Sometimes scalable icons or icons within the thresholds from the desired
resolutions aren't available. In this case it's still nicer to end up
with a blocky scaled icon rather than the generic default.
In order to compose a `.icns` file containing multiple icon sizes I had
to pass `--toc` to `icnsutil`. This did not seem to have a negative
effect on `.icns` containing only a single icon size.
On macOS 10.13 the 48x48 icon size is not supported. It results in a
corrupted image being displayed. I suspect the image data is being
truncated to what it expects for 32x32 or maybe data is read for
128x128, which would be a buffer overflow.
- Convert icons to a single .icns file; and
- Provide an opt-out via X-macOS-Squircle in the desktop item to
override the squircle behavior when the source icons look bad when
converted automatically.
