From 6b5d7f45cb142b95ee5225ddc25e57502ae5b7d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>
Date: Tue, 20 Oct 2020 11:57:34 +0200
Subject: [PATCH] cogl/gl-framebuffer: Check Y-flipped-ness instead of
 framebuffer type

In a few places coordinates were flipped if driven framebuffer was or
wasn't a CoglOffscreen. Change this to use the existing Y-flipped-ness
class vfunc.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1514>
---
 cogl/cogl/cogl-framebuffer-private.h      | 10 ++++++++++
 cogl/cogl/cogl-framebuffer.c              |  2 +-
 cogl/cogl/driver/gl/cogl-framebuffer-gl.c | 20 ++++++--------------
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/cogl/cogl/cogl-framebuffer-private.h b/cogl/cogl/cogl-framebuffer-private.h
index 0c9af2d92..f4edadd89 100644
--- a/cogl/cogl/cogl-framebuffer-private.h
+++ b/cogl/cogl/cogl-framebuffer-private.h
@@ -310,4 +310,14 @@ cogl_framebuffer_get_journal (CoglFramebuffer *framebuffer);
 CoglFramebufferDriver *
 cogl_framebuffer_get_driver (CoglFramebuffer *framebuffer);
 
+/**
+ * cogl_framebuffer_is_y_flipped:
+ * @framebuffer: a #CoglFramebuffer
+ *
+ * Returns %TRUE if the Y coordinate 0 means the bottom of the framebuffer, and
+ * %FALSE if the Y coordinate means the top.
+ */
+gboolean
+cogl_framebuffer_is_y_flipped (CoglFramebuffer *framebuffer);
+
 #endif /* __COGL_FRAMEBUFFER_PRIVATE_H */
diff --git a/cogl/cogl/cogl-framebuffer.c b/cogl/cogl/cogl-framebuffer.c
index 41194829c..16324a0ad 100644
--- a/cogl/cogl/cogl-framebuffer.c
+++ b/cogl/cogl/cogl-framebuffer.c
@@ -1577,7 +1577,7 @@ cogl_framebuffer_read_pixels (CoglFramebuffer *framebuffer,
   return ret;
 }
 
-static gboolean
+gboolean
 cogl_framebuffer_is_y_flipped (CoglFramebuffer *framebuffer)
 {
   return COGL_FRAMEBUFFER_GET_CLASS (framebuffer)->is_y_flipped (framebuffer);
diff --git a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
index 6e807fa71..de5ed30d9 100644
--- a/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
+++ b/cogl/cogl/driver/gl/cogl-framebuffer-gl.c
@@ -77,9 +77,8 @@ cogl_gl_framebuffer_flush_viewport_state (CoglGlFramebuffer *gl_framebuffer)
   /* Convert the Cogl viewport y offset to an OpenGL viewport y offset
    * NB: OpenGL defines its window and viewport origins to be bottom
    * left, while Cogl defines them to be top left.
-   * NB: We render upside down to offscreen framebuffers so we don't
-   * need to convert the y offset in this case. */
-  if (COGL_IS_OFFSCREEN (framebuffer))
+   */
+  if (cogl_framebuffer_is_y_flipped (framebuffer))
     gl_viewport_y = viewport_y;
   else
     gl_viewport_y =
@@ -441,12 +440,9 @@ cogl_gl_framebuffer_read_pixels_into_bitmap (CoglFramebufferDriver  *driver,
                                         COGL_FRAMEBUFFER_STATE_BIND);
 
   /* The y coordinate should be given in OpenGL's coordinate system
-   * so 0 is the bottom row
-   *
-   * NB: all offscreen rendering is done upside down so no conversion
-   * is necissary in this case.
+   * so 0 is the bottom row.
    */
-  if (!COGL_IS_OFFSCREEN (framebuffer))
+  if (!cogl_framebuffer_is_y_flipped (framebuffer))
     y = framebuffer_height - y - height;
 
   required_format = ctx->driver_vtable->pixel_format_to_gl (ctx,
@@ -455,11 +451,9 @@ cogl_gl_framebuffer_read_pixels_into_bitmap (CoglFramebufferDriver  *driver,
                                                             &gl_format,
                                                             &gl_type);
 
-  /* NB: All offscreen rendering is done upside down so there is no need
-   * to flip in this case... */
   if (_cogl_has_private_feature (ctx, COGL_PRIVATE_FEATURE_MESA_PACK_INVERT) &&
       (source & COGL_READ_PIXELS_NO_FLIP) == 0 &&
-      !COGL_IS_OFFSCREEN (framebuffer))
+      !cogl_framebuffer_is_y_flipped (framebuffer))
     {
       if (ctx->driver == COGL_DRIVER_GLES2)
         gl_pack_enum = GL_PACK_REVERSE_ROW_ORDER_ANGLE;
@@ -614,9 +608,7 @@ cogl_gl_framebuffer_read_pixels_into_bitmap (CoglFramebufferDriver  *driver,
         goto EXIT;
     }
 
-  /* NB: All offscreen rendering is done upside down so there is no need
-   * to flip in this case... */
-  if (!COGL_IS_OFFSCREEN (framebuffer) &&
+  if (!cogl_framebuffer_is_y_flipped (framebuffer) &&
       (source & COGL_READ_PIXELS_NO_FLIP) == 0 &&
       !pack_invert_set)
     {