meta: Add a meta implementation of GL_ARB_clear_texture

Adds an implementation of the ClearTexSubImage driver entry point that tries
to set up an FBO to render to the texture and then calls glClearBuffer with a
scissor to perform the actual clear. If an FBO can't be created for the
texture then it will fall back to using _mesa_store_ClearTexSubImage.

When used in combination with _mesa_store_ClearTexSubImage this should provide
an implementation that works for all DRI-based drivers. However as this has
only been tested with the i965 driver it is currently only enabled there.

v2: Only enable the extension for the i965 driver instead of all DRI drivers.
    Remove an unnecessary goto. Don't require GL_ARB_framebuffer_object. Add
    some more comments.

v3: Use glClearBuffer* to avoid having to modify glClearColor and friends.
    Handle sRGB textures. Explicitly disable dithering.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/drivers/common/meta.h b/src/mesa/drivers/common/meta.h
index b8d992ce96f..b269dceedde 100644
--- a/src/mesa/drivers/common/meta.h
+++ b/src/mesa/drivers/common/meta.h
@@ -477,6 +477,13 @@ _mesa_meta_CopyTexSubImage(struct gl_context *ctx, GLuint dims,
                            GLsizei width, GLsizei height);
 
 extern void
+_mesa_meta_ClearTexSubImage(struct gl_context *ctx,
+                            struct gl_texture_image *texImage,
+                            GLint xoffset, GLint yoffset, GLint zoffset,
+                            GLsizei width, GLsizei height, GLsizei depth,
+                            const GLvoid *clearValue);
+
+extern void
 _mesa_meta_GetTexImage(struct gl_context *ctx,
                        GLenum format, GLenum type, GLvoid *pixels,
                        struct gl_texture_image *texImage);