One option for blocking keyboard input you could try is to register a keyboard event callback e.g. via the emscripten library_html5.h handlers, and having ms_getchar() pause the main loop like you now do, and when you do get a key press, call resume on the main loop. Alternatively, if you don't want to keep pausing and resuming the main loop, you could just track a boolean that avoids the execution of any instructions in your interpreter while the key event query is pending. Unfortunately real blocking input is not possible without a dialog box.
You will need to break up the code that calls ms_getchar() to immediately return out of the event handler, and have the rest of the original code after ms_getchar() to be executed only after the keyboard event is received. Jukka 2014-02-06 Stefan Meier <[email protected]>: > Hi, > > first of all I want to apologize if this is not the right group for my > questions, but I didn't find a more appropriate one. Recently I started my > very first steps with emscripten - which btw is almost too cool to be > really existing .-) > > What I intended to do is porting an interpreter for text adventures > written in C (called Magnetic, available under GPL). The interpreter is > written in C und uses only stdio for input and output. There is no SDL > version and considering the "nature" of the tool, SDL would be a lot > overhead with gaining nothing, probably. > > While I managed to get the emscripten version to do its output to plain > html after a while I am now completely stuck when trying to get the user > input working. Before I throw everything into the garbage can, perhaps > someone with better JS skills than I have (and that's not a major > challenge), can take a look at the following parts and confirm my current > assumption: not solvable - or better, give me some hints what can be done. > > The main loop of the interpreter is as simple as this: > *running = 1;* > > > *while (running) running=ms_rungame();* > The interpreter core is actually some kind of very reduced 68k emulator > and each call to the ms_rungame "executes" one instruction. Now, when the > interpreter is running, at some point it runs to a function called ms_flush > for doing the output. I was able to gain from the various samples in the > emsdk a way to get the output written to plain html with something like > this: > *sprintf(outBuffer, "reformatAndSet('%c','textout')",buffer[j]);* > *emscripten_run_script(outBuffer);* > in the C code and this in the JS code: > > > > > > > * function reformatAndSet(text, target) { text = > text.replace(/&/g, "&"); text = text.replace(/</g, "<"); > text = text.replace(/>/g, ">"); text = text.replace('\n', '<br>', > 'g'); document.getElementById(target).innerHTML += text; }* > Most probably not a nice solution, but at least it works. But then I reach > my showstopper. So when contuing at some point the interpreter calls a > function named ms_getchar, which does fill an internal buffer array with > the user input in a loop of getchar calls and then return the chars after > after the other in subsequent calls to the ms_getchar routine. In the C > version this function waits for the user input. Emscripten replaces the > getchar calls with window.prompt calls, which actually do work, but from > the point of the user experience are no real option. So, the problem is: Is > it possible to keep the ms_getchar busy or blocked until the user has done > his input (without locking up the browser). I tried a lot of different > approaches, but never came close to a solution and as far as I understand > JS can not be blocked or kept busy with threads, so it seems I am lost > here?!?. > My last try was something like this, but this didn't work, either, most > probably because I got wrong what the emscripten_start_main_loop and > emscripten_stop_main_loop calls do. I also found a reference to a function > emcripten_push_Main_loop_blocker, but couldn't find a sample how to use it. > Another thought was if it might be possible to run the interpreter loop in > a web worker, but I guess I will run into problems with filling my html > then? > > Last try (partly reconstructed, tried such much with the source that I > messed it up at some point). Please bear with me if that is pure nonsense, > I am not very familiar with JS, especially not with the parts beyond simple > web pages. > in the HTML: > *<form onsubmit="setInternalBuffer();return false;"><input type="text" > size="50" maxlength="255" id="textin"></form>* > and > *function setInternalBuffer() {* > * var userinput = document.getElementById('textin').value;* > * var cstyle_ptr = allocate(intArrayFromString(userinput), 'i8', > ALLOC_NORMAL);* > * transferbuffer = Module.cwrap('transferbuffer', 'void', > ['string']);* > * transferbuffer(cstyle_ptr);* > * emscripten_start_main_loop();* > > * }* > in the C code: > *void transferbuffer(char * input)* > *{* > * strcpy(inbuf,input);* > *}* > and > > > > > > > > > > > > > *char ms_getchar(){ int c=0; emscripten_pause_main_loop(); if > ((c = inbuf[inpos]) == '\n' || !c) { inpos = 0; > memset(inbuf,0x00,256); c=0; } return (char)c;}* > > I guess, the transferbuffer call in the JS function is not executed > because the main loop is stopped?!? > > Any chance to get this working or is it as simple as this not being > suitable for JS? > > Many, many thanks for listening and your help. If you want to mess around > with the stuff yourself, please let me know and I'll make it available, > it's open source anyway. > > Stefan Meier > > -- > You received this message because you are subscribed to the Google Groups > "emscripten-discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
