gl1: honour xmb_shadows_enable

Same fix as 709d462 for GDI. gl1 was clobbering xmb_shadows_enable
alongside menu_shader_pipeline. The latter is correct -- gl1
fixed-function has no programmable pipeline, so the animated XMB
backgrounds (Ribbon / Snow / Bokeh / etc.) can't run. But shadow
draws are just vertex-color-modulated textured quads: the default
GL_MODULATE texture environment with vertex color (0,0,0,a) plus
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) darkens the
destination to dst*(1-a), and the gl1 raster font driver's
drop_x/drop_y path handles text shadows the same way.

Author: LibretroAdmin

gfx/drivers/gl1.c

@@ -1641,8 +1641,18 @@ static bool gl1_frame(void *data, const void *frame,
       &video_info->osd_stat_params;
    bool overlay_behind_menu         = video_info->overlay_behind_menu;
 
-   /* FIXME: Force these settings off as they interfere with the rendering */
-   video_info->xmb_shadows_enable   = false;
+   /* gl1 fixed-function has no programmable pipeline, so the
+    * animated XMB backgrounds (Ribbon / Snow / Bokeh / etc.) can't
+    * run -- force that off so XMB falls back to the static gradient.
+    *
+    * xmb_shadows_enable, on the other hand, is just "draw the icon
+    * and text once at +offset with a black tint, then once more on
+    * top".  The default GL_MODULATE texture environment with vertex
+    * color (0,0,0,a) plus glBlendFunc(GL_SRC_ALPHA,
+    * GL_ONE_MINUS_SRC_ALPHA) darkens the destination to dst*(1-a),
+    * and the gl1 raster font driver's drop_x/drop_y path handles
+    * text shadows the same way, so this flag is honoured rather
+    * than clobbered. */
    video_info->menu_shader_pipeline = 0;
 
    if (gl1->flags & GL1_FLAG_SHOULD_RESIZE)