Disappearing Cursor

[cristophercutas]

Current behavior

Cursor disappears when clicking at the end of the line.

Expected behavior

Cursor should always be visible during edit mode.

Steps to reproduce

1. Edit a document
2. Click at the end of the line (highly reproducible on the list below ##When)
3. Observe.

When

1. Clicking at the far end of the line, meaning pixels away from the character.
2. Clicking at the far end of the line with the last character as space.
3. Clicking at the of a Header

Environment

• Version :Version 0.11.8 (0.11.8)
• OS Version and name :
  macOS High Sierra 10.13.3 (17D47)
  MacBook Pro (Retina, 13-inch, Early 2015)

[abbasaleid-zz]

Same here. Could not understand why would this would happen? I would appreciate a fix for it as soon as possible. It's actually so annoying and confusing.

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[daiyam]

@cristophercutas are you still having the issue? I can't reproduce it.

[cristophercutas]

Apologies for the delayed response. Yes, I can still reproduce it. I am on version 0.11.10 (0.11.10).

I tried it on another machine (same specs) and it was reproducible. I could not reproduce it on 100% zoom setting, but on 80% zoom setting the cursor disappears, although the scenario may vary. On machine 1 it only disappears on empty new lines, on machine 2 it only disappears at the end of a non-empty line.

Hope this helps.

[willurd]

Digging around a little bit on this. It looks like this is an issue with CodeMirror. CodeMirror implements its own cursor, styled with a single border. When the app is zoomed to certain levels, the cursor disappears, but it's just a rounding error. If you set the border-width of .CodeMirror-cursor to 3px, it should be visible at all zoom levels.

You can also see correct cursor render behavior by putting your cursor in the tags field and zooming in and out - you should be able to see the cursor at all zoom levels.

Potential fixes for this include:

• Making the .CodeMirror-cursor element wider so it's always visible. It looks like the Jupyterlab people had this same issue and addressed it last October: Ensure codemirror cursor size jupyterlab/jupyterlab#3164
• Submit a patch for CodeMirror 5 that addresses this. The CodeMirror team said it is difficult to fix with the way CodeMirror 5 is written, and they plan to address this and other issues in CodeMirror 6: cursor invisible on empty lines in chrome 62 codemirror/codemirror5#5056
• Use another editor component

[shriram-svg]

Opened #3793 with a small global CodeMirror cursor-width fix for the zoom-level disappearing cursor issue.