(GL1) Fix on-screen overlay rendering

gl1_render_overlay was missing essentially all of the GL state setup
needed to actually draw anything. Three issues, all fixed by mirroring
the patterns already used in gfx_display_gl1_draw and
gl1_raster_font_draw_vertices:

1. Client arrays were never enabled. The function assigned values to
   gl->coords.vertex/tex_coord/color, but those struct fields don't
   drive GL state — they need to be wired up via glEnableClientState
   plus glVertexPointer/glTexCoordPointer/glColorPointer pointing at
   the overlay coord buffers. Without them glDrawArrays runs with
   whatever client array state happened to be active from the
   previous draw, which generally meant nothing rendered.

2. The PROJECTION matrix was pushed but never popped, leaking a
   matrix-stack entry every frame. The MODELVIEW matrix was also
   never reset to identity.

3. The viewport size source was wrong. Callers pass video_width/
   video_height from video_info, which in gl1 is the emulated core
   frame size (e.g. 256x224 for SNES, 320x240 default for the menu
   surface) — not the window size. Fullscreen overlays need the
   actual window viewport, so use gl->screen_width/height (set from
   the context driver's get_video_size) instead, with fallback to the
   passed-in width/height for safety. Same semantic mismatch fixed
   recently for the statistics font in commit 1224324.

Additionally, the projection itself was loaded as identity, which
gives clip space [-1,1] x [-1,1]. Overlay vertices are emitted in
[0,1] UI space by gl1_overlay_vertex_geom, so an identity projection
mapped them into the upper-right quadrant of the viewport instead of
filling it. Load gl->mvp_no_rot — the pre-built ortho(0,1,0,1,-1,1)
matrix — for the projection so [0,1] vertices map to the full
viewport, matching what gl3 does with the same matrix in its shader
uniform.

With these changes overlays render at the correct full-screen size
and position, matching the gl/glcore behaviour.

Author: LibretroAdmin

gfx/drivers/gl1.c

@@ -999,6 +999,17 @@ static void gl1_render_overlay(gl1_t *gl,
 {
    int i;
 
+   /* gl1 reuses video_width/height for the emulated core frame size
+    * (e.g. 256x224 for SNES, 320x240 default for the menu surface),
+    * not the window size. Fullscreen overlays must be drawn into the
+    * actual window viewport, so use screen_width/height instead.
+    * Fall back to the passed-in width/height if the context driver
+    * has not reported a screen size yet. */
+   if (gl->screen_width)
+      width  = gl->screen_width;
+   if (gl->screen_height)
+      height = gl->screen_height;
+
    glEnable(GL_BLEND);
 
    if (gl->flags & GL1_FLAG_OVERLAY_FULLSCREEN)
@@ -1009,16 +1020,46 @@ static void gl1_render_overlay(gl1_t *gl,
    gl->coords.color     = gl->overlay_color_coord;
    gl->coords.vertices  = 4 * gl->overlays;
 
+   /* Fixed-function pipeline draws need the projection set, the
+    * modelview reset to identity and the client arrays bound to the
+    * overlay coord buffers. Previously this function only assigned
+    * pointers to gl->coords (which is just a struct field, not GL
+    * state) and pushed PROJECTION without popping it — so glDrawArrays
+    * ran with whatever client array state happened to be active and
+    * nothing rendered. Match the pattern used in
+    * gfx_display_gl1_draw and gl1_raster_font_draw_vertices. */
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
+   glLoadMatrixf(gl->mvp_no_rot.data);
+
+   glMatrixMode(GL_MODELVIEW);
+   glPushMatrix();
    glLoadIdentity();
 
+   glEnable(GL_TEXTURE_2D);
+   glEnableClientState(GL_VERTEX_ARRAY);
+   glEnableClientState(GL_TEXTURE_COORD_ARRAY);
+   glEnableClientState(GL_COLOR_ARRAY);
+
+   glVertexPointer(2, GL_FLOAT, 0, gl->overlay_vertex_coord);
+   glTexCoordPointer(2, GL_FLOAT, 0, gl->overlay_tex_coord);
+   glColorPointer(4, GL_FLOAT, 0, gl->overlay_color_coord);
+
    for (i = 0; i < (int)gl->overlays; i++)
    {
       glBindTexture(GL_TEXTURE_2D, gl->overlay_tex[i]);
       glDrawArrays(GL_TRIANGLE_STRIP, 4 * i, 4);
    }
 
+   glDisableClientState(GL_COLOR_ARRAY);
+   glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+   glDisableClientState(GL_VERTEX_ARRAY);
+
+   glMatrixMode(GL_MODELVIEW);
+   glPopMatrix();
+   glMatrixMode(GL_PROJECTION);
+   glPopMatrix();
+
    glDisable(GL_BLEND);
    gl->coords.vertex    = gl->vertex_ptr;
    gl->coords.tex_coord = gl->tex_info.coord;