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

/// Current cursor location
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd)]
pub struct Cursor {
    /// Index of [`BufferLine`] in [`Buffer::lines`]
    pub line: usize,
    /// First-byte-index of glyph at cursor (will insert behind this glyph)
    pub index: usize,
    /// Whether to associate the cursor with the run before it or the run after it if placed at the
    /// boundary between two runs
    pub affinity: Affinity,
}

impl Cursor {
    /// Create a new cursor
    pub const fn new(line: usize, index: usize) -> Self {
        Self::new_with_affinity(line, index, Affinity::Before)
    }

    /// Create a new cursor, specifying the affinity
    pub const fn new_with_affinity(line: usize, index: usize, affinity: Affinity) -> Self {
        Self {
            line,
            index,
            affinity,
        }
    }
}

/// Whether to associate cursors placed at a boundary between runs with the run before or after it.
#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, Ord, PartialOrd)]
pub enum Affinity {
    #[default]
    Before,
    After,
}

impl Affinity {
    pub fn before(&self) -> bool {
        *self == Self::Before
    }

    pub fn after(&self) -> bool {
        *self == Self::After
    }

    pub fn from_before(before: bool) -> Self {
        if before {
            Self::Before
        } else {
            Self::After
        }
    }

    pub fn from_after(after: bool) -> Self {
        if after {
            Self::After
        } else {
            Self::Before
        }
    }
}

/// The position of a cursor within a [`Buffer`].
#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
pub struct LayoutCursor {
    /// Index of [`BufferLine`] in [`Buffer::lines`]
    pub line: usize,
    /// Index of [`LayoutLine`] in [`BufferLine::layout`]
    pub layout: usize,
    /// Index of [`LayoutGlyph`] in [`LayoutLine::glyphs`]
    pub glyph: usize,
}

impl LayoutCursor {
    /// Create a new [`LayoutCursor`]
    pub const fn new(line: usize, layout: usize, glyph: usize) -> Self {
        Self {
            line,
            layout,
            glyph,
        }
    }
}

/// A motion to perform on a [`Cursor`]
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Motion {
    /// Apply specific [`LayoutCursor`]
    LayoutCursor(LayoutCursor),
    /// Move cursor to previous character ([Self::Left] in LTR, [Self::Right] in RTL)
    Previous,
    /// Move cursor to next character ([Self::Right] in LTR, [Self::Left] in RTL)
    Next,
    /// Move cursor left
    Left,
    /// Move cursor right
    Right,
    /// Move cursor up
    Up,
    /// Move cursor down
    Down,
    /// Move cursor to start of line
    Home,
    /// Move cursor to start of line, skipping whitespace
    SoftHome,
    /// Move cursor to end of line
    End,
    /// Move cursor to start of paragraph
    ParagraphStart,
    /// Move cursor to end of paragraph
    ParagraphEnd,
    /// Move cursor up one page
    PageUp,
    /// Move cursor down one page
    PageDown,
    /// Move cursor up or down by a number of pixels
    Vertical(i32),
    /// Move cursor to previous word boundary
    PreviousWord,
    /// Move cursor to next word boundary
    NextWord,
    /// Move cursor to next word boundary to the left
    LeftWord,
    /// Move cursor to next word boundary to the right
    RightWord,
    /// Move cursor to the start of the document
    BufferStart,
    /// Move cursor to the end of the document
    BufferEnd,
    /// Move cursor to specific line
    GotoLine(usize),
}

/// Scroll position in [`Buffer`]
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq, Ord, PartialOrd)]
pub struct Scroll {
    /// Index of [`BufferLine`] in [`Buffer::lines`]. This will be adjusted as needed if layout is
    /// out of bounds
    pub line: usize,
    /// Index of [`LayoutLine`] in [`BufferLine::layout`]. This will be adjusted as needed
    /// if it is negative or exceeds the number of layout lines
    pub layout: i32,
}

impl Scroll {
    /// Create a new cursor
    pub const fn new(line: usize, layout: i32) -> Self {
        Self { line, layout }
    }
}