class QGlyphRun

The QGlyphRun class provides direct access to the internal glyphs in a font. More…

Synopsis

Methods

Note

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Detailed Description

When Qt displays a string of text encoded in Unicode, it will first convert the Unicode points into a list of glyph indexes and a list of positions based on one or more fonts. The Unicode representation of the text and the QFont object will in this case serve as a convenient abstraction that hides the details of what actually takes place when displaying the text on-screen. For instance, by the time the text actually reaches the screen, it may be represented by a set of fonts in addition to the one specified by the user, e.g. in case the originally selected font did not support all the writing systems contained in the text.

Under certain circumstances, it can be useful as an application developer to have more low-level control over which glyphs in a specific font are drawn to the screen. This could for instance be the case in applications that use an external font engine and text shaper together with Qt. QGlyphRun provides an interface to the raw data needed to get text on the screen. It contains a list of glyph indexes, a position for each glyph and a font.

It is the user’s responsibility to ensure that the selected font actually contains the provided glyph indexes.

glyphRuns() or glyphRuns() can be used to convert unicode encoded text into a list of QGlyphRun objects, and drawGlyphRun() can be used to draw the glyphs.

Note

Please note that QRawFont is considered local to the thread in which it is constructed. This in turn means that a new QRawFont will have to be created and set on the QGlyphRun if it is moved to a different thread. If the QGlyphRun contains a reference to a QRawFont from a different thread than the current, it will not be possible to draw the glyphs using a QPainter , as the QRawFont is considered invalid and inaccessible in this case.

class GlyphRunFlag

(inherits enum.Flag) This enum describes flags that alter the way the run of glyphs might be presented or behave in a visual layout. The layout which generates the glyph runs can set these flags based on relevant internal data, to retain information needed to present the text as intended by the user of the layout.

Constant

Description

QGlyphRun.Overline

Indicates that the glyphs should be visualized together with an overline.

QGlyphRun.Underline

Indicates that the glyphs should be visualized together with an underline.

QGlyphRun.StrikeOut

Indicates that the glyphs should be struck out visually.

QGlyphRun.RightToLeft

Indicates that the glyphs are ordered right to left. This can affect the positioning of other screen elements that are relative to the glyph run, such as an inline text object.

QGlyphRun.SplitLigature

Indicates that the glyph run splits a ligature glyph. This means that a ligature glyph is included in the run, but the characters represented by it corresponds only to part of that ligature. The glyph run’s boundingRect() function can in this case be used to retrieve the area covered by glyphs that correspond to the characters represented by the glyph run. When visualizing the glyphs, care needs to be taken to clip to this bounding rect to ensure that only the corresponding part of the ligature is painted. In particular, this can be the case when retrieving a glyph run from a QTextLayout for a specific character range, e.g. when retrieving the selected area of a QTextLayout .
__init__()

Constructs an empty QGlyphRun object.

__init__(other)
Parameters:

other – QGlyphRun

Constructs a QGlyphRun object which is a copy of other.

boundingRect()
Return type:

QRectF

Returns the smallest rectangle that contains all glyphs in this QGlyphRun . If a bounding rect has been set using setBoundingRect() , then this will be returned. Otherwise the bounding rect will be calculated based on the font metrics of the glyphs in the glyph run.

clear()

Clears all data in the QGlyphRun object.

flags()
Return type:

Combination of GlyphRunFlag

Returns the flags set for this QGlyphRun .

glyphIndexes()
Return type:

.list of quint32

Returns the glyph indexes for this QGlyphRun object.

isEmpty()
Return type:

bool

Returns true if the QGlyphRun does not contain any glyphs.

isRightToLeft()
Return type:

bool

Returns true if this QGlyphRun contains glyphs that are painted from the right to the left.

__ne__(other)
Parameters:

other – QGlyphRun

Return type:

bool

Compares other to this QGlyphRun object. Returns true if any of the list of glyph indexes, the list of positions or the font are different, otherwise returns false.

__eq__(other)
Parameters:

other – QGlyphRun

Return type:

bool

Compares other to this QGlyphRun object. Returns true if the list of glyph indexes, the list of positions and the font are all equal, otherwise returns false.

overline()
Return type:

bool

Returns true if this QGlyphRun should be painted with an overline decoration.

positions()
Return type:

.list of QPointF

Returns the position of the edge of the baseline for each glyph in this set of glyph indexes.

See also

setPositions()

rawFont()
Return type:

QRawFont

Returns the font selected for this QGlyphRun object.

