[MacOS] Resize flicker

[filipkrw]

Hi, I'm experiencing a flicker when resizing the window on MacOS. See:

Screen.Recording.2025-01-24.at.21.21.52.mov

It looks as if SDL3 can't keep up with rendering frames on time, but the program is dead simple -- a single rectangle. It also doesn't happen on Windows.

Source code:

#define SDL_MAIN_USE_CALLBACKS 1
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>

static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;

static int window_width = 640;
static int window_height = 480;

SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
    SDL_SetAppMetadata("Example Renderer Rectangles", "1.0", "com.example.renderer-rectangles");

    if (!SDL_Init(SDL_INIT_VIDEO))
    {
        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }

    if (!SDL_CreateWindowAndRenderer("SDL3", window_width, window_height, SDL_WINDOW_RESIZABLE, &window, &renderer))
    {
        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }

    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
    if (event->type == SDL_EVENT_QUIT)
    {
        return SDL_APP_SUCCESS;
    }
    else if (event->type == SDL_EVENT_WINDOW_RESIZED)
    {
        window_width = event->window.data1;
        window_height = event->window.data2;
    }
    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppIterate(void *appstate)
{
    SDL_SetWindowMinimumSize(window, 320, 240);

    SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
    SDL_RenderClear(renderer);

    SDL_FRect rounded_rect = {
        .x = 30.0f,
        .y = 30.0f,
        .w = window_width - 60.0f,
        .h = window_height - 60.0f};
    SDL_SetRenderDrawColor(renderer, 180, 180, 180, SDL_ALPHA_OPAQUE);
    SDL_RenderFillRect(renderer, &rounded_rect);

    SDL_RenderPresent(renderer);

    return SDL_APP_CONTINUE;
}

void SDL_AppQuit(void *appstate, SDL_AppResult result)
{
}

And build config:

