kas_core/theme/
traits.rs

1// Licensed under the Apache License, Version 2.0 (the "License");
2// you may not use this file except in compliance with the License.
3// You may obtain a copy of the License in the LICENSE-APACHE file or at:
4//     https://www.apache.org/licenses/LICENSE-2.0
5
6//! Theme traits
7
8use super::{ColorsLinear, ThemeDraw, ThemeSize};
9use crate::autoimpl;
10use crate::config::{Config, WindowConfig};
11use crate::draw::{DrawIface, DrawSharedImpl, color};
12use crate::event::EventState;
13use std::any::Any;
14use std::cell::RefCell;
15
16#[allow(unused)] use crate::event::EventCx;
17
18/// A *theme* provides widget sizing and drawing implementations.
19///
20/// The theme is generic over some `DrawIface`.
21///
22/// Objects of this type are copied within each window's data structure. For
23/// large resources (e.g. fonts and icons) consider using external storage.
24#[autoimpl(for<T: trait + ?Sized> Box<T>)]
25pub trait Theme<DS: DrawSharedImpl> {
26    /// The associated [`Window`] implementation.
27    type Window: Window;
28
29    /// The associated [`ThemeDraw`] implementation.
30    type Draw<'a>: ThemeDraw
31    where
32        DS: 'a,
33        Self: 'a;
34
35    /// Theme initialisation
36    ///
37    /// The toolkit must call this method before [`Theme::new_window`]
38    /// to allow initialisation specific to the `DrawIface`.
39    fn init(&mut self, config: &RefCell<Config>);
40
41    /// Construct per-window storage
42    ///
43    /// Updates theme from configuration and constructs a scaled per-window size
44    /// cache.
45    ///
46    /// On "standard" monitors, the `dpi_factor` is 1. High-DPI screens may
47    /// have a factor of 2 or higher. The factor may not be an integer; e.g.
48    /// `9/8 = 1.125` works well with many 1440p screens. It is recommended to
49    /// round dimensions to the nearest integer, and cache the result:
50    /// ```notest
51    /// self.margin = i32::conv_nearest(MARGIN * factor);
52    /// ```
53    ///
54    /// A reference to the draw backend is provided allowing configuration.
55    fn new_window(&mut self, config: &WindowConfig) -> Self::Window;
56
57    /// Update a window created by [`Theme::new_window`]
58    ///
59    /// This is called when the DPI factor changes or theme config or dimensions change.
60    fn update_window(&mut self, window: &mut Self::Window, config: &WindowConfig);
61
62    /// Prepare to draw and construct a [`ThemeDraw`] object
63    ///
64    /// This is called once per window per frame and should do any necessary
65    /// preparation such as loading fonts and textures which are loaded on
66    /// demand.
67    ///
68    /// Drawing via this [`ThemeDraw`] object is restricted to the specified `rect`.
69    ///
70    /// The `window` is guaranteed to be one created by a call to
71    /// [`Theme::new_window`] on `self`.
72    fn draw<'a>(
73        &'a self,
74        draw: DrawIface<'a, DS>,
75        ev: &'a mut EventState,
76        window: &'a mut Self::Window,
77    ) -> Self::Draw<'a>;
78
79    /// Construct a draw object from parts
80    ///
81    /// This method allows a "derived" theme to construct a draw object for the
82    /// inherited theme.
83    fn draw_upcast<'a>(
84        draw: DrawIface<'a, DS>,
85        ev: &'a mut EventState,
86        w: &'a mut Self::Window,
87        cols: &'a ColorsLinear,
88    ) -> Self::Draw<'a>;
89
90    /// The window/scene clear color
91    ///
92    /// This is not used when the window is transparent.
93    fn clear_color(&self) -> color::Rgba;
94}
95
96/// Per-window storage for the theme
97///
98/// Constructed via [`Theme::new_window`].
99///
100/// The main reason for this separation is to allow proper handling of
101/// multi-window applications across screens with differing DPIs.
102#[autoimpl(for<T: trait + ?Sized> Box<T>)]
103pub trait Window: 'static {
104    /// Construct a [`ThemeSize`] object
105    fn size(&self) -> &dyn ThemeSize;
106
107    fn as_any_mut(&mut self) -> &mut dyn Any;
108}
kas_core/theme/traits.rs

kas_core/theme/
traits.rs
