* Add Shape::Callback to do custom rendering inside of an egui UI
* Use Rc<glow::Context> everywhere
* Remove trait WebPainter
* Add glow::Context to epi::App::setup
* egui_web: always use the glow painter, and remove the old WebGL code.
* Clean up the WebPainter trait
* Clarify WebGL1 warning text in color test
The glow painter became standard in egui 0.17, and I've heard no complaints! So let's simplify and go all in on glow.
Part of https://github.com/emilk/egui/issues/1198
* egui_web: use tracing crate
* egui_glow: use tracing crate
* Log at the debug level
* egui_demo_app: enable tracing to log to stdout
* Use tracing in egui-winit
* Add opt-in tracing support to egui
* Refactor text layout: don't need &Fonts in all functions
* Replace indexing in Fonts with member function
* Wrap Fonts in a Mutex
* Remove mutex for Font::glyph_info_cache
* Remove RwLock around Font::characters
* Put FontsImpl and GalleyCache behind the same Mutex
* Round font sizes to whole pixels before deduplicating them
* Make TextStyle !Copy
* Implement user-named TextStyle:s
* round font size earlier
* Cache fonts based on family and size
* Move TextStyle into egui and Style
* Remove body_text_style
* Query graphics about max texture size and use that as font atlas size
* Recreate texture atlas when it is getting full
* Move texture allocation into epaint/egui proper
* Add TextureHandle
* egui_glow: cast using bytemuck instead of unsafe code
* Optimize glium painter
* Optimize WebGL
* Add example of loading an image from file
* Re-add check of WEBGL_debug_renderer_info to avoid OpenGL error
I removed this check in https://github.com/emilk/egui/pull/1020
because it produced a warning on Firefox. Better a warning
than an OpenGL error though.
* Bug fix: don't ask for webgl context and then later for webgl2 context
The browser will only allow the first thing we check, so this will
prevent webgl2 from working.
* Switch to using glow as the default renderer both on native and the web
* Simplify code to find WebGL context for glow
* egui_web: make webgl an opt-in feature
* Stop using deprecated WEBGL_debug_renderer_info
