vo_opengl: do not block on wayland

When not receiving frame callbacks, we should not draw anything to avoid
blocking the OpenGL renderer. We do this by extending gl context api, by
introducing new optional function 'is_active', that indicates whether
OpenGL renderers should draw or not.

This fixes issue #249.

video/out/gl_common.h

@@ -109,6 +109,10 @@ typedef struct MPGLContext {
     void (*register_resize_callback)(struct vo *vo,
                                      void (*cb)(struct vo *vo, int w, int h));
 
+    // Optional activity state of context.
+    // If false, OpenGL renderers should not draw anything.
+    bool (*is_active)(struct MPGLContext *);
+
     // For free use by the backend.
     void *priv;
 } MPGLContext;

video/out/gl_video.c

@@ -1976,6 +1976,13 @@ static bool get_image(struct gl_video *p, struct mp_image *mpi)
     return true;
 }
 
+void gl_video_skip_image(struct gl_video *p, struct mp_image *mpi)
+{
+    struct video_image *vimg = &p->image;
+    talloc_free(vimg->mpi);
+    vimg->mpi = mpi;
+}
+
 void gl_video_upload_image(struct gl_video *p, struct mp_image *mpi)
 {
     GL *gl = p->gl;

video/out/gl_video.h

@@ -73,6 +73,7 @@ bool gl_video_check_format(struct gl_video *p, int mp_format);
 void gl_video_config(struct gl_video *p, struct mp_image_params *params);
 void gl_video_set_output_depth(struct gl_video *p, int r, int g, int b);
 void gl_video_set_lut3d(struct gl_video *p, struct lut3d *lut3d);
+void gl_video_skip_image(struct gl_video *p, struct mp_image *mpi);
 void gl_video_upload_image(struct gl_video *p, struct mp_image *img);
 void gl_video_render_frame(struct gl_video *p, int fbo, struct frame_timing *t);
 void gl_video_resize(struct gl_video *p, int vp_w, int vp_h,

video/out/gl_wayland.c

@@ -215,6 +215,12 @@ static int control(struct vo *vo, int *events, int request, void *data)
     return r;
 }
 
+static bool is_active(struct MPGLContext *ctx)
+{
+    struct vo_wayland_state *wl = ctx->vo->wayland;
+    return wl->frame.pending;
+}
+
 void mpgl_set_backend_wayland(MPGLContext *ctx)
 {
     ctx->config_window = config_window_wayland;
@@ -223,4 +229,5 @@ void mpgl_set_backend_wayland(MPGLContext *ctx)
     ctx->vo_control = control;
     ctx->vo_init = vo_wayland_init;
     ctx->vo_uninit = vo_wayland_uninit;
+    ctx->is_active = is_active;
 }

video/out/vo_opengl.c

@@ -122,6 +122,9 @@ static void flip_page(struct vo *vo)
     struct gl_priv *p = vo->priv;
     GL *gl = p->gl;
 
+    if (p->glctx->is_active && !p->glctx->is_active(p->glctx))
+        return;
+
     mpgl_lock(p->glctx);
 
     p->glctx->swapGlBuffers(p->glctx);
@@ -160,6 +163,12 @@ static void draw_image_timed(struct vo *vo, mp_image_t *mpi,
     struct gl_priv *p = vo->priv;
     GL *gl = p->gl;
 
+    if (p->glctx->is_active && !p->glctx->is_active(p->glctx)) {
+        if (mpi)
+            gl_video_skip_image(p->renderer, mpi);
+        return;
+    }
+
     if (p->vo_flipped)
         mp_image_vflip(mpi);
 
@@ -376,6 +385,9 @@ static int control(struct vo *vo, uint32_t request, void *data)
         request_hwdec_api(p, data);
         return true;
     case VOCTRL_REDRAW_FRAME:
+        if (p->glctx->is_active && !p->glctx->is_active(p->glctx))
+            return true;
+
         mpgl_lock(p->glctx);
         gl_video_render_frame(p->renderer, 0, NULL);
         mpgl_unlock(p->glctx);