SDL/Cocoa embedding

SDL Development
1

Hello,

I’ve been trying in vain to integrate an SDL renderer into an existing Cocoa window. I’m struggling to find information in the SDL3 documentation.

The programme runs without a hitch but displays two windows. This makes sense, as the programme is supposed to create two, as the code below shows. However, it must also embed one within the other.

#include "SDL3/SDL_error.h"
#include "SDL3/SDL_events.h"
#include "SDL3/SDL_init.h"
#include "SDL3/SDL_log.h"
#include "SDL3/SDL_properties.h"
#include "SDL3/SDL_render.h"
#include "SDL3/SDL_video.h"
#import <Cocoa/Cocoa.h>
#import <CoreGraphics/CoreGraphics.h>
#include <Foundation/Foundation.h>
#include <cstddef>
#include <cstdlib>

#include <SDL3/SDL.h>

extern "C" void sdl_render_frame(SDL_Renderer *renderer, void *user);

static bool g_running = false;

static SDL_Window *g_sdlWindow = nullptr;
static SDL_Renderer *g_sdlRenderer = nullptr;

@interface BridgeView : NSView
@property(nonatomic, assign) NSTimer *sdlTimer;
@end

@implementation BridgeView
- (void)dealloc {
  if (_sdlTimer) {
    [_sdlTimer invalidate];
    _sdlTimer = nil;
  }
  [super dealloc];
}
- (void)viewDidMoveToWindow {
  [super viewDidMoveToWindow];
  if (!self.sdlTimer) {
    self.sdlTimer = [NSTimer scheduledTimerWithTimeInterval:(1.0 / 120.0)
                                                     target:self
                                                   selector:@selector(sdlTick:)
                                                   userInfo:nil
                                                    repeats:YES];
  }
}
- (void)sdlTick:(NSTimer *)t {
  SDL_Event ev;
  while (SDL_PollEvent(&ev)) {
    if (ev.type == SDL_EVENT_QUIT) {
      g_running = false;
      [NSApp terminate:nil];
      return;
    }
  }
  if (g_sdlRenderer) {
    SDL_SetRenderDrawColor(g_sdlRenderer, 50, 50, 50, 255);
    SDL_RenderClear(g_sdlRenderer);
    extern void sdl_render_frame(SDL_Renderer * renderer, void *user);
    sdl_render_frame(g_sdlRenderer, NULL);
    SDL_RenderPresent(g_sdlRenderer);
  }
}
@end

static SDL_PropertiesID make_propes_for_ns_view(void *nsViewPtr, int w, int h,
                                                const char *title) {
  SDL_PropertiesID props = SDL_CreateProperties();
  if (!props)
    return 0;
  SDL_SetPointerProperty(props, SDL_PROP_WINDOW_COCOA_WINDOW_POINTER,
                         nsViewPtr);
  SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_WIDTH_NUMBER, w);
  SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_HEIGHT_NUMBER, h);
  if (title)
    SDL_SetStringProperty(props, SDL_PROP_WINDOW_CREATE_TITLE_STRING, title);
  return props;
}

#pragma mark - Public API

extern "C" int app_bridge_init_and_run(int width, int height,
                                       const char *title) {
  @autoreleasepool {
    [NSApplication sharedApplication];
    [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];

    NSRect frame = NSMakeRect(0, 0, width, height);
    NSUInteger style = NSWindowStyleMaskTitled | NSWindowStyleMaskClosable |
                       NSWindowStyleMaskResizable |
                       NSWindowStyleMaskMiniaturizable;
    NSWindow *win = [[NSWindow alloc] initWithContentRect:frame
                                                styleMask:style
                                                  backing:NSBackingStoreBuffered
                                                    defer:NO];
    if (title)
      [win setTitle:[NSString stringWithUTF8String:title]];
    [win center];

    NSRect contentFrame = NSMakeRect(0, 0, width, height);
    BridgeView *view = [[BridgeView alloc] initWithFrame:contentFrame];
    view.wantsLayer = YES;
    view.autoresizingMask = NSViewWidthSizable | NSViewHeightSizable;

    NSView *content = [win contentView];
    [content addSubview:view];

    [win makeKeyAndOrderFront:nil];
    [NSApp activateIgnoringOtherApps:YES];

    if (SDL_Init(SDL_INIT_EVENTS | SDL_INIT_VIDEO) != 1) {
      NSLog(@"SDL_Init failed: %s", SDL_GetError());
      return EXIT_FAILURE;
    }

    void *nativeViewPtr = (__bridge void *)view;
    SDL_PropertiesID props =
        make_propes_for_ns_view(nativeViewPtr, width, height, title);
    if (!props) {
      NSLog(@"Failed to create SDL props");
      SDL_Quit();
      return EXIT_FAILURE;
    }

    g_sdlWindow = SDL_CreateWindowWithProperties(props);
    SDL_DestroyProperties(props);
    if (!g_sdlWindow) {
      NSLog(@"SDL_CreateWindowWithProperties failed: %s", SDL_GetError());
      SDL_Quit();
      return EXIT_FAILURE;
    }

    g_sdlRenderer = SDL_CreateRenderer(g_sdlWindow, title);

    [NSApp run];

    if (g_sdlRenderer) {
      SDL_DestroyRenderer(g_sdlRenderer);
      g_sdlRenderer = NULL;
    }
    if (g_sdlWindow) {
      SDL_DestroyWindow(g_sdlWindow);
      g_sdlWindow = NULL;
    }

    SDL_Quit();
    return EXIT_SUCCESS;
  }
}

extern "C" void request_redraw() {
  @autoreleasepool {
    NSWindow *win = [NSApp mainWindow];
    if (!win)
      return;
    NSView *v = [win contentView];
    if (v)
      [v setNeedsDisplay:YES];
  }
}

Could you help me?

2

I’m not familiar with Cocoa so I’m not sure but the docs seem to be saying you should pass the window …

SDL_PROP_WINDOW_COCOA_WINDOW_POINTER: the (__unsafe_unretained) NSWindow associated with the window

… but it looks like you’re passing a BridgeView/NSView instead.