-- Checking for module 'libusb-1.0>=1.0.16'
--   No package 'libusb-1.0' found
-- Could NOT find LibUSB (missing: LibUSB_LIBRARY LibUSB_INCLUDE_PATH) (found version "LibUSB_VERSION-NOTFOUND")
-- 
-- SDL3 was configured with the following options:
-- 
-- Platform: Darwin-24.0.0
-- 64-bit:   TRUE
-- Compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Revision: SDL3-3.2.1-release-3.2.0-30-g17c4bdd75
-- Vendor:   
-- 
-- Subsystems:
--   Audio:    ON
--   Video:    ON
--   GPU:      ON
--   Render:   ON
--   Camera:   ON
--   Joystick: ON
--   Haptic:   ON
--   Hidapi:   ON
--   Power:    ON
--   Sensor:   ON
--   Dialog:   ON
-- 
-- Options:
--   SDL_ALSA                    (Wanted: OFF): OFF
--   SDL_ALSA_SHARED             (Wanted: OFF): OFF
--   SDL_ALTIVEC                 (Wanted: OFF): OFF
--   SDL_ARMNEON                 (Wanted: ON): ON
--   SDL_ASAN                    (Wanted: OFF): OFF
--   SDL_ASSEMBLY                (Wanted: ON): ON
--   SDL_ASSERTIONS              (Wanted: auto): auto
--   SDL_AVX                     (Wanted: OFF): OFF
--   SDL_AVX2                    (Wanted: OFF): OFF
--   SDL_AVX512F                 (Wanted: OFF): OFF
--   SDL_BACKGROUNDING_SIGNAL    (Wanted: OFF): OFF
--   SDL_CCACHE                  (Wanted: OFF): OFF
--   SDL_CLANG_TIDY              (Wanted: OFF): OFF
--   SDL_CLOCK_GETTIME           (Wanted: OFF): OFF
--   SDL_COCOA                   (Wanted: ON): ON
--   SDL_DBUS                    (Wanted: OFF): OFF
--   SDL_DIRECTX                 (Wanted: OFF): OFF
--   SDL_DISKAUDIO               (Wanted: ON): ON
--   SDL_DUMMYAUDIO              (Wanted: ON): ON
--   SDL_DUMMYCAMERA             (Wanted: ON): ON
--   SDL_DUMMYVIDEO              (Wanted: ON): ON
--   SDL_EXAMPLES                (Wanted: OFF): OFF
--   SDL_EXAMPLES_LINK_SHARED    (Wanted: ON): OFF
--   SDL_FOREGROUNDING_SIGNAL    (Wanted: OFF): OFF
--   SDL_GCC_ATOMICS             (Wanted: ON): ON
--   SDL_GPU_DXVK                (Wanted: OFF): OFF
--   SDL_HIDAPI                  (Wanted: ON): ON
--   SDL_HIDAPI_JOYSTICK         (Wanted: ON): ON
--   SDL_HIDAPI_LIBUSB           (Wanted: ON): OFF
--   SDL_HIDAPI_LIBUSB_SHARED    (Wanted: ON): OFF
--   SDL_IBUS                    (Wanted: OFF): OFF
--   SDL_INSTALL                 (Wanted: OFF): OFF
--   SDL_INSTALL_TESTS           (Wanted: OFF): OFF
--   SDL_JACK                    (Wanted: OFF): OFF
--   SDL_JACK_SHARED             (Wanted: OFF): OFF
--   SDL_KMSDRM                  (Wanted: OFF): OFF
--   SDL_KMSDRM_SHARED           (Wanted: OFF): OFF
--   SDL_LASX                    (Wanted: OFF): OFF
--   SDL_LIBC                    (Wanted: ON): ON
--   SDL_LIBICONV                (Wanted: OFF): OFF
--   SDL_LIBUDEV                 (Wanted: ON): OFF
--   SDL_LIBURING                (Wanted: OFF): OFF
--   SDL_LSX                     (Wanted: OFF): OFF
--   SDL_METAL                   (Wanted: ON): ON
--   SDL_MMX                     (Wanted: OFF): OFF
--   SDL_OFFSCREEN               (Wanted: ON): ON
--   SDL_OPENGL                  (Wanted: ON): ON
--   SDL_OPENGLES                (Wanted: ON): ON
--   SDL_OPENVR                  (Wanted: OFF): OFF
--   SDL_OSS                     (Wanted: OFF): OFF
--   SDL_PIPEWIRE                (Wanted: OFF): OFF
--   SDL_PIPEWIRE_SHARED         (Wanted: OFF): OFF
--   SDL_PTHREADS                (Wanted: ON): ON
--   SDL_PTHREADS_SEM            (Wanted: ON): ON
--   SDL_PULSEAUDIO              (Wanted: OFF): OFF
--   SDL_PULSEAUDIO_SHARED       (Wanted: OFF): OFF
--   SDL_RENDER_D3D              (Wanted: OFF): OFF
--   SDL_RENDER_D3D11            (Wanted: OFF): OFF
--   SDL_RENDER_D3D12            (Wanted: OFF): OFF
--   SDL_RENDER_GPU              (Wanted: ON): ON
--   SDL_RENDER_METAL            (Wanted: ON): ON
--   SDL_RENDER_VULKAN           (Wanted: ON): ON
--   SDL_ROCKCHIP                (Wanted: OFF): OFF
--   SDL_RPATH                   (Wanted: ON): ON
--   SDL_RPI                     (Wanted: OFF): OFF
--   SDL_SNDIO                   (Wanted: OFF): OFF
--   SDL_SNDIO_SHARED            (Wanted: OFF): OFF
--   SDL_SSE                     (Wanted: OFF): OFF
--   SDL_SSE2                    (Wanted: OFF): OFF
--   SDL_SSE3                    (Wanted: OFF): OFF
--   SDL_SSE4_1                  (Wanted: OFF): OFF
--   SDL_SSE4_2                  (Wanted: OFF): OFF
--   SDL_SYSTEM_ICONV            (Wanted: OFF): OFF
--   SDL_TESTS                   (Wanted: OFF): OFF
--   SDL_TESTS_LINK_SHARED       (Wanted: ON): OFF
--   SDL_UNINSTALL               (Wanted: OFF): OFF
--   SDL_VIRTUAL_JOYSTICK        (Wanted: ON): ON
--   SDL_VIVANTE                 (Wanted: OFF): OFF
--   SDL_VULKAN                  (Wanted: ON): ON
--   SDL_WASAPI                  (Wanted: OFF): OFF
--   SDL_WAYLAND                 (Wanted: OFF): OFF
--   SDL_WAYLAND_LIBDECOR        (Wanted: OFF): OFF
--   SDL_WAYLAND_LIBDECOR_SHARED (Wanted: OFF): OFF
--   SDL_WAYLAND_SHARED          (Wanted: OFF): OFF
--   SDL_X11                     (Wanted: OFF): OFF
--   SDL_X11_SHARED              (Wanted: OFF): OFF
--   SDL_X11_XCURSOR             (Wanted: OFF): OFF
--   SDL_X11_XDBE                (Wanted: OFF): OFF
--   SDL_X11_XFIXES              (Wanted: OFF): OFF
--   SDL_X11_XINPUT              (Wanted: OFF): OFF
--   SDL_X11_XRANDR              (Wanted: OFF): OFF
--   SDL_X11_XSCRNSAVER          (Wanted: OFF): OFF
--   SDL_X11_XSHAPE              (Wanted: OFF): OFF
--   SDL_X11_XSYNC               (Wanted: OFF): OFF
--   SDL_XINPUT                  (Wanted: OFF): OFF
-- 
--  Build Shared Library: ON
--  Build Static Library: OFF
--  Build libraries as Apple Framework: OFF
-- 
-- If something was not detected, although the libraries
-- were installed, then make sure you have set the
-- CMAKE_C_FLAGS and CMAKE_PREFIX_PATH CMake variables correctly.
-- 
-- Configuring done (0.3s)
-- Generating done (0.1s)

[playmer]

In your reddit post, you mentioned this working alright in sokol on Mac, can you provide a sample of that so that it can be compared?

[filipkrw]

Hey, thanks for reaching out!

I'm not doing anything special, simply drawing some text using sokol_fontstash and a rectangle using sokol_gl. At some point I also used sokol_gp and similarly had no issues with resizing on MacOS (M1 Max chip).

See the code here: https://github.com/filipkrw/hello-sokol. It should build on Windows and MacOS, but let me know in case you try it out and encounter some issues.

Screen.Recording.2025-01-27.at.23.36.20.mov

[LeonardoTemperanza]

I'd like to add that with this exact example, this does happen on Windows (10), if you resize the window from the left or top instead of the right or bottom. Actually in all cases the rendering seems to be consistently a single frame behind. It's just that it's less noticeable when resizing from the right/bottom because your pointer is also moving. Given how finnicky/random Windows is regarding window resizing i'm not sure if this can even be fixed.