glamor: Fix one bug for Xephyr.

Xephyr doesn't has a bounded valid texture. It seems that we can't
load texture 0 directly sometimes. Especially in the copyarea, function
if that is the case, we prefer to use fbo blit to read the screen pixmap
rather than load the bound texture.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>

glamor/glamor.c

@@ -200,7 +200,7 @@ glamor_create_screen_pixmap(ScreenPtr screen, int w, int h, int depth,
     pixmap_priv = glamor_get_pixmap_private(pixmap);
     pixmap_priv->tex = 0; 
     pixmap_priv->gl_fbo = 1;
-    pixmap_priv->gl_tex = 1;
+    pixmap_priv->gl_tex = 0;
     pixmap_priv->container = pixmap;
     pixmap_priv->pending_op.type = GLAMOR_PENDING_NONE;
     

glamor/glamor_copyarea.c

@@ -293,7 +293,8 @@ glamor_copy_n_to_n(DrawablePtr src,
     }
     /* XXX need revisit to handle overlapped area copying. */
 
-    if ( overlaped  
+    if ((overlaped 
+          || !src_pixmap_priv->gl_tex  || !dst_pixmap_priv->gl_tex )
         && glamor_copy_n_to_n_fbo_blit(src, dst, gc, box, nbox, dx, dy)) {
         goto done;
 	return;

glamor/glamor_render.c

@@ -765,7 +765,11 @@ glamor_composite_with_shader(CARD8 op,
       glamor_fallback("source == dest\n");
       goto fail;
     }
-    if (!source_pixmap_priv || source_pixmap_priv->gl_tex == 0) {
+    if (!source_pixmap_priv || source_pixmap_priv->gl_fbo == 0) {
+    /* XXX in Xephyr, we may have gl_fbo equal to 1 but gl_tex 
+     * equal to zero when the pixmap is screen pixmap. Then we may
+     * refer the tex zero directly latter in the composition. 
+     * It seems that it works fine, but it may have potential problem*/
 #ifdef GLAMOR_PIXMAP_DYNAMIC_UPLOAD
       source_status = GLAMOR_UPLOAD_PENDING;
 #else
@@ -786,7 +790,7 @@ glamor_composite_with_shader(CARD8 op,
       glamor_fallback("mask == dest\n");
       goto fail;
     }
-    if (!mask_pixmap_priv || mask_pixmap_priv->gl_tex == 0) {
+    if (!mask_pixmap_priv || mask_pixmap_priv->gl_fbo == 0) {
 #ifdef GLAMOR_PIXMAP_DYNAMIC_UPLOAD
       mask_status = GLAMOR_UPLOAD_PENDING;
 #else