[Mesa-dev] [PATCH] st/mesa: don't allocate mipmapped texture for NEAREST_MIPMAP_LINEAR

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

---
 src/mesa/state_tracker/st_cb_texture.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/mesa/state_tracker/st_cb_texture.c b/src/mesa/state_tracker/st_cb_texture.c
index 0edb3ea5c7e..1ace61863ff 100644
--- a/src/mesa/state_tracker/st_cb_texture.c
+++ b/src/mesa/state_tracker/st_cb_texture.c
@@ -516,20 +516,32 @@ allocate_full_mipmap(const struct st_texture_object *stObj,
       return FALSE;
 
    if (stObj->base.BaseLevel == 0 && stObj->base.MaxLevel == 0)
       return FALSE;
 
    if (stObj->base.Sampler.MinFilter == GL_NEAREST ||
        stObj->base.Sampler.MinFilter == GL_LINEAR)
       /* not a mipmap minification filter */
       return FALSE;
 
+   /* If the following sequence of GL calls is used:
+    *   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, ...
+    *   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    *
+    * we would needlessly allocate a mipmapped texture, because the initial
+    * MinFilter is GL_NEAREST_MIPMAP_LINEAR. Catch this case and don't
+    * allocate a mipmapped texture by default. This may cause texture
+    * reallocation later, but GL_NEAREST_MIPMAP_LINEAR is pretty rare.
+    */
+   if (stObj->base.Sampler.MinFilter == GL_NEAREST_MIPMAP_LINEAR)
+      return FALSE;
+
    if (stObj->base.Target == GL_TEXTURE_3D)
       /* 3D textures are seldom mipmapped */
       return FALSE;
 
    return TRUE;
 }
 
 
 /**
  * Try to allocate a pipe_resource object for the given st_texture_object.
-- 
2.17.1