xwayland/present: Add xwl_present_maybe_(un)redirect_window

A later commit will use these to (un)redirect the surface window on
demand.

Not used yet, so no functional change intended.

v2:
* Use "surface_window_damage" instead of "surf_win_damage".
  (Olivier Fourdan)
* Slightly simplify logic in xwl_unrealize_window.
v3:
* Add comment in xwl_present_maybe_unredirect_window explaining why we
  use a timer. (Olivier Fourdan)
v4:
* Rename unredir_timer field to unredirect_timer.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1300>

hw/xwayland/xwayland-present.c

@@ -25,6 +25,7 @@
 
 #include <xwayland-config.h>
 
+#include <compint.h>
 #ifdef XWL_HAS_GLAMOR
 #include <glamor.h>
 #endif
@@ -484,6 +485,7 @@ xwl_present_cleanup(WindowPtr window)
 
     /* Clear timer */
     xwl_present_free_timer(xwl_present_window);
+    TimerFree(xwl_present_window->unredirect_timer);
 
     /* Remove from privates so we don't try to access it later */
     dixSetPrivate(&window->devPrivates,
@@ -1263,6 +1265,67 @@ xwl_present_unrealize_window(struct xwl_present_window *xwl_present_window)
     xwl_present_reset_timer(xwl_present_window);
 }
 
+Bool
+xwl_present_maybe_redirect_window(WindowPtr window, PixmapPtr pixmap)
+{
+    struct xwl_present_window *xwl_present_window = xwl_present_window_get_priv(window);
+    struct xwl_window *xwl_window = xwl_window_from_window(window);
+
+    if (xwl_present_window->redirect_failed)
+        return FALSE;
+
+    if (compRedirectWindow(serverClient, window, CompositeRedirectManual) != Success) {
+        xwl_present_window->redirect_failed = TRUE;
+        return FALSE;
+    }
+
+    xwl_window_update_surface_window(xwl_window);
+    if (xwl_window->surface_window != window) {
+        compUnredirectWindow(serverClient, window, CompositeRedirectManual);
+        xwl_present_window->redirect_failed = TRUE;
+        return FALSE;
+    }
+
+    if (!xwl_window->surface_window_damage)
+        xwl_window->surface_window_damage = RegionCreate(NullBox, 1);
+
+    xwl_present_window->redirected = TRUE;
+    return TRUE;
+}
+
+static CARD32
+unredirect_window(OsTimerPtr timer, CARD32 time, void *arg)
+{
+    WindowPtr window = arg;
+    struct xwl_present_window *xwl_present_window = xwl_present_window_get_priv(window);
+
+    compUnredirectWindow(serverClient, window, CompositeRedirectManual);
+    xwl_present_window->redirected = FALSE;
+
+    xwl_present_window->unredirect_timer = NULL;
+    return 0;
+}
+
+Bool
+xwl_present_maybe_unredirect_window(WindowPtr window)
+{
+    struct xwl_present_window *xwl_present_window = xwl_present_window_get_priv(window);
+
+    if (!xwl_present_window || !xwl_present_window->redirected)
+        return FALSE;
+
+    /* This function may get called from composite layer code, in which case
+     * calling compUnredirectWindow would blow up. To avoid this, set up a timer
+     * which will call it "as soon as possible".
+     */
+    if (!xwl_present_window->unredirect_timer) {
+        xwl_present_window->unredirect_timer =
+            TimerSet(NULL, 0, 1, unredirect_window, window);
+    }
+
+    return TRUE;
+}
+
 Bool
 xwl_present_init(ScreenPtr screen)
 {

hw/xwayland/xwayland-present.h

@@ -54,6 +54,10 @@ struct xwl_present_window {
 
     present_vblank_ptr flip_active;
     uint64_t blocking_event;
+
+    OsTimerPtr unredirect_timer;
+    Bool redirected;
+    Bool redirect_failed;
 };
 
 struct xwl_present_event {
@@ -77,5 +81,7 @@ void xwl_present_frame_callback(struct xwl_present_window *xwl_present_window);
 Bool xwl_present_init(ScreenPtr screen);
 void xwl_present_cleanup(WindowPtr window);
 void xwl_present_unrealize_window(struct xwl_present_window *xwl_present_window);
+Bool xwl_present_maybe_redirect_window(WindowPtr window, PixmapPtr pixmap);
+Bool xwl_present_maybe_unredirect_window(WindowPtr window);
 
 #endif /* XWAYLAND_PRESENT_H */

hw/xwayland/xwayland-window.c

@@ -1221,7 +1221,7 @@ err_surf:
     return FALSE;
 }
 
-static void
+void
 xwl_window_update_surface_window(struct xwl_window *xwl_window)
 {
     WindowPtr surface_window = xwl_window->toplevel;
@@ -1512,6 +1512,8 @@ xwl_unrealize_window(WindowPtr window)
 
     xwl_screen = xwl_screen_get(screen);
 
+    xwl_window = xwl_window_get(window);
+    if (xwl_window)
         compUnredirectWindow(serverClient, window, CompositeRedirectManual);
 
     screen->UnrealizeWindow = xwl_screen->UnrealizeWindow;
@@ -1519,7 +1521,6 @@ xwl_unrealize_window(WindowPtr window)
     xwl_screen->UnrealizeWindow = screen->UnrealizeWindow;
     screen->UnrealizeWindow = xwl_unrealize_window;
 
-    xwl_window = xwl_window_get(window);
     if (!xwl_window)
         return ret;
 

hw/xwayland/xwayland-window.h

@@ -82,6 +82,7 @@ struct xwl_window {
      * can also be used for the X dimensions of the Wayland surface though.
      */
     WindowPtr surface_window;
+    RegionPtr surface_window_damage;
 
     struct xorg_list link_damage;
     struct xorg_list link_window;
@@ -121,6 +122,7 @@ void xwl_window_rootful_update_title(struct xwl_window *xwl_window);
 void xwl_window_rootful_update_fullscreen(struct xwl_window *xwl_window,
                                           struct xwl_output *xwl_output);
 void xwl_window_set_window_pixmap(WindowPtr window, PixmapPtr pixmap);
+void xwl_window_update_surface_window(struct xwl_window *xwl_window);
 
 void xwl_window_leave_output(struct xwl_window *xwl_window,
                              struct xwl_output *xwl_output);