Implements display overlap algorithm for GTK. Needs to be implemented manually

since gdk only provides a function to do display matching
using a window handle (cmp. gdk-screen-get-monitor-at-window()).

BUG=135681
TEST=Manually tested on a dual screen configuration under Unity by
drag a tab out of one tabstrip on the primary display
to a new spot on the secondary display and back for example.
R=oshima@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23579005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@222774 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 15 insertions, 2 deletions

diff --git a/ui/gfx/screen_gtk.cc b/ui/gfx/screen_gtk.cc
index 372b6a6..ac2464b 100644
--- a/ui/gfx/screen_gtk.cc
+++ b/ui/gfx/screen_gtk.cc
@@ -162,8 +162,21 @@ class ScreenGtk : public gfx::Screen {
   // Returns the display that most closely intersects the provided bounds.
   virtual gfx::Display GetDisplayMatching(
       const gfx::Rect& match_rect) const OVERRIDE {
-    // TODO(thestig) Implement multi-monitor support.
-    return GetPrimaryDisplay();
+    std::vector<gfx::Display> displays = GetAllDisplays();
+    gfx::Display maxIntersectDisplay;
+    gfx::Rect maxIntersection;
+    for (std::vector<gfx::Display>::iterator it = displays.begin();
+         it != displays.end(); ++it) {
+      gfx::Rect displayIntersection = it->bounds();
+      displayIntersection.Intersect(match_rect);
+      if (displayIntersection.size().GetArea() >
+          maxIntersection.size().GetArea()) {
+        maxIntersectDisplay = *it;
+        maxIntersection = displayIntersection;
+      }
+    }
+    return maxIntersectDisplay.is_valid() ?
+        maxIntersectDisplay : GetPrimaryDisplay();
   }
 
   // Returns the primary display.