From e4b2234d9918e9d3357ac3c7ca3898599725d3da Mon Sep 17 00:00:00 2001

From: Pekka Paalanen <pekka.paalanen@collabora.com>

Date: Mon, 6 May 2019 15:08:29 +0300

Subject: [PATCH 05/12] cogl: Allow glBlitFramebuffer between

 onscreen/offscreen

Depends on "cogl: Replace ANGLE with GLES3 and NV framebuffer_blit"

Allow blitting between onscreen and offscreen framebuffers by doing the y-flip

as necessary. This was not possible with ANGLE, but now with ANGLE gone,

glBlitFramebuffer supports flipping the copied image.

This will be useful in follow-up work to copy from onscreen primary GPU

framebuffer to an offscreen secondary GPU framebuffer.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/615

(cherry picked from commit 45289b3d65e308117f1bc8fe6a4c88c1baaacca7)

---

 cogl/cogl/cogl-framebuffer-private.h      | 14 +++----

 cogl/cogl/cogl-framebuffer.c              | 46 ++++++++++++++++++-----

 cogl/cogl/driver/gl/cogl-framebuffer-gl.c |  5 +--

 3 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/cogl/cogl/cogl-framebuffer-private.h b/cogl/cogl/cogl-framebuffer-private.h

index b06fbaee1..f68153d8b 100644

--- a/cogl/cogl/cogl-framebuffer-private.h

+++ b/cogl/cogl/cogl-framebuffer-private.h

@@ -381,7 +381,11 @@ _cogl_push_framebuffers (CoglFramebuffer *draw_buffer,

  * This blits a region of the color buffer of the source buffer

  * to the destination buffer. This function should only be

  * called if the COGL_PRIVATE_FEATURE_OFFSCREEN_BLIT feature is

- * advertised. The two buffers must both be offscreen.

+ * advertised.

+ *

+ * The source and destination rectangles are defined in offscreen

+ * framebuffer orientation. When copying between an offscreen and

+ * onscreen framebuffers, the image is y-flipped accordingly.

  *

  * The two buffers must have the same value types (e.g. floating-point,

  * unsigned int, signed int, or fixed-point), but color formats do not

@@ -396,14 +400,6 @@ _cogl_push_framebuffers (CoglFramebuffer *draw_buffer,

  * scale the results it may make more sense to draw a primitive

  * instead.

  *

- * We can only really support blitting between two offscreen buffers

- * for this function on GLES2.0. This is because we effectively render

- * upside down to offscreen buffers to maintain Cogl's representation

- * of the texture coordinate system where 0,0 is the top left of the

- * texture. If we were to blit from an offscreen to an onscreen buffer

- * then we would need to mirror the blit along the x-axis but the GLES

- * extension does not support this.

- *

  * The GL function is documented to be affected by the scissor. This

  * function therefore ensure that an empty clip stack is flushed

  * before performing the blit which means the scissor is effectively

diff --git a/cogl/cogl/cogl-framebuffer.c b/cogl/cogl/cogl-framebuffer.c

index 0bc225945..90976a611 100644

--- a/cogl/cogl/cogl-framebuffer.c

+++ b/cogl/cogl/cogl-framebuffer.c

@@ -1460,15 +1460,12 @@ _cogl_blit_framebuffer (CoglFramebuffer *src,

                         int height)

 {

   CoglContext *ctx = src->context;

+  int src_x1, src_y1, src_x2, src_y2;

+  int dst_x1, dst_y1, dst_x2, dst_y2;

   _COGL_RETURN_IF_FAIL (_cogl_has_private_feature

                         (ctx, COGL_PRIVATE_FEATURE_OFFSCREEN_BLIT));

-  /* We can only support blitting between offscreen buffers because

-     otherwise we would need to mirror the image and GLES2.0 doesn't

-     support this */

-  _COGL_RETURN_IF_FAIL (cogl_is_offscreen (src));

-  _COGL_RETURN_IF_FAIL (cogl_is_offscreen (dest));

   /* The buffers must use the same premult convention */

   _COGL_RETURN_IF_FAIL ((src->internal_format & COGL_PREMULT_BIT) ==

                         (dest->internal_format & COGL_PREMULT_BIT));

@@ -1492,10 +1489,41 @@ _cogl_blit_framebuffer (CoglFramebuffer *src,

    * as changed */

   ctx->current_draw_buffer_changes |= COGL_FRAMEBUFFER_STATE_CLIP;

-  ctx->glBlitFramebuffer (src_x, src_y,

-                          src_x + width, src_y + height,

-                          dst_x, dst_y,

-                          dst_x + width, dst_y + height,

+  /* Offscreens we do the normal way, onscreens need an y-flip. Even if

+   * we consider offscreens to be rendered upside-down, the offscreen

+   * orientation is in this function's API. */

+  if (cogl_is_offscreen (src))

+    {

+      src_x1 = src_x;

+      src_y1 = src_y;

+      src_x2 = src_x + width;

+      src_y2 = src_y + height;

+    }

+  else

+    {

+      src_x1 = src_x;

+      src_y1 = cogl_framebuffer_get_height (src) - src_y;

+      src_x2 = src_x + width;

+      src_y2 = src_y1 - height;

+    }

+

+  if (cogl_is_offscreen (dest))

+    {

+      dst_x1 = dst_x;

+      dst_y1 = dst_y;

+      dst_x2 = dst_x + width;

+      dst_y2 = dst_y + height;

+    }

+  else

+    {

+      dst_x1 = dst_x;

+      dst_y1 = cogl_framebuffer_get_height (dest) - dst_y;

+      dst_x2 = dst_x + width;

+      dst_y2 = dst_y1 - height;

+    }

+

+  ctx->glBlitFramebuffer (src_x1, src_y1, src_x2, src_y2,

+                          dst_x1, dst_y1, dst_x2, dst_y2,

                           GL_COLOR_BUFFER_BIT,

                           GL_NEAREST);

 }

diff --git a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c

index 5402a7075..83e1d263a 100644

--- a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c

+++ b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c

@@ -400,12 +400,9 @@ _cogl_framebuffer_gl_flush_state (CoglFramebuffer *draw_buffer,

       else

         {

           /* NB: Currently we only take advantage of binding separate

-           * read/write buffers for offscreen framebuffer blit

-           * purposes.  */

+           * read/write buffers for framebuffer blit purposes. */

           _COGL_RETURN_IF_FAIL (_cogl_has_private_feature

                                 (ctx, COGL_PRIVATE_FEATURE_OFFSCREEN_BLIT));

-          _COGL_RETURN_IF_FAIL (draw_buffer->type == COGL_FRAMEBUFFER_TYPE_OFFSCREEN);

-          _COGL_RETURN_IF_FAIL (read_buffer->type == COGL_FRAMEBUFFER_TYPE_OFFSCREEN);

           _cogl_framebuffer_gl_bind (draw_buffer, GL_DRAW_FRAMEBUFFER);

           _cogl_framebuffer_gl_bind (read_buffer, GL_READ_FRAMEBUFFER);

-- 

2.21.0