Asyncify event.preventDefault() test

build.sh

mkdir -p bin
emcc -o bin/main.html main.c -s SINGLE_FILE=1
emcc -o bin/main-asyncify.html main.c -s ASYNCIFY=1 -s SINGLE_FILE=1

main.c

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

EM_BOOL focus_handler(int eventType, const EmscriptenFocusEvent *focusEvent, void *userData)
{
    printf("FAIL: Mouse event should have been consumed and canvas focus prevented.\n");
    return EM_FALSE;
}

EM_BOOL mouse_handler(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData)
{
    printf("Mouse event %d\n", eventType);
    return EM_TRUE;
}

int main(int argc, char **argv)
{
    emscripten_set_focus_callback("#canvas", NULL, EM_FALSE, focus_handler);
    emscripten_set_mousedown_callback("#canvas", NULL, EM_FALSE, mouse_handler);
    emscripten_set_mouseup_callback("#canvas", NULL, EM_FALSE, mouse_handler);
    emscripten_set_dblclick_callback("#canvas", NULL, EM_FALSE, mouse_handler);
    return 0;
}