From 2a94a2b119a9efd2cd06ded03280872c81abe6b4 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sun, 11 Apr 2021 15:01:05 +0200
Subject: [PATCH] Remove video_buffer callbacks

Now that screen is both the owner and the listener of the video buffer,
execute the code directly without callbacks.
---
 app/src/screen.c       | 49 ++++++++++++++++++------------------------
 app/src/video_buffer.c | 31 +++++---------------------
 app/src/video_buffer.h | 20 +----------------
 3 files changed, 27 insertions(+), 73 deletions(-)

diff --git a/app/src/screen.c b/app/src/screen.c
index c067ab7a..ddf81b08 100644
--- a/app/src/screen.c
+++ b/app/src/screen.c
@@ -193,27 +193,6 @@ screen_update_content_rect(struct screen *screen) {
     }
 }
 
-static void
-on_frame_available(struct video_buffer *vb, void *userdata) {
-    (void) vb;
-    (void) userdata;
-
-    static SDL_Event new_frame_event = {
-        .type = EVENT_NEW_FRAME,
-    };
-
-    // Post the event on the UI thread
-    SDL_PushEvent(&new_frame_event);
-}
-
-static void
-on_frame_skipped(struct video_buffer *vb, void *userdata) {
-    (void) vb;
-
-    struct screen *screen = userdata;
-    fps_counter_add_skipped_frame(screen->fps_counter);
-}
-
 static inline SDL_Texture *
 create_texture(struct screen *screen) {
     SDL_Renderer *renderer = screen->renderer;
@@ -284,7 +263,27 @@ screen_frame_sink_close(struct sc_frame_sink *sink) {
 static bool
 screen_frame_sink_push(struct sc_frame_sink *sink, const AVFrame *frame) {
     struct screen *screen = DOWNCAST(sink);
-    return video_buffer_push(&screen->vb, frame);
+
+    bool previous_frame_skipped;
+    bool ok = video_buffer_push(&screen->vb, frame, &previous_frame_skipped);
+    if (!ok) {
+        return false;
+    }
+
+    if (previous_frame_skipped) {
+        fps_counter_add_skipped_frame(screen->fps_counter);
+        // The EVENT_NEW_FRAME triggered for the previous frame will consume
+        // this new frame instead
+    } else {
+        static SDL_Event new_frame_event = {
+            .type = EVENT_NEW_FRAME,
+        };
+
+        // Post the event on the UI thread
+        SDL_PushEvent(&new_frame_event);
+    }
+
+    return true;
 }
 
 bool
@@ -303,12 +302,6 @@ screen_init(struct screen *screen, struct fps_counter *fps_counter,
         return false;
     }
 
-    static const struct video_buffer_callbacks cbs = {
-        .on_frame_available = on_frame_available,
-        .on_frame_skipped = on_frame_skipped,
-    };
-    video_buffer_set_consumer_callbacks(&screen->vb, &cbs, screen);
-
     screen->frame_size = params->frame_size;
     screen->rotation = params->rotation;
     if (screen->rotation) {
diff --git a/app/src/video_buffer.c b/app/src/video_buffer.c
index 18a180fa..7adf098b 100644
--- a/app/src/video_buffer.c
+++ b/app/src/video_buffer.c
@@ -29,10 +29,6 @@ video_buffer_init(struct video_buffer *vb) {
     // there is initially no frame, so consider it has already been consumed
     vb->pending_frame_consumed = true;
 
-    // The callbacks must be set by the consumer via
-    // video_buffer_set_consumer_callbacks()
-    vb->cbs = NULL;
-
     return true;
 }
 
@@ -50,21 +46,9 @@ swap_frames(AVFrame **lhs, AVFrame **rhs) {
     *rhs = tmp;
 }
 
-void
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
-                                    const struct video_buffer_callbacks *cbs,
-                                    void *cbs_userdata) {
-    assert(!vb->cbs); // must be set only once
-    assert(cbs);
-    assert(cbs->on_frame_available);
-    vb->cbs = cbs;
-    vb->cbs_userdata = cbs_userdata;
-}
-
 bool
-video_buffer_push(struct video_buffer *vb, const AVFrame *frame) {
-    assert(vb->cbs);
-
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame,
+                  bool *previous_frame_skipped) {
     sc_mutex_lock(&vb->mutex);
 
     // Use a temporary frame to preserve pending_frame in case of error.
@@ -80,18 +64,13 @@ video_buffer_push(struct video_buffer *vb, const AVFrame *frame) {
     swap_frames(&vb->pending_frame, &vb->tmp_frame);
     av_frame_unref(vb->tmp_frame);
 
-    bool skipped = !vb->pending_frame_consumed;
+    if (previous_frame_skipped) {
+        *previous_frame_skipped = !vb->pending_frame_consumed;
+    }
     vb->pending_frame_consumed = false;
 
     sc_mutex_unlock(&vb->mutex);
 
-    if (skipped) {
-        if (vb->cbs->on_frame_skipped)
-            vb->cbs->on_frame_skipped(vb, vb->cbs_userdata);
-    } else {
-        vb->cbs->on_frame_available(vb, vb->cbs_userdata);
-    }
-
     return true;
 }
 
diff --git a/app/src/video_buffer.h b/app/src/video_buffer.h
index cdecb259..b9478f4c 100644
--- a/app/src/video_buffer.h
+++ b/app/src/video_buffer.h
@@ -33,19 +33,6 @@ struct video_buffer {
     sc_mutex mutex;
 
     bool pending_frame_consumed;
-
-    const struct video_buffer_callbacks *cbs;
-    void *cbs_userdata;
-};
-
-struct video_buffer_callbacks {
-    // Called when a new frame can be consumed.
-    // This callback is mandatory (it must not be NULL).
-    void (*on_frame_available)(struct video_buffer *vb, void *userdata);
-
-    // Called when a pending frame has been overwritten by the producer.
-    // This callback is optional (it may be NULL).
-    void (*on_frame_skipped)(struct video_buffer *vb, void *userdata);
 };
 
 bool
@@ -54,13 +41,8 @@ video_buffer_init(struct video_buffer *vb);
 void
 video_buffer_destroy(struct video_buffer *vb);
 
-void
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
-                                    const struct video_buffer_callbacks *cbs,
-                                    void *cbs_userdata);
-
 bool
-video_buffer_push(struct video_buffer *vb, const AVFrame *frame);
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame, bool *skipped);
 
 void
 video_buffer_consume(struct video_buffer *vb, AVFrame *dst);