simulator: Adjust scaling using keyboard shortcuts

Press 0-3 to to adjust current zoom level
to 50% (0), 100% (1), 200% (2), or 300% (3).

Press 4 to switch between "best" (linear)
and nearest pixel sampling.

Change-Id: Id10d361659855a0ad9c97e6b341f498f72709ef5

firmware/target/hosted/sdl/button-sdl.c

@@ -351,6 +351,30 @@ static void button_event(int key, bool pressed)
     switch (key)
     {
 #ifdef SIMULATOR
+    case SDLK_0:
+        display_zoom = 0.5;
+    case SDLK_1:
+        display_zoom = display_zoom ?: 1;
+    case SDLK_2:
+        display_zoom = display_zoom ?: 2;
+    case SDLK_3:
+        display_zoom = display_zoom ?: 3;
+    case SDLK_4:
+        if (pressed)
+        {
+            display_zoom = 0;
+            return;
+        }
+        if (!display_zoom)
+            SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY,
+                        strcmp(SDL_GetHint(SDL_HINT_RENDER_SCALE_QUALITY) ?:
+                        "best", "best") ? "best": "nearest");
+
+        sdl_window_needs_update();
+#if !defined(__WIN32) && !defined (__APPLE__)
+        button_queue_post(SDLK_UNKNOWN, 0); /* update window on main thread */
+#endif
+        return;
     case USB_KEY:
         if (!pressed)
         {

firmware/target/hosted/sdl/lcd-sdl.c

@@ -65,37 +65,45 @@ static inline void sdl_render(void)
 #define SNAP_MARGIN 50
 int sdl_update_window(void)
 {
+    int w, h;
+
     if (!window_needs_update)
         return false;
     window_needs_update = false;
 
-#if defined (__APPLE__) || defined(__WIN32) /* Constrain aspect ratio */
+    sdl_get_window_dimensions(&w, &h);
+
     if (!(SDL_GetWindowFlags(window) & (SDL_WINDOW_MAXIMIZED | SDL_WINDOW_FULLSCREEN)))
     {
-        float aspect_ratio;
+        if (display_zoom)
-        int w, h;
-
-        sdl_get_window_dimensions(&w, &h);
-        aspect_ratio = (float) h / w;
-
-        int original_height = h;
-        int original_width = w;
-
-        SDL_GetWindowSize(window, &w, &h);
-        if (w != original_width || h != original_height)
         {
-            if (abs(original_width - w) < SNAP_MARGIN)
+            SDL_SetWindowSize(window, display_zoom * w, display_zoom * h);
-            {
+        }
-                w = original_width;
+#if defined(__APPLE__) || defined(__WIN32)
-                h = original_height;
+        else /* Constrain aspect ratio on Windows and MacOS */
-            }
+        {
-            else
+
-                h = w * aspect_ratio;
+            float aspect_ratio = (float) h / w;
-
+            int original_height = h;
-            SDL_SetWindowSize(window, w, h);
+            int original_width = w;
+
+            SDL_GetWindowSize(window, &w, &h);
+            if (w != original_width || h != original_height)
+            {
+                if (abs(original_width - w) < SNAP_MARGIN)
+                {
+                    w = original_width;
+                    h = original_height;
+                }
+                else
+                    h = w * aspect_ratio;
+
+                SDL_SetWindowSize(window, w, h);
+            }
         }
-    }
 #endif
+    }
+    display_zoom = 0;
     sdl_render();
     return true;
 }

firmware/target/hosted/sdl/system-sdl.c

@@ -113,6 +113,7 @@ static void sdl_window_setup(void)
         panicf("%s", SDL_GetError());
 
     SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, display_zoom == 1 ? "best" : "nearest");
+    display_zoom = 0; /* keeps track of user requesting a scale level change */
     SDL_RenderSetLogicalSize(sdlRenderer, width, height);
 
     if ((gui_surface = SDL_CreateRGBSurface(0, width, height, depth,