GFX/DISPLAY: Move gfx_display_draw_bg coords to caller stack

The video_coords struct filled by gfx_display_draw_bg is stored in
the caller's draw struct and read after the function returns, so it
must outlive the call. Previously this was a function-scope static,
which worked but was shared mutable state — racy under threaded
video when multiple draws overlap.

Make coords a parameter, and have each caller declare it as a stack
local alongside its existing gfx_display_ctx_draw_t draw. Per-frame,
per-caller ownership: no dangling pointer, no shared state.

Resolves the thread-safety concern from 0abe6dc without the
use-after-return bug that 904c384 reverted.

Author: LibretroAdmin

gfx/gfx_display.c

@@ -458,14 +458,14 @@ void gfx_display_draw_text(
 void gfx_display_draw_bg(
       gfx_display_t *p_disp,
       gfx_display_ctx_draw_t *draw,
+      struct video_coords *coords,
       void *userdata, bool add_opacity_to_wallpaper,
       float override_opacity)
 {
-   static struct video_coords coords;
    const float           *new_vertex = NULL;
    const float        *new_tex_coord = NULL;
    gfx_display_ctx_driver_t *dispctx = p_disp->dispctx;
-   if (!dispctx || !draw)
+   if (!dispctx || !draw || !coords)
       return;
 
    if (draw->vertex)
@@ -478,13 +478,13 @@ void gfx_display_draw_bg(
    else if (dispctx->get_default_tex_coords)
       new_tex_coord                  = dispctx->get_default_tex_coords();
 
-   coords.vertices                   = (unsigned)draw->vertex_count;
-   coords.vertex                     = new_vertex;
-   coords.tex_coord                  = new_tex_coord;
-   coords.lut_tex_coord              = new_tex_coord;
-   coords.color                      = (const float*)draw->color;
+   coords->vertices                  = (unsigned)draw->vertex_count;
+   coords->vertex                    = new_vertex;
+   coords->tex_coord                 = new_tex_coord;
+   coords->lut_tex_coord             = new_tex_coord;
+   coords->color                     = (const float*)draw->color;
 
-   draw->coords                      = &coords;
+   draw->coords                      = coords;
    draw->scale_factor                = 1.0f;
    draw->rotation                    = 0.0f;
 

gfx/gfx_display.h

@@ -247,9 +247,13 @@ void gfx_display_draw_keyboard(
       char *grid[], unsigned id,
       unsigned text_color);
 
+/* Note: coords must outlive the call — its address is stored in
+ * draw->coords and read by the caller's subsequent dispctx->draw().
+ * Callers should declare coords as a stack local alongside draw. */
 void gfx_display_draw_bg(
       gfx_display_t *p_disp,
       gfx_display_ctx_draw_t *draw,
+      struct video_coords *coords,
       void *userdata,
       bool add_opacity, float opacity_override);
 

menu/drivers/materialui.c

@@ -6211,9 +6211,10 @@ static void materialui_render_background(
    /* Draw background */
    if (dispctx)
    {
+      struct video_coords coords;
       if (dispctx->blend_begin)
          dispctx->blend_begin(userdata);
-      gfx_display_draw_bg(p_disp, &draw, userdata,
+      gfx_display_draw_bg(p_disp, &draw, &coords, userdata,
             add_opacity, opacity_override);
       if (dispctx->draw)
          if (draw.height > 0 && draw.width > 0)

menu/drivers/xmb.c

@@ -7372,6 +7372,7 @@ static void xmb_draw_bg(
       float *coord_white)
 {
    gfx_display_ctx_draw_t draw;
+   struct video_coords coords;
 
    draw.x                    = 0;
    draw.y                    = 0;
@@ -7400,7 +7401,7 @@ static void xmb_draw_bg(
       draw.color = &coord_white[0];
 
       gfx_display_set_alpha(draw.color, coord_white[3]);
-      gfx_display_draw_bg(p_disp, &draw, userdata, true, menu_wallpaper_opacity);
+      gfx_display_draw_bg(p_disp, &draw, &coords, userdata, true, menu_wallpaper_opacity);
 
       if (dispctx->draw)
          dispctx->draw(&draw, userdata, video_width, video_height);
@@ -7412,7 +7413,7 @@ static void xmb_draw_bg(
       draw.texture = 0;
 
       gfx_display_set_alpha(draw.color, coord_white[3]);
-      gfx_display_draw_bg(p_disp, &draw, userdata, true, alpha);
+      gfx_display_draw_bg(p_disp, &draw, &coords, userdata, true, alpha);
 
       if (dispctx->draw)
          dispctx->draw(&draw, userdata, video_width, video_height);
@@ -7473,6 +7474,7 @@ static void xmb_draw_dark_layer(
       float alpha)
 {
    gfx_display_ctx_draw_t draw;
+   struct video_coords coords;
    float black[16]      = {
          0, 0, 0, 1,
          0, 0, 0, 1,
@@ -7496,7 +7498,7 @@ static void xmb_draw_dark_layer(
 
    if (dispctx->blend_begin)
       dispctx->blend_begin(userdata);
-   gfx_display_draw_bg(p_disp, &draw, userdata, true, MIN(xmb->alpha, alpha));
+   gfx_display_draw_bg(p_disp, &draw, &coords, userdata, true, MIN(xmb->alpha, alpha));
    if (draw.height > 0 && draw.width > 0)
       if (dispctx && dispctx->draw)
          dispctx->draw(&draw, userdata, width, height);