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        <title>A Possible Fix for X11 Programs Refusing to Start on Wayland - Blog of ltlnx</title>
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<h1 id="a-possible-fix-for-x11-programs-refusing-to-start-on-wayland">A
Possible Fix for X11 Programs Refusing to Start on Wayland</h1>
<p>As Wayland and KDE on Wayland matures, I’ve switched my entire
environment to KDE Wayland. Serious props to KDE developers — all of the
Konsole and Kwin gliches I experienced in the early days are long
gone.</p>
<h3 id="a-short-aside-why-wayland">A short aside: Why Wayland?</h3>
<p>As an end user of Slackware, KDE and related software, I find these
advantages good enough to make me switch:</p>
<ul>
<li>Touchpad gestures. On Wayland three- and four-finger swipes are
readily available, while on KDE X11 I’ll have to set up stuff like <a
href="https://github.com/JoseExposito/touchegg">Touchegg</a>, and still
it doesn’t integrate as well as KDE Wayland does.</li>
<li>Correct scaling for mixed DPI situations. I have a Macbook set at
150% scaling, and an external screen set at 100%. Wayland can do that
without hacks.</li>
<li>KDE supporting a global scale for all X11 and Wayland applications
across GTK and Qt. Xlib and FLTK aside, no more scaling hacks.</li>
</ul>
<p>Things like Pipewire and XDG portals are still rough on the edges,
and parts of the Wayland stack (libinput) is not as configurable as say,
xf86-input-synaptics and synclient, but I’d say the status quo is good
enough for laymen like me to make the switch.</p>
<p>Enough rambling, let’s get on to the topic…</p>
<h3 id="what-environment-variables">What environment variables?</h3>
<p>When I started toying with KDE on Wayland (with
<code>startkwayland</code> in Slackware), I had to run all KDE apps (KDE
Gear they call it) under Wayland, otherwise they would look blurry.<a
href="#fn1" class="footnote-ref" id="fnref1"><sup>1</sup></a> Therefore
I added the following to <code>/etc/environment</code>:</p>
<pre><code>QT_QPA_PLATFORM=wayland</code></pre>
<p>which makes Qt apps, which most KDE apps are, to use Wayland. Next up
is to make GTK apps use Wayland too, so I added:</p>
<pre><code>GDK_BACKEND=wayland</code></pre>
<p>Also some documentation recommends setting the XDG session type to
Wayland too, so:</p>
<pre><code>XDG_SESSION_TYPE=wayland</code></pre>
<p>Under Qt things are all good: If a Qt app only runs on X11, typically
I don’t need additional configuration to make them start with Xwayland,
the method to run X11 programs on Wayland. However with GTK it’s not the
case, as when I try to start <a href="">Seamonkey</a> it errors out:</p>
<pre><code>Error: cannot open display: :0</code></pre>
<p>I’ve fiddled with the <code>DISPLAY</code> and
<code>WAYLAND_DISPLAY</code> to no avail, and put the problem aside
until I remembered the Wayland environment variables. So I tried
<code>GDK_BACKEND=x11 seamonkey</code> and sure enough, Seamonkey
started up.</p>
<h3 id="onto-the-solution">Onto the solution</h3>
<p>I’ve written this helper script to start programs with the correct
variables set, named <code>xenv</code>:</p>
<pre><code>#!/bin/sh
# Set some environment variables to X11

export GDK_BACKEND=x11
export QT_QPA_PLATFORM=xcb
export XDG_SESSION_TYPE=x11
$@</code></pre>
<p>Put this in your path and use as
<code>xenv &lt;problematic_app&gt;</code>.</p>
<p>Have fun!</p>
<p><span class="tags">標籤：<a href="/tags/slackware.html">slackware</a>
</span></p>
<p>2023-10-25</p>
<div class="footnotes footnotes-end-of-document">
<hr />
<ol>
<li id="fn1"><p>This isn’t the case anymore, but still, running with
native Wayland makes programs integrate better with the system.<a
href="#fnref1" class="footnote-back">↩︎</a></p></li>
</ol>
</div>
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