Only grab keyboard when we have focus

There was an issue with the new grabs that were introduced in commit
2289342de7222e4ff2483eae95bb9898830e6097. On macOS when running
vncviewer in fullscreen on one monitor, we saw that we sometimes got
resize and fullscreen events when switching the focus away from
vncviewer. With the changes in the commit mentioned above this meant
that we immediately grabbed the keyboard again, thus never releasing it.

Fixes #1332.

2 files changed, 17 insertions, 1 deletions

diff --git a/vncviewer/DesktopWindow.cxx b/vncviewer/DesktopWindow.cxx
index 31b5c4c6..d379a712 100644
--- a/vncviewer/DesktopWindow.cxx
+++ b/vncviewer/DesktopWindow.cxx
@@ -1007,9 +1007,23 @@ Bool eventIsFocusWithSerial(Display *display, XEvent *event, XPointer arg)
 }
 #endif
 
+bool DesktopWindow::hasFocus()
+{
+  Fl_Widget* focus;
+
+  focus = Fl::grab();
+  if (!focus)
+    focus = Fl::focus();
+
+  if (!focus)
+    return false;
+
+  return focus->window() == this;
+}
+
 void DesktopWindow::maybeGrabKeyboard()
 {
-  if (fullscreenSystemKeys && fullscreen_active())
+  if (fullscreenSystemKeys && fullscreen_active() && hasFocus())
     grabKeyboard();
 }
 
diff --git a/vncviewer/DesktopWindow.h b/vncviewer/DesktopWindow.h
index 04539700..a654b126 100644
--- a/vncviewer/DesktopWindow.h
+++ b/vncviewer/DesktopWindow.h
@@ -95,6 +95,8 @@ private:
   static int fltkDispatch(int event, Fl_Window *win);
   static int fltkHandle(int event);
 
+  bool hasFocus();
+
   void maybeGrabKeyboard();
   void grabKeyboard();
   void ungrabKeyboard();