[mutter/gbsneto/dmabuf-screencast: 1/8] cogl: Add cogl_framebuffer_flush

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 6b9f019d92bcf1f0b74a61d07daba4d09da20926
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Feb 24 12:44:52 2020 -0300

    cogl: Add cogl_framebuffer_flush
    
    In future patches, we'll create additional CoglFramebuffers that
    will be shared via DMA-Buf with PipeWire. When recording frames,
    we'll blit the current onscreen framebuffer into the shared one.
    
    However, that presents a problem: cogl_framebuffer_blit() mimics
    glBlitFramebuffer() semantics, and doesn't do an implicit flush
    of the GPU command stream. As a consequence, clients may receive
    unblitted or incomplete framebuffers.
    
    We could use cogl_framebuffer_finish() to ensure the commands were
    submitted to the GPU, but it is too harsh -- it blocks the CPU
    completely until the commands are finished!
    
    Add cogl_framebuffer_flush(), which ensures the command stream is
    submitted to the GPU without blocking the CPU.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1086

 cogl/cogl/cogl-driver.h                             |  3 +++
 cogl/cogl/cogl-framebuffer.c                        | 11 +++++++++++
 cogl/cogl/cogl-framebuffer.h                        | 12 ++++++++++++
 cogl/cogl/driver/gl/cogl-framebuffer-gl-private.h   |  3 +++
 cogl/cogl/driver/gl/cogl-framebuffer-gl.c           |  6 ++++++
 cogl/cogl/driver/gl/gl/cogl-driver-gl.c             |  1 +
 cogl/cogl/driver/gl/gles/cogl-driver-gles.c         |  1 +
 cogl/cogl/driver/nop/cogl-driver-nop.c              |  1 +
 cogl/cogl/driver/nop/cogl-framebuffer-nop-private.h |  3 +++
 cogl/cogl/driver/nop/cogl-framebuffer-nop.c         |  5 +++++
 10 files changed, 46 insertions(+)
---
diff --git a/cogl/cogl/cogl-driver.h b/cogl/cogl/cogl-driver.h
index f9b779fa7..9d0bc1b99 100644
--- a/cogl/cogl/cogl-driver.h
+++ b/cogl/cogl/cogl-driver.h
@@ -93,6 +93,9 @@ struct _CoglDriverVtable
   void
   (* framebuffer_finish) (CoglFramebuffer *framebuffer);
 
+  void
+  (* framebuffer_flush) (CoglFramebuffer *framebuffer);
+
   void
   (* framebuffer_discard_buffers) (CoglFramebuffer *framebuffer,
                                    unsigned long buffers);
diff --git a/cogl/cogl/cogl-framebuffer.c b/cogl/cogl/cogl-framebuffer.c
index d10ae5cc5..6edb7f042 100644
--- a/cogl/cogl/cogl-framebuffer.c
+++ b/cogl/cogl/cogl-framebuffer.c
@@ -1396,6 +1396,17 @@ cogl_framebuffer_finish (CoglFramebuffer *framebuffer)
   ctx->driver_vtable->framebuffer_finish (framebuffer);
 }
 
+void
+cogl_framebuffer_flush (CoglFramebuffer *framebuffer)
+{
+
+  CoglContext *ctx = framebuffer->context;
+
+  _cogl_framebuffer_flush_journal (framebuffer);
+
+  ctx->driver_vtable->framebuffer_flush (framebuffer);
+}
+
 void
 cogl_framebuffer_push_matrix (CoglFramebuffer *framebuffer)
 {
diff --git a/cogl/cogl/cogl-framebuffer.h b/cogl/cogl/cogl-framebuffer.h
index 2046d459d..eef5089b0 100644
--- a/cogl/cogl/cogl-framebuffer.h
+++ b/cogl/cogl/cogl-framebuffer.h
@@ -1555,6 +1555,18 @@ cogl_blit_framebuffer (CoglFramebuffer *src,
                        int height,
                        GError **error);
 
+/**
+ * cogl_framebuffer_flush:
+ * @framebuffer: A #CoglFramebuffer pointer
+ *
+ * Flushes @framebuffer to ensure the current batch of commands is
+ * submitted to the GPU.
+ *
+ * Unlike cogl_framebuffer_finish(), this does not block the CPU.
+ */
+void
+cogl_framebuffer_flush (CoglFramebuffer *framebuffer);
+
 G_END_DECLS
 
 #endif /* __COGL_FRAMEBUFFER_H */
diff --git a/cogl/cogl/driver/gl/cogl-framebuffer-gl-private.h 
b/cogl/cogl/driver/gl/cogl-framebuffer-gl-private.h
index 57c146b39..3e9333a24 100644
--- a/cogl/cogl/driver/gl/cogl-framebuffer-gl-private.h
+++ b/cogl/cogl/driver/gl/cogl-framebuffer-gl-private.h
@@ -61,6 +61,9 @@ _cogl_framebuffer_gl_query_bits (CoglFramebuffer *framebuffer,
 void
 _cogl_framebuffer_gl_finish (CoglFramebuffer *framebuffer);
 
