pango-Glyph-Storage {RGtk2} | R Documentation

## Glyph Storage

### Description

Structures for storing information about glyphs

### Methods and Functions

`pangoUnitsToDouble(i)`
`pangoUnitsFromDouble(d)`
`pangoExtentsToPixels(inclusive, nearest)`
`pangoMatrixCopy(object)`
`pangoMatrixTranslate(object, tx, ty)`
`pangoMatrixScale(object, scale.x, scale.y)`
`pangoMatrixRotate(object, degrees)`
`pangoMatrixConcat(object, new.matrix)`
`pangoMatrixTransformPoint(object, x, y)`
`pangoMatrixTransformDistance(object, dx, dy)`
`pangoMatrixTransformRectangle(object, rect)`
`pangoMatrixTransformPixelRectangle(object, rect)`
`pangoMatrixGetFontScaleFactor(object)`
`pangoGlyphStringNew()`
`pangoGlyphStringCopy(object)`
`pangoGlyphStringSetSize(object, new.len)`
`pangoGlyphStringExtents(object, font)`
`pangoGlyphStringExtentsRange(object, start, end, font)`
`pangoGlyphStringGetWidth(object)`
`pangoGlyphStringIndexToX(object, text, analysis, index, trailing)`
`pangoGlyphStringXToIndex(object, text, analysis, x.pos)`
`pangoGlyphStringGetLogicalWidths(object, text, embedding.level)`
`pangoGlyphItemSplit(orig, text, split.index)`
`pangoGlyphItemApplyAttrs(glyph.item, text, list)`
`pangoGlyphItemLetterSpace(glyph.item, text, log.attrs)`
`pangoGlyphItemGetLogicalWidths(glyph.item, text)`
`pangoGlyphItemIterInitStart(object, glyph.item, text)`
`pangoGlyphItemIterInitEnd(object, glyph.item, text)`
`pangoGlyphItemIterNextCluster(object)`
`pangoGlyphItemIterPrevCluster(object)`

### Detailed Description

`pangoShape` produces a string of glyphs which can be measured or drawn to the screen. The following structures are used to store information about glyphs.

### Structures

`PangoRectangle`

  The `PangoRectangle` structure represents a rectangle. It is frequently used to represent the logical or ink extents of a single glyph or section of text. (See, for instance, `pangoFontGetGlyphExtents`) `PangoRectangle` is a transparent-type.

  `x`

    [integer] X coordinate of the left side of the rectangle.

  `y`

    [integer] Y coordinate of the the top side of the rectangle.

  `width`

    [integer] width of the rectangle.

  `height`

    [integer] height of the rectangle.

`PangoMatrix`

  A structure specifying a transformation between user-space coordinates and device coordinates. The transformation is given by

      x_device = x_user * matrix->xx + y_user * matrix->xy + matrix->x0;
      y_device = x_user * matrix->yx + y_user * matrix->yy + matrix->y0;

  Since 1.6

  `xx`

    [numeric] 1st component of the transformation matrix

  `xy`

    [numeric] 2nd component of the transformation matrix

  `yx`

    [numeric] 3rd component of the transformation matrix

  `yy`

    [numeric] 4th component of the transformation matrix

  `x0`

    [numeric] x translation

  `y0`

    [numeric] y translation

`PangoGlyphInfo`

  The `PangoGlyphInfo` structure represents a single glyph together with positioning information and visual attributes. It contains the following fields.

  `glyph`

    [numeric] the glyph itself.

  `geometry`

    [`PangoGlyphGeometry`] the positional information about the glyph.

  `attr`

    [`PangoGlyphVisAttr`] the visual attributes of the glyph.

`PangoGlyphGeometry`

  The `PangoGlyphGeometry` structure contains width and positioning information for a single glyph.

  `width`

    [integer] the logical width to use for the the character.

  `xOffset`

    [integer] horizontal offset from nominal character position.

