80 lines
3.7 KiB
Markdown
80 lines
3.7 KiB
Markdown
<!-- 12 april 2019 -->
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# Initialization and the Main Loop
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## Overview
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TODO
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## Reference
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### `uiInit()`
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```c
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bool uiInit(void *options, uiInitError *err);
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```
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`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.
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`err` is required and must be properly initialized. It is a programmer error for `err` to be `NULL` or for `err->Size` to not match `sizeof (uiError)`, `uiInit()`. If any of the other fields of `err` are not zero-initialized as with `memset(0)`, the behavior is undefined.
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`options` must be `NULL`; no options are currently defined. It is a programmer error for `options` to not be `NULL`.
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It is a programmer error to call `uiInit()` more than once, even if `uiMain()` has already returned (meaning you cannot re-initialize libui). It is a programmer error to call libui functions before `uiInit()` has been called.
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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, libui will behave in an undefined way if it is called from the wrong thread; to avoid this, you should always call `uiInit()` (and by extension all libui functions) from the thread that `main()` itself is called from.
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If `uiInit()` fails, it will be a programmer error to call any other libui function. This means that you cannot use any of libui's message box functions to report the error.
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**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.
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### `uiInitError`
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```c
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typedef struct uiInitError uiInitError;
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struct uiInitError {
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size_t Size;
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char Message[256];
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};
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```
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`uiInitError` describes an error returned by `uiInit()`.
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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.
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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.
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### `uiMain()`
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```c
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void uiMain(void);
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```
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`uiMain()` runs the main event loop. It does not return until `uiQuit()` is called.
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It is a programmer error to call `uiMain()` more than once.
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### `uiQuit()`
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```c
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void uiQuit(void);
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```
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`uiQuit()` causes `uiMain()` to return once the current event has finished processing.
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It is an error to call `uiQuit()` before `uiMain()` is called or after `uiMain()` returns. It is a programmer error to call `uiQuit()` more than once.
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### `uiQueueMain()`
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```c
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void uiQueueMain(void (*f)(void *data), void *data);
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```
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`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.
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`uiQueueMain()` can safely be called from any thread, not just the UI thread.
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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.
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If `uiQuit()` is called, it is undefined whether any still-queued functions will be called.
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