_info_provider_gtk.cc

Index: chrome/browser/extensions/api/system_display/display_info_provider_gtk.cc
diff --git a/chrome/browser/extensions/api/system_display/display_info_provider_x11.cc b/chrome/browser/extensions/api/system_display/display_info_provider_gtk.cc
similarity index 62%
rename from chrome/browser/extensions/api/system_display/display_info_provider_x11.cc
rename to chrome/browser/extensions/api/system_display/display_info_provider_gtk.cc
index 3776bf90bb496b07dfd5eb437a4dd5d98c7bfa41..9f8f899e3d633de9c5b3e54db95d38b6c0f6a888 100644
--- a/chrome/browser/extensions/api/system_display/display_info_provider_x11.cc
+++ b/chrome/browser/extensions/api/system_display/display_info_provider_gtk.cc
@@ -4,6 +4,11 @@
 
 #include "chrome/browser/extensions/api/system_display/display_info_provider.h"
 
+#include <gdk/gdk.h>
+
+#include "ui/gfx/display.h"
+#include "ui/gfx/screen.h"
+
 namespace extensions {
 
 void DisplayInfoProvider::SetInfo(
@@ -18,7 +23,13 @@ void DisplayInfoProvider::SetInfo(
 void DisplayInfoProvider::UpdateDisplayUnitInfoForPlatform(
     const gfx::Display& display,
     extensions::api::system_display::DisplayUnitInfo* unit) {
-  NOTIMPLEMENTED();
+  // TODO(Haojian): determine the DPI of the display

[Haojian Wu, 2013/08/26 11:58:36]

oshima@, I find a strange problem while calculating DPI for monitor.
I plan to calculate in the following way:
  dpi = N * 25.4 pixels / M inch

I use gdk_screen_get_monitor_height/width_mm methods to get height/width in
millimeters. But the result is always 0 which I think is not correct. I have
tested on ubuntu 12.04 with gnome/xfce, both of them show the same result 0.

Do you have any idea about this? Thanks.  

[oshima, 2013/08/26 20:27:57]

Monitor's info may or may not be available. Can you check what you get with
xrandr?

[Haojian Wu, 2013/08/27 01:35:48]

Running xrandr command, the output also shows 0mm*0mm.

+  GdkScreen* screen = gdk_screen_get_default();
+  // The |id| in Display for GTK is the monitor index.
+  gint monitor_num = static_cast<gint>(display.id());
+  char* monitor_name = reinterpret_cast<char*>(gdk_screen_get_monitor_plug_name(
+       screen, monitor_num));
+  unit->name = std::string(monitor_name);
 }
 
 }  // namespace extensions