Allow user to select exclusive fullscreen mode

config_spec.yml

@@ -244,6 +244,9 @@ display:
   window:
     fullscreen_on_startup: bool
     fullscreen_exclusive: bool
+    fullscreen_resolution:
+      type: integer
+      default: 0
     startup_size:
       type: enum
       values: [last_used, 640x480, 720x480, 1280x720, 1280x800, 1280x960, 1920x1080, 2560x1440, 2560x1600, 2560x1920, 3840x2160]

ui/xemu.c

@@ -293,8 +293,12 @@ static void set_full_screen(struct xemu_console *scon, bool set)
                 int num_modes = 0;
                 modes = SDL_GetFullscreenDisplayModes(display, &num_modes);
                 if (modes && num_modes > 0) {
-                    // First mode is the highest resolution, typically the native resolution
-                    mode = modes[0];
+                    // Use configured fullscreen resolution index, defaulting to 0 (highest resolution)
+                    int mode_index = g_config.display.window.fullscreen_resolution;
+                    if (mode_index < 0 || mode_index >= num_modes) {
+                        mode_index = 0; // Fallback to highest resolution
+                    }
+                    mode = modes[mode_index];
                 }
             }
             if (mode) {

ui/xui/main-menu.cc

@@ -31,6 +31,11 @@
 #include "qapi/error.h"
 #include "actions.hh"
 
+#include <SDL3/SDL.h>
+
+#include <vector>
+#include <string>
+
 #include "../xemu-input.h"
 #include "../xemu-notifications.h"
 #include "../xemu-settings.h"
@@ -775,6 +780,34 @@ void MainMenuDisplayView::Draw()
     Toggle("Exclusive fullscreen",
            &g_config.display.window.fullscreen_exclusive,
            "May improve responsiveness, but slows window switching");
+    if (g_config.display.window.fullscreen_exclusive) {
+        // Get available fullscreen display modes
+        SDL_DisplayID display = SDL_GetDisplayForWindow(xemu_get_window());
+        int num_modes = 0;
+        SDL_DisplayMode **modes = SDL_GetFullscreenDisplayModes(display, &num_modes);
+
+        if (modes && num_modes > 0) {
+            // Create a list of mode strings
+            std::vector<std::string> mode_strings;
+            for (int i = 0; i < num_modes; i++) {
+                char buf[64];
+                snprintf(buf, sizeof(buf), "%dx%d @ %.0fHz", modes[i]->w, modes[i]->h, modes[i]->refresh_rate);
+                mode_strings.push_back(buf);
+            }
+
+            // Create null-separated string for ChevronCombo
+            std::string items;
+            for (const auto& str : mode_strings) {
+                items += str;
+                items += '\0';
+            }
+            items += '\0'; // Double null terminate
+
+            ChevronCombo("Fullscreen resolution", &g_config.display.window.fullscreen_resolution,
+                        items.c_str(), "Select preferred fullscreen resolution");
+        }
+        SDL_free(modes);
+    }
     if (ChevronCombo("Window size", &g_config.display.window.startup_size,
                      "Last Used\0"
                      "640x480\0"