vo_opengl: add hw overlay support and use it for RPI

This overlay support specifically skips the OpenGL rendering chain, and
uses GL rendering only for OSD/subtitles. This is for devices which
don't have performant GL support.

hwdec_rpi.c contains code ported from vo_rpi.c. vo_rpi.c is going to be
deprecated. I left in the code for uploading sw surfaces (as it might
be slightly more efficient for rendering sw decoded video), although
it's dead code for now.

1 files changed, 17 insertions, 0 deletions

diff --git a/video/out/opengl/hwdec.h b/video/out/opengl/hwdec.h
index 29ccd18a42..ce59b67e58 100644
--- a/video/out/opengl/hwdec.h
+++ b/video/out/opengl/hwdec.h
@@ -16,6 +16,8 @@ struct gl_hwdec {
     void *priv;
     // For working around the vdpau vs. vaapi mess.
     bool probing;
+    // Used in overlay mode only.
+    float overlay_colorkey[4];
 };
 
 struct gl_hwdec_plane {
@@ -53,6 +55,21 @@ struct gl_hwdec_driver {
     void (*unmap)(struct gl_hwdec *hw);
 
     void (*destroy)(struct gl_hwdec *hw);
+
+    // The following functions provide an alternative API. Each gl_hwdec_driver
+    // must have either map_frame or overlay_frame set (not both or none), and
+    // if overlay_frame is set, it operates in overlay mode. In this mode,
+    // OSD etc. is rendered via OpenGL, but the video is rendered as a separate
+    // layer below it.
+    // Non-overlay mode is strictly preferred, so try not to use overlay mode.
+
+    // Set the given frame as overlay, replacing the previous one.
+    // hw_image==NULL is passed to clear the overlay.
+    int (*overlay_frame)(struct gl_hwdec *hw, struct mp_image *hw_image);
+
+    // Move overlay position within the "window".
+    void (*overlay_adjust)(struct gl_hwdec *hw, int w, int h,
+                           struct mp_rect *src, struct mp_rect *dst);
 };
 
 struct gl_hwdec *gl_hwdec_load_api(struct mp_log *log, GL *gl,