[1.5/2][Ozone-Drm] Keep track of display origin

ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc

Index: ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc
diff --git a/ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc b/ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc
index bb29a42dfb292d4acf1240e7c79610cc54213e74..3883debb4a07f06bd12bfc522f4c80533e8944e6 100644
--- a/ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc
+++ b/ui/ozone/platform/drm/gpu/drm_gpu_display_manager.cc
@@ -84,15 +84,26 @@ std::vector<DisplaySnapshot_Params> DrmGpuDisplayManager::GetDisplays() {
     ScopedVector<HardwareDisplayControllerInfo> display_infos =
         GetAvailableDisplayControllerInfos(drm->get_fd());
     for (auto* display_info : display_infos) {
-      DisplaySnapshot_Params params =
-          CreateDisplaySnapshotParams(display_info, drm->get_fd(), index++);
+      auto it = std::find_if(
+          old_displays.begin(), old_displays.end(),

[spang, 2015/05/13 19:01:20]

I'm not a fan of this.

Can you update displays_ first, then convert displays_ to
std::vector<DisplaySnapshot_Params>()?

[dnicoara, 2015/05/13 19:10:36]

Hmm, it is simpler to create the std::vector<DisplaySnapshot_Params>, then
update displays_ since the display ID is needed from DisplaySnapshot_Params. I
don't think this has a huge mental overhead given that the important operations
are just push_back(). Though I'm happy to change if you think that's cleaner :)

+          DisplayComparator(drm, display_info->crtc()->crtc_id,
+                            display_info->connector()->connector_id));
+      gfx::Point origin;
+      // Because each display has its own surface, display layout isn't tracked
+      // at the DRM level. We must keep track of the display origins otherwise
+      // we'll lose the layout information.
+      if (it != old_displays.end())
+        origin = (*it)->origin();
+
+      DisplaySnapshot_Params params = CreateDisplaySnapshotParams(
+          display_info, drm->get_fd(), index++, origin);
       params_list.push_back(params);
 
       displays_.push_back(
           new DrmDisplay(screen_manager_, params.display_id, drm,
                          display_info->crtc()->crtc_id,
                          display_info->connector()->connector_id,
-                         GetDrmModeVector(display_info->connector())));
+                         GetDrmModeVector(display_info->connector()), origin));
     }
   }