GL_REPEAT vs new wrap modes in SDL 3.4...

[icculus]

Not supporting GL_REPEAT is potentially a showstopper for the new wrap modes in SDL 3.4...

Originally posted by @slouken in #13887

Basically GL_REPEAT never works on NPOT textures unless you have:

• OpenGL 2.0 or later
• GLES 3.0 or later
• the GL_ARB_texture_non_power_of_two extension on either OpenGL or GLES.

GL_REPEAT with work on power-of-two textures everywhere, though.

Opening a bug so I remember to look at the new 3.4 stuff.

[icculus]

This code:

SDL/src/render/SDL_render.c

Lines 5345 to 5375 in 9cf7cdf

	if (texture &&
	(texture_address_mode_u == SDL_TEXTURE_ADDRESS_AUTO ||
	texture_address_mode_v == SDL_TEXTURE_ADDRESS_AUTO)) {
	for (i = 0; i < num_vertices; ++i) {
	const float *uv_ = (const float *)((const char *)uv + i * uv_stride);
	float u = uv_[0];
	float v = uv_[1];
	if (u < 0.0f || u > 1.0f) {
	if (texture_address_mode_u == SDL_TEXTURE_ADDRESS_AUTO) {
	texture_address_mode_u = SDL_TEXTURE_ADDRESS_WRAP;
	if (texture_address_mode_v != SDL_TEXTURE_ADDRESS_AUTO) {
	break;
	}
	}
	}
	if (v < 0.0f || v > 1.0f) {
	if (texture_address_mode_v == SDL_TEXTURE_ADDRESS_AUTO) {
	texture_address_mode_v = SDL_TEXTURE_ADDRESS_WRAP;
	if (texture_address_mode_u != SDL_TEXTURE_ADDRESS_AUTO) {
	break;
	}
	}
	}
	}
	if (texture_address_mode_u == SDL_TEXTURE_ADDRESS_AUTO) {
	texture_address_mode_u = SDL_TEXTURE_ADDRESS_CLAMP;
	}
	if (texture_address_mode_v == SDL_TEXTURE_ADDRESS_AUTO) {
	texture_address_mode_v = SDL_TEXTURE_ADDRESS_CLAMP;
	}
	}

Sees the thing set to SDL_TEXTURE_ADDRESS_AUTO and decides whether to choose SDL_TEXTURE_ADDRESS_WRAP or SDL_TEXTURE_ADDRESS_CLAMP based on whether it sees a texcoord outside the 0.0-1.0 range...but that basically means that AUTO works like WRAP all the time.

We should remove AUTO if I'm correct about this.

[icculus]

PS Vita's SCE_GXM_TEXTURE_ADDR_REPEAT will not work without NPOT textures afaict. I assume PSP, PS2, and NGAGE are the same.

OpenGL needs an extension: GL_ARB_texture_non_power_of_two (or core OpenGL 2.0 and later).

Allegedly GLES has this extension, too, but it may or may not be widely supported. WebGL1 does not have it at all. GLES3 has it by default, which means WebGL2 might have it?

Metal, Direct3D 11, Direct3D 12, GPU, and Vulkan should be good to go.

[icculus]

So for WRAP mode, we either need to move things into a power-of-two texture, refuse to work, or...simulate it ourselves in these backends?

[icculus]

Direct3D9 can do it if D3DPTEXTURECAPS_NONPOW2CONDITIONAL is set (which I presume it always is on modern hardware and Windows releases that probably build their D3D9 support on top of newer D3D versions).

[slouken]

Sees the thing set to SDL_TEXTURE_ADDRESS_AUTO and decides whether to choose SDL_TEXTURE_ADDRESS_WRAP or SDL_TEXTURE_ADDRESS_CLAMP based on whether it sees a texcoord outside the 0.0-1.0 range...but that basically means that AUTO works like WRAP all the time.

We should remove AUTO if I'm correct about this.

This affects how coordinates at 0 and 1 are handled. When linear interpolation is enabled, if WRAP is enabled, pixels from the other side of the texture are blended in. If CLAMP is enabled, they're not. This is a visible difference in output, so we want to only do that if the texture coordinates intentionally go outside the 0-1 range.

[slouken]

I think we should document that setting wrap mode can fail, and return appropriately.