dix: Add hybrid full-size/empty-clip mode to SetRootClip

216bdbc735 removed the SetRootClip call in the XWayland output-hotplug
handler when running rootless (e.g. as a part of Weston/Mutter), since
the root window has no storage, so generating exposures will result in
writes to invalid memory.

Unfortunately, preventing the segfault also breaks sprite confinement.
SetRootClip updates winSize and borderSize for the root window, which
when combined with RRScreenSizeChanged calling ScreenRestructured,
generates a new sprite-confinment area to update it to the whole screen.

Removing this call results in the window geometry being reported
correctly, but winSize/borderSize never changing from their values at
startup, i.e. out of sync with the root window geometry / screen
information in the connection info / XRandR.

This patch introduces a hybrid mode, where we update winSize and
borderSize for the root window, enabling sprite confinement to work
correctly, but keep the clip emptied so exposures are never generated.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Tested-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>

15 files changed, 59 insertions, 35 deletions

diff --git a/dix/window.c b/dix/window.c
index 25d29ecd4..ead4dc27f 100644
--- a/dix/window.c
+++ b/dix/window.c
@@ -3647,7 +3647,7 @@ WindowParentHasDeviceCursor(WindowPtr pWin,
  *	all of the windows
  */
 void
-SetRootClip(ScreenPtr pScreen, Bool enable)
+SetRootClip(ScreenPtr pScreen, int enable)
 {
     WindowPtr pWin = pScreen->root;
     WindowPtr pChild;
@@ -3655,6 +3655,7 @@ SetRootClip(ScreenPtr pScreen, Bool enable)
     Bool anyMarked = FALSE;
     WindowPtr pLayerWin;
     BoxRec box;
+    enum RootClipMode mode = enable;
 
     if (!pWin)
         return;
@@ -3679,23 +3680,32 @@ SetRootClip(ScreenPtr pScreen, Bool enable)
         }
     }
 
-    /*
-     * Use REGION_BREAK to avoid optimizations in ValidateTree
-     * that assume the root borderClip can't change well, normally
-     * it doesn't...)
-     */
-    if (enable) {
+    if (mode != ROOT_CLIP_NONE) {
+        pWin->drawable.width = pScreen->width;
+        pWin->drawable.height = pScreen->height;
+
         box.x1 = 0;
         box.y1 = 0;
         box.x2 = pScreen->width;
         box.y2 = pScreen->height;
+
         RegionInit(&pWin->winSize, &box, 1);
         RegionInit(&pWin->borderSize, &box, 1);
-        if (WasViewable)
-            RegionReset(&pWin->borderClip, &box);
-        pWin->drawable.width = pScreen->width;
-        pWin->drawable.height = pScreen->height;
+
+        /*
+         * Use REGION_BREAK to avoid optimizations in ValidateTree
+         * that assume the root borderClip can't change well, normally
+         * it doesn't...)
+         */
         RegionBreak(&pWin->clipList);
+
+	/* For INPUT_ONLY, empty the borderClip so no rendering will ever
+	 * be attempted to the screen pixmap (only redirected windows),
+	 * but we keep borderSize as full regardless. */
+        if (WasViewable && mode == ROOT_CLIP_FULL)
+            RegionReset(&pWin->borderClip, &box);
+        else
+            RegionEmpty(&pWin->borderClip);
     }
     else {
         RegionEmpty(&pWin->borderClip);
diff --git a/hw/kdrive/src/kdrive.c b/hw/kdrive/src/kdrive.c
index dddbe6e96..582ff66d2 100644
--- a/hw/kdrive/src/kdrive.c
+++ b/hw/kdrive/src/kdrive.c
@@ -99,7 +99,7 @@ KdDisableScreen(ScreenPtr pScreen)
     if (!pScreenPriv->enabled)
         return;
     if (!pScreenPriv->closed)
-        SetRootClip(pScreen, FALSE);
+        SetRootClip(pScreen, ROOT_CLIP_NONE);
     KdDisableColormap(pScreen);
     if (!pScreenPriv->screen->dumb && pScreenPriv->card->cfuncs->disableAccel)
         (*pScreenPriv->card->cfuncs->disableAccel) (pScreen);
@@ -182,7 +182,7 @@ KdEnableScreen(ScreenPtr pScreen)
     if (!pScreenPriv->screen->dumb && pScreenPriv->card->cfuncs->enableAccel)
         (*pScreenPriv->card->cfuncs->enableAccel) (pScreen);
     KdEnableColormap(pScreen);
-    SetRootClip(pScreen, TRUE);
+    SetRootClip(pScreen, ROOT_CLIP_FULL);
     if (pScreenPriv->card->cfuncs->dpms)
         (*pScreenPriv->card->cfuncs->dpms) (pScreen, pScreenPriv->dpmsState);
     return TRUE;
diff --git a/hw/vfb/InitOutput.c b/hw/vfb/InitOutput.c
index 9e8dd7a3b..01bb63128 100644
--- a/hw/vfb/InitOutput.c
+++ b/hw/vfb/InitOutput.c
@@ -763,7 +763,7 @@ vfbRRScreenSetSize(ScreenPtr  pScreen,
                    CARD32     mmHeight)
 {
     // Prevent screen updates while we change things around
-    SetRootClip(pScreen, FALSE);
+    SetRootClip(pScreen, ROOT_CLIP_NONE);
 
