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, 23 insertions, 0 deletions

diff --git a/libmpv/opengl_cb.h b/libmpv/opengl_cb.h
index 8751ca01e0..6500b4ef65 100644
--- a/libmpv/opengl_cb.h
+++ b/libmpv/opengl_cb.h
@@ -190,6 +190,29 @@ extern "C" {
  * In previous libmpv releases, this used "GL_MP_D3D_interfaces" and
  * "glMPGetD3DInterface". This is deprecated; use glMPGetNativeDisplay instead
  * (the semantics are 100% compatible).
+ *
+ * Windowing system interop on RPI
+ * -------------------------------
+ *
+ * The RPI uses no proper interop, but hardware overlays instead. To place the
+ * overlay correctly, you can communicate the window parameters as follows to
+ * libmpv. gl->MPGetNativeDisplay("MPV_RPI_WINDOW") return an array of type int
+ * with the following 4 elements:
+ *      0: display number (default 0)
+ *      1: layer number of the GL layer - video will be placed in the layer
+ *         directly below (default: 0)
+ *      2: absolute x position of the GL context (default: 0)
+ *      3: absolute y position of the GL context (default: 0)
+ * The (x,y) position must be the absolute screen pixel position of the
+ * top/left pixel of the dispmanx layer used for the GL context. If you render
+ * to a FBO, the position must be that of the final position of the FBO
+ * contents on screen. You can't transform or scale the video other than what
+ * mpv will render to the video overlay. The defaults are suitable for
+ * rendering the video at fullscreen.
+ * The parameters are checked on every draw by calling MPGetNativeDisplay and
+ * checking the values in the returned array for changes. The returned array
+ * must remain valid until the libmpv render function returns; then it can be
+ * deallocated by the API user.
  */
 
 /**