[cogl] Convert the two SDL examples to use the frame callback

[Neil Roberts <nroberts src gnome org>]

commit 97cdd832dded2ebfaa42ee4bc43319cb8648d01b
Author: Neil Roberts <neil linux intel com>
Date:   Thu Jan 31 12:06:52 2013 +0000

    Convert the two SDL examples to use the frame callback
    
    The two SDL examples now throttle their rendering to the
    COGL_FRAME_EVENT_SYNC event. Previously the examples would redraw
    whenever a mouse motion event is received but now they additionally
    wait for the sync event which means that if another mouse event comes
    immediately after rendering the last frame it theoretically could
    avoid blocking waiting for the last frame to complete. In practice
    however the SDL winsys doesn't support swap events so it will get the
    sync event immediately anyway, but it's nice to have the code as an
    example and a test.
    
    This patch also changes the mainloop a bit to do the equivalent steps
    without the outer main loop which I think makes it a bit easier to
    follow.
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 examples/cogl-sdl-hello.c  |   52 +++++++++++++++++++++++++++++--------------
 examples/cogl-sdl2-hello.c |   52 +++++++++++++++++++++++++++++--------------
 2 files changed, 70 insertions(+), 34 deletions(-)
---
diff --git a/examples/cogl-sdl-hello.c b/examples/cogl-sdl-hello.c
index 987cc13..961137a 100644
--- a/examples/cogl-sdl-hello.c
+++ b/examples/cogl-sdl-hello.c
@@ -13,9 +13,10 @@ typedef struct Data
   CoglFramebuffer *fb;
   CoglBool quit;
   CoglBool redraw_queued;
+  CoglBool ready_to_draw;
 } Data;
 
-static CoglBool
+static void
 redraw (Data *data)
 {
   CoglFramebuffer *fb = data->fb;
@@ -29,8 +30,6 @@ redraw (Data *data)
   cogl_framebuffer_pop_matrix (fb);
 
   cogl_onscreen_swap_buffers (COGL_ONSCREEN (fb));
-
-  return FALSE;
 }
 
 static void
@@ -62,6 +61,18 @@ handle_event (Data *data, SDL_Event *event)
     }
 }
 
+static void
+frame_cb (CoglOnscreen *onscreen,
+          CoglFrameEvent event,
+          CoglFrameInfo *info,
+          void *user_data)
+{
+  Data *data = user_data;
+
+  if (event == COGL_FRAME_EVENT_SYNC)
+    data->ready_to_draw = TRUE;
+}
+
 int
 main (int argc, char **argv)
 {
@@ -86,6 +97,11 @@ main (int argc, char **argv)
   onscreen = cogl_onscreen_new (ctx, 800, 600);
   data.fb = COGL_FRAMEBUFFER (onscreen);
 
+  cogl_onscreen_add_frame_callback (onscreen,
+                                    frame_cb,
+                                    &data,
+                                    NULL /* destroy callback */);
+
   data.center_x = 0.0f;
   data.center_y = 0.0f;
   data.quit = FALSE;
@@ -97,28 +113,30 @@ main (int argc, char **argv)
   data.pipeline = cogl_pipeline_new (ctx);
 
   data.redraw_queued = TRUE;
+  data.ready_to_draw = TRUE;
+
   while (!data.quit)
     {
-      while (!data.quit)
+      if (!SDL_PollEvent (&event))
         {
-          if (!SDL_PollEvent (&event))
+          if (data.redraw_queued && data.ready_to_draw)
             {
-              if (data.redraw_queued)
-                break;
-
-              cogl_sdl_idle (ctx);
-              if (!SDL_WaitEvent (&event))
-                {
-                  fprintf (stderr, "Error waiting for SDL events");
-                  return 1;
-                }
+              redraw (&data);
+              data.redraw_queued = FALSE;
+              data.ready_to_draw = FALSE;
+              continue;
             }
 
-          handle_event (&data, &event);
-          cogl_sdl_handle_event (ctx, &event);
+          cogl_sdl_idle (ctx);
+          if (!SDL_WaitEvent (&event))
+            {
+              fprintf (stderr, "Error waiting for SDL events");
+              return 1;
+            }
         }
 
-      data.redraw_queued = redraw (&data);
+      handle_event (&data, &event);
+      cogl_sdl_handle_event (ctx, &event);
     }
 
   cogl_object_unref (ctx);
diff --git a/examples/cogl-sdl2-hello.c b/examples/cogl-sdl2-hello.c
index 0370460..405cb92 100644
--- a/examples/cogl-sdl2-hello.c
+++ b/examples/cogl-sdl2-hello.c
@@ -13,9 +13,10 @@ typedef struct Data
   CoglFramebuffer *fb;
   CoglBool quit;
   CoglBool redraw_queued;
+  CoglBool ready_to_draw;
 } Data;
 
-static CoglBool
+static void
 redraw (Data *data)
 {
   CoglFramebuffer *fb = data->fb;
@@ -29,8 +30,6 @@ redraw (Data *data)
   cogl_framebuffer_pop_matrix (fb);
 
   cogl_onscreen_swap_buffers (COGL_ONSCREEN (fb));
-
-  return FALSE;
 }
 
 static void
@@ -71,6 +70,18 @@ handle_event (Data *data, SDL_Event *event)
     }
 }
 
+static void
+frame_cb (CoglOnscreen *onscreen,
+          CoglFrameEvent event,
+          CoglFrameInfo *info,
+          void *user_data)
+{
+  Data *data = user_data;
+
+  if (event == COGL_FRAME_EVENT_SYNC)
+    data->ready_to_draw = TRUE;
+}
+
 int
 main (int argc, char **argv)
 {
@@ -95,6 +106,11 @@ main (int argc, char **argv)
   onscreen = cogl_onscreen_new (ctx, 800, 600);
   data.fb = COGL_FRAMEBUFFER (onscreen);
 
+  cogl_onscreen_add_frame_callback (onscreen,
+                                    frame_cb,
+                                    &data,
+                                    NULL /* destroy callback */);
+
   data.center_x = 0.0f;
   data.center_y = 0.0f;
   data.quit = FALSE;
@@ -110,28 +126,30 @@ main (int argc, char **argv)
   data.pipeline = cogl_pipeline_new (ctx);
 
   data.redraw_queued = TRUE;
+  data.ready_to_draw = TRUE;
+
   while (!data.quit)
     {
-      while (!data.quit)
+      if (!SDL_PollEvent (&event))
         {
-          if (!SDL_PollEvent (&event))
+          if (data.redraw_queued && data.ready_to_draw)
             {
-              if (data.redraw_queued)
-                break;
-
-              cogl_sdl_idle (ctx);
-              if (!SDL_WaitEvent (&event))
-                {
-                  fprintf (stderr, "Error waiting for SDL events");
-                  return 1;
-                }
+              redraw (&data);
+              data.redraw_queued = FALSE;
+              data.ready_to_draw = FALSE;
+              continue;
             }
 
-          handle_event (&data, &event);
-          cogl_sdl_handle_event (ctx, &event);
+          cogl_sdl_idle (ctx);
+          if (!SDL_WaitEvent (&event))
+            {
+              fprintf (stderr, "Error waiting for SDL events");
+              return 1;
+            }
         }
 
-      data.redraw_queued = redraw (&data);
+      handle_event (&data, &event);
+      cogl_sdl_handle_event (ctx, &event);
     }
 
   cogl_object_unref (ctx);