[Piglit] [PATCH] arb_clear_texture: add a trivial test

[Eric Anholt]

Ilia Mirkin <imirkin at alum.mit.edu> writes:

> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
>
> This is my first foray into piglit test-writing. Let me know if I missed
> anything (except for better tests -- I know that this is very limited).
>
> This mechanism of transferring the texture to the screen is pretty poor -- it
> entirely defeats the point of ARB_clear_texture, which is to allow one to
> clear even non-renderable-to textures. I guess I need to create a shader that
> uses the texture? Is there an example of a test that does this?
>
> For all its simplicity, this allowed me to debug my impl of this extension on
> nv50, which is now no longer completely broken.

> +enum piglit_result
> +piglit_display(void)
> +{
> +	const float clearColor[3] = { 0.0, 1.0, 0.0 };
> +	GLuint fbo;
> +	GLenum status;
> +	bool pass = true;
> +
> +	/* Clear texture with glClearTexImage() */
> +	glClearTexImage(texture, 0, GL_RGB, GL_FLOAT, clearColor);
> +
> +	glGenFramebuffers(1, &fbo);
> +	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +	glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, texture, 0);
> +	status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
> +	if (status != GL_FRAMEBUFFER_COMPLETE) {
> +		printf("Framebuffer Status: %s\n",
> +		       piglit_get_gl_enum_name(status));
> +		return PIGLIT_FAIL;
> +	}
> +
> +	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, piglit_winsys_fbo);
> +	glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo);
> +	glBlitFramebuffer(0, 0, piglit_width, piglit_height,
> +			  0, 0, piglit_width, piglit_height,
> +			  GL_COLOR_BUFFER_BIT, GL_NEAREST);
> +
> +	if (!piglit_check_gl_error(GL_NO_ERROR))
> +		pass = false;

Instead of making an FBO and using BlitFramebuffer, I'd just draw the
texture to the screen using texture sampling.
tests/spec/ext_unpack_subimage/ext_unpack_subimage.c has some very easy
code to copy from for the shader and the draw call.

I do really like that you're drawing to the screen.  It's important for
people debugging drivers, and I wouldn't want to see it go away.

Other than that, this is a nice simple test.  We're going to want an
all-the-formats testcase before we land clear_texture in Mesa, but this
is a good start.
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