From b1215fb075b0166d5742c72041f58d512273bb50 Mon Sep 17 00:00:00 2001
From: Pierre Ossman <ossman@cendio.se>
Date: Wed, 3 Oct 2018 10:28:52 +0200
Subject: [PATCH] Switch automatic composite update to WorkQueue

It is currently (ab)using the screen BlockHandler callback to do
this. But this can cause problems with other extension as their
block handlers might have executed before Composite's. And the
operations Composite does might result in them wanting to change
timeouts.

Practically this caused problems for TigerVNC's VNC extension which
failed to send out updates for Composite's screen updates.

(cherry picked from commit 1bd5d0a53c5ff4169c5a6704c1c4b276f998b938)
---
 composite/compalloc.c | 28 +++++++++++-----------------
 composite/compinit.c  |  4 ++--
 composite/compint.h   |  3 ++-
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/composite/compalloc.c b/composite/compalloc.c
index 433dc820a..3e2f14fb0 100644
--- a/composite/compalloc.c
+++ b/composite/compalloc.c
@@ -47,24 +47,18 @@
 
 #include "compint.h"
 
-static void
-compScreenUpdate(ScreenPtr pScreen)
-{
-    compCheckTree(pScreen);
-    compPaintChildrenToWindow(pScreen->root);
-}
-
-static void
-compBlockHandler(ScreenPtr pScreen, void *pTimeout)
+static Bool
+compScreenUpdate(ClientPtr pClient, void *closure)
 {
+    ScreenPtr pScreen = closure;
     CompScreenPtr cs = GetCompScreen(pScreen);
 
-    pScreen->BlockHandler = cs->BlockHandler;
-    compScreenUpdate(pScreen);
-    (*pScreen->BlockHandler) (pScreen, pTimeout);
+    compCheckTree(pScreen);
+    compPaintChildrenToWindow(pScreen->root);
 
-    /* Next damage will restore the block handler */
-    cs->BlockHandler = NULL;
+    /* Next damage will restore the worker */
+    cs->pendingScreenUpdate = FALSE;
+    return TRUE;
 }
 
 void
@@ -87,9 +81,9 @@ compReportDamage(DamagePtr pDamage, RegionPtr pRegion, void *closure)
     CompScreenPtr cs = GetCompScreen(pScreen);
     CompWindowPtr cw = GetCompWindow(pWin);
 
-    if (!cs->BlockHandler) {
-        cs->BlockHandler = pScreen->BlockHandler;
-        pScreen->BlockHandler = compBlockHandler;
+    if (!cs->pendingScreenUpdate) {
+        QueueWorkProc(compScreenUpdate, serverClient, pScreen);
+        cs->pendingScreenUpdate = TRUE;
     }
     cw->damaged = TRUE;
 
diff --git a/composite/compinit.c b/composite/compinit.c
index 2590aa46d..6ea33ea4e 100644
--- a/composite/compinit.c
+++ b/composite/compinit.c
@@ -387,6 +387,8 @@ compScreenInit(ScreenPtr pScreen)
     cs->pOverlayWin = NULL;
     cs->pOverlayClients = NULL;
 
+    cs->pendingScreenUpdate = FALSE;
+
     cs->numAlternateVisuals = 0;
     cs->alternateVisuals = NULL;
     cs->numImplicitRedirectExceptions = 0;
@@ -442,8 +444,6 @@ compScreenInit(ScreenPtr pScreen)
     cs->ChangeWindowAttributes = pScreen->ChangeWindowAttributes;
     pScreen->ChangeWindowAttributes = compChangeWindowAttributes;
 
-    cs->BlockHandler = NULL;
-
     cs->CloseScreen = pScreen->CloseScreen;
     pScreen->CloseScreen = compCloseScreen;
 
diff --git a/composite/compint.h b/composite/compint.h
index 89f6507b9..d501bad65 100644
--- a/composite/compint.h
+++ b/composite/compint.h
@@ -156,7 +156,8 @@ typedef struct _CompScreen {
      */
     ChangeWindowAttributesProcPtr ChangeWindowAttributes;
 
-    ScreenBlockHandlerProcPtr BlockHandler;
+    Bool pendingScreenUpdate;
+
     CloseScreenProcPtr CloseScreen;
     int numAlternateVisuals;
     VisualID *alternateVisuals;