sdl: make window resizable, enable high DPI

Tested on Linux, MacOS, and Windows.

On MacOS and Windows, we constrain the window's aspect
ratio by adjusting the size when responding to resize
events.

On Linux, I've not found a way to do so, that doesn't
result in fairly stuttery behavior and weird jumpy
behavior of the resize handle, possibly depending
on your window manager. So, black bars are displayed
around the content.
Maybe someone, at some point, finds a way.
(SDL3 seems to have SDL_SetWindowAspectRatio)

When the window is in fullscreen, black bars are
display necessarily, of course, on all systems,
unless the player GUI has exactly the same aspect
ratio as the screen...

Change-Id: I535e6617497611ea57a4c19e08e552f990859cfe

firmware/drivers/button_queue.c

@@ -24,6 +24,7 @@
 #include "button.h"
 #ifdef HAVE_SDL
 #include "button-sdl.h"
+#include "lcd-sdl.h"
 #endif
 
 static struct event_queue button_queue SHAREDBSS_ATTR;
@@ -100,7 +101,7 @@ static inline void button_queue_wait(struct queue_event *evp, int timeout)
     unsigned long curr_tick, remaining;
     while(true)
     {
-        handle_sdl_events();
+        handle_sdl_events(); /* Includes window updates after resize events */
         queue_wait_w_tmo(&button_queue, evp, TIMEOUT_NOBLOCK);
         if (evp->id != SYS_TIMEOUT || timeout == TIMEOUT_NOBLOCK)
             return;
@@ -117,6 +118,9 @@ static inline void button_queue_wait(struct queue_event *evp, int timeout)
     }
 #else
     queue_wait_w_tmo(&button_queue, evp, timeout);
+#ifdef HAVE_SDL
+    sdl_update_window(); /* Window may have been resized */
+#endif
 #endif
 }
 #endif /* HAVE_ADJUSTABLE_CPU_FREQ */

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

@@ -31,6 +31,7 @@
 #include "backlight.h"
 #include "system.h"
 #include "button-sdl.h"
+#include "lcd-sdl.h"
 #include "sim_tasks.h"
 #include "buttonmap.h"
 #include "debug.h"
@@ -240,6 +241,17 @@ static bool event_handler(SDL_Event *event)
             sdl_app_has_input_focus = 1;
         else if (event->window.event == SDL_WINDOWEVENT_FOCUS_LOST)
             sdl_app_has_input_focus = 0;
+        else if(event->window.event == SDL_WINDOWEVENT_RESIZED)
+        {
+            sdl_window_needs_update();
+#if !defined (__APPLE__) && !defined(__WIN32)
+            static unsigned long last_tick;
+            if (TIME_AFTER(current_tick, last_tick + HZ/20) && !button_queue_full())
+                  button_queue_post(SDLK_UNKNOWN, 0); /* update window on main thread */
+            else
+                  last_tick = current_tick;
+#endif
+        }
         break;
     case SDL_KEYDOWN:
     case SDL_KEYUP:

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

@@ -23,9 +23,99 @@
 #include "lcd-sdl.h"
 #include "sim-ui-defines.h"
 #include "system.h" /* for MIN() and MAX() */
+#include "misc.h"
 
 double display_zoom = 1;
 
+static bool window_needs_update;
+
+void sdl_get_window_dimensions(int *w, int *h)
+{
+    if (background)
+    {
+        *w = UI_WIDTH;
+        *h = UI_HEIGHT;
+    }
+    else
+    {
+#ifdef HAVE_REMOTE_LCD
+        if (showremote)
+        {
+            *w = SIM_LCD_WIDTH > SIM_REMOTE_WIDTH ? SIM_LCD_WIDTH : SIM_REMOTE_WIDTH;
+            *h = SIM_LCD_HEIGHT + SIM_REMOTE_HEIGHT;
+        }
+        else
+#endif
+        {
+            *w = SIM_LCD_WIDTH;
+            *h = SIM_LCD_HEIGHT;
+        }
+    }
+}
+
+static inline void sdl_render(void)
+{
+    SDL_Texture *sdlTexture = SDL_CreateTextureFromSurface(sdlRenderer, gui_surface);
+    SDL_RenderClear(sdlRenderer);
+    SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
+    SDL_RenderPresent(sdlRenderer);
+    SDL_DestroyTexture(sdlTexture);
+}
+
+
+#define SNAP_MARGIN 50
+int sdl_update_window(void)
+{
+    if (!window_needs_update)
+        return false;
+    window_needs_update = false;
+
+#if defined (__APPLE__) || defined(__WIN32) /* Constrain aspect ratio */
+    if (!(SDL_GetWindowFlags(window) & (SDL_WINDOW_MAXIMIZED | SDL_WINDOW_FULLSCREEN)))
+    {
+        float aspect_ratio;
+        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)
+            {
+                w = original_width;
+                h = original_height;
+            }
+            else
+                h = w * aspect_ratio;
+
+            SDL_SetWindowSize(window, w, h);
+        }
+    }
+#endif
+    sdl_render();
+    return true;
+}
+
+void sdl_window_needs_update(void)
+{
+    window_needs_update = true;
+
+    /* For MacOS and Windows, we're on a main or
+    display thread already, and can immediately
+    update the window.
+    On Linux, we have to defer the update, until
+    it is handled by the main thread later. */
+#if defined (__APPLE__) || defined(__WIN32)
+    sdl_update_window();
+#endif
+}
+
+
 void sdl_update_rect(SDL_Surface *surface, int x_start, int y_start, int width,
                      int height, int max_x, int max_y,
                      unsigned long (*getpixel)(int, int))
@@ -117,15 +207,12 @@ void sdl_gui_update(SDL_Surface *surface, int x_start, int y_start, int width,
 