+void
+_cogl_framebuffer_gl_flush (CoglFramebuffer *framebuffer);
+
 void
 _cogl_framebuffer_gl_discard_buffers (CoglFramebuffer *framebuffer,
                                       unsigned long buffers);
diff --git a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
index 4eb914052..2848d7183 100644
--- a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
+++ b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
@@ -1031,6 +1031,12 @@ _cogl_framebuffer_gl_finish (CoglFramebuffer *framebuffer)
   GE (framebuffer->context, glFinish ());
 }
 
+void
+_cogl_framebuffer_gl_flush (CoglFramebuffer *framebuffer)
+{
+  GE (framebuffer->context, glFlush ());
+}
+
 void
 _cogl_framebuffer_gl_discard_buffers (CoglFramebuffer *framebuffer,
                                       unsigned long buffers)
diff --git a/cogl/cogl/driver/gl/gl/cogl-driver-gl.c b/cogl/cogl/driver/gl/gl/cogl-driver-gl.c
index 8b3ff64e2..f1b748118 100644
--- a/cogl/cogl/driver/gl/gl/cogl-driver-gl.c
+++ b/cogl/cogl/driver/gl/gl/cogl-driver-gl.c
@@ -554,6 +554,7 @@ _cogl_driver_gl =
     _cogl_framebuffer_gl_clear,
     _cogl_framebuffer_gl_query_bits,
     _cogl_framebuffer_gl_finish,
+    _cogl_framebuffer_gl_flush,
     _cogl_framebuffer_gl_discard_buffers,
     _cogl_framebuffer_gl_draw_attributes,
     _cogl_framebuffer_gl_draw_indexed_attributes,
diff --git a/cogl/cogl/driver/gl/gles/cogl-driver-gles.c b/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
index 2f98b3bd8..e0c8ca1fa 100644
--- a/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
+++ b/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
@@ -403,6 +403,7 @@ _cogl_driver_gles =
     _cogl_framebuffer_gl_clear,
     _cogl_framebuffer_gl_query_bits,
     _cogl_framebuffer_gl_finish,
+    _cogl_framebuffer_gl_flush,
     _cogl_framebuffer_gl_discard_buffers,
     _cogl_framebuffer_gl_draw_attributes,
     _cogl_framebuffer_gl_draw_indexed_attributes,
diff --git a/cogl/cogl/driver/nop/cogl-driver-nop.c b/cogl/cogl/driver/nop/cogl-driver-nop.c
index 4fffd3686..7802803e2 100644
--- a/cogl/cogl/driver/nop/cogl-driver-nop.c
+++ b/cogl/cogl/driver/nop/cogl-driver-nop.c
@@ -78,6 +78,7 @@ _cogl_driver_nop =
     _cogl_framebuffer_nop_clear,
     _cogl_framebuffer_nop_query_bits,
     _cogl_framebuffer_nop_finish,
+    _cogl_framebuffer_nop_flush,
     _cogl_framebuffer_nop_discard_buffers,
     _cogl_framebuffer_nop_draw_attributes,
     _cogl_framebuffer_nop_draw_indexed_attributes,
diff --git a/cogl/cogl/driver/nop/cogl-framebuffer-nop-private.h 
b/cogl/cogl/driver/nop/cogl-framebuffer-nop-private.h
index c04da9d6a..95b636517 100644
--- a/cogl/cogl/driver/nop/cogl-framebuffer-nop-private.h
+++ b/cogl/cogl/driver/nop/cogl-framebuffer-nop-private.h
@@ -64,6 +64,9 @@ _cogl_framebuffer_nop_query_bits (CoglFramebuffer *framebuffer,
 void
 _cogl_framebuffer_nop_finish (CoglFramebuffer *framebuffer);
 
+void
+_cogl_framebuffer_nop_flush (CoglFramebuffer *framebuffer);
+
 void
 _cogl_framebuffer_nop_discard_buffers (CoglFramebuffer *framebuffer,
                                        unsigned long buffers);
diff --git a/cogl/cogl/driver/nop/cogl-framebuffer-nop.c b/cogl/cogl/driver/nop/cogl-framebuffer-nop.c
index f94bab641..f9db69c91 100644
--- a/cogl/cogl/driver/nop/cogl-framebuffer-nop.c
+++ b/cogl/cogl/driver/nop/cogl-framebuffer-nop.c
@@ -76,6 +76,11 @@ _cogl_framebuffer_nop_finish (CoglFramebuffer *framebuffer)
 {
 }
 
+void
+_cogl_framebuffer_nop_flush (CoglFramebuffer *framebuffer)
+{
+}
+
 void
 _cogl_framebuffer_nop_discard_buffers (CoglFramebuffer *framebuffer,
                                        unsigned long buffers)