https://bugs.kde.org/show_bug.cgi?id=523028
Bug ID: 523028
Summary: Make runtime Noto Sans / Hack font defaults
configurable at CMake time and degrade gracefully when
absent
Classification: Plasma
Product: plasma-integration
Version First master
Reported In:
Platform: unspecified
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
KDEPlasmaPlatformTheme6.so (built from plasma-integration) hardcodes "Noto
Sans" as
the default UI font for six font slots and "Hack" for the monospace slot in
qt6/src/platformtheme/kfontsettingsdata.cpp:41-50. This makes every downstream
distro implicitly depend on Noto Sans -- distros that standardize on a
different
sans (Cantarell, Inter, IBM Plex) cannot override the platform theme's default
without patching source. The kconf_update migration script (fonts_global.pl)
further rewrites user configs to "Noto Sans" on upgrade, making the
brand-default
invasive even when Noto isn't installed.
The CMake side already half-supports this: CMakeLists.txt exposes
find_package(FontNotoSans) with a
-DCMAKE_DISABLE_FIND_PACKAGE_FontNotoSans=true
escape hatch, but it only suppresses a build-time warning; the literal in
kfontsettingsdata.cpp is unchanged. The hook is there, the matching source-side
change isn't.
Prior community discussion on the resulting hard dep: Gentoo bug 922794 (open),
Arch BBS 294551, Debian/Ubuntu ship it as soft Recommends: instead of hard
Depends: -- proving the plugin works without Noto.
PROPOSED FIX (hybrid, two small additive changes)
(a) Expose defaults as CMake cache variables, with current values as defaults
so
an unset build is byte-equivalent:
set(PLASMA_INTEGRATION_DEFAULT_SANS_FONT "Noto Sans"
CACHE STRING "Default sans-serif font family used by the platform theme
when the user has not set one in kdeglobals.")
set(PLASMA_INTEGRATION_DEFAULT_MONO_FONT "Hack"
CACHE STRING "Default monospace font family used by the platform theme
when the user has not set one in kdeglobals.")
configure_file(${CMAKE_CURRENT_SOURCE_DIR}/kfontdefaults.h.in
${CMAKE_CURRENT_BINARY_DIR}/generated/kfontdefaults.h @ONLY)
(b) Add a runtime fallback in KFontSettingsData::font() so a missing compiled
default gracefully resolves via fontconfig's sans-serif/monospace alias
instead of producing a QFont whose family silently fails every paint:
if (!QFontDatabase::families().contains(compiledFamily))
cachedFont = new QFont(); // empty family -> fontconfig sans-serif /
mono
BACKWARD COMPATIBILITY
- Unset build produces an identical binary (defaults match current literals).
- find_package(FontNotoSans) is preserved so distros that want the runtime hint
still see it.
- kconf_update migration scripts are untouched in this change (a sensible
follow-up, but a separate concern).
TEST PLAN
1. Default build: strings build/.../KDEPlasmaPlatformTheme6.so | grep 'Noto
Sans'
returns identical output to current master.
2. Override build: cmake -B build -S .
-DPLASMA_INTEGRATION_DEFAULT_SANS_FONT=Cantarell
-- generated header contains "Cantarell" and the binary's string table
reflects it.
3. Runtime fallback: with the compiled default uninstalled, launch a Qt app
under
the platform theme and verify qDebug() << QApplication::font().family()
returns
the fontconfig alias, not the missing family.
RELATED
- VDG rationale for the original Noto Sans switch: commit 4d274c9 (2015).
The argument holds; the implementation shouldn't be welded to one font brand.
- Hack switch: commit 0ad3465 (2016).
- Patch (3 files, ~40 net lines) ready to attach as a merge request on
invent.kde.org/plasma/plasma-integration once bug number is assigned.
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