[Mesa-dev] [PATCH 2/4] mesa/readpix: Clip ReadPixels() area to the ReadBuffer's

[Nanley Chery]

From: Nanley Chery <nanley.g.chery at intel.com>

The fast path for Intel's ReadPixels() unintentionally omits clipping
the specified area to a valid one. Rather than clip in various
corner-cases, perform this operation in the API validation stage.

The bug in intel_readpixels_tiled_memcpy() showed itself when the winsys
ReadBuffer's height was smaller than the one specified by ReadPixels().
yoffset became negative, which was an invalid input for tiled_to_linear().

v2: Move clipping to validation stage (Jason)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92193
Reported-by: Marta Löfstedt <marta.lofstedt at intel.com>
Cc: "11.0 11.1" <mesa-stable at lists.freedesktop.org>
Signed-off-by: Nanley Chery <nanley.g.chery at intel.com>
---
 src/mesa/main/readpix.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/mesa/main/readpix.c b/src/mesa/main/readpix.c
index 8cdc9fe..a5b74bc 100644
--- a/src/mesa/main/readpix.c
+++ b/src/mesa/main/readpix.c
@@ -993,6 +993,7 @@ _mesa_ReadnPixelsARB( GLint x, GLint y, GLsizei width, GLsizei height,
 {
    GLenum err = GL_NO_ERROR;
    struct gl_renderbuffer *rb;
+   struct gl_pixelstore_attrib clippedPacking;
 
    GET_CURRENT_CONTEXT(ctx);
 
@@ -1094,7 +1095,9 @@ _mesa_ReadnPixelsARB( GLint x, GLint y, GLsizei width, GLsizei height,
       }
    }
 
-   if (width == 0 || height == 0)
+   /* Do all needed clipping here, so that we can forget about it later */
+   clippedPacking = ctx->Pack;
+   if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height, &clippedPacking))
       return; /* nothing to do */
 
    if (!_mesa_validate_pbo_access(2, &ctx->Pack, width, height, 1,
@@ -1118,7 +1121,7 @@ _mesa_ReadnPixelsARB( GLint x, GLint y, GLsizei width, GLsizei height,
    }
 
    ctx->Driver.ReadPixels(ctx, x, y, width, height,
-			  format, type, &ctx->Pack, pixels);
+                          format, type, &clippedPacking, pixels);
 }
 
 void GLAPIENTRY
-- 
2.7.0