[PATCH xserver 1/2] animcur: Fix transitions between animated cursors

[Adam Jackson]

We weren't cancelling the old timer when changing cursors, making things
go all crashy. Logically we could always cancel the timer first, but
then we'd have to call TimerSet to re-arm ourselves, and GetTimeInMillis
is potentially expensive.

Reported-by: https://devtalk.nvidia.com/default/topic/1028172/linux/titan-v-ubuntu-16-04lts-and-387-34-driver-crashes-badly/post/5230967/#5230967
Signed-off-by: Adam Jackson <ajax at redhat.com>
---
 render/animcur.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/render/animcur.c b/render/animcur.c
index 058bc1b323..797029443c 100644
--- a/render/animcur.c
+++ b/render/animcur.c
@@ -151,11 +151,20 @@ AnimCurTimerNotify(OsTimerPtr timer, CARD32 now, void *arg)
     return ac->elts[elt].delay;
 }
 
+static void
+AnimCurCancelTimer(DeviceIntPtr pDev)
+{
+    CursorPtr cur = pDev->spriteInfo->anim.pCursor;
+
+    if (IsAnimCur(cur))
+        TimerCancel(GetAnimCur(cur)->timer);
+}
+
 static Bool
 AnimCurDisplayCursor(DeviceIntPtr pDev, ScreenPtr pScreen, CursorPtr pCursor)
 {
     AnimCurScreenPtr as = GetAnimCurScreen(pScreen);
-    Bool ret;
+    Bool ret = TRUE;
 
     if (IsFloating(pDev))
         return FALSE;
@@ -165,8 +174,10 @@ AnimCurDisplayCursor(DeviceIntPtr pDev, ScreenPtr pScreen, CursorPtr pCursor)
         if (pCursor != pDev->spriteInfo->anim.pCursor) {
             AnimCurPtr ac = GetAnimCur(pCursor);
 
-            ret = (*pScreen->DisplayCursor)
-                (pDev, pScreen, ac->elts[0].pCursor);
+            AnimCurCancelTimer(pDev);
+            ret = (*pScreen->DisplayCursor) (pDev, pScreen,
+                                             ac->elts[0].pCursor);
+
             if (ret) {
                 pDev->spriteInfo->anim.elt = 0;
                 pDev->spriteInfo->anim.pCursor = pCursor;
@@ -176,15 +187,9 @@ AnimCurDisplayCursor(DeviceIntPtr pDev, ScreenPtr pScreen, CursorPtr pCursor)
                                      AnimCurTimerNotify, pDev);
             }
         }
-        else
-            ret = TRUE;
     }
     else {
-        CursorPtr old = pDev->spriteInfo->anim.pCursor;
-
-        if (old && IsAnimCur(old))
-            TimerCancel(GetAnimCur(old)->timer);
-
+        AnimCurCancelTimer(pDev);
         pDev->spriteInfo->anim.pCursor = 0;
         pDev->spriteInfo->anim.pScreen = 0;
         ret = (*pScreen->DisplayCursor) (pDev, pScreen, pCursor);
-- 
2.14.3