Confirmed bug: RGUI renders with swapped R and B channels on Metal

The convert_bgra4444_to_bgra8888 kernel in Shaders.metal expects input bits laid out as B(15:12) G(11:8) R(7:4) A(3:0) — the D3D10/11/12 packing convention. But when the Metal driver is active, rgui_set_pixel_format_function (menu/drivers/rgui.c:1412-1413) falls through to the else branch and packs with argb32_to_rgba4444, producing R(15:12) G(11:8) B(7:4) A(3:0). The shader then decodes the bytes swapped — a red RGUI pixel 0xF00F gets rendered as blue.
This has presumably been wrong since whenever the Metal driver first shipped with 4444 support, but nobody ever pulled the thread.

Author: LibretroAdmin

menu/drivers/rgui.c

@@ -1400,7 +1400,8 @@ static bool rgui_set_pixel_format_function(void)
       argb32_to_pixel_platform_format = argb32_to_argb4444;
    else if (   string_is_equal(driver_ident, "d3d10")         /* D3D10/11/12 */
             || string_is_equal(driver_ident, "d3d11")
-            || string_is_equal(driver_ident, "d3d12"))
+            || string_is_equal(driver_ident, "d3d12")
+            || string_is_equal(driver_ident, "metal"))        /* Metal */
       argb32_to_pixel_platform_format = argb32_to_bgra4444;
    else if (   string_is_equal(driver_ident, "sdl_dingux")    /* DINGUX SDL */
             || string_is_equal(driver_ident, "sdl_rs90")