  `yOffset`

    [integer] vertical offset from nominal character position.

`PangoGlyphVisAttr`

  The PangoGlyphVisAttr is used to communicate information between the shaping phase and the rendering phase. More attributes may be added in the future.

  `isClusterStart`

    [numeric] set for the first logical glyph in each cluster. (Clusters are stored in visual order, within the cluster, glyphs are always ordered in logical order, since visual order is meaningless; that is, in Arabic text, accent glyphs follow the glyphs for the base character.)

`PangoGlyphString`

  The `PangoGlyphString` structure is used to store strings of glyphs with geometry and visual attribute information. The storage for the glyph information is owned by the structure which simplifies memory management.

  `numGlyphs`

    [integer] the number of glyphs in the string.

  `glyphs`

    [`PangoGlyphInfo`] a list of `PangoGlyphInfo` structures of length `num_glyphs`.

  `logClusters`

    [integer] for each glyph, byte index of the starting character for the cluster. The indices are relative to the start of the text corresponding to the PangoGlyphString.

`PangoGlyphItem`

  A `PangoGlyphItem` is a pair of a `PangoItem` and the glyphs resulting from shaping the text corresponding to an item. As an example of the usage of `PangoGlyphItem`, the results of shaping text with `PangoLayout` is a list of `PangoLayoutLine`, each of which contains a list of `PangoGlyphItem`.

  `item`

    [`PangoItem`] a `PangoItem` structure that provides information about a segment of text.

  `glyphs`

    [`PangoGlyphString`] the glyphs obtained by shaping the text corresponding to `item`.

`PangoGlyphItemIter`

  A `PangoGlyphItemIter` is an iterator over the clusters in a `PangoGlyphItem`. The forward direction of the iterator is the logical direction of text. That is, with increasing `start.index` and `start.char` values. If `glyph.item` is right-to-left (that is, if `glyph_item->item->analysis.level` is odd), then `start.glyph` decreases as the iterator moves forward. Moreover, in right-to-left cases, `start.glyph` is greater than `end.glyph`. An iterator should be initialized using either of `pangoGlyphItemIterInitStart` and `pangoGlyphItemIterInitEnd`, for forward and backward iteration respectively, and walked over using any desired mixture of `pangoGlyphItemIterNextCluster` and `pangoGlyphItemIterPrevCluster`. A common idiom for doing a forward iteration over the clusters is:

      PangoGlyphItemIter cluster_iter;
      gboolean have_cluster;
      for (have_cluster = pango_glyph_item_iter_init_start (&cluster_iter,
                                                            glyph_item, text);
           have_cluster;
           have_cluster = pango_glyph_item_iter_next_cluster (&cluster_iter))
      {
        ...
      }

  Note that `text` is the start of the text for layout, which is then indexed by `glyph_item->item->offset` to get to the text of `glyph.item`. The `start.index` and `end.index` values can directly index into `text`. The `start.glyph`, `end.glyph`, `start.char`, and `end.char` values however are zero-based for the `glyph.item`. For each cluster, the item pointed at by the start variables is included in the cluster while the one pointed at by end variables is not. None of the members of a `PangoGlyphItemIter` should be modified manually. Since 1.22

  `glyph_item`

    [`PangoGlyphItem`] the `PangoGlyphItem` this iterator iterates over

  `text`

    [character] the UTF-8 text that `glyph.item` refers to

  `start_glyph`

    [integer] starting glyph of the cluster

  `start_index`

    [integer] starting text index of the cluster

  `start_char`

    [integer] starting number of characters of the cluster

  `end_glyph`

    [integer] ending glyph of the cluster

  `end_index`

    [integer] ending text index of the cluster

  `end_char`

    [integer] ending number of characters of the cluster

### Author(s)

Derived by RGtkGen from GTK+ documentation

### References

https://developer.gnome.org/pango/stable/pango-Glyph-Storage.html

[Package RGtk2 version 2.20.36.3 Index]