GeezerVison

appimagetool creates the AppImage's .DirIcon from <Icon>.png/.xpm in the
AppDir root, and refuses to build when .DirIcon is missing, broken or an
SVG. linuxdeploy preferred an SVG for the root icon and never created a
.DirIcon, so AppDirs that deploy their icon as SVG (plus PNGs under
usr/share/icons) ended up without a usable PNG .DirIcon.

Now a matching PNG is preferred over an SVG, which in turn is preferred over
an XPM; an SVG is still used if no PNG is deployed, and an Icon= entry with
an explicit extension is still honored. Among PNGs, the one whose size is
closest to 256x256 (the size recommended for .DirIcon by the AppImage
specification) is picked instead of the one closest to 64x64.

Additionally, <AppDir>/.DirIcon is created as a relative symlink to the
chosen icon. A regular .DirIcon file in the AppDir is kept; existing symlinks
(also dangling ones) are replaced. If the chosen icon is not a PNG, a warning
is logged.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ezEw8e4Q7Zv69hLFbq8kv