Trait TextHitSource

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pub trait TextHitSource {
    // Required methods
    fn offset_at(&self, point: Point) -> usize;
    fn caret_rect(&self, offset: usize) -> Rect;
    fn word_range_at(&self, offset: usize) -> Range<usize> ⓘ;
    fn line_range_at(&self, offset: usize) -> Range<usize> ⓘ;
    fn selection(&self) -> Range<usize> ⓘ;
    fn set_selection(&mut self, range: Range<usize>);
    fn selection_bounds(&self) -> Option<Rect>;
    fn viewport(&self) -> Rect;
    fn document_len(&self) -> usize;
    fn is_editable(&self) -> bool;

    // Provided methods
    fn allows_copy(&self) -> bool { ... }
    fn clipboard_actions(&self) -> ClipboardActions { ... }
}

Expand description

The geometry and selection state of one text surface, as the touch controller needs to see it.

§Relationship to `TextSurface`

The two do not overlap and neither subsumes the other. TextSurface answers “perform this command” — undo, cut, paste — for a host that routes a chord or a menu row into whatever has focus. This trait answers “where is the text”, which is what a finger needs. The one place they meet is clipboard_actions, which says which commands to offer; invoking them stays with TextSurface, so there is exactly one implementation of each command.

Required Methods§

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fn offset_at(&self, point: Point) -> usize

The text offset nearest point.

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fn caret_rect(&self, offset: usize) -> Rect

The caret rectangle at offset — a thin, line-height-tall rectangle. Handles hang off it, so a host that returns a zero-height rectangle gets handles that sit on the baseline.

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fn word_range_at(&self, offset: usize) -> Range<usize> ⓘ

The word containing offset, for the long-press selection.

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fn line_range_at(&self, offset: usize) -> Range<usize> ⓘ

The line containing offset.

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fn selection(&self) -> Range<usize> ⓘ

The current selection, as a half-open offset range. An empty range is a collapsed caret.

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fn set_selection(&mut self, range: Range<usize>)

Move the selection. Called on every sample of a handle drag, so an implementation that rebuilds the document here will be felt.

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fn selection_bounds(&self) -> Option<Rect>

The selection’s bounding rectangle, or None when nothing is selected.

Deliberately one rectangle and not a list of per-line rectangles: the only consumer is the toolbar’s AboveSelection placement, which wants the block to hang above, and the engines behind the shipped editors expose a union box rather than per-line geometry. A surface that has per-line rectangles should still return their union.

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fn viewport(&self) -> Rect

The visible rectangle of this surface. Affordances are clamped into it, and a caret outside it has no handle.

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fn document_len(&self) -> usize

The largest offset a caret may take — the length of the text.

Not geometry, and not in the original contract: a handle is exposed to assistive technology as a slider, and a slider without a maximum announces a position out of nothing. Every engine behind the shipped editors knows this number.

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