# Struct GlyphInfo

    #[repr(C)]pub struct GlyphInfo {
        pub glyph_id: u32,
        pub cluster: u32,
        /* private fields */
    }

Expand description

A glyph info.

Structure that holds information about the glyphs and their relation to input text.

HarfBuzz calls this `hb_glyph_info_t`. See the documentation and source.

## Fields§

§`glyph_id: u32`

A selected glyph.

Guarantee to be <= `u16::MAX`.

§`cluster: u32`

An index to the start of the grapheme cluster in the original string.

Read more on clusters.

## Implementations§

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### impl GlyphInfo

#### pub fn unsafe_to_break(&self) -> bool

Indicates that if input text is broken at the beginning of the cluster this glyph is part of, then both sides need to be re-shaped, as the result might be different.

On the flip side, it means that when this flag is not present, then it’s safe to break the glyph-run at the beginning of this cluster, and the two sides represent the exact same result one would get if breaking input text at the beginning of this cluster and shaping the two sides separately. This can be used to optimize paragraph layout, by avoiding re-shaping of each line after line-breaking, or limiting the reshaping to a small piece around the breaking point only.

#### pub fn unsafe_to_concat(&self) -> bool

Indicates that if input text is changed on one side of the beginning of the cluster this glyph is part of, then the shaping results for the other side might change. Note that the absence of this flag will NOT by itself mean that it IS safe to concat text. Only two pieces of text both of which clear of this flag can be concatenated safely.

This can be used to optimize paragraph layout, by avoiding re-shaping of each line after line-breaking, by limiting the reshaping to a small piece around the breaking position only, even if the breaking position carries the unsafe-to-break flag or when hyphenation or other text transformation happens at line-break position, in the following way:

1. Iterate back from the line-break position until the first cluster start position that is NOT unsafe-to-concat.
2. Shape the segment from there till the end of line.
3. Check whether the resulting glyph-run also is clear of the unsafe-to-concat at its start-of-text position; if it is, just splice it into place and the line is shaped; If not, move on to a position further back that is clear of unsafe-to-concat and retry from there, and repeat.

At the start of next line a similar algorithm can be implemented. That is:

1. Iterate forward from the line-break position until the first cluster start position that is NOT unsafe-to-concat.
2. Shape the segment from beginning of the line to that position.
3. Check whether the resulting glyph-run also is clear of the unsafe-to-concat at its end-of-text position; if it is, just splice it into place and the beginning is shaped; If not, move on to a position further forward that is clear of unsafe-to-concat and retry up to there, and repeat. A slight complication will arise in the implementation of the algorithm above, because while our buffer API has a way to return flags for position corresponding to start-of-text, there is currently no position corresponding to end-of-text. This limitation can be alleviated by shaping more text than needed and looking for unsafe-to-concat flag within text clusters. The unsafe-to-break flag will always imply this flag. To use this flag, you must enable the buffer flag `BufferFlags::PRODUCE_UNSAFE_TO_CONCAT` during shaping, otherwise the buffer flag will not be reliably produced.

#### pub fn safe_to_insert_tatweel(&self) -> bool

In scripts that use elongation (Arabic, Mongolian, Syriac, etc.), this flag signifies that it is safe to insert a U+0640 TATWEEL character before this cluster for elongation. This flag does not determine the script-specific elongation places, but only when it is safe to do the elongation without interrupting text shaping.

## Trait Implementations§

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### impl Clone for GlyphInfo

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#### fn clone(&self) -> GlyphInfo

Returns a duplicate of the value. Read more
1.0.0 · Source§

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for GlyphInfo

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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### impl Default for GlyphInfo

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#### fn default() -> GlyphInfo

Returns the “default value” for a type. Read more
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### impl Zeroable for GlyphInfo

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#### fn zeroed() -> Self

Calls `zeroed`. Read more
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### impl Copy for GlyphInfo

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### impl Pod for GlyphInfo

## Auto Trait Implementations§

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### impl Freeze for GlyphInfo

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### impl RefUnwindSafe for GlyphInfo

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### impl Send for GlyphInfo

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### impl Sync for GlyphInfo

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### impl Unpin for GlyphInfo

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### impl UnwindSafe for GlyphInfo

## Blanket Implementations§

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#### fn adapt_into_using<M>(self, method: M) -> D
where M: TransformMatrix<T>,

Convert the source color to the destination color using the specified method.
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#### fn adapt_into(self) -> D

Convert the source color to the destination color using the bradford method by default.
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Apply a function to this value and return the (possibly) modified value.
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Gets the `TypeId` of `self`. Read more
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Apply a function which takes the parameter by value.
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Apply a function which takes the parameter by reference.
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Apply a function which takes the parameter by mutable reference.
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#### fn arrays_from(colors: C) -> T

Cast a collection of colors into a collection of arrays.
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#### fn arrays_into(self) -> C

Cast this collection of arrays into a collection of colors.
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Immutably borrows from an owned value. Read more
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🔬This is a nightly-only experimental API. (`clone_to_uninit`)
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#### type Error = <C as TryFromComponents<T>>::Error

The error for when `try_into_colors` fails to cast.
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Try to cast this collection of color components into a collection of colors. Read more
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Convert into T, returning ok if the color is inside of its defined range, otherwise an `OutOfBounds` error is returned which contains the unclamped color. Read more
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Cast a collection of colors into a collection of unsigned integers.
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