     pScreen->width = width;
     pScreen->height = height;
@@ -771,7 +771,7 @@ vfbRRScreenSetSize(ScreenPtr  pScreen,
     pScreen->mmHeight = mmHeight;
 
     // Restore the ability to update screen, now with new dimensions
-    SetRootClip(pScreen, TRUE);
+    SetRootClip(pScreen, ROOT_CLIP_FULL);
 
     RRScreenSizeNotify (pScreen);
     RRTellChanged(pScreen);
diff --git a/hw/xfree86/common/xf86Helper.c b/hw/xfree86/common/xf86Helper.c
index c42e93ed8..3b01a49b5 100644
--- a/hw/xfree86/common/xf86Helper.c
+++ b/hw/xfree86/common/xf86Helper.c
@@ -1076,14 +1076,14 @@ xf86EnableDisableFBAccess(ScrnInfoPtr pScrnInfo, Bool enable)
          * Restore all of the clip lists on the screen
          */
         if (!xf86Resetting)
-            SetRootClip(pScreen, TRUE);
+            SetRootClip(pScreen, ROOT_CLIP_FULL);
 
     }
     else {
         /*
          * Empty all of the clip lists on the screen
          */
-        SetRootClip(pScreen, FALSE);
+        SetRootClip(pScreen, ROOT_CLIP_NONE);
     }
 }
 
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index eae701624..60d22543e 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -1848,13 +1848,13 @@ xf86RandR14ProviderSetOutputSource(ScreenPtr pScreen,
     if (provider->output_source == source_provider)
         return TRUE;
 
-    SetRootClip(source_provider->pScreen, FALSE);
+    SetRootClip(source_provider->pScreen, ROOT_CLIP_NONE);
 
     DetachUnboundGPU(pScreen);
     AttachOutputGPU(source_provider->pScreen, pScreen);
 
     provider->output_source = source_provider;
-    SetRootClip(source_provider->pScreen, TRUE);
+    SetRootClip(source_provider->pScreen, ROOT_CLIP_FULL);
     return TRUE;
 }
 
diff --git a/hw/xquartz/darwinEvents.c b/hw/xquartz/darwinEvents.c
index 557729768..7f34e0c68 100644
--- a/hw/xquartz/darwinEvents.c
+++ b/hw/xquartz/darwinEvents.c
@@ -275,7 +275,7 @@ DarwinEventHandler(int screenNum, InternalEvent *ie, DeviceIntPtr dev)
         break;
 
     case kXquartzSetRootClip:
-        QuartzSetRootClip((Bool)e->data[0]);
+        QuartzSetRootClip(e->data[0]);
         break;
 
     case kXquartzQuit:
diff --git a/hw/xquartz/quartz.c b/hw/xquartz/quartz.c
index d3ec133f6..c8b6f966d 100644
--- a/hw/xquartz/quartz.c
+++ b/hw/xquartz/quartz.c
@@ -485,7 +485,7 @@ QuartzHide(void)
  *  Enable or disable rendering to the X screen.
  */
 void
-QuartzSetRootClip(BOOL enable)
+QuartzSetRootClip(int mode)
 {
     int i;
 
