mesa: Require mipmap completeness for glCopyImageSubData() at times.

This patch makes glCopyImageSubData require mipmap completeness when the
texture object's built-in sampler object has a mipmapping MinFilter.
This is apparently the de facto behavior and mandated by Android's CTS.

One exception is that we ignore format based completeness rules
(specifically integer formats with linear filtering), as this is
also the de facto behavior that until recently was mandated by the
OpenGL 4.5 CTS.

This was discussed with both the OpenGL and OpenGL ES working groups,
and while everyone agrees this behavior is unfortunate and complicated,
it is what it is at this point.  There was little appetite for relaxing
restrictions given that all conformant Android drivers followed the
mipmapping rule, and all conformant GL 4.5 implementations ignored the
integer/linear rule.

Fixes (on i965):
dEQP-GLES31.functional.debug.negative_coverage.*.buffer.copy_image_sub_data

Bugzilla: https://cvs.khronos.org/bugzilla/show_bug.cgi?id=16224
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

diff --git a/src/mesa/main/copyimage.c b/src/mesa/main/copyimage.c
index 2cb617ca811e662d0f45d03e7569177b6de9cc87..10777cfdf0570e877ef89e6c22cbd40103f16b6f 100644 (file)
--- a/src/mesa/main/copyimage.c
+++ b/src/mesa/main/copyimage.c
@@ -149,9 +149,64 @@ prepare_target_err(struct gl_context *ctx, GLuint name, GLenum target,
          return false;
       }
 
+      /* The ARB_copy_image specification says:
+       *
+       *    "INVALID_OPERATION is generated if either object is a texture and
+       *     the texture is not complete (as defined in section 3.9.14)"
+       *
+       * The cited section says:
+       *
+       *    "Using the preceding definitions, a texture is complete unless any
+       *     of the following conditions hold true: [...]
+       *
+       *     * The minification filter requires a mipmap (is neither NEAREST
+       *       nor LINEAR), and the texture is not mipmap complete."
+       *
+       * This imposes the bizarre restriction that glCopyImageSubData requires
+       * mipmap completion based on the sampler minification filter, even
+       * though the call fundamentally ignores the sampler.  Additionally, it
+       * doesn't work with texture units, so it can't consider any bound
+       * separate sampler objects.  It appears that you're supposed to use
+       * the sampler object which is built-in to the texture object.
+       *
+       * dEQP and the Android CTS mandate this behavior, and the Khronos
+       * GL and ES working groups both affirmed that this is unfortunate but
+       * correct.  See https://cvs.khronos.org/bugzilla/show_bug.cgi?id=16224.
+       *
+       * Integer textures with filtering cause another completeness snag:
+       *
+       *    "Any of:
+       *     – The internal format of the texture is integer (see table 8.12).
+       *     – The internal format is STENCIL_INDEX.
+       *     – The internal format is DEPTH_STENCIL, and the value of
+       *       DEPTH_STENCIL_TEXTURE_MODE for the texture is STENCIL_INDEX.
+       *     and either the magnification filter is not NEAREST, or the
+       *     minification filter is neither NEAREST nor
+       *     NEAREST_MIPMAP_NEAREST."
+       *
+       * However, applications in the wild (such as "Total War: WARHAMMER")
+       * appear to call glCopyImageSubData with integer textures and the
+       * default mipmap filters of GL_LINEAR and GL_NEAREST_MIPMAP_LINEAR,
+       * which would be considered incomplete, but expect this to work.  In
+       * fact, until VK-GL-CTS commit fef80039ff875a51806b54d151c5f2d0c12da,
+       * the GL 4.5 CTS contained three tests which did the exact same thing
+       * by accident, and all conformant implementations allowed it.
+       *
+       * A proposal was made to amend the spec to say "is not complete (as
+       * defined in section <X>, but ignoring format-based completeness
+       * rules)" to allow this case.  It makes some sense, given that
+       * glCopyImageSubData copies raw data without considering format.
+       * While the official edits have not yet been made, the OpenGL
+       * working group agreed with the idea of allowing this behavior.
+       *
+       * To ignore formats, we check texObj->_MipmapComplete directly
+       * rather than calling _mesa_is_texture_complete().
+       */
       _mesa_test_texobj_completeness(ctx, texObj);
-      if (!texObj->_BaseComplete ||
-          (level != 0 && !texObj->_MipmapComplete)) {
+      const bool texture_complete_aside_from_formats =
+         _mesa_is_mipmap_filter(&texObj->Sampler) ? texObj->_MipmapComplete
+                                                  : texObj->_BaseComplete;
+      if (!texture_complete_aside_from_formats) {
          _mesa_error(ctx, GL_INVALID_OPERATION,
                      "glCopyImageSubData(%sName incomplete)", dbg_prefix);
          return false;