[cogl] Use GL_PACK_ALIGNMENT of 1 whenever possible



commit ec5009fa23b11f9df9ffeead7bdf0de3fa12cd07
Author: Neil Roberts <neil linux intel com>
Date:   Thu Mar 22 11:40:16 2012 +0000

    Use GL_PACK_ALIGNMENT of 1 whenever possible
    
    The Intel driver currently has an optimisation when calling
    glReadPixels into a PBO so that it will use a blit instead of the Mesa
    fallback path. However this only works if the GL_PACK_ALIGNMENT is
    exactly 1, even if this would be equivalent to a higher alignment
    value because the bpp*width is already aligned. To make it more likely
    to hit this fast path, we now detect this situation and explicitly use
    an alignment of 1. To make this work the texture driver needs to be
    passed down the bpp*width as well as the rowstride when configuring
    the alignment.
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 cogl/cogl-framebuffer.c                     |   10 ++++++++--
 cogl/cogl-texture-2d.c                      |    5 ++++-
 cogl/cogl-texture-driver.h                  |    1 +
 cogl/cogl-texture-private.h                 |    4 +++-
 cogl/cogl-texture-rectangle.c               |    5 ++++-
 cogl/cogl-texture.c                         |   23 ++++++++++++++++++++---
 cogl/driver/gl/cogl-texture-driver-gl.c     |   13 +++++++++++--
 cogl/driver/gles/cogl-texture-driver-gles.c |    5 ++++-
 8 files changed, 55 insertions(+), 11 deletions(-)
---
diff --git a/cogl/cogl-framebuffer.c b/cogl/cogl-framebuffer.c
index dff08ff..b55b016 100644
--- a/cogl/cogl-framebuffer.c
+++ b/cogl/cogl-framebuffer.c
@@ -2065,7 +2065,10 @@ cogl_framebuffer_read_pixels_into_bitmap (CoglFramebuffer *framebuffer,
       bpp = _cogl_pixel_format_get_bytes_per_pixel (read_format);
       rowstride = cogl_bitmap_get_rowstride (tmp_bmp);
 
-      ctx->texture_driver->prep_gl_for_pixels_download (ctx, rowstride, bpp);
+      ctx->texture_driver->prep_gl_for_pixels_download (ctx,
+                                                        rowstride,
+                                                        width,
+                                                        bpp);
 
       tmp_data = _cogl_bitmap_bind (tmp_bmp,
                                     COGL_BUFFER_ACCESS_WRITE,
@@ -2113,7 +2116,10 @@ cogl_framebuffer_read_pixels_into_bitmap (CoglFramebuffer *framebuffer,
 
       bpp = _cogl_pixel_format_get_bytes_per_pixel (bmp_format);
 
-      ctx->texture_driver->prep_gl_for_pixels_download (ctx, rowstride, bpp);
+      ctx->texture_driver->prep_gl_for_pixels_download (ctx,
+                                                        rowstride,
+                                                        width,
+                                                        bpp);
 
       pixels = _cogl_bitmap_bind (shared_bmp,
                                   COGL_BUFFER_ACCESS_WRITE,
diff --git a/cogl/cogl-texture-2d.c b/cogl/cogl-texture-2d.c
index 7328423..5e988bd 100644
--- a/cogl/cogl-texture-2d.c
+++ b/cogl/cogl-texture-2d.c
@@ -832,7 +832,10 @@ _cogl_texture_2d_get_data (CoglTexture     *tex,
                                           &gl_format,
                                           &gl_type);
 
-  ctx->texture_driver->prep_gl_for_pixels_download (ctx, rowstride, bpp);
+  ctx->texture_driver->prep_gl_for_pixels_download (ctx,
+                                                    rowstride,
+                                                    tex_2d->width,
+                                                    bpp);
 
   _cogl_bind_gl_texture_transient (GL_TEXTURE_2D,
                                    tex_2d->gl_texture,
diff --git a/cogl/cogl-texture-driver.h b/cogl/cogl-texture-driver.h
index bd48b76..56ec805 100644
--- a/cogl/cogl-texture-driver.h
+++ b/cogl/cogl-texture-driver.h
@@ -123,6 +123,7 @@ struct _CoglTextureDriver
    * this function that it uses internally. */
   void
   (* prep_gl_for_pixels_download) (CoglContext *ctx,
+                                   int image_width,
                                    int pixels_rowstride,
                                    int pixels_bpp);
 
diff --git a/cogl/cogl-texture-private.h b/cogl/cogl-texture-private.h
index 1fd6bb1..8cec89f 100644
--- a/cogl/cogl-texture-private.h
+++ b/cogl/cogl-texture-private.h
@@ -246,7 +246,9 @@ void
 _cogl_texture_prep_gl_alignment_for_pixels_upload (int pixels_rowstride);
 
 void
-_cogl_texture_prep_gl_alignment_for_pixels_download (int pixels_rowstride);
+_cogl_texture_prep_gl_alignment_for_pixels_download (int bpp,
+                                                     int width,
+                                                     int rowstride);
 
