[WIP] Add port of SDL3

So far I haven't got any browser tests working.

Fixes: #23608

test/browser/test_sdl2_canvas_write.c

@@ -5,73 +5,75 @@
 
 #include <assert.h>
 #include <SDL.h>
-#include <emscripten.h>
+#include <emscripten/em_asm.h>
 
-static void sdlError(const char *str) 
-{
-    fprintf(stderr, "Error at %s: %s\n", str, SDL_GetError());
-    emscripten_force_exit(1);
+static void sdlError(const char* str) {
+  fprintf(stderr, "Error at %s: %s\n", str, SDL_GetError());
+  exit(1);
 }
 
-void draw(SDL_Window *window, SDL_Surface *surface) {
-    int x, y;
+void draw(SDL_Window* window, SDL_Surface* surface) {
+  int x, y;
 
-    if (SDL_MUSTLOCK(surface)) {
-        if (SDL_LockSurface(surface) != 0) sdlError("SDL_LockSurface");
-    }
+  if (SDL_MUSTLOCK(surface)) {
+    if (SDL_LockSurface(surface) != 0)
+      sdlError("SDL_LockSurface");
+  }
 
-    for (y = 0; y < 256; y++) {
-        Uint32 *p = (Uint32 *)(((Uint8 *)surface->pixels) +
-                               surface->pitch * y);
-        for (x = 0; x < 256; x++) {
-            *(p++) = SDL_MapRGB(surface->format, x, x ^ y, y);
-        }
+  for (y = 0; y < 256; y++) {
+    Uint32* p = (Uint32*)(((Uint8*)surface->pixels) + surface->pitch * y);
+    for (x = 0; x < 256; x++) {
+      *(p++) = SDL_MapRGB(surface->format, x, x ^ y, y);
     }
+  }
 
-    if (SDL_MUSTLOCK(surface)) SDL_UnlockSurface(surface);
-    if (SDL_UpdateWindowSurface(window) != 0)
-        sdlError("SDL_UpdateWindowSurface");
+  if (SDL_MUSTLOCK(surface))
+    SDL_UnlockSurface(surface);
+  if (SDL_UpdateWindowSurface(window) != 0)
+    sdlError("SDL_UpdateWindowSurface");
 }
 
 void verify(void) {
-    int res = EM_ASM_INT({
-        var ctx = Module['canvas'].getContext('2d');
-        var data = ctx.getImageData(0, 0, 256, 256).data;
-        var idx = 0;
-        for (var y = 0; y < 256; y++) {
-            for (var x = 0; x < 256; x++) {
-                if (data[idx    ] !== x || 
-                    data[idx + 1] !== (x ^ y) || 
-                    data[idx + 2] !== y ||
-                    data[idx + 3] !== 255) {
-                    return 1;
-                }
-                idx += 4;
+  int res = EM_ASM_INT({
+    var ctx = Module['canvas'].getContext('2d');
+    var data = ctx.getImageData(0, 0, 256, 256).data;
+    var idx = 0;
+    for (var y = 0; y < 256; y++) {
+        for (var x = 0; x < 256; x++) {
+            if (data[idx    ] !== x || 
+                data[idx + 1] !== (x ^ y) || 
+                data[idx + 2] !== y ||
+                data[idx + 3] !== 255) {
+                return 1;
             }
+            idx += 4;
         }
-        return 0;
-    });
+    }
+    return 0;
+  });
 
-    printf("%s\n", res ? "FAIL" : "PASS");
-    assert(res == 0);
+  printf("%s\n", res ? "FAIL" : "PASS");
+  assert(res == 0);
 }
 
 int main(void) {
-    SDL_Window *window;
-    SDL_Surface *surface;
+  SDL_Window* window;
+  SDL_Surface* surface;
 
-    if (SDL_Init(SDL_INIT_VIDEO) != 0) sdlError("SDL_Init");
+  if (SDL_Init(SDL_INIT_VIDEO) != 0)
+    sdlError("SDL_Init");
 
