[fpc-pascal] PostMessage vs. QueueAsyncCall

Mattias Gaertner nc-gaertnma at netcologne.de
Fri Sep 19 11:56:29 CEST 2014

On Fri, 19 Sep 2014 17:20:27 +0800
Xiangrong Fang <xrfang at gmail.com> wrote:

> My question is, why cannot Lazarus just use PostMessage, but invent the
> QueueAsyncCall() method?  What is the rationale, or, why PostMessage is
> considered windows-ish (read: not fit into LCL very well?), apart from the
> fact that it is a Windows API?

Please ask Lazarus question on the Lazarus lists.

PostMessage is a WinAPI function that sends an uint, and two pointer
sized integers to a Windows Handle with a queue, even to another
process. See here:

The LCL emulates some parts of PostMessage on other widget sets.

TApplication.QueueAsyncCall on the other side allows to call a method in
the main thread with an optional data pointer. And the call can be
removed from the queue.


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