Arch Linux User Repository

Important note: Is recommended to receive the following key before to install:

$ gpg --recv-keys F4928C4DD24D4DF8

Also is possible skip the verification, adding the flag for (e.g makepkg, yay) --skippgpcheck, --nopgpfetch, respectively.

@bsdice

Just enable this option:

Settings > Graphics > Use device pixel ratio

Before "discovering" this option above, I tried the solution you mentioned. But notice that, both environment variables are set, QT_ENABLE_HIGHDPI_SCALING=0 and QT_QPA_PLATFORM=xcb.

And after that, although the fonts are rendered better than before, but both document and interface's fonts are blurry.

@bsdice you may want to report it upstream. In fact, there has been about 13 commits since the last released version (0.5.0).

Thank you to l42 and dolph for taking the time to offer suggestions. I tried QT_QPA_PLATFORM=xcb and then the rendering quality jumped to "much better". But not perfectly "spline" or "vector" if you know what I mean. With QT_ENABLE_HIGHDPI_SCALING=0 I get perfect glyph rendering on Qt6. So I have set that now in /etc/environment. Because I really do look at ALOT of PDFs of scientific papers, articles etc. Thanks!

re antialiasing: for me, with wayland and qt6, launch qpdfview with environment variable QT_QPA_PLATFORM=xcb, then antialiasing is ok

re antialiasing: for me the problem goes away if the program is launched with QT_ENABLE_HIGHDPI_SCALING=0

@bsdice Well, for me qpdfview renders fine with Qt6, also under X11 with i3 and 4k display /o\ But I have terrible font rendering with qutebrowser under Wayland with fractional scale factor so there is definitely something wrong with Qt6...

Yo, just a heads up: The migration to Qt6 broke anti-aliasing on my X11 i3 i915 4k-display system. Fonts are rendered thin, jagged edges, readable, but horrible. I switched the current PKGBUILD back to Qt5 and everything is nice again. I know nothing about Qt, and I have never willingly configured anything special for Qt6 on the system, but would try patches looking to fix it. Thanks!

You can update the package for Qt6:

--- a/PKGBUILD
+++ b/PKGBUILD
@@ -4,13 +4,13 @@
 # Contributor: Adam Reichold <adam.reichold@t-online.de>
 pkgname=qpdfview
 pkgver=0.5.0
-pkgrel=2
+pkgrel=3
 pkgdesc="A tabbed PDF viewer using the poppler library"
 url="https://launchpad.net/${pkgname}"
 arch=(x86_64)
 license=(GPL2)
-depends=(libcups libsynctex poppler-qt5 qt5-svg)
-makedepends=(qt5-tools libspectre djvulibre)
+depends=(libcups libsynctex poppler-qt6 qt6-svg)
+makedepends=(qt6-tools libspectre djvulibre)
 optdepends=('libspectre: for PostScript support'
   'djvulibre: for DjVu support')
 source=(${url}/trunk/${pkgver}/+download/${pkgname}-${pkgver::-2}.tar.gz{,.asc})
@@ -24,8 +24,8 @@ prepare() {

 build() {
   cd ${pkgname}-${pkgver::-2}
-  lrelease-qt5 qpdfview.pro
-  qmake-qt5 qpdfview.pro
+  /usr/lib/qt6/bin/lrelease qpdfview.pro
+  qmake6 qpdfview.pro
   make
 }

Try this:

$ gpg --recv-keys --keyserver keys.openpgp.org F4928C4DD24D4DF8