vo_opengl: add ability to render to an arbitrary backing framebuffer

Most of the functionality already exists for the sake of vo_opengl_cb.
We only have to use it.

This will be used by dxinterop in the following commit.

3 files changed, 9 insertions, 1 deletions

diff --git a/video/out/opengl/common.h b/video/out/opengl/common.h
index 7427befe99..71129ac320 100644
--- a/video/out/opengl/common.h
+++ b/video/out/opengl/common.h
@@ -91,6 +91,7 @@ struct GL {
     char *extensions;           // Equivalent to GL_EXTENSIONS
     int mpgl_caps;              // Bitfield of MPGL_CAP_* constants
     bool debug_context;         // use of e.g. GLX_CONTEXT_DEBUG_BIT_ARB
+    GLuint main_fb;             // framebuffer to render to (normally 0)
 
     void (GLAPIENTRY *Viewport)(GLint, GLint, GLsizei, GLsizei);
     void (GLAPIENTRY *Clear)(GLbitfield);
diff --git a/video/out/opengl/video.c b/video/out/opengl/video.c
index 0bbc979476..6282d296cc 100644
--- a/video/out/opengl/video.c
+++ b/video/out/opengl/video.c
@@ -3342,7 +3342,12 @@ static void init_gl(struct gl_video *p)
     }
 
     if ((gl->es >= 300 || gl->version) && (gl->mpgl_caps & MPGL_CAP_FB)) {
+        gl->BindFramebuffer(GL_FRAMEBUFFER, gl->main_fb);
+
         GLenum obj = gl->version ? GL_BACK_LEFT : GL_BACK;
+        if (gl->main_fb)
+            obj = GL_COLOR_ATTACHMENT0;
+
         GLint depth_r = -1, depth_g = -1, depth_b = -1;
 
         gl->GetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, obj,
@@ -3356,6 +3361,8 @@ static void init_gl(struct gl_video *p)
                    depth_r, depth_g, depth_b);
 
         p->fb_depth = depth_g > 0 ? depth_g : 8;
+
+        gl->BindFramebuffer(GL_FRAMEBUFFER, 0);
     }
 
     p->upload_timer = gl_timer_create(p->gl);
diff --git a/video/out/vo_opengl.c b/video/out/vo_opengl.c
index 426236e436..08b9b11fe0 100644
--- a/video/out/vo_opengl.c
+++ b/video/out/vo_opengl.c
@@ -130,7 +130,7 @@ static void draw_frame(struct vo *vo, struct vo_frame *frame)
             p->vsync_fences[p->num_vsync_fences++] = fence;
     }
 
-    gl_video_render_frame(p->renderer, frame, 0);
+    gl_video_render_frame(p->renderer, frame, gl->main_fb);
 
     if (p->use_glFinish)
         gl->Finish();