Prefer Xft.dpi for fractional Linux DPI scaling - #11
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ElCruncharino wants to merge 1 commit into
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Problem
GetSurfaceDPI()on Linux only ever derived an integer scale factor (viagdk_screen_get_monitor_scale_factoror theGDK_SCALEenv var). On desktops using fractional scaling (e.g. 1.75x, common on KDE/GNOME HiDPI setups), this either rounds to the nearest integer (making the UI noticeably too large or too small) or fails entirely under Flatpak sandboxing, where GDK's monitor-scale detection can't see the compositor's scale at all - resulting in the UI rendering at 1x regardless of the actual display scale.Fix
Adds
BackendXLib::QueryXftDPI(), which reads theXft.dpiX resource viaXResourceManagerString(). This is the desktop-independent mechanism used by GNOME, KDE and XFCE alike to communicate display DPI to legacy toolkits. It already supports fractional values, and - unlike the GDK monitor scale factor - remains available to sandboxed applications (e.g. Flatpak) that only have access to the X11 socket, since it requires no filesystem or GTK theme access.This value is now preferred over the integer GDK-based detection in both the cairo and plain xlib surface backends.
Testing
Verified visually on KDE Plasma (Wayland session, XWayland client) at 1.75x scale - the UI now renders at the correct scale instead of rounding to 2x.