msaa: Avoid undefined behavior in visualize_image function

Test uses glDrawPixels with dual source blending and fixed function
pipeline in visualize_image(). According to ARB_blend_func_extended
specs:

"Rendering using any of the blend functions that consume the second
input color (SRC1_COLOR, ONE_MINUS_SRC1_COLOR, SRC1_ALPHA or
ONE_MINUS_SRC1_ALPHA) using fixed function will produce undefined
results."

Fix this by disabling the blending temporarily in visualize_image
function.

Reported-by: Vadim Girlin <vadimgirlin@gmail.com>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp
index 1a898b2ba..6f54dfe86 100644
--- a/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp
+++ b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp
@@ -699,9 +699,19 @@ draw_image_to_window_system_fb(int draw_buffer_count, bool rhs)
 			     GL_RGBA,
 			     GL_FLOAT, image);
 	}
+
+	/* Rendering using gldrawPixels() with dual source blending enabled
+	 * produces undefined results. So, disable blending in visualize_image
+	 * function to avoid undefined behavior.
+	 */
+	GLboolean isBlending;
+        glGetBooleanv(GL_BLEND, &isBlending);
+	glDisable(GL_BLEND);
 	visualize_image(image, GL_RGBA,
 			pattern_width, pattern_height,
 			draw_buffer_count + 1, rhs);
+	if(isBlending)
+		glEnable(GL_BLEND);
 	free(image);
 }