libui/doc/init-main.md

Initialization and the Main Loop

Overview

TODO

Reference

uiInit()

bool uiInit(void *options, uiInitError *err);

uiInit() initializes libui. It returns true on success and false on failure; in the event of a failure, err is filled with relevant information explaining the failure.

err is required and must be properly initialized. If err is NULL or err->Size does not match sizeof (uiError), uiInit() immediately returns false without doing anything. If any of the other fields of err are not zero-initialized as with memset(0), the behavior is undefined.

options must be NULL; no options are currently defined. If options is not NULL, uiInit() will return an error without initializing anything.

As part of initialization, the thread that uiInit() is called on becomes the GUI thread. All of the functions of libui except uiQueueMain() must be called from this thread. On platforms where which thread you run GUI code on is restricted, uiMain() will return an error if it is called from the wrong thread; to avoid this, you should always call uiInit() from the thread that main() itself is called from.

If uiInit() fails, no other libui function is safe to call. This means that you cannot use any of libui's message box functions to report the error.

Notes for language binding authors: Your language will likely provide its own preferred mechanism for reporting errors. You should wrap uiInit() to return errors this way, creating and managing the memory for uiInitError yourself and transforming the returned error according to both the format of uiInitError described below and the rules for encoding errors in your language of choice.

uiInitError

typedef struct uiInitError uiInitError;
struct uiInitError {
	size_t Size;
	char Message[256];
};

uiInitError describes an error returned by uiInit().

You are responsible for allocating and initializing this struct. To do so, you simply zero the memory for this struct and set its Size field to sizeof (uiInitError). The example in the main section of this page demonstrates how to do this.

In the event of an error, Message will contain a NUL-terminated C string in the encoding expected by fprintf(). This is in contrast to the rest of libui, which uses UTF-8 strings.

uiMain()

void uiMain(void);

uiMain() runs the main event loop. It does not return until uiQuit() is called.

TODO make it illegal to call more than once?

uiQuit()

void uiQuit(void);

uiQuit() causes uiMain() to return once the current event has finished processing.

TODO safety of calling uiMain() again after uiQuit()?

TODO behavior of calling uiQuit() outside of a uiMain() (before, after, etc.)

uiQueueMain()

void uiQueueMain(void (*f)(void *data), void *data);

uiQueueMain() schedules f to be called with data as a parameter on the next iteration of the main loop when no event is pending. It returns immediately.

uiQueueMain() can safely be called from any thread, not just the UI thread.

If you call uiQueueMain() in sequence, the functions will execute in that order; if other threads are calling uiQueueMain() at the same time, there is no guarantee as to whether the calls are interleaved, but the order per-thread will be maintained.