     uint8_t alpha;
     if (SDL_GetSurfaceAlphaMod(surface,&alpha) == 0 && alpha < 255)
-        SDL_FillRect(gui_surface, &dest, 0);
+        SDL_FillRect(gui_surface, &dest, 0); /* alpha needs a black background */
 
-    SDL_BlitSurface(surface, &src, gui_surface, &dest); /* alpha needs a black background */
+    SDL_BlitSurface(surface, &src, gui_surface, &dest);
 
-    SDL_Texture *sdlTexture = SDL_CreateTextureFromSurface(sdlRenderer, gui_surface);
-    SDL_RenderClear(sdlRenderer);
-    SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
-    SDL_RenderPresent(sdlRenderer);
-    SDL_DestroyTexture(sdlTexture);
+    if (!sdl_update_window()) /* already calls sdl_render itself */
+        sdl_render();
 }
 
 /* set a range of bitmap indices to a gradient from startcolour to endcolour */

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

@@ -28,6 +28,11 @@
 /* Default display zoom level */
 extern SDL_Surface *gui_surface;
 extern SDL_Renderer *sdlRenderer;
+extern SDL_Window *window;
+
+void sdl_get_window_dimensions(int *w, int *h);
+int sdl_update_window(void);
+void sdl_window_needs_update(void);
 
 void sdl_update_rect(SDL_Surface *surface, int x_start, int y_start, int width,
                      int height, int max_x, int max_y,

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

@@ -91,28 +91,7 @@ static void sdl_window_setup(void)
         }
     }
 
-    /* Set things up */
-    if (background)
-    {
-        width = UI_WIDTH;
-        height = UI_HEIGHT;
-    }
-    else
-    {
-#ifdef HAVE_REMOTE_LCD
-        if (showremote)
-        {
-            width = SIM_LCD_WIDTH > SIM_REMOTE_WIDTH ? SIM_LCD_WIDTH : SIM_REMOTE_WIDTH;
-            height = SIM_LCD_HEIGHT + SIM_REMOTE_HEIGHT;
-        }
-        else
-#endif
-        {
-            width = SIM_LCD_WIDTH;
-            height = SIM_LCD_HEIGHT;
-        }
-    }
-
+    sdl_get_window_dimensions(&width, &height);
     depth = LCD_DEPTH;
     if (depth < 8)
         depth = 16;
@@ -122,11 +101,20 @@ static void sdl_window_setup(void)
     flags |= SDL_WINDOW_FULLSCREEN;
 #endif
 
+    if (display_zoom == 1)
+        flags |= SDL_WINDOW_RESIZABLE;
+
+    flags |= SDL_WINDOW_ALLOW_HIGHDPI;
+
     if ((window = SDL_CreateWindow(UI_TITLE, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
                       width * display_zoom, height * display_zoom , flags)) == NULL)
         panicf("%s", SDL_GetError());
     if ((sdlRenderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_PRESENTVSYNC)) == NULL)
         panicf("%s", SDL_GetError());
+
+    SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
+    SDL_RenderSetLogicalSize(sdlRenderer, width * display_zoom, height * display_zoom);
+
     if ((gui_surface = SDL_CreateRGBSurface(0, width * display_zoom, height * display_zoom, depth,
                                        0, 0, 0, 0)) == NULL)
         panicf("%s", SDL_GetError());
@@ -152,6 +140,7 @@ static void sdl_window_setup(void)
 static int sdl_event_thread(void * param)
 {
 #ifdef __WIN32 /* Fails on Linux and MacOS */
+    SDL_SetHint(SDL_HINT_WINDOWS_DPI_SCALING, "1");
     SDL_InitSubSystem(SDL_INIT_VIDEO);
     sdl_window_setup();
 #endif