Improve documentation and examples

[emilk]

Tracking issue for improving the egui docs. Other suggestions for improvements welcome!

All doc-examples need to be part of the doctests (i.e. they should never be marked ignore, though no_run can maybe sometimes be motivated).

egui

The crate-level docs for egui (at https://docs.rs/egui generated from egui/src/lib.rs) should be improved with a tutorial. In addition, all major parts of egui should have a quick example in the crate-level docs

• Crate-level:
  • intro tutorial
  • FAQ (see https://github.com/emilk/egui/issues and https://github.com/emilk/egui/discussions/categories/q-a for what the common questions are)
  • examples for common widgets, layouts etc (see below)
• Crate-level AND item-level examples for:
  • Label
  • Hyperlink
  • TextEdit
  • Button
  • CheckBox
  • RadioButton
  • SelectableLabel
  • Image
  • ComboBox
  • Slider
  • DragValue
  • Separator
  • CollapsingHeader
  • horizontal and vertcial layouts
  • centered vertical layouts
  • Grid
  • tooltips (on_hover_text)
• Add a few gifs to the docs (not too many though, as they are difficult to maintain)
• Links from the web demo to the docs
  • Link from the widget gallery to the docs
  • Link from the slider demo to the docs for the slider
  • …
• Links from the docs to the web demo
  • Link from the crate-level docs to the web demo
  • Link from the Slider-docs to the slider demo window
• Links from the web demo to its own source code

other

• Meta: make the CI run all the doc tests
• Fix the eframe doc build issues: build failures on docs.rs #146
• Add simple demo of loading and displaying an image
• epi::http in not showing up in the documentations

[olivereanderson]

Thank you for creating this issue Emil :)

[pm100]

Also note that the eframe tutorial video is 3 years old and the code created does not compile anymore

[CalinZBaenen]

I think egui::Options needs better documentation.
I feel like "Some global options that you can read and write." doesn't really explain what it's meant to be used for. — At least with egui::ImageOptions and egui::TextureOptions their purpose is in the name.

This, or maybe Options should be renamed to make its usage more clear.

(I'm a noob though, so maybe I just have to use the library more.)