Fix grabbing capture when the mouse is pressed on Desktop Linux.

ui/views/widget/desktop_aura/x11_pointer_grab.cc

Index: ui/views/widget/desktop_aura/x11_pointer_grab.cc
diff --git a/ui/views/widget/desktop_aura/x11_pointer_grab.cc b/ui/views/widget/desktop_aura/x11_pointer_grab.cc
index 13541599684428769595749d177177207183f77d..fc3ee5b32a9d2a20500ddd050b75729c249c276a 100644
--- a/ui/views/widget/desktop_aura/x11_pointer_grab.cc
+++ b/ui/views/widget/desktop_aura/x11_pointer_grab.cc
@@ -3,8 +3,11 @@
 // found in the LICENSE file.
 
 #include "base/logging.h"
+#include "ui/base/x/x11_util.h"
+#include "ui/events/devices/x11/device_data_manager_x11.h"
 #include "ui/views/widget/desktop_aura/x11_pointer_grab.h"
 
+#include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
 
 namespace views {
@@ -20,10 +23,41 @@ bool g_owner_events = false;
 }  // namespace
 
 int GrabPointer(XID window, bool owner_events, ::Cursor cursor) {
-  int event_mask = PointerMotionMask | ButtonReleaseMask | ButtonPressMask;
-  int result = XGrabPointer(gfx::GetXDisplay(), window, owner_events,
-                            event_mask, GrabModeAsync, GrabModeAsync, None,
-                            cursor, CurrentTime);
+  int result = GrabInvalidTime;
+  if (ui::IsXInput2Available()) {
+    // Do an XINPUT2 pointer grab. If there is an active XINPUT2 pointer grab
+    // as a result of normal button press, XGrabPointer() will fail.
+    const std::vector<int>& master_pointers =
+        ui::DeviceDataManagerX11::GetInstance()->master_pointers();
+    for (auto master_pointer : master_pointers) {

[sadrul, 2015/02/03 01:22:49]

int

[pkotwicz, 2015/02/03 15:51:59]

Done.

+      unsigned char mask[XIMaskLen(XI_LASTEVENT)];
+      memset(mask, 0, sizeof(mask));
+      XISetMask(mask, XI_ButtonPress);
+      XISetMask(mask, XI_ButtonRelease);
+      XISetMask(mask, XI_Motion);
+      XIEventMask evmask;
+      evmask.deviceid = master_pointer;
+      evmask.mask_len = sizeof(mask);
+      evmask.mask = mask;

[sadrul, 2015/02/03 01:22:48]

Can you move initialization of |mask|/|evmask| out of the loop, and just change
|deviceid| inside before calling XIGrabDevice()?

[pkotwicz, 2015/02/03 15:51:59]

Done.

+      result = XIGrabDevice(
+          gfx::GetXDisplay(), master_pointer, window, CurrentTime, cursor,
+          GrabModeAsync, GrabModeAsync, owner_events, &evmask);
+      // Assume that the grab will succeed on either all or none of the master
+      // pointers.
+      if (result != GrabSuccess) {
+        // Try core pointer grab.
+        break;
+      }
+    }
+  }
+
+  if (result != GrabSuccess) {
+    int event_mask = PointerMotionMask | ButtonReleaseMask | ButtonPressMask;
+    result =
+        XGrabPointer(gfx::GetXDisplay(), window, owner_events, event_mask,
+                     GrabModeAsync, GrabModeAsync, None, cursor, CurrentTime);
+  }
+
   if (result == GrabSuccess) {
     g_grab_window = window;
     g_owner_events = owner_events;
@@ -38,7 +72,14 @@ void ChangeActivePointerGrabCursor(::Cursor cursor) {
 
 void UngrabPointer() {
   g_grab_window = None;
-  XUngrabPointer(gfx::GetXDisplay(), CurrentTime);
+  if (ui::IsXInput2Available()) {
+    const std::vector<int>& master_pointers =
+        ui::DeviceDataManagerX11::GetInstance()->master_pointers();
+    for (auto master_pointer : master_pointers)

[sadrul, 2015/02/03 01:22:49]

int

[pkotwicz, 2015/02/03 15:51:59]

Done.

+      XIUngrabDevice(gfx::GetXDisplay(), master_pointer, CurrentTime);

[sadrul, 2015/02/03 01:22:49]

What happens if GrabPointer() ended up calling XGrabPointer? Would calling
XIUgrabDevice() do the right thing in that case? Or would it be necessary to
call XUngragPointer() instead?

[pkotwicz, 2015/02/03 15:51:59]

Thanks for catching this. We need to call XUngrabPointer() regardless of whether
XI2 is available.

+  } else {
+    XUngrabPointer(gfx::GetXDisplay(), CurrentTime);
+  }
 }
 
 }  // namespace views