Function isFramebufferFormatValidPerSpec

3rdparty/bgfx/src/renderer_gl.cpp:1943–2068

#if BX_PLATFORM_EMSCRIPTEN
	static bool isFramebufferFormatValidPerSpec(
		  TextureFormat::Enum _format
		, bool _srgb
		, bool _writeOnly
		)
	{
		// Avoid creating test textures for WebGL, that causes error noise in the browser console; instead examine the supported texture formats from the spec.
		EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_get_current_context();

		EmscriptenWebGLContextAttributes attrs;
		EMSCRIPTEN_CHECK(emscripten_webgl_get_context_attributes(ctx, &attrs) );

		const int glesVersion = attrs.majorVersion + 1;

		switch(_format)
		{
			// GLES2 textures
			case TextureFormat::B5G6R5:
			case TextureFormat::R5G6B5:
			case TextureFormat::BGRA4:
			case TextureFormat::RGBA4:
			case TextureFormat::BGR5A1:
			case TextureFormat::RGB5A1:
			case TextureFormat::D16:
				return !_srgb;

			// GLES2 renderbuffers not a texture in GLES3
			case TextureFormat::D0S8:
				return !_srgb
					&& _writeOnly
					;

			// GLES2 textures that are not renderbuffers
			case TextureFormat::RGB8:
			case TextureFormat::RGBA8:
				return !_srgb
					&& (!_writeOnly || glesVersion >= 3)
					;

			// GLES3 EXT_color_buffer_float renderbuffer formats
			case TextureFormat::R16F:
			case TextureFormat::RG16F:
			case TextureFormat::R32F:
			case TextureFormat::RG32F:
			case TextureFormat::RG11B10F:
				if (_writeOnly)
				{
					return emscripten_webgl_enable_extension(ctx, "EXT_color_buffer_float");
				}

				return !_srgb && glesVersion >= 3;

			// GLES2 float extension:
			case TextureFormat::RGBA16F:
				if (_writeOnly && emscripten_webgl_enable_extension(ctx, "EXT_color_buffer_half_float") )
				{
					return true;
				}