cairoScaledFontTextToGlyphs {RGtk2} | R Documentation

## cairoScaledFontTextToGlyphs

### Description

Converts UTF-8 text to a list of glyphs, optionally with cluster mapping, that can be used to render later using `scaled.font`.

### Usage

    cairoScaledFontTextToGlyphs(scaled.font, x, y, utf8, utf8.len = -1)

### Arguments

``scaled.font`` | [`CairoScaledFont`] a `CairoScaledFont`
``x`` | [numeric] X position to place first glyph
``y`` | [numeric] Y position to place first glyph
``utf8`` | [char] a string of text encoded in UTF-8
``utf8.len`` | [integer] length of `utf8` in bytes, or -1 if it is NUL-terminated

### Details

If `glyphs` initially points to a non-`NULL` value, that list is used as a glyph buffer, and `num.glyphs` should point to the number of glyph entries available there. If the provided glyph list is too short for the conversion, Upon return, `num.glyphs` always contains the number of generated glyphs. If the value `glyphs` points to has changed after the call, This may happen even if the provided array was large enough.

If `clusters` is not `NULL`, `num.clusters` and `cluster.flags` should not be `NULL`, and cluster mapping will be computed. The semantics of how cluster list allocation works is similar to the glyph array. That is, if `clusters` initially points to a non-`NULL` value, that list is used as a cluster buffer, and `num.clusters` should point to the number of cluster entries available there. If the provided cluster list is too short for the conversion, Upon return, `num.clusters` always contains the number of generated clusters. If the value `clusters` points at has changed after the call, This may happen even if the provided array was large enough.

In the simplest case, `glyphs` and `clusters` can point to `NULL` initially and a suitable list will be allocated. In code:

    glyphs <- scaled_font$textToGlyphs(x, y, utf8, utf8_len)

    if (glyphs$retval == CairoStatus["success"])
      cr$showTextGlyphs(utf8, utf8_len,
                        glyphs$glyphs, glyphs$num_glyphs,
                        glyphs$clusters, glyphs$num_clusters,
                        glyphs$cluster_flags)

If no cluster mapping is needed:

    glyphs <- scaled_font$textToGlyphs(x, y, utf8, utf8_len)

    if (glyphs$retval == CairoStatus["success"]) {
      cr$showGlyphs(glyphs$glyphs, glyphs$num_glyphs)
    }

If stack-based glyph and cluster lists are to be used for small arrays:

    ## R user obviously does not allocate things on the stack.
    ## This is the same as the first example.

    glyphs <- scaled_font$textToGlyphs(x, y, utf8, utf8_len)

    if (glyphs$retval == CairoStatus["success"])
      cr$showTextGlyphs(utf8, utf8_len,
                        glyphs$glyphs, glyphs$num_glyphs,
                        glyphs$clusters, glyphs$num_clusters,
                        glyphs$cluster_flags)

For details of how `clusters`, `num.clusters`, and `cluster.flags` map input UTF-8 text to the output glyphs see `cairoShowTextGlyphs`.

The output values can be readily passed to `cairoShowTextGlyphs` `cairoShowGlyphs`, or related functions, assuming that the exact same `scaled.font` is used for the operation. Since 1.8

### Value

A list containing the following elements:

`retval` | [`CairoStatus`] `CAIRO_STATUS_SUCCESS` upon success, or an error status if the input values are wrong or if conversion failed. If the input values are correct but the conversion failed, the error status is also set on `scaled.font`.
``glyphs`` | [`CairoGlyph`] pointer to list of glyphs to fill
``num.glyphs`` | [integer] pointer to number of glyphs
``clusters`` | [`CairoTextCluster`] pointer to list of cluster mapping information to fill, or `NULL`
``num.clusters`` | [integer] pointer to number of clusters, or `NULL`
``cluster.flags`` | [`CairoTextClusterFlags`] pointer to location to store cluster flags corresponding to the output `clusters`, or `NULL`

### Author(s)

Derived by RGtkGen from GTK+ documentation

[Package RGtk2 version 2.20.36.3 Index]