@@ -494,7 +494,7 @@ QuartzSetRootClip(BOOL enable)
 
     for (i = 0; i < screenInfo.numScreens; i++) {
         if (screenInfo.screens[i]) {
-            SetRootClip(screenInfo.screens[i], enable);
+            SetRootClip(screenInfo.screens[i], mode);
         }
     }
 }
diff --git a/hw/xquartz/quartz.h b/hw/xquartz/quartz.h
index 47c44162f..ddbf2e780 100644
--- a/hw/xquartz/quartz.h
+++ b/hw/xquartz/quartz.h
@@ -149,7 +149,7 @@ QuartzShow(void);
 void
 QuartzHide(void);
 void
-QuartzSetRootClip(BOOL enable);
+QuartzSetRootClip(int mode);
 void
 QuartzSpaceChanged(uint32_t space_id);
 
diff --git a/hw/xwayland/xwayland-glamor.c b/hw/xwayland/xwayland-glamor.c
index 7f6fb9ae8..8e77a84e2 100644
--- a/hw/xwayland/xwayland-glamor.c
+++ b/hw/xwayland/xwayland-glamor.c
@@ -236,7 +236,6 @@ xwl_glamor_create_screen_resources(ScreenPtr screen)
     if (xwl_screen->rootless) {
         screen->devPrivate =
             fbCreatePixmap(screen, 0, 0, screen->rootDepth, 0);
-        SetRootClip(screen, FALSE);
     }
     else {
         screen->devPrivate =
@@ -247,6 +246,8 @@ xwl_glamor_create_screen_resources(ScreenPtr screen)
             glamor_set_screen_pixmap(screen->devPrivate, NULL);
     }
 
+    SetRootClip(screen, xwl_screen->root_clip_mode);
+
     return screen->devPrivate != NULL;
 }
 
diff --git a/hw/xwayland/xwayland-output.c b/hw/xwayland/xwayland-output.c
index e9ec190f0..5263cb3e9 100644
--- a/hw/xwayland/xwayland-output.c
+++ b/hw/xwayland/xwayland-output.c
@@ -164,8 +164,8 @@ update_screen_size(struct xwl_output *xwl_output, int width, int height)
     struct xwl_screen *xwl_screen = xwl_output->xwl_screen;
     double mmpd;
 
-    if (!xwl_screen->rootless)
-        SetRootClip(xwl_screen->screen, FALSE);
+    if (xwl_screen->root_clip_mode == ROOT_CLIP_FULL)
+        SetRootClip(xwl_screen->screen, ROOT_CLIP_NONE);
 
     xwl_screen->width = width;
     xwl_screen->height = height;
@@ -181,6 +181,8 @@ update_screen_size(struct xwl_output *xwl_output, int width, int height)
         xwl_screen->screen->mmHeight = height * mmpd;
     }
 
+    SetRootClip(xwl_screen->screen, xwl_screen->root_clip_mode);
+
     if (xwl_screen->screen->root) {
         xwl_screen->screen->root->drawable.width = width;
         xwl_screen->screen->root->drawable.height = height;
@@ -188,9 +190,6 @@ update_screen_size(struct xwl_output *xwl_output, int width, int height)
     }
 
     update_desktop_dimensions();
-
-    if (!xwl_screen->rootless)
-        SetRootClip(xwl_screen->screen, TRUE);
 }
 
 static void
diff --git a/hw/xwayland/xwayland-shm.c b/hw/xwayland/xwayland-shm.c
index 7072be4bc..1b388f0ca 100644
--- a/hw/xwayland/xwayland-shm.c
+++ b/hw/xwayland/xwayland-shm.c
@@ -279,16 +279,16 @@ xwl_shm_create_screen_resources(ScreenPtr screen)
     if (!ret)
         return ret;
 
