Make it clear how and where application icons should be installed

The current convention is to install .png icons in $basedir/hicolor/$size/apps and .svg icons in $basedir/hicolor/scalable/apps. This should be explicitly mentioned in the specification. The para for installing application icons is a bit vague.

Some applications are putting .svg icons in $basedir/hicolor/$size/apps and .png icons $basedir/hicolor/scalable/apps.

https://specifications.freedesktop.org/icon-theme-spec/latest/ar01s07.html

This means installing a PNG file in $prefix/share/icons/hicolor/48x48/apps. Optionally you can install icons in different sizes. For example, installing a svg icon in $prefix/share/icons/hicolor/scalable/apps means most desktops will have one icon that works for all sizes.

Also the specification should make it clear that icons must go to their correct sized folder, for example a 128x128 PNG must go to $basedir/hicolor/128x128/apps and not to a 256x256 or any other hicolor/$size subfolder.

Some applications are wrongly installing a 128x128 PNG to an incorrectly sized subfolder.