feat: tab dnd

[wash2]

No description provided.

[jacobgkau]

I'm seeing a weird behavior remaining that's not present in pop-os/cosmic-files#1535. I think it's either because COSMIC Edit doesn't fill the entire tab space by default like COSMIC Files does, or because COSMIC Edit has the modified indicator dot that sometimes shows up in tabs.

If I press Shift while hovering over a tab, the tab gets slightly larger until I either press Shift over a different tab or click somewhere in the app. See the result of pressing Shift over one tab and then the other below:

2026-01-29.12-58-08.mp4

[jackpot51]

@wash2 can you update this PR?

[jacobgkau]

The issue I described in #490 (review) is still present in this one.

[wash2]

The issue I described in #490 (review) is still present in this one.

Ya, I'm not sure that I have a great fix for that issue at this time.

[jacobgkau]

I will open an issue for the modifiers causing tabs to resize and proceed with regression testing the rest of this, since the issue is minor compared to the functionality being added (and is not a regression).

[jacobgkau]

Tab interaction has no regressions with the new dragging functionality.

Regression testing passed:

Basic operations

• Type three lines of text (no trailing newline).
• Copy the last two lines.
• Paste at the end of the third line (file should now have four lines).
• Ctrl-Z to undo the paste.
• Press Enter to add a trailing newline.
• Paste again (file should now have five lines).
• Ctrl-Z to undo the paste.
• Ctrl-Shift-Z to redo the paste.
• Save the file.
• Ctrl-F and search for something that has a match.
• Press Esc twice to exit the Find dialog.
• Press Ctrl-X to cut the selected search result.
• Paste the cut text on a new line (file should now have six lines).
• Re-save the file.
• Narrow the window until the lines start wrapping (make a line longer if necessary to observe line wrapping).
• Turn word wrapping off.
• Scroll right to the end of the document, then left to the beginning again.
  • Active line highlight stops after visible part scrolls; not a regression.
• Click and drag to select some text past the horizontal edge of the window.
• Close the file, open COSMIC Edit again, and open the file via the recents list.
  • Doesn't show up; not a regression: #460
• Close the file again, open COSMIC Edit again, and open the file via the Open dialog.
• Turn word wrapping back on.

Settings

• Open View -> Settings.
• All Appearance settings work.
• Vim bindings work.

Projects & Git Management

• Clone the cosmic-edit Git repo and open its directory as a project.
• Edit -> Find in project... works.
• Make a change in a file.
• File -> Git management shows the change and staging it works.
• Make another change while Git management's open; it updates to show the new change.
• Un-staging a change works.