-    if (xwl_screen->rootless) {
+    if (xwl_screen->rootless)
         screen->devPrivate =
             fbCreatePixmap(screen, 0, 0, screen->rootDepth, 0);
-        SetRootClip(screen, FALSE);
-    }
     else
         screen->devPrivate =
             xwl_shm_create_pixmap(screen, screen->width, screen->height,
                                   screen->rootDepth,
                                   CREATE_PIXMAP_USAGE_BACKING_PIXMAP);
 
+    SetRootClip(screen, xwl_screen->root_clip_mode);
+
     return screen->devPrivate != NULL;
 }
diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index 3d362054f..c97f57dc8 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -590,6 +590,13 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
         }
     }
 
+    /* In rootless mode, we don't have any screen storage, and the only
+     * rendering should be to redirected mode. */
+    if (xwl_screen->rootless)
+        xwl_screen->root_clip_mode = ROOT_CLIP_INPUT_ONLY;
+    else
+        xwl_screen->root_clip_mode = ROOT_CLIP_FULL;
+
     if (xwl_screen->listen_fd_count > 0) {
         if (xwl_screen->wm_fd >= 0)
             AddCallback(&SelectionCallback, wm_selection_callback, xwl_screen);
diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
index a7d71193d..4fcdee5c9 100644
--- a/hw/xwayland/xwayland.h
+++ b/hw/xwayland/xwayland.h
@@ -49,6 +49,7 @@ struct xwl_screen {
     ScreenPtr screen;
     WindowPtr pointer_limbo_window;
     int expecting_event;
+    enum RootClipMode root_clip_mode;
 
     int wm_fd;
     int listen_fds[5];
diff --git a/hw/xwin/winrandr.c b/hw/xwin/winrandr.c
index f4ba054bc..c29d7b37a 100644
--- a/hw/xwin/winrandr.c
+++ b/hw/xwin/winrandr.c
@@ -75,7 +75,7 @@ winDoRandRScreenSetSize(ScreenPtr pScreen,
     WindowPtr pRoot = pScreen->root;
 
     // Prevent screen updates while we change things around
-    SetRootClip(pScreen, FALSE);
+    SetRootClip(pScreen, ROOT_CLIP_NONE);
 
     /* Update the screen size as requested */
     pScreenInfo->dwWidth = width;
@@ -101,7 +101,7 @@ winDoRandRScreenSetSize(ScreenPtr pScreen,
     // does this emit a ConfigureNotify??
 
     // Restore the ability to update screen, now with new dimensions
-    SetRootClip(pScreen, TRUE);
+    SetRootClip(pScreen, ROOT_CLIP_FULL);
 
     // and arrange for it to be repainted
     pScreen->PaintWindow(pRoot, &pRoot->borderClip, PW_BACKGROUND);
diff --git a/include/window.h b/include/window.h
index f13ed5115..7a22febf8 100644
--- a/include/window.h
+++ b/include/window.h
@@ -72,6 +72,12 @@ struct _Cursor;
 typedef struct _BackingStore *BackingStorePtr;
 typedef struct _Window *WindowPtr;
 
+enum RootClipMode {
+    ROOT_CLIP_NONE = 0, /**< resize the root window to 0x0 */
+    ROOT_CLIP_FULL = 1, /**< resize the root window to fit screen */
+    ROOT_CLIP_INPUT_ONLY = 2, /**< as above, but no rendering to screen */
+};
+
 typedef int (*VisitWindowProcPtr) (WindowPtr pWin,
                                    void *data);
 
@@ -221,7 +227,7 @@ extern _X_EXPORT RegionPtr CreateBoundingShape(WindowPtr /* pWin */ );
 
 extern _X_EXPORT RegionPtr CreateClipShape(WindowPtr /* pWin */ );
 
-extern _X_EXPORT void SetRootClip(ScreenPtr pScreen, Bool enable);
+extern _X_EXPORT void SetRootClip(ScreenPtr pScreen, int enable);
 extern _X_EXPORT void PrintWindowTree(void);
 extern _X_EXPORT void PrintPassiveGrabs(void);