Implement Display id field in ScreenWin.

ui/gfx/screen_win.cc

Index: ui/gfx/screen_win.cc
diff --git a/ui/gfx/screen_win.cc b/ui/gfx/screen_win.cc
index 23dbc9d60fbb865a6124b32d57690bbb41d21ba2..67ce034c48d36c0fc45e4858ae334e7e0db20d49 100644
--- a/ui/gfx/screen_win.cc
+++ b/ui/gfx/screen_win.cc
@@ -6,26 +6,35 @@
 
 #include <windows.h>
 
+#include "base/hash.h"
 #include "base/logging.h"
+#include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ui/base/win/dpi.h"
 #include "ui/gfx/display.h"
 
 namespace {
 
-MONITORINFO GetMonitorInfoForMonitor(HMONITOR monitor) {
-  MONITORINFO monitor_info = { 0 };

[oshima, 2013/08/30 18:15:13]

Any reason to prefer ZeroMemory over standard initialization?

[Haojian Wu, 2013/08/31 14:17:07]

According to http://en.cppreference.com/w/cpp/language/aggregate_initialization

Since MONITORINFOEX is a subclass of MONITORINFO, we can't use aggregate
initialization here.

[oshima, 2013/09/03 18:04:44]

but according to
http://msdn.microsoft.com/en-us/library/windows/desktop/dd145066(v=vs.85).aspx,
MONITORINFOEX is plain struct, 
not subclass. (I believe this still has to work with C, not C++?)

+MONITORINFOEX GetMonitorInfoForMonitor(HMONITOR monitor) {
+  MONITORINFOEX monitor_info;
+  ZeroMemory(&monitor_info, sizeof(MONITORINFOEX));
   monitor_info.cbSize = sizeof(monitor_info);
   base::win::GetMonitorInfoWrapper(monitor, &monitor_info);
   return monitor_info;
 }
 
-gfx::Display GetDisplay(MONITORINFO& monitor_info) {
-  // TODO(oshima): Implement ID and Observer.
+gfx::Display GetDisplay(MONITORINFOEX& monitor_info) {
+  // TODO(oshima): Implement Observer.
   gfx::Rect bounds = gfx::Rect(monitor_info.rcMonitor);
   gfx::Display display(0, bounds);
   display.set_work_area(gfx::Rect(monitor_info.rcWork));
   display.SetScaleAndBounds(ui::win::GetDeviceScaleFactor(), bounds);
+  DISPLAY_DEVICE device;
+  device.cb = sizeof(device);
+  if (EnumDisplayDevices(monitor_info.szDevice, 0, &device, 0)) {
+    int64 id = static_cast<int64>(base::Hash(WideToUTF8(device.DeviceID)));

[oshima, 2013/08/30 18:15:13]

Hmm, according to
http://msdn.microsoft.com/en-us/library/windows/desktop/dd183569(v=vs.85).aspx

DeviceID is marked as "Not Used", although one comment says
it does have some value. I'm not familiar enough on windows to
say this is safe to use or not. Do you think szDevice is safer to use?

Also please get the id first:

int64 id = 0;
if (..)
  id = 

gfx::Display(id, bounds)

[Haojian Wu, 2013/08/31 14:17:07]

Done.

+    display.set_id(id);
+  }
   return display;
 }
 
@@ -73,7 +82,7 @@ gfx::Display ScreenWin::GetDisplayNearestWindow(gfx::NativeView window) const {
     return GetPrimaryDisplay();
   }
 
-  MONITORINFO monitor_info;
+  MONITORINFOEX monitor_info;
   monitor_info.cbSize = sizeof(monitor_info);
   base::win::GetMonitorInfoWrapper(
       MonitorFromWindow(window_hwnd, MONITOR_DEFAULTTONEAREST), &monitor_info);
@@ -83,7 +92,8 @@ gfx::Display ScreenWin::GetDisplayNearestWindow(gfx::NativeView window) const {
 gfx::Display ScreenWin::GetDisplayNearestPoint(const gfx::Point& point) const {
   POINT initial_loc = { point.x(), point.y() };
   HMONITOR monitor = MonitorFromPoint(initial_loc, MONITOR_DEFAULTTONEAREST);
-  MONITORINFO mi = {0};
+  MONITORINFOEX mi;
+  ZeroMemory(&mi, sizeof(MONITORINFOEX));
   mi.cbSize = sizeof(mi);
   if (monitor && base::win::GetMonitorInfoWrapper(monitor, &mi)) {
     return GetDisplay(mi);
@@ -93,13 +103,13 @@ gfx::Display ScreenWin::GetDisplayNearestPoint(const gfx::Point& point) const {
 
 gfx::Display ScreenWin::GetDisplayMatching(const gfx::Rect& match_rect) const {
   RECT other_bounds_rect = match_rect.ToRECT();
-  MONITORINFO monitor_info = GetMonitorInfoForMonitor(MonitorFromRect(
+  MONITORINFOEX monitor_info = GetMonitorInfoForMonitor(MonitorFromRect(
       &other_bounds_rect, MONITOR_DEFAULTTONEAREST));
   return GetDisplay(monitor_info);
 }
 
 gfx::Display ScreenWin::GetPrimaryDisplay() const {
-  MONITORINFO mi = GetMonitorInfoForMonitor(
+  MONITORINFOEX mi = GetMonitorInfoForMonitor(
       MonitorFromWindow(NULL, MONITOR_DEFAULTTOPRIMARY));
   gfx::Display display = GetDisplay(mi);
   // TODO(kevers|girard): Test if these checks can be reintroduced for high-DIP