touchring: prevent touchring to remain visible when using multi/virtu…

…al keyboard + fix touch grabbing issue when window is used. Closes kivy#1335

kivy/core/window/__init__.py

@@ -22,6 +22,7 @@
 from kivy.properties import ListProperty, ObjectProperty, AliasProperty, \
         NumericProperty, OptionProperty, StringProperty
 from kivy.utils import platform, reify
+from kivy.context import get_current_context
 
 # late import
 VKeyboard = None
@@ -481,6 +482,10 @@ def __init__(self, **kwargs):
         # manage keyboard(s)
         self.configure_keyboards()
 
+        # assign the default context of the widget creation
+        if not hasattr(self, '_context'):
+            self._context = get_current_context()
+
         # mark as initialized
         self.initialized = True
 

kivy/modules/touchring.py

@@ -50,6 +50,10 @@ def _touch_down(win, touch):
             size=(iw * pointer_scale, ih * pointer_scale),
             texture=pointer_image.texture)
 
+    if not ud.get('tr.grab', False):
+        ud['tr.grab'] = True
+        touch.grab(win)
+
 
 def _touch_move(win, touch):
     ud = touch.ud
@@ -59,9 +63,14 @@ def _touch_move(win, touch):
 
 
 def _touch_up(win, touch):
-    ud = touch.ud
-    win.canvas.after.remove(ud['tr.color'])
-    win.canvas.after.remove(ud['tr.rect'])
+    if touch.grab_current is win:
+        ud = touch.ud
+        win.canvas.after.remove(ud['tr.color'])
+        win.canvas.after.remove(ud['tr.rect'])
+
+        if ud.get('tr.grab') is True:
+            touch.ungrab(win)
+            ud['tr.grab'] = False
 
 
 def start(win, ctx):