emscripten_request_fullscreen_strategy callback order

[Daft-Freak]

With this test code:

#include <stdio.h>

#include <emscripten/emscripten.h>
#include <emscripten/html5.h>

EM_BOOL is_fs = EM_FALSE;

EM_BOOL fullscreen_change(int eventType, const EmscriptenFullscreenChangeEvent *fullscreenChangeEvent, void *userData)
{
    is_fs = fullscreenChangeEvent->isFullscreen;

    printf("%s fullscreen\n", is_fs ? "entered" : "left");

    return 0;
}

EM_BOOL canvas_resize(int eventType, const void *reserved, void *userData)
{

    double css_w, css_h;
    emscripten_get_element_css_size("#canvas", &css_w, &css_h);

    printf("resized to %fx%f\n", css_w, css_h);

    return 0;
}

EM_BOOL key_down(int eventType, const EmscriptenKeyboardEvent *keyEvent, void *userData)
{
    if(keyEvent->keyCode == 0x46/*f*/) {
        if(is_fs)
            emscripten_exit_fullscreen();
        else {
            EmscriptenFullscreenStrategy strategy;
            strategy.scaleMode = EMSCRIPTEN_FULLSCREEN_SCALE_STRETCH;
            strategy.canvasResolutionScaleMode = EMSCRIPTEN_FULLSCREEN_CANVAS_SCALE_STDDEF;
            strategy.filteringMode = EMSCRIPTEN_FULLSCREEN_FILTERING_DEFAULT;
            strategy.canvasResizedCallback = canvas_resize;
            strategy.canvasResizedCallbackUserData = NULL;

            emscripten_request_fullscreen_strategy("#canvas", 1, &strategy);
        }
    }

    return 1;
}

void loop() {}

int main(int argc, char** argv) {

    emscripten_set_canvas_element_size("#canvas", 800, 600);

    emscripten_set_fullscreenchange_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, NULL, 0, fullscreen_change);
    emscripten_set_keydown_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, NULL, 0, key_down);
    emscripten_set_main_loop(loop, 0, 1);

    return 0;
}

Pressing F, F (using emscripten_exit_fullscreen) results in:

resized to 1920.000000x1080.000000
entered fullscreen
resized to 1920.000000x1080.000000
left fullscreen

And pressing F, Esc (cancelling through the browser) results in:

resized to 1920.000000x1080.000000
entered fullscreen
left fullscreen
resized to 800.000000x600.000000

When using emscripten_exit_fullscreen, the resize callback gets called before restoring the old size. It looks like what happens is:

• emscripten_exit_fullscreen calls .exitFullscreen
• Then it calls the resize callback and resets __currentFullscreenStrategy
• The fullscreen change happens and the fullscreenchange handler for restoreOldStyle gets called
• The canvas style is restored, but __currentFullscreenStrategy is 0 so the resize callback doesn't get called.

Removing the if (__currentFullscreenStrategy.canvasResizedCallback) block in emscripten_exit_fullscreen seems to work, but I'm not sure if that would break something else.

See: emscripten-ports/SDL2#87

[kripken]

Interesting. It may be worth looking at the fullscreen tests in the interactive test suite. Those may not be up to date, but maybe they'll show a possible problem with your proposed fix.

cc @juj who wrote most of that code.

[Beuc]

For the record no issues to report in RenPyWeb so far (besides actually fixing full-screen support ;)).

[kripken]

Thanks, yeah, that seems right to me. I opened #9765