 /* Utility function to use as a fallback for getting the data of any
    texture via the framebuffer */
diff --git a/cogl/cogl-texture-rectangle.c b/cogl/cogl-texture-rectangle.c
index 3f8594f..192e0dc 100644
--- a/cogl/cogl-texture-rectangle.c
+++ b/cogl/cogl-texture-rectangle.c
@@ -561,7 +561,10 @@ _cogl_texture_rectangle_get_data (CoglTexture     *tex,
                                           &gl_format,
                                           &gl_type);
 
-  ctx->texture_driver->prep_gl_for_pixels_download (ctx, rowstride, bpp);
+  ctx->texture_driver->prep_gl_for_pixels_download (ctx,
+                                                    rowstride,
+                                                    tex_rect->width,
+                                                    bpp);
 
   _cogl_bind_gl_texture_transient (GL_TEXTURE_RECTANGLE_ARB,
                                    tex_rect->gl_texture,
diff --git a/cogl/cogl-texture.c b/cogl/cogl-texture.c
index 2617345..2948983 100644
--- a/cogl/cogl-texture.c
+++ b/cogl/cogl-texture.c
@@ -274,12 +274,29 @@ _cogl_texture_prep_gl_alignment_for_pixels_upload (int pixels_rowstride)
 }
 
 void
-_cogl_texture_prep_gl_alignment_for_pixels_download (int pixels_rowstride)
+_cogl_texture_prep_gl_alignment_for_pixels_download (int bpp,
+                                                     int width,
+                                                     int rowstride)
 {
+  int alignment;
+
   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
 
-  GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT,
-                          calculate_alignment (pixels_rowstride)) );
+  /* If no padding is needed then we can always use an alignment of 1.
+   * We want to do this even though it is equivalent to the alignment
+   * of the rowstride because the Intel driver in Mesa currently has
+   * an optimisation when reading data into a PBO that only works if
+   * the alignment is exactly 1.
+   *
+   * https://bugs.freedesktop.org/show_bug.cgi?id=46632
+   */
+
+  if (rowstride == bpp * width)
+    alignment = 1;
+  else
+    alignment = calculate_alignment (rowstride);
+
+  GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT, alignment) );
 }
 
 /* FIXME: wrap modes should be set on pipelines not textures */
diff --git a/cogl/driver/gl/cogl-texture-driver-gl.c b/cogl/driver/gl/cogl-texture-driver-gl.c
index 31f6f83..bb8c67d 100644
--- a/cogl/driver/gl/cogl-texture-driver-gl.c
+++ b/cogl/driver/gl/cogl-texture-driver-gl.c
@@ -116,6 +116,7 @@ _cogl_texture_driver_prep_gl_for_pixels_upload (CoglContext *ctx,
  * a larger destination buffer */
 static void
 prep_gl_for_pixels_download_full (CoglContext *ctx,
+                                  int image_width,
                                   int pixels_rowstride,
                                   int image_height,
                                   int pixels_src_x,
@@ -130,15 +131,23 @@ prep_gl_for_pixels_download_full (CoglContext *ctx,
   if (cogl_has_feature (ctx, COGL_FEATURE_ID_TEXTURE_3D))
     GE( ctx, glPixelStorei (GL_PACK_IMAGE_HEIGHT, image_height) );
 
-  _cogl_texture_prep_gl_alignment_for_pixels_download (pixels_rowstride);
+  _cogl_texture_prep_gl_alignment_for_pixels_download (pixels_bpp,
+                                                       image_width,
+                                                       pixels_rowstride);
 }
 
 static void
 _cogl_texture_driver_prep_gl_for_pixels_download (CoglContext *ctx,
+                                                      int image_width,
                                                   int pixels_rowstride,
                                                   int pixels_bpp)
 {
-  prep_gl_for_pixels_download_full (ctx, pixels_rowstride, 0, 0, 0, pixels_bpp);
+  prep_gl_for_pixels_download_full (ctx,
+                                    pixels_rowstride,
+                                    image_width,
+                                    0 /* image height */,
+                                    0, 0, /* pixels_src_x/y */
+                                    pixels_bpp);
 }
 
 static void
diff --git a/cogl/driver/gles/cogl-texture-driver-gles.c b/cogl/driver/gles/cogl-texture-driver-gles.c
index e6a67d6..bce772e 100644
--- a/cogl/driver/gles/cogl-texture-driver-gles.c
+++ b/cogl/driver/gles/cogl-texture-driver-gles.c
@@ -132,9 +132,12 @@ _cogl_texture_driver_prep_gl_for_pixels_upload (CoglContext *ctx,
 static void
 _cogl_texture_driver_prep_gl_for_pixels_download (CoglContext *ctx,
                                                   int pixels_rowstride,
+                                                  int image_width,
                                                   int pixels_bpp)
 {
-  _cogl_texture_prep_gl_alignment_for_pixels_download (pixels_rowstride);
+  _cogl_texture_prep_gl_alignment_for_pixels_download (pixels_bpp,
+                                                       image_width,
+                                                       pixels_rowstride);
 }
 
 static CoglBitmap *



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