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, 1 insertions, 0 deletions

diff --git a/src/mesa/drivers/common/driverfuncs.c b/src/mesa/drivers/common/driverfuncs.c
index 6ece5d80e1a..4f0f7a686ab 100644
--- a/src/mesa/drivers/common/driverfuncs.c
+++ b/src/mesa/drivers/common/driverfuncs.c
@@ -95,6 +95,7 @@ _mesa_init_driver_functions(struct dd_function_table *driver)
    driver->TexImage = _mesa_store_teximage;
    driver->TexSubImage = _mesa_store_texsubimage;
    driver->GetTexImage = _mesa_meta_GetTexImage;
+   driver->ClearTexSubImage = _mesa_meta_ClearTexSubImage;
    driver->CopyTexSubImage = _mesa_meta_CopyTexSubImage;
    driver->GenerateMipmap = _mesa_meta_GenerateMipmap;
    driver->TestProxyTexImage = _mesa_test_proxy_teximage;