[PATCH] ui/dbus: implement damage regions for GL

[Bilal Elmoussaoui <belmouss@redhat.com>]

Currently, when using `-display dbus,gl=on` all updates to the client
become "full scanout" updates, meaning there is no way for the client to
limit damage regions to the display server.

Instead of using an "update count", this patch tracks the damage region
and propagates it to the client.

This was less of an issue when clients were using GtkGLArea for
rendering,
as you'd be doing full-surface redraw. To be efficient, the client needs
both a DMA-BUF and the damage region to be updated.

Co-authored-by: Christian Hergert <chergert@redhat.com>
Signed-off-by: Bilal Elmoussaoui <belmouss@redhat.com>
---
 ui/dbus-listener.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/ui/dbus-listener.c b/ui/dbus-listener.c
index 30917271ab..d015e8d759 100644
--- a/ui/dbus-listener.c
+++ b/ui/dbus-listener.c
@@ -26,6 +26,9 @@
 #include "qapi/error.h"
 #include "sysemu/sysemu.h"
 #include "dbus.h"
+#ifdef CONFIG_OPENGL
+#include <pixman.h>
+#endif
 #ifdef G_OS_UNIX
 #include <gio/gunixfdlist.h>
 #endif
@@ -59,12 +62,15 @@ struct _DBusDisplayListener {
 
     QemuDBusDisplay1Listener *proxy;
 
+#ifdef CONFIG_OPENGL
+    /* Keep track of the damage region */
+    pixman_region32_t gl_damage;
+#endif
+
     DisplayChangeListener dcl;
     DisplaySurface *ds;
     enum share_kind ds_share;
 
-    int gl_updates;
-
     bool ds_mapped;
     bool can_share_map;
 
@@ -539,11 +545,16 @@ static void dbus_gl_refresh(DisplayChangeListener *dcl)
         return;
     }
 
-    if (ddl->gl_updates) {
-        dbus_call_update_gl(dcl, 0, 0,
-                            surface_width(ddl->ds), surface_height(ddl->ds));
-        ddl->gl_updates = 0;
+    int n_rects = pixman_region32_n_rects(&ddl->gl_damage);
+
+    for (int i = 0; i < n_rects; i++) {
+        pixman_box32_t *box;
+        box = pixman_region32_rectangles(&ddl->gl_damage, NULL) + i;
+
+        dbus_call_update_gl(dcl, box->x1, box->y1,
+                            box->x2 - box->x1, box->y2 - box->y1);
     }
+    pixman_region32_clear(&ddl->gl_damage);
 }
 #endif /* OPENGL */
 
@@ -558,7 +569,10 @@ static void dbus_gl_gfx_update(DisplayChangeListener *dcl,
 {
     DBusDisplayListener *ddl = container_of(dcl, DBusDisplayListener, dcl);
 
-    ddl->gl_updates++;
+    pixman_region32_t rect_region;
+    pixman_region32_init_rect(&rect_region, x, y, w, h);
+    pixman_region32_union(&ddl->gl_damage, &ddl->gl_damage, &rect_region);
+    pixman_region32_fini(&rect_region);
 }
 #endif
 
@@ -933,7 +947,9 @@ dbus_display_listener_new(const char *bus_name,
         g_object_unref(ddl);
         return NULL;
     }
-
+#ifdef CONFIG_OPENGL
+    pixman_region32_init(&ddl->gl_damage);
+#endif
     ddl->bus_name = g_strdup(bus_name);
     ddl->conn = conn;
     ddl->console = console;
-- 
2.41.0