[Mesa-dev] [PATCH] st/mesa: fix mipmap generation for immutable textures with incomplete pyramids

[Nicolai Hähnle]

(This is an alternative to my previous patch, "mesa: clamp MaxLevel for
immutable textures at initialization"; this patch has no opinion about
how the spec should be interpreted.)

Without the clamping by NumLevels, the state tracker would reallocate the
texture storage (incorrect) and even fail to copy the base level image
after reallocation, leading to the graphical glitch of
https://bugs.freedesktop.org/show_bug.cgi?id=91993 .

A piglit test has been submitted for review as well (subtest of
arb_texture_storage-texture-storage).
---
 src/mesa/state_tracker/st_gen_mipmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/mesa/state_tracker/st_gen_mipmap.c b/src/mesa/state_tracker/st_gen_mipmap.c
index 26e1c21..3125b2a 100644
--- a/src/mesa/state_tracker/st_gen_mipmap.c
+++ b/src/mesa/state_tracker/st_gen_mipmap.c
@@ -61,6 +61,8 @@ compute_num_levels(struct gl_context *ctx,
 
    numLevels = texObj->BaseLevel + baseImage->MaxNumLevels;
    numLevels = MIN2(numLevels, (GLuint) texObj->MaxLevel + 1);
+   if (texObj->Immutable)
+      numLevels = MIN2(numLevels, texObj->NumLevels);
    assert(numLevels >= 1);
 
    return numLevels;
-- 
2.1.4