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/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
index fe40068..4ee8636 100644
--- a/src/mesa/drivers/dri/i965/intel_extensions.c
+++ b/src/mesa/drivers/dri/i965/intel_extensions.c
@@ -163,6 +163,7 @@ intelInitExtensions(struct gl_context *ctx)
    assert(brw->gen >= 4);
 
    ctx->Extensions.ARB_buffer_storage = true;
+   ctx->Extensions.ARB_clear_texture = true;
    ctx->Extensions.ARB_depth_buffer_float = true;
    ctx->Extensions.ARB_depth_clamp = true;
    ctx->Extensions.ARB_depth_texture = true;