[PATCH xserver v2 20/22] xwayland: Add fallback timer for msc counting

[Roman Gilg]

When the compositor is not sending frame callbacks while we still wait
on buffer release events fake a continuous msc counter with a timer.

Having this timer is a prerequisite for queuing events.

Signed-off-by: Roman Gilg <subdiff at gmail.com>
---
 hw/xwayland/xwayland-present.c | 70 ++++++++++++++++++++++++++++++++++++++++++
 hw/xwayland/xwayland.h         |  3 ++
 2 files changed, 73 insertions(+)

diff --git a/hw/xwayland/xwayland-present.c b/hw/xwayland/xwayland-present.c
index 2798c2a..3088f03 100644
--- a/hw/xwayland/xwayland-present.c
+++ b/hw/xwayland/xwayland-present.c
@@ -27,6 +27,34 @@
 
 #include <present.h>
 
+#define TIMER_LEN_FLIP    1000  // 1fps
+
+static void
+xwl_present_free_timer(struct xwl_window *xwl_window)
+{
+    TimerFree(xwl_window->present_timer);
+    xwl_window->present_timer = NULL;
+}
+
+static CARD32
+xwl_present_timer_callback(OsTimerPtr timer,
+                           CARD32 time,
+                           void *arg);
+
+static void
+xwl_present_reset_timer(struct xwl_window *xwl_window)
+{
+    if ( !xorg_list_is_empty(&xwl_window->present_release_queue) ) {
+        xwl_window->present_timer = TimerSet(xwl_window->present_timer,
+                                             0,
+                                             TIMER_LEN_FLIP,
+                                             &xwl_present_timer_callback,
+                                             xwl_window);
+    } else {
+        xwl_present_free_timer(xwl_window);
+    }
+}
+
 void
 xwl_present_cleanup(WindowPtr window)
 {
@@ -51,6 +79,10 @@ xwl_present_cleanup(WindowPtr window)
             event->abort = TRUE;
         }
     }
+
+    /* Clear timer */
+    if ( xorg_list_is_empty(&xwl_window->present_release_queue) )
+        xwl_present_free_timer(xwl_window);
 }
 
 static void
@@ -90,6 +122,27 @@ static const struct wl_buffer_listener xwl_present_release_listener = {
     xwl_present_buffer_release
 };
 
+CARD32
+xwl_present_timer_callback(OsTimerPtr timer,
+                           CARD32 time,
+                           void *arg)
+{
+    struct xwl_window *xwl_window = arg;
+
+    xwl_window->present_timer_firing = TRUE;
+    xwl_window->present_msc++;
+    xwl_window->present_ust = GetTimeInMicros();
+
+    if ( !xorg_list_is_empty(&xwl_window->present_release_queue) ) {
+        /* Still events, restart timer */
+        return TIMER_LEN_FLIP;
+    } else {
+        /* No more events, do not restart timer and delete it instead */
+        xwl_present_free_timer(xwl_window);
+        return 0;
+    }
+}
+
 static void
 xwl_present_frame_callback(void *data,
                struct wl_callback *callback,
@@ -100,8 +153,18 @@ xwl_present_frame_callback(void *data,
     wl_callback_destroy(xwl_window->present_frame_callback);
     xwl_window->present_frame_callback = NULL;
 
+    if (xwl_window->present_timer_firing) {
+        /* If the timer is firing, this frame callback is too late */
+        return;
+    }
+
     xwl_window->present_msc++;
     xwl_window->present_ust = GetTimeInMicros();
+
+    /* we do not need the timer anymore for this frame,
+     * reset it for potentially the next one
+     */
+    xwl_present_reset_timer(xwl_window);
 }
 
 static const struct wl_callback_listener xwl_present_frame_listener = {
@@ -307,6 +370,13 @@ xwl_present_flip(WindowPtr present_window,
     /* We can flip directly to the main surface (full screen window without clips) */
     wl_surface_attach(xwl_window->surface, buffer, 0, 0);
 
+    if (!xwl_window->present_timer ||
+            xwl_window->present_timer_firing) {
+        /* Realign timer */
+        xwl_window->present_timer_firing = FALSE;
+        xwl_present_reset_timer(xwl_window);
+    }
+
     if (!xwl_window->present_frame_callback) {
         xwl_window->present_frame_callback = wl_surface_frame(xwl_window->surface);
         wl_callback_add_listener(xwl_window->present_frame_callback,
diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
index a41c8ca..a64498a 100644
--- a/hw/xwayland/xwayland.h
+++ b/hw/xwayland/xwayland.h
@@ -124,6 +124,9 @@ struct xwl_window {
     uint64_t present_msc;
     uint64_t present_ust;
 
+    OsTimerPtr present_timer;
+    Bool present_timer_firing;
+
     struct wl_callback *present_frame_callback;
     struct wl_callback *present_sync_callback;
     struct xorg_list present_release_queue;
-- 
2.7.4