egui/text_selection/
visuals.rs

1use std::sync::Arc;
2
3use crate::{Galley, Painter, Rect, Ui, Visuals, pos2, vec2};
4
5use super::CCursorRange;
6
7#[derive(Clone, Debug)]
8pub struct RowVertexIndices {
9    pub row: usize,
10    pub vertex_indices: [u32; 6],
11}
12
13/// Adds text selection rectangles to the galley.
14pub fn paint_text_selection(
15    galley: &mut Arc<Galley>,
16    visuals: &Visuals,
17    cursor_range: &CCursorRange,
18    mut new_vertex_indices: Option<&mut Vec<RowVertexIndices>>,
19) {
20    if cursor_range.is_empty() {
21        return;
22    }
23
24    // We need to modify the galley (add text selection painting to it),
25    // and so we need to clone it if it is shared:
26    let galley: &mut Galley = Arc::make_mut(galley);
27
28    let color = visuals.selection.bg_fill;
29    let [min, max] = cursor_range.sorted_cursors();
30    let min = galley.layout_from_cursor(min);
31    let max = galley.layout_from_cursor(max);
32
33    for ri in min.row..=max.row {
34        let row = Arc::make_mut(&mut galley.rows[ri].row);
35
36        let left = if ri == min.row {
37            row.x_offset(min.column)
38        } else {
39            0.0
40        };
41        let right = if ri == max.row {
42            row.x_offset(max.column)
43        } else {
44            let newline_size = if row.ends_with_newline {
45                row.height() / 2.0 // visualize that we select the newline
46            } else {
47                0.0
48            };
49            row.size.x + newline_size
50        };
51
52        let rect = Rect::from_min_max(pos2(left, 0.0), pos2(right, row.size.y));
53        let mesh = &mut row.visuals.mesh;
54
55        // Time to insert the selection rectangle into the row mesh.
56        // It should be on top (after) of any background in the galley,
57        // but behind (before) any glyphs. The row visuals has this information:
58        let glyph_index_start = row.visuals.glyph_index_start;
59
60        // Start by appending the selection rectangle to end of the mesh, as two triangles (= 6 indices):
61        let num_indices_before = mesh.indices.len();
62        mesh.add_colored_rect(rect, color);
63        assert_eq!(
64            num_indices_before + 6,
65            mesh.indices.len(),
66            "We expect exactly 6 new indices"
67        );
68
69        // Copy out the new triangles:
70        let selection_triangles = [
71            mesh.indices[num_indices_before],
72            mesh.indices[num_indices_before + 1],
73            mesh.indices[num_indices_before + 2],
74            mesh.indices[num_indices_before + 3],
75            mesh.indices[num_indices_before + 4],
76            mesh.indices[num_indices_before + 5],
77        ];
78
79        // Move every old triangle forwards by 6 indices to make room for the new triangle:
80        for i in (glyph_index_start..num_indices_before).rev() {
81            mesh.indices.swap(i, i + 6);
82        }
83        // Put the new triangle in place:
84        mesh.indices[glyph_index_start..glyph_index_start + 6]
85            .clone_from_slice(&selection_triangles);
86
87        row.visuals.mesh_bounds = mesh.calc_bounds();
88
89        if let Some(new_vertex_indices) = &mut new_vertex_indices {
90            new_vertex_indices.push(RowVertexIndices {
91                row: ri,
92                vertex_indices: selection_triangles,
93            });
94        }
95    }
96}
97
98/// Paint one end of the selection, e.g. the primary cursor.
99///
100/// This will never blink.
101pub fn paint_cursor_end(painter: &Painter, visuals: &Visuals, cursor_rect: Rect) {
102    let stroke = visuals.text_cursor.stroke;
103
104    let top = cursor_rect.center_top();
105    let bottom = cursor_rect.center_bottom();
106
107    painter.line_segment([top, bottom], (stroke.width, stroke.color));
108
109    if false {
110        // Roof/floor:
111        let extrusion = 3.0;
112        let width = 1.0;
113        painter.line_segment(
114            [top - vec2(extrusion, 0.0), top + vec2(extrusion, 0.0)],
115            (width, stroke.color),
116        );
117        painter.line_segment(
118            [bottom - vec2(extrusion, 0.0), bottom + vec2(extrusion, 0.0)],
119            (width, stroke.color),
120        );
121    }
122}
123
124/// Paint one end of the selection, e.g. the primary cursor, with blinking (if enabled).
125pub fn paint_text_cursor(
126    ui: &Ui,
127    painter: &Painter,
128    primary_cursor_rect: Rect,
129    time_since_last_interaction: f64,
130) {
131    if ui.visuals().text_cursor.blink {
132        let on_duration = ui.visuals().text_cursor.on_duration;
133        let off_duration = ui.visuals().text_cursor.off_duration;
134        let total_duration = on_duration + off_duration;
135
136        let time_in_cycle = (time_since_last_interaction % (total_duration as f64)) as f32;
137
138        let wake_in = if time_in_cycle < on_duration {
139            // Cursor is visible
140            paint_cursor_end(painter, ui.visuals(), primary_cursor_rect);
141            on_duration - time_in_cycle
142        } else {
143            // Cursor is not visible
144            total_duration - time_in_cycle
145        };
146
147        ui.ctx().request_repaint_after_secs(wake_in);
148    } else {
149        paint_cursor_end(painter, ui.visuals(), primary_cursor_rect);
150    }
151}
egui/text_selection/visuals.rs

egui/text_selection/
visuals.rs
