<p></p>
<p>Thanks guys, for your suggestions.</p>
<p>Was could it have been?</p>
<ul>
<li>CSD</li>
<li>any kind of timing issue related to setting the pane position</li>
<li>nor a GTK bug</li>
<li>...</li>
</ul>
<p>And the winner is:<br>
some old <em>eht16-Windows-special-hack</em></p>
<p>For reasons I don't remember anymore, I added in <a class="commit-link" data-hovercard-type="commit" data-hovercard-url="https://github.com/geany/geany/commit/9431eea2445ccf191777cf3667a9292cf4ddcb65/hovercard" href="https://github.com/geany/geany/commit/9431eea2445ccf191777cf3667a9292cf4ddcb65"><tt>9431eea</tt></a> (in 2009) a Windows only change to realize the main windows <em>before</em> setting the window geometry and position.<br>
Maybe it was related to off-screen window positions or so. Or some GTK2 behavior required it which is no longer the case.</p>
<p>After removing the <code>gtk_widget_realize</code> call, the message window height is stable, i.e. stays at where is has been left off. Also, I couldn't find any other negative impact of the removed call, even weird off-screen positions worked as expected (the window is moved to the visible screen area).</p>
<p>Too bad I don't know why the realize call was added initially :(.<br>
At least, it pretty good explains why it happened only on Windows. Apparently, something in GTK3 has changed in that regard.</p>
<p><a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="988517636" data-permission-text="Title is private" data-url="https://github.com/geany/geany/issues/2892" data-hovercard-type="pull_request" data-hovercard-url="/geany/geany/pull/2892/hovercard" href="https://github.com/geany/geany/pull/2892">#2892</a> is here to fix it.</p>

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