dix: rename mieqSwitchScreen argument fromDix → set_dequeue_screen, document

fromDIX is neither exactly true nor particularly helpful in understanding
what this parameter triggers. Rename to set_dequeue_screen, because that's
exactly what happens.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>

mi/mi.h

@@ -206,7 +206,7 @@ extern _X_EXPORT void mieqEnqueue(
 extern _X_EXPORT void mieqSwitchScreen(
     DeviceIntPtr /* pDev */,
     ScreenPtr /*pScreen*/,
-    Bool /*fromDIX*/
+    Bool /*set_dequeue_screen*/
 );
 
 extern _X_EXPORT void mieqProcessDeviceEvent(

mi/mieq.c

@@ -209,14 +209,29 @@ mieqEnqueue(DeviceIntPtr pDev, InternalEvent *e)
 #endif
 }
 
+/**
+ * Changes the screen reference events are being enqueued from.
+ * Input events are enqueued with a screen reference and dequeued and
+ * processed with a (potentially different) screen reference.
+ * This function is called whenever a new event has changed screen but is
+ * still logically on the previous screen as seen by the client.
+ * This usually happens whenever the visible cursor moves across screen
+ * boundaries during event generation, before the same event is processed
+ * and sent down the wire.
+ *
+ * @param pDev The device that triggered a screen change.
+ * @param pScreen The new screen events are being enqueued for.
+ * @param set_dequeue_screen If TRUE, pScreen is set as both enqueue screen
+ * and dequeue screen.
+ */
 void
-mieqSwitchScreen(DeviceIntPtr pDev, ScreenPtr pScreen, Bool fromDIX)
+mieqSwitchScreen(DeviceIntPtr pDev, ScreenPtr pScreen, Bool set_dequeue_screen)
 {
 #ifdef XQUARTZ
     pthread_mutex_lock(&miEventQueueMutex);
 #endif
     EnqueueScreen(pDev) = pScreen;
-    if (fromDIX)
+    if (set_dequeue_screen)
         DequeueScreen(pDev) = pScreen;
 #ifdef XQUARTZ
     pthread_mutex_unlock(&miEventQueueMutex);

mi/mipointer.h

@@ -87,7 +87,7 @@ typedef struct _miPointerScreenFuncRec {
     void	(*NewEventScreen)(
 		    DeviceIntPtr /* pDev */,
                     ScreenPtr /* pScr */,
-		    Bool /* fromDIX */
+		    Bool /* set_dequeue_screen */
                     );
 } miPointerScreenFuncRec, *miPointerScreenFuncPtr;