1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207

//! Scrolling vertical text alignment.
use crate::{
    alignment::{HorizontalTextAlignment, VerticalTextAlignment},
    rendering::cursor::Cursor,
    style::height_mode::HeightMode,
    StyledTextBox,
};
use embedded_graphics::prelude::*;

/// Align text to the TextBox so that the last lines are always displayed.
///
/// Scrolling alignment works well for terminal-like applications. When text fits into the bounding
/// box, it will be top aligned. After that, rendering switches to bottom aligned, making sure the
/// last lines are always visible.
#[derive(Copy, Clone, Debug)]
pub struct Scrolling;

impl VerticalTextAlignment for Scrolling {
    #[inline]
    fn apply_vertical_alignment<'a, C, F, A, H>(
        cursor: &mut Cursor<F>,
        styled_text_box: &'a StyledTextBox<'a, C, F, A, Self, H>,
    ) where
        C: PixelColor,
        F: Font + Copy,
        A: HorizontalTextAlignment,
        H: HeightMode,
    {
        let text_height = styled_text_box
            .style
            .measure_text_height(styled_text_box.text_box.text, cursor.line_width())
            as i32;

        let box_height = styled_text_box.size().height as i32;
        if text_height > box_height {
            let offset = box_height - text_height;

            cursor.position.y += offset
        }
    }
}

#[cfg(test)]
mod test {
    use embedded_graphics::{
        fonts::Font6x8, mock_display::MockDisplay, pixelcolor::BinaryColor, prelude::*,
        primitives::Rectangle,
    };

    use crate::{
        alignment::Scrolling,
        style::{height_mode::Exact, vertical_overdraw::Hidden, TextBoxStyleBuilder},
        TextBox,
    };

    #[test]
    fn scrolling_behaves_as_top_if_lines_dont_overflow() {
        let mut display = MockDisplay::new();
        let style = TextBoxStyleBuilder::new(Font6x8)
            .vertical_alignment(Scrolling)
            .text_color(BinaryColor::On)
            .background_color(BinaryColor::Off)
            .build();

        TextBox::new("word", Rectangle::new(Point::zero(), Point::new(54, 15)))
            .into_styled(style)
            .draw(&mut display)
            .unwrap();

        assert_eq!(
            display,
            MockDisplay::from_pattern(&[
                "......................#.",
                "......................#.",
                "#...#..###..#.##...##.#.",
                "#...#.#...#.##..#.#..##.",
                "#.#.#.#...#.#.....#...#.",
                "#.#.#.#...#.#.....#...#.",
                ".#.#...###..#......####.",
                "........................",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
            ])
        );
    }

    #[test]
    fn scrolling_behaves_as_bottom_if_lines_overflow() {
        let mut display = MockDisplay::new();
        let style = TextBoxStyleBuilder::new(Font6x8)
            .vertical_alignment(Scrolling)
            .text_color(BinaryColor::On)
            .background_color(BinaryColor::Off)
            .build();

        TextBox::new(
            "word word2 word3 word4",
            Rectangle::new(Point::zero(), Point::new(54, 15)),
        )
        .into_styled(style)
        .draw(&mut display)
        .unwrap();

        assert_eq!(
            display,
            MockDisplay::from_pattern(&[
                "......................#..###..",
                "......................#.#...#.",
                "#...#..###..#.##...##.#.....#.",
                "#...#.#...#.##..#.#..##...##..",
                "#.#.#.#...#.#.....#...#.....#.",
                "#.#.#.#...#.#.....#...#.#...#.",
                ".#.#...###..#......####..###..",
                "..............................",
                "......................#....#..",
                "......................#...##..",
                "#...#..###..#.##...##.#..#.#..",
                "#...#.#...#.##..#.#..##.#..#..",
                "#.#.#.#...#.#.....#...#.#####.",
                "#.#.#.#...#.#.....#...#....#..",
                ".#.#...###..#......####....#..",
                "..............................",
            ])
        );
    }

    #[test]
    fn scrolling_applies_full_rows_vertical_overflow() {
        let mut display = MockDisplay::new();
        let style = TextBoxStyleBuilder::new(Font6x8)
            .vertical_alignment(Scrolling)
            .text_color(BinaryColor::On)
            .background_color(BinaryColor::Off)
            .build();

        TextBox::new(
            "word word2 word3 word4",
            Rectangle::new(Point::zero(), Point::new(54, 12)),
        )
        .into_styled(style)
        .draw(&mut display)
        .unwrap();

        assert_eq!(
            display,
            MockDisplay::from_pattern(&[
                "                              ",
                "                              ",
                "                              ",
                "                              ",
                "                              ",
                "......................#....#..",
                "......................#...##..",
                "#...#..###..#.##...##.#..#.#..",
                "#...#.#...#.##..#.#..##.#..#..",
                "#.#.#.#...#.#.....#...#.#####.",
                "#.#.#.#...#.#.....#...#....#..",
                ".#.#...###..#......####....#..",
                "..............................",
            ])
        );
    }

    #[test]
    fn scrolling_applies_hidden_vertical_overflow() {
        let mut display = MockDisplay::new();
        let style = TextBoxStyleBuilder::new(Font6x8)
            .vertical_alignment(Scrolling)
            .text_color(BinaryColor::On)
            .background_color(BinaryColor::Off)
            .height_mode(Exact(Hidden))
            .build();

        TextBox::new(
            "word word2 word3 word4",
            Rectangle::new(Point::zero(), Point::new(54, 12)),
        )
        .into_styled(style)
        .draw(&mut display)
        .unwrap();

        assert_eq!(
            display,
            MockDisplay::from_pattern(&[
                "#...#.#...#.##..#.#..##...##..",
                "#.#.#.#...#.#.....#...#.....#.",
                "#.#.#.#...#.#.....#...#.#...#.",
                ".#.#...###..#......####..###..",
                "..............................",
                "......................#....#..",
                "......................#...##..",
                "#...#..###..#.##...##.#..#.#..",
                "#...#.#...#.##..#.#..##.#..#..",
                "#.#.#.#...#.#.....#...#.#####.",
                "#.#.#.#...#.#.....#...#....#..",
                ".#.#...###..#......####....#..",
                "..............................",
            ])
        );
    }
}