Modernize UI

[YiqiXu]

The user interface of TeXmacs doesn't change much over the last two decades. According to my own experiences, the outdated UI has constantly pushed away newcomers interested in TeXmacs. I think that modernizing the UI should be a long-term goal of Mogan.

The following two issues could be solved in the short term.

1. Updating the icons on the menu seems a viable option and a great improvement in the short term.
2. The dark mode is far beyond ideal for daily usage (see the first screenshot). The switch between light and dark mode should follow the system settings (either automatically or manually in preferences). It would be even better if the paper and character color changed accordingly, like Microsoft Word (see the second screenshot).

[da-liii]

We could use the icons from the KDE project.

[da-liii]

derived issues: #26 and #27

[fbob]

Speaking about the UI, some other improvements could be:

• a Command Palette to access all the features of Texmacs without having to remember key strokes.
• a TOC panel to be able to switch to a particular heading and move them easily. Can be useful for slides too.
• inline text, math symbols completion with dropdown list
• inline spellchecking correction propositions with a dropdown list
• tabs like firefox tabs for document management
• split views to see more documents at the same time or different parts of the same document
• ....

[da-liii]

I think the dropdown list for completion is the most urgent one.

[PikachuHy]

document tab is here. #142

[fbob]

Nice one ! 👍