FredyGames: changes to the Neverball 1.6.0 source (commit 84d4264992fd9b469510f5268cd662ce9d5022b5)
for the browser build of Neverputt served by fredygames.com. Active only with __EMSCRIPTEN__:
- putt/main.c: the canvas drawing buffer follows the size the page gives the canvas (as in
  Neverball's own web build); F11 (full screen) and F12 (screenshot) do nothing, because the player
  page has its own full-screen button; emscripten_sleep() every frame (the build uses Asyncify);
  fredygames_save(), which the page calls when the tab is hidden or closed, writes the settings.
- share/base_config.c: the user folder can be set at build time (EMSCRIPTEN_USER_DIR); Neverputt
  uses /neverputt, so it keeps its own IndexedDB database, apart from Neverball's.

--- a/putt/main.c
+++ b/putt/main.c
@@ -14,6 +14,11 @@
 
 /*---------------------------------------------------------------------------*/
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#include <emscripten/html5.h>
+#endif
+
 #include <SDL.h>
 #include <time.h>
 #include <stdio.h>
@@ -88,6 +93,26 @@
 
     int ax, ay, dx, dy;
 
+#ifdef __EMSCRIPTEN__
+    /* FredyGames: as in Neverball's web build, the canvas drawing buffer
+     * follows the size the page gives the canvas. */
+
+    double clientWidth, clientHeight;
+
+    int w, h;
+
+    emscripten_get_element_css_size("#canvas", &clientWidth, &clientHeight);
+
+    w = (int) clientWidth;
+    h = (int) clientHeight;
+
+    if (w > 0 && h > 0 && (w != video.window_w || h != video.window_h))
+    {
+        video_set_window_size(w, h);
+        gui_resize();
+    }
+#endif
+
     while (d && SDL_PollEvent(&e))
     {
         if (e.type == SDL_QUIT)
@@ -143,18 +168,23 @@
 
             switch (c)
             {
+#ifndef __EMSCRIPTEN__
+            /* FredyGames: the player page has its own full-screen button. */
             case KEY_SCREENSHOT:
                 shot();
                 break;
+#endif
             case KEY_FPS:
                 config_tgl_d(CONFIG_FPS);
                 break;
             case KEY_WIREFRAME:
                 toggle_wire();
                 break;
+#ifndef __EMSCRIPTEN__
             case KEY_FULLSCREEN:
                 video_fullscreen(!config_get_d(CONFIG_FULLSCREEN));
                 break;
+#endif
             case SDLK_RETURN:
             case SDLK_KP_ENTER:
                 d = st_buttn(config_get_d(CONFIG_JOYSTICK_BUTTON_A), 1);
@@ -257,6 +287,18 @@
 
 /*---------------------------------------------------------------------------*/
 
+#ifdef __EMSCRIPTEN__
+/* FredyGames: the page calls this when the tab is hidden or closed, because
+ * the game only writes its settings when it quits. */
+
+EMSCRIPTEN_KEEPALIVE void fredygames_save(void)
+{
+    config_save();
+}
+#endif
+
+/*---------------------------------------------------------------------------*/
+
 static char *opt_data;
 static char *opt_hole;
 
@@ -383,9 +425,19 @@
 
                     t0 = t1;
 
+#ifdef __EMSCRIPTEN__
+                    /* FredyGames: give the browser its turn every frame
+                     * (the build uses Asyncify). */
+                    emscripten_sleep(0);
+#else
                     if (config_get_d(CONFIG_NICE))
                         SDL_Delay(1);
+#endif
                 }
+#ifdef __EMSCRIPTEN__
+                else
+                    emscripten_sleep(1);
+#endif
 
             mtrl_quit();
         }
--- a/share/base_config.c
+++ b/share/base_config.c
@@ -103,7 +103,12 @@
 
 #ifdef __EMSCRIPTEN__
     /* Force IndexedDB-backed location created during Module['preRun']. */
+#ifdef EMSCRIPTEN_USER_DIR
+    /* FredyGames: Neverputt keeps its own folder (and IndexedDB database). */
+    user = strdup(EMSCRIPTEN_USER_DIR);
+#else
     user = strdup("/neverball");
+#endif
 #else
     user = concat_string(home, "/", CONFIG_USER, NULL);
 #endif