Xnest: Implement xnestModifyPixmapHeader

Xnest variant of ModifyPixmapHeader that creates new Pixmap in parent X
server if it's size is modified from 0x0 to anything bigger.

xnestCreatePixmap doesn't create pixmap in parent X server if it has
dimensions 0x0. If it is later resized and accessed, Xnest will be
aborted with BadDrawable error from parent X server because it will
use XID 0. This happens with ScratchPixmap, for example as used from
XaceCensorImage. Applications using XACE crash Xnest.

Reviewed-by: Adam Jackson <ajax@redhat.com>

hw/xnest/Pixmap.c

@@ -78,6 +78,21 @@ xnestDestroyPixmap(PixmapPtr pPixmap)
     return TRUE;
 }
 
+Bool
+xnestModifyPixmapHeader(PixmapPtr pPixmap, int width, int height, int depth,
+                        int bitsPerPixel, int devKind, pointer pPixData)
+{
+  if(!xnestPixmapPriv(pPixmap)->pixmap && width > 0 && height > 0) {
+    xnestPixmapPriv(pPixmap)->pixmap =
+        XCreatePixmap(xnestDisplay,
+                      xnestDefaultWindows[pPixmap->drawable.pScreen->myNum],
+                      width, height, depth);
+  }
+
+  return miModifyPixmapHeader(pPixmap, width, height, depth,
+                              bitsPerPixel, devKind, pPixData);
+}
+
 RegionPtr
 xnestPixmapToRegion(PixmapPtr pPixmap)
 {

hw/xnest/Screen.c

@@ -282,6 +282,7 @@ xnestOpenScreen(ScreenPtr pScreen, int argc, char *argv[])
 
     pScreen->CreatePixmap = xnestCreatePixmap;
     pScreen->DestroyPixmap = xnestDestroyPixmap;
+    pScreen->ModifyPixmapHeader = xnestModifyPixmapHeader;
 
     /* Font procedures */
 

hw/xnest/XNPixmap.h

@@ -33,6 +33,8 @@ typedef struct {
 PixmapPtr xnestCreatePixmap(ScreenPtr pScreen, int width, int height,
                             int depth, unsigned usage_hint);
 Bool xnestDestroyPixmap(PixmapPtr pPixmap);
+Bool xnestModifyPixmapHeader(PixmapPtr pPixmap, int width, int height, int depth,
+                             int bitsPerPixel, int devKind, pointer pPixData);
 RegionPtr xnestPixmapToRegion(PixmapPtr pPixmap);
 
 #endif                          /* XNESTPIXMAP_H */