MENU/XMB: render blank-less while icon thumbnails are loading

Complement to the prior deferral commit, addressing the user-visible
"stuttery" feel of playlist icon-thumbnail loading.

xmb_render caps synchronous icon loads at 2 per frame to avoid
frame-time spikes on slow storage (SD card, Android SAF, spinning
rust). That cap itself is fine and is retained here. The problem is
what the dispatcher did to entries past the budget: it set
node->icon_hide = true, and the per-entry draw at line 5534 gated
the entire icon block (including any default-fallback texture) on
!node->icon_hide. So on a playlist with N > 2 visible entries, each
frame drew 2 newly-loaded icons and left the rest as empty slots
until their turn arrived. On a 30-visible-entry playlist that's 15
frames (~250 ms) of icons rippling in against blanks — which reads
as the "stutter" in the original complaint.

This branch was introduced alongside the per-frame cap itself in
2073b8a "XMB: Icon thumbnail improvements" (Feb 2025). Before that,
the dispatcher loaded every visible icon in one frame, and no
icon_hide mechanism existed — budget-exceeded entries just kept
whatever icon they already had (default fallback on first frame).
That pre-regression behaviour is what this commit restores.

Removes node->icon_hide entirely (struct field, init in
xmb_alloc_node, guard in xmb_draw_item, both assignments in
xmb_render). Entries past the per-frame budget still get skipped —
pending_icons is re-raised so we resume next frame — but they render
their existing default icon instead of rendering as nothing. The
paint now fills in rather than pops in.

The 2-per-frame cap is retained, so slow-storage frame-time
protection is unchanged. The render dispatcher comment is updated to
clarify that only synchronous loads count toward the budget; async
requests via gfx_thumbnail_request_stream run on a worker thread and
land via task callback, so they do not contribute to this frame's
work and are correctly uncounted.

Author: LibretroAdmin

menu/drivers/xmb.c

@@ -302,7 +302,6 @@ typedef struct
    float zoom;
    float x;
    float y;
-   bool icon_hide;
 } xmb_node_t;
 
 enum xmb_drag_mode
@@ -646,7 +645,6 @@ static xmb_node_t *xmb_alloc_node(void)
    node->thumbnail_icon.icon.texture       = 0;
    node->fullpath     = NULL;
    node->console_name = NULL;
-   node->icon_hide    = false;
 
    return node;
 }
@@ -5536,7 +5534,6 @@ static int xmb_draw_item(
    gfx_display_set_alpha(color, MIN(node->alpha * xmb->alpha_list, xmb->alpha));
 
    if (     (!xmb->assets_missing)
-         && (!node->icon_hide)
          && (color[3] != 0)
          && (  (entry.flags & MENU_ENTRY_FLAG_CHECKED)
             || !( entry_type >= MENU_SETTING_DROPDOWN_ITEM
@@ -7375,8 +7372,12 @@ static void xmb_render(void *data,
    /* Handle any pending icon thumbnail load requests */
    if (xmb->thumbnails.pending_icons != XMB_PENDING_THUMBNAIL_NONE)
    {
-      /* Limit image loading per frame to prevent slowdowns,
-       * and hide the usual icon while pending */
+      /* Limit synchronous image loading per frame to prevent
+       * frame-time spikes on slow storage (SD card, Android SAF
+       * behind fuse, etc.). Async requests via
+       * gfx_thumbnail_request_stream are not counted — they run on
+       * a worker thread and land via task callback on subsequent
+       * frames, so they do not contribute to this frame's work. */
       uint8_t max_per_frame = 2;
       uint8_t cur_per_frame = 0;
 
@@ -7396,17 +7397,21 @@ static void xmb_render(void *data,
 
          thumbnail_icon = &node->thumbnail_icon;
 
+         /* Budget exceeded: skip this entry this frame, keep
+          * pending_icons raised so we resume next frame. The entry
+          * continues to render its existing icon (default fallback
+          * if nothing has been loaded yet) rather than rendering as
+          * blank, so the user sees a steady draw with icons filling
+          * in progressively, not a wave of empty slots. */
          if (cur_per_frame >= max_per_frame)
          {
-            node->icon_hide = true;
             xmb->thumbnails.pending_icons = XMB_PENDING_THUMBNAIL_ICONS;
             continue;
          }
 
          if (     thumbnail_icon->icon.status == GFX_THUMBNAIL_STATUS_UNKNOWN
                && *thumbnail_icon->thumbnail_path_data.icon_path)
          {
-            node->icon_hide = false;
             if (!xmb_load_dynamic_icon(
                      thumbnail_icon->thumbnail_path_data.icon_path,
                      &thumbnail_icon->icon))