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gui-native-win-poll.md

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Win32 Message Poll Helpers (gui-native-win-poll)

Overview

gui-native-win-poll wraps PeekMessage / TranslateMessage / DispatchMessage into a single Oak function used by the gui-native-win event loop. It handles the closed-window detection case where PeekMessage returns errno 1400 (invalid window handle).

This module is part of the native Windows GUI backend and is not intended for direct use in application code. Message polling is managed by the GUI module's event loop.

Import

poll := import('gui-native-win-poll')
{ pollWindowMessages: pollWindowMessages } := import('gui-native-win-poll')

Functions

pollWindowMessages(window)

Calls PeekMessage with PM_REMOVE on the message buffer pre-allocated in window.msgBuf. Returns a tagged result object:

Return value Condition
{ type: :dispatch, detail: msg } A message was retrieved and dispatched successfully.
{ type: :idle, detail: msg } No message was available (PeekMessage returned 0).
{ type: :closed } errno 1400 — window handle is invalid; sets window.closed = true. 
result := pollWindowMessages(window)
if result.type {
    :dispatch -> handleMessage(result.detail)
    :closed   -> printf('window closed')
    _ -> ?  // idle, continue loop
}

Note: The function calls TranslateMessage and DispatchMessage only when a message is actually retrieved; virtual key codes are translated to WM_CHAR messages before dispatch.