Choose your own font and size (#1154)

* 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

egui_glow/src/painter.rs

@@ -24,6 +24,8 @@ const FRAG_SRC: &str = include_str!("shader/fragment.glsl");
 /// This struct must be destroyed with [`Painter::destroy`] before dropping, to ensure OpenGL
 /// objects have been properly deleted and are not leaked.
 pub struct Painter {
+    max_texture_side: usize,
+
     program: glow::Program,
     u_screen_size: glow::UniformLocation,
     u_sampler: glow::UniformLocation,
@@ -90,6 +92,8 @@ impl Painter {
     ) -> Result<Painter, String> {
         check_for_gl_error(gl, "before Painter::new");
 
+        let max_texture_side = unsafe { gl.get_parameter_i32(glow::MAX_TEXTURE_SIZE) } as usize;
+
         let support_vao = crate::misc_util::supports_vao(gl);
         let shader_version = ShaderVersion::get(gl);
         let is_webgl_1 = shader_version == ShaderVersion::Es100;
@@ -203,6 +207,7 @@ impl Painter {
             check_for_gl_error(gl, "after Painter::new");
 
             Ok(Painter {
+                max_texture_side,
                 program,
                 u_screen_size,
                 u_sampler,
@@ -223,6 +228,10 @@ impl Painter {
         }
     }
 
+    pub fn max_texture_side(&self) -> usize {
+        self.max_texture_side
+    }
+
     unsafe fn prepare_painting(
         &mut self,
         [width_in_pixels, height_in_pixels]: [u32; 2],