gfx: Provide functions for fullscreen handling

src/gfx/inc/gfx.h

@@ -13,6 +13,8 @@ extern "C"
 int gfx_init(void);
 int gfx_draw(void);
 int gfx_toggle_fullscreen(void);
+bool gfx_toggle_fullscreen_available(void);
+bool gfx_fullscreen(void);
 void sprite_sort(struct sprite *s);
 int sprite_clone(const struct sprite *src, struct sprite *dst);
 void rect_init(struct rect *r);

src/gfx/ps1/src/env.c

@@ -38,6 +38,16 @@ int gfx_toggle_fullscreen(void)
     return -1;
 }
 
+bool gfx_toggle_fullscreen_available(void)
+{
+    return false;
+}
+
+bool gfx_fullscreen(void)
+{
+    return true;
+}
+
 bool gfx_inside_drawenv(const short x, const short y, const short w,
     const short h)
 {

src/gfx/sdl-1.2/src/env.c

@@ -163,6 +163,16 @@ int gfx_toggle_fullscreen(void)
     return 0;
 }
 
+bool gfx_toggle_fullscreen_available(void)
+{
+    return true;
+}
+
+bool gfx_fullscreen(void)
+{
+    return fullscreen;
+}
+
 int gfx_draw(void)
 {
     enum {FPS = 50, REFRESH_MS = 1000 / FPS};