-    window = SDL_CreateWindow("SDL 2 test",
-                              0, 0,
-                              256, 256,
-                              SDL_WINDOW_SHOWN);
-    if (window == NULL) sdlError("SDL_CreateWindow");
-    surface = SDL_GetWindowSurface(window);
-    if (surface == NULL) sdlError("SDL_GetWindowSurface");
+  window = SDL_CreateWindow("SDL 2 test", 0, 0, 256, 256, SDL_WINDOW_SHOWN);
+  if (window == NULL) {
+    sdlError("SDL_CreateWindow");
+  }
+  surface = SDL_GetWindowSurface(window);
+  if (surface == NULL)  {
+    sdlError("SDL_GetWindowSurface");
+  }
 
-    draw(window, surface);
+  draw(window, surface);
 
-    verify();
-    return 0;
+  verify();
+  return 0;
 }

test/browser/test_sdl2_misc.c

@@ -13,40 +13,40 @@
 
 #include <emscripten.h>
 
-int main(int argc, char *argv[])
-{
-    SDL_Window *window;
-
-    if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
-        printf("Unable to initialize SDL: %s\n", SDL_GetError());
-        return 1;
-    }
-
-    window = SDL_CreateWindow(
-        "sdl2_misc",
-        SDL_WINDOWPOS_UNDEFINED,
-        SDL_WINDOWPOS_UNDEFINED,
-        100,
-        100,
-        0
-    );
-
-    EM_ASM({
-      assert(document.title === 'sdl2_misc');
-    });
-    const char* intended = "a custom window title";
-    SDL_SetWindowTitle(window, intended);
-    const char* seen = SDL_GetWindowTitle(window);
-    if (strcmp(intended, seen) != 0) {
-        printf("Got a weird title back: %s\n", seen);
-        return 1;
-    }
-    EM_ASM({
-      assert(document.title === 'a custom window title');
-    });
-
-    SDL_DestroyWindow(window);
-    SDL_Quit();
-
-    return 0;
+int main(int argc, char *argv[]) {
+  SDL_Window *window;
+
+  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
+    printf("Unable to initialize SDL: %s\n", SDL_GetError());
+    return 1;
+  }
+
+  window = SDL_CreateWindow(
+    "sdl2_misc",
+    SDL_WINDOWPOS_UNDEFINED,
+    SDL_WINDOWPOS_UNDEFINED,
+    100,
+    100,
+    0
+  );
+
+  EM_ASM({
+    assert(document.title === 'sdl2_misc');
+  });
+  const char* intended = "a custom window title";
+  SDL_SetWindowTitle(window, intended);
+  const char* seen = SDL_GetWindowTitle(window);
+  if (strcmp(intended, seen) != 0) {
+      printf("Got a weird title back: %s\n", seen);
+      return 1;
+  }
+
+  EM_ASM({
+    assert(document.title === 'a custom window title');
+  });
+
+  SDL_DestroyWindow(window);
+  SDL_Quit();
+
+  return 0;
 }

test/browser/test_sdl3_canvas_write.c

@@ -0,0 +1,85 @@
+// Copyright 2015 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <SDL3/SDL.h>
+#include <emscripten/em_asm.h>
+
+static void sdlError(const char* str) {
+  fprintf(stderr, "Error at %s: %s\n", str, SDL_GetError());
+  exit(1);
+}
+
+void draw(SDL_Window* window, SDL_Surface* surface) {
+  int x, y;
+
+  if (SDL_MUSTLOCK(surface)) {
+    if (!SDL_LockSurface(surface)) {
+      sdlError("SDL_LockSurface");
+    }
+  }
+
+  for (y = 0; y < 256; y++) {
+    Uint32* p = (Uint32*)(((Uint8*)surface->pixels) + surface->pitch * y);
+    for (x = 0; x < 256; x++) {
+      *(p++) = SDL_MapSurfaceRGB(surface, x, x ^ y, y);
+    }
+  }
+
+  if (SDL_MUSTLOCK(surface)) {
+    SDL_UnlockSurface(surface);
+  }
+  if (!SDL_UpdateWindowSurface(window)) {
+    sdlError("SDL_UpdateWindowSurface");
+  }
+}
+
+void verify(void) {
+  int res = EM_ASM_INT({
+    var ctx = Module['canvas'].getContext('2d');
+    var data = ctx.getImageData(0, 0, 256, 256).data;
+    var idx = 0;
+    for (var y = 0; y < 256; y++) {
+        for (var x = 0; x < 256; x++) {
+            if (data[idx    ] !== x || 
+                data[idx + 1] !== (x ^ y) || 
+                data[idx + 2] !== y ||
+                data[idx + 3] !== 255) {
+                return 1;
+            }
+            idx += 4;
+        }
+    }
+    return 0;
+  });
+
+  printf("%s\n", res ? "FAIL" : "PASS");
+  assert(res == 0);
+}
+
+int main(void) {
+  SDL_Window* window;
+  SDL_Surface* surface;
+
+  if (!SDL_Init(SDL_INIT_VIDEO)) {
+    sdlError("SDL_Init");
+  }
+
+  window = SDL_CreateWindow("SDL 2 test", 256, 256, 0);
+  if (window == NULL) {
+    sdlError("SDL_CreateWindow");
+  }
+  surface = SDL_GetWindowSurface(window);
+  if (surface == NULL)  {
+    sdlError("SDL_GetWindowSurface");
+  }
+
+  draw(window, surface);
+
+  verify();
+  return 0;
+}

