From 05b71ace4f2669b253ac62fd9bedee40fb4c32f2 Mon Sep 17 00:00:00 2001
From: Cpasjuste <cpasjuste@gmail.com>
Date: Wed, 28 Mar 2018 00:17:08 +0200
Subject: [PATCH] switch: handle aspect ratio correction in fullscreen mode

---
 src/video/switch/SDL_switchvideo.c | 27 ++++++++++++++-------
 test/testswitch.c                  | 39 +++++++++++++++---------------
 2 files changed, 38 insertions(+), 28 deletions(-)

diff --git a/src/video/switch/SDL_switchvideo.c b/src/video/switch/SDL_switchvideo.c
index aee219b3b..86091afd4 100644
--- a/src/video/switch/SDL_switchvideo.c
+++ b/src/video/switch/SDL_switchvideo.c
@@ -37,6 +37,7 @@
 typedef struct
 {
     SDL_Surface *surface;
+    int x_offset;
 } SWITCH_WindowData;
 
 static int SWITCH_VideoInit(_THIS);
@@ -157,23 +158,31 @@ static int SWITCH_CreateWindowFramebuffer(_THIS, SDL_Window *window, Uint32 *for
         return -1;
     }
 
-    // hold a pointer to our surface
+    // hold a pointer to our stuff
     data = SDL_calloc(1, sizeof(SWITCH_WindowData));
     data->surface = surface;
-    SDL_SetWindowData(window, SWITCH_DATA, data);
 
     // use switch hardware scaling in fullscreen mode
     if (window->flags & SDL_WINDOW_FULLSCREEN) {
-        gfxConfigureResolution(window->w, window->h);
+        float scaling = (float) window->h / (float) SCREEN_HEIGHT;
+        float w = SDL_min(SCREEN_WIDTH, SCREEN_WIDTH * scaling);
+        // calculate x offset, to respect aspect ratio
+        // round down to multiple of 4 for faster fb writes
+        int offset = (int) (w - (window->w)) / 2;
+        data->x_offset = offset & ~3;
+        gfxConfigureResolution((int) w, window->h);
     }
     else {
         gfxConfigureResolution(0, 0);
+        data->x_offset = 0;
     }
 
     *format = SDL_PIXELFORMAT_ABGR8888;
     *pixels = surface->pixels;
     *pitch = surface->pitch;
 
+    SDL_SetWindowData(window, SWITCH_DATA, data);
+
     // inform SDL we're ready to accept inputs
     SDL_SetKeyboardFocus(window);
 
@@ -189,25 +198,25 @@ static int SWITCH_UpdateWindowFramebuffer(_THIS, SDL_Window *window, const SDL_R
     u32 *src = (u32 *) data->surface->pixels;
     u32 *dst = (u32 *) gfxGetFramebuffer(&fb_w, &fb_h);
 
-    // prevent framebuffer overflow in case of resolution change outside SDL,
-    // which should not happen
-    if(window->x + w > fb_w) {
+    // prevent fb overflow in case of resolution change outside SDL
+    if (window->x + w > fb_w) {
         w = fb_w - window->x;
     }
-    if(window->y + h > fb_h) {
+    if (window->y + h > fb_h) {
         h = fb_h - window->y;
     }
 
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x += 4) {
-            *((u128 *) &dst[gfxGetFramebufferDisplayOffset((u32) (x + window->x), (u32) (y + window->y))]) =
+            *((u128 *) &dst[gfxGetFramebufferDisplayOffset(
+                (u32) (x + window->x + data->x_offset), (u32) (y + window->y))]) =
                 *((u128 *) &src[y * w + x]);
         }
     }
 
     gfxFlushBuffers();
     gfxSwapBuffers();
-    // TODO: handle SDL_RENDERER_PRESENTVSYNC (SW_RenderDriver not using flags)
+    // TODO: handle SDL_RENDERER_PRESENTVSYNC (SW_RenderDriver not accepting flags)
     gfxWaitForVsync();
 
     return 0;
diff --git a/test/testswitch.c b/test/testswitch.c
index 6429ccdbf..4c1613d40 100644
--- a/test/testswitch.c
+++ b/test/testswitch.c
@@ -34,10 +34,11 @@ int main(int argc, char *argv[])
         return -1;
     }
 
-    // create a 800x600 centered window for demonstration.
-    // if SDL_WINDOW_FULLSCREEN flag is passed, the window will be hardware scaled to fit switch screen.
+    // create a 800x600 window for demonstration.
+    // if SDL_WINDOW_FULLSCREEN flag is passed, it will be hardware scaled (stretched) to fit screen,
+    // will always be centered and aspect ratio maintained.
     // maximum window dimension is currently limited to 1280x720
-    window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, 0);
+    window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, SDL_WINDOW_FULLSCREEN);
     if (!window) {
         printf("SDL_CreateWindow: %s\n", SDL_GetError());
         SDL_Quit();
@@ -70,24 +71,24 @@ int main(int argc, char *argv[])
 
             switch (event.type) {
 
-            case SDL_JOYAXISMOTION:
-                printf("Joystick %d axis %d value: %d\n",
-                       event.jaxis.which,
-                       event.jaxis.axis, event.jaxis.value);
-                break;
+                case SDL_JOYAXISMOTION:
+                    printf("Joystick %d axis %d value: %d\n",
+                           event.jaxis.which,
+                           event.jaxis.axis, event.jaxis.value);
+                    break;
 
-            case SDL_JOYBUTTONDOWN:
-                printf("Joystick %d button %d down\n",
-                       event.jbutton.which, event.jbutton.button);
-                // seek for joystick #0 down (B)
-                // https://github.com/devkitPro/SDL/blob/switch-sdl2/src/joystick/switch/SDL_sysjoystick.c#L51
-                if (event.jbutton.which == 0 && event.jbutton.button == 1) {
-                    done = 1;
-                }
-                break;
+                case SDL_JOYBUTTONDOWN:
+                    printf("Joystick %d button %d down\n",
+                           event.jbutton.which, event.jbutton.button);
+                    // seek for joystick #0 down (B)
+                    // https://github.com/devkitPro/SDL/blob/switch-sdl2/src/joystick/switch/SDL_sysjoystick.c#L51
+                    if (event.jbutton.which == 0 && event.jbutton.button == 1) {
+                        done = 1;
+                    }
+                    break;
 
-            default:
-                break;
+                default:
+                    break;
             }
         }