+/**
+ * Helper function for checking if the datatypes of color buffers are
+ * compatible for glBlitFramebuffer. From the 3.1 spec, page 198:
+ *
+ * "GL_INVALID_OPERATION is generated if mask contains GL_COLOR_BUFFER_BIT
+ * and any of the following conditions hold:
+ * - The read buffer contains fixed-point or floating-point values and any
+ * draw buffer contains neither fixed-point nor floating-point values.
+ * - The read buffer contains unsigned integer values and any draw buffer
+ * does not contain unsigned integer values.
+ * - The read buffer contains signed integer values and any draw buffer
+ * does not contain signed integer values."
+ */
+static GLboolean
+compatible_color_datatypes(gl_format srcFormat, gl_format dstFormat)
+{
+ GLenum srcType = _mesa_get_format_datatype(srcFormat);
+ GLenum dstType = _mesa_get_format_datatype(dstFormat);
+
+ if (srcType != GL_INT && srcType != GL_UNSIGNED_INT) {
+ assert(srcType == GL_UNSIGNED_NORMALIZED ||
+ srcType == GL_SIGNED_NORMALIZED ||
+ srcType == GL_FLOAT);
+ /* Boil any of those types down to GL_FLOAT */
+ srcType = GL_FLOAT;
+ }
+
+ if (dstType != GL_INT && dstType != GL_UNSIGNED_INT) {
+ assert(dstType == GL_UNSIGNED_NORMALIZED ||
+ dstType == GL_SIGNED_NORMALIZED ||
+ dstType == GL_FLOAT);
+ /* Boil any of those types down to GL_FLOAT */
+ dstType = GL_FLOAT;
+ }
+
+ return srcType == dstType;
+}
+
+
+/**
+ * Return the equivalent non-generic internal format.
+ * This is useful for comparing whether two internal formats are semantically
+ * equivalent.
+ */
+static GLenum
+get_nongeneric_internalformat(GLenum format)
+{
+ switch (format) {
+ /* GL 1.1 formats. */
+ case 4:
+ case GL_RGBA:
+ return GL_RGBA8;
+
+ case 3:
+ case GL_RGB:
+ return GL_RGB8;
+
+ case 2:
+ case GL_LUMINANCE_ALPHA:
+ return GL_LUMINANCE8_ALPHA8;
+
+ case 1:
+ case GL_LUMINANCE:
+ return GL_LUMINANCE8;
+
+ case GL_ALPHA:
+ return GL_ALPHA8;
+
+ case GL_INTENSITY:
+ return GL_INTENSITY8;
+
+ /* GL_ARB_texture_rg */
+ case GL_RED:
+ return GL_R8;
+
+ case GL_RG:
+ return GL_RG8;
+
+ /* GL_EXT_texture_sRGB */
+ case GL_SRGB:
+ return GL_SRGB8;
+
+ case GL_SRGB_ALPHA:
+ return GL_SRGB8_ALPHA8;
+
+ case GL_SLUMINANCE:
+ return GL_SLUMINANCE8;
+
+ case GL_SLUMINANCE_ALPHA:
+ return GL_SLUMINANCE8_ALPHA8;
+
+ /* GL_EXT_texture_snorm */
+ case GL_RGBA_SNORM:
+ return GL_RGBA8_SNORM;
+
+ case GL_RGB_SNORM:
+ return GL_RGB8_SNORM;
+
+ case GL_RG_SNORM:
+ return GL_RG8_SNORM;
+
+ case GL_RED_SNORM:
+ return GL_R8_SNORM;
+
+ case GL_LUMINANCE_ALPHA_SNORM:
+ return GL_LUMINANCE8_ALPHA8_SNORM;
+
+ case GL_LUMINANCE_SNORM:
+ return GL_LUMINANCE8_SNORM;
+
+ case GL_ALPHA_SNORM:
+ return GL_ALPHA8_SNORM;
+
+ case GL_INTENSITY_SNORM:
+ return GL_INTENSITY8_SNORM;
+
+ default:
+ return format;
+ }
+}
+
+
+static GLboolean
+compatible_resolve_formats(const struct gl_renderbuffer *colorReadRb,
+ const struct gl_renderbuffer *colorDrawRb)
+{
+ /* The simple case where we know the backing formats are the same.
+ */
+ if (_mesa_get_srgb_format_linear(colorReadRb->Format) ==
+ _mesa_get_srgb_format_linear(colorDrawRb->Format)) {
+ return GL_TRUE;
+ }
+
+ /* The Mesa formats are different, so we must check whether the internal
+ * formats are compatible.
+ *
+ * Under some circumstances, the user may request e.g. two GL_RGBA8
+ * textures and get two entirely different Mesa formats like RGBA8888 and
+ * ARGB8888. Drivers behaving like that should be able to cope with
+ * non-matching formats by themselves, because it's not the user's fault.
+ */
+ if (get_nongeneric_internalformat(colorReadRb->InternalFormat) ==
+ get_nongeneric_internalformat(colorDrawRb->InternalFormat)) {
+ return GL_TRUE;
+ }
+
+ return GL_FALSE;
+}
+