test/browser/test_sdl3_misc.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2025 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#include "SDL3/SDL.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include <emscripten.h>
+
+int main(int argc, char* argv[]) {
+  SDL_Window* window;
+
+  if (!SDL_Init(SDL_INIT_VIDEO)) {
+    printf("Unable to initialize SDL: %s\n", SDL_GetError());
+    assert(false);
+  }
+
+  window = SDL_CreateWindow("sdl3_misc", 100, 100, 0);
+
+  EM_ASM({
+    assert(document.title == 'sdl3_misc');
+  });
+  const char* intended = "a custom window title";
+  SDL_SetWindowTitle(window, intended);
+  const char* seen = SDL_GetWindowTitle(window);
+  if (strcmp(intended, seen) != 0) {
+    printf("Got a weird title back: %s\n", seen);
+    assert(false);
+  }
+  EM_ASM({
+    assert(document.title == 'a custom window title');
+  });
+
+  SDL_DestroyWindow(window);
+  SDL_Quit();
+
+  return 0;
+}

test/test_browser.py

@@ -3245,6 +3245,13 @@ def test_sdl2_mixer_music(self, formats, flags, music_name):
       args += ['-lc++', '-lc++abi']
     self.btest_exit('test_sdl2_mixer_music.c', args=args)
 
+  def test_sdl3_misc(self):
+    self.emcc_args.append('-Wno-experimental')
+    self.btest_exit('test_sdl3_misc.c', args=['-sUSE_SDL=3'])
+
+  def test_sdl3_canvas_write(self):
+    self.btest_exit('test_sdl3_canvas_write.c', args=['-sUSE_SDL=3'])
+
   @requires_graphics_hardware
   @no_wasm64('cocos2d ports does not compile with wasm64')
   def test_cocos2d_hello(self):

test/test_other.py

@@ -2476,6 +2476,13 @@ def test_sdl2_linkable(self):
     self.emcc(test_file('browser/test_sdl2_misc.c'), ['-sLINKABLE', '-sUSE_SDL=2'], output_filename='a.out.js')
     self.emcc(test_file('browser/test_sdl2_misc.c'), ['-sLINKABLE', '--use-port=sdl2'], output_filename='a.out.js')
 
+  def test_sdl3_linkable(self):
+    # Ensure that SDL2 can be built with LINKABLE.  This implies there are no undefined
+    # symbols in the library (because LINKABLE includes the entire library).
+    self.emcc_args.append('-Wno-experimental')
+    self.emcc(test_file('browser/test_sdl3_misc.c'), ['-sLINKABLE', '-sUSE_SDL=3'], output_filename='a.out.js')
+    self.emcc(test_file('browser/test_sdl3_misc.c'), ['-sLINKABLE', '--use-port=sdl3'], output_filename='a.out.js')
+
   @requires_network
   def test_sdl2_gfx_linkable(self):
     # Same as above but for sdl2_gfx library