X11: Avoid round-tripping to get the cursor position

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index 96f20cca2160c9983c4ea002fb5be5eec4dd92e0..9dec99ad80e7765559635cda06ce27b7c0785656 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -4,6 +4,7 @@
 
 #include "ui/views/widget/desktop_aura/desktop_screen_x11.h"
 
+#include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/Xlib.h>
 
@@ -22,6 +23,7 @@
 #include "ui/display/util/display_util.h"
 #include "ui/display/util/x11/edid_parser_x11.h"
 #include "ui/events/platform/platform_event_source.h"
+#include "ui/events/platform/x11/x11_event_source.h"
 #include "ui/gfx/font_render_params.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
@@ -133,20 +135,47 @@ DesktopScreenX11::~DesktopScreenX11() {
 gfx::Point DesktopScreenX11::GetCursorScreenPoint() {
   TRACE_EVENT0("views", "DesktopScreenX11::GetCursorScreenPoint()");
 
-  XDisplay* display = gfx::GetXDisplay();
+  const XEvent* event =
+      ui::X11EventSource::HasInstance()
+          ? ui::X11EventSource::GetInstance()->get_dispatching_event()
+          : nullptr;
+
+  if (event) {
+    switch (event->type) {
+      case ButtonPress:
+      case ButtonRelease:
+        return gfx::Point(event->xbutton.x_root, event->xbutton.y_root);
+      case MotionNotify:
+        return gfx::Point(event->xmotion.x_root, event->xmotion.y_root);
+      case EnterNotify:
+      case LeaveNotify:
+        return gfx::Point(event->xcrossing.x_root, event->xcrossing.y_root);
+      case GenericEvent:
+        const XIEvent* xi_event =

[Tom (Use chromium acct), 2016/10/07 00:23:18]

Do we need to check for deviceid or sourceid here?

[sadrul, 2016/10/07 02:12:51]

Probably check with TouchFactory first (like in
https://cs.chromium.org/chromium/src/ui/views/widget/desktop_aura/desktop_win...)

[Tom (Use chromium acct), 2016/10/07 21:13:18]

Done.

+            static_cast<const XIEvent*>(event->xcookie.data);
+        switch (xi_event->evtype) {
+          case XI_ButtonPress:
+          case XI_ButtonRelease:
+          case XI_Motion: {
+            const XIDeviceEvent* device_event =
+                static_cast<const XIDeviceEvent*>(event->xcookie.data);
+            return gfx::Point(device_event->root_x, device_event->root_y);
+          }
+          case XI_Enter:
+          case XI_Leave: {
+            const XIEnterEvent* enter_event =
+                static_cast<const XIEnterEvent*>(event->xcookie.data);
+            return gfx::Point(enter_event->root_x, enter_event->root_y);
+          }

[Tom (Use chromium acct), 2016/10/07 00:23:18]

Do we also need to handle XI_Touch{Begin,Update,End}?

[sadrul, 2016/10/07 02:12:51]

Let's not. chrome generally expects that touch events do not affect the mouse
cursor.

[Tom (Use chromium acct), 2016/10/07 21:13:18]

Acknowledged.

+        }
+    }
+  }
 
   ::Window root, child;
   int root_x, root_y, win_x, win_y;
   unsigned int mask;
-  XQueryPointer(display,
-                DefaultRootWindow(display),
-                &root,
-                &child,
-                &root_x,
-                &root_y,
-                &win_x,
-                &win_y,
-                &mask);
+  XQueryPointer(xdisplay_, x_root_window_, &root, &child, &root_x, &root_y,
+                &win_x, &win_y, &mask);
 
   return PixelToDIPPoint(gfx::Point(root_x, root_y));
 }