Character grid misalignment issue

[rbanffy]

When running Sage on Konsole (tested on Ubuntu 20.10, qtermwidget 0.15.0 both locally and over a network to a Mac running XQuartz) a user of my font (rbanffy/3270font#88) noticed an alignment issue that we thought was caused by a missing glyph. The issue is present with other fonts as well. We didn't rule out a missing glyph being the cause, but I noticed changes in the character cell alignment when selecting cells.

Expected Behavior

All characters in in a monospaced font should show the same width and be aligned.

Current Behavior

Currently the character cells are misaligned:

More interestingly, it seems to be related to the '⋅' glyph, as grid alignment changes when it's selected:

konsole-misalignment.mov

Possible Solution

Steps to Reproduce (for bugs)

1. Run Sage (docker run -it sagemath/sagemath)
2. Enter %display unicode_art and diff(sin(x ** 2), x, 4) commands
3. Observe the misalignment
4. Start selecting characters in the bottom row of the expression
5. See the alignments change

Context

System Information

• Distribution & Version: Ubuntu 20.10, qtermwidget 0.15.0
• Kernel:
• Qt Version: 5.14.2
• lxqt-build-tools Version:
• Package version: 0.15.0