See also

setRawFont()

setBoundingRect(boundingRect)
Parameters:

boundingRect – QRectF

Sets the bounding rect of the glyphs in this QGlyphRun to be boundingRect. This rectangle will be returned by boundingRect() unless it is null, in which case the bounding rectangle of the glyphs in the glyph run will be returned instead.

Note

Unless you are implementing text shaping, you should not have to use this function. It is used specifically when the QGlyphRun should represent an area which is smaller than the area of the glyphs it contains. This could happen e.g. if the glyph run is retrieved by calling glyphRuns() and the specified range only includes part of a ligature (where two or more characters are combined to a single glyph.) When this is the case, the bounding rect should only include the appropriate part of the ligature glyph, based on a calculation of the average width of the characters in the ligature.

In order to support such a case (an example is selections which should be drawn with a different color than the main text color), it is necessary to clip the painting mechanism to the rectangle returned from boundingRect() to avoid drawing the entire ligature glyph.

See also

boundingRect()

setFlag(flag[, enabled=true])
Parameters:

If enabled is true, then flag is enabled; otherwise, it is disabled.

See also

flags() setFlags()

setFlags(flags)
Parameters:

flags – Combination of GlyphRunFlag

Sets the flags of this QGlyphRun to flags.

See also

setFlag() flags()

setGlyphIndexes(glyphIndexes)
Parameters:

glyphIndexes – .list of quint32

Set the glyph indexes for this QGlyphRun object to glyphIndexes. The glyph indexes must be valid for the selected font.

See also

glyphIndexes()

setOverline(overline)
Parameters:

overline – bool

Indicates that this QGlyphRun should be painted with an overline decoration if overline is true. Otherwise the QGlyphRun should be painted with no overline decoration.

setPositions(positions)
Parameters:

positions – .list of QPointF

Sets the positions of the edge of the baseline for each glyph in this set of glyph indexes to positions.

See also

positions()

setRawData(glyphIndexArray, glyphPositionArray, size)
Parameters:

  • glyphIndexArray – quint32

  • glyphPositionArray – QPointF

  • size – int

Sets the glyph indexes and positions of this QGlyphRun to use the first size elements in the arrays glyphIndexArray and glyphPositionArray. The data is not copied. The caller must guarantee that the arrays are not deleted as long as this QGlyphRun and any copies of it exists.

setRawFont(rawFont)
Parameters:

rawFont – QRawFont

Sets the font in which to look up the glyph indexes to the rawFont specified.

setRightToLeft(on)
Parameters:

on – bool

Indicates that this QGlyphRun contains glyphs that should be ordered from the right to left if rightToLeft is true. Otherwise the order of the glyphs is assumed to be left to right.

setSourceString(sourceString)
Parameters:

sourceString – str

Set the string corresponding to the glyph run to sourceString. If set, the indexes returned by stringIndexes() should be indexes into this string.

setStrikeOut(strikeOut)
Parameters:

strikeOut – bool

Indicates that this QGlyphRun should be painted with an strike out decoration if strikeOut is true. Otherwise the QGlyphRun should be painted with no strike out decoration.

setStringIndexes(stringIndexes)
Parameters:

stringIndexes – .list of qsizetype

Sets the list of string indexes corresponding to the glyph indexes to stringIndexes

See stringIndexes() for more details on the conventions of this list.

setUnderline(underline)
Parameters:

underline – bool

Indicates that this QGlyphRun should be painted with an underline decoration if underline is true. Otherwise the QGlyphRun should be painted with no underline decoration.

sourceString()
Return type:

str

Returns the string corresponding to the glyph run, if the glyph run has been created from a string and the string has been requested from the layout.

strikeOut()
Return type:

bool

Returns true if this QGlyphRun should be painted with a strike out decoration.

stringIndexes()
Return type:

.list of qsizetype

Returns the string indexes corresponding to each glyph index, if the glyph run has been constructed from a string and string indexes have been requested from the layout. In this case, the length of the returned vector will correspond to the length of glyphIndexes() . In other cases, it will be empty.

Since a single glyph may correspond to multiple characters in the source string, there may be gaps in the list of string indexes. For instance, if the string “first” is processed by a font which contains a ligature for the character pair “fi”, then the five character string will generate a glyph run consisting of only four glyphs. Then the glyph indexes may in this case be (1, 2, 3, 4) (four arbitrary glyph indexes) whereas the string indexes would be (0, 2, 3, 4). The glyphs are in the logical order of the string, thus it is implied that the first glyphs spans characters 0 and 1 in this case.

Inversely, a single character may also generate multiple glyphs, in which case there will be duplicate entries in the list of string indexes.

The string indexes correspond to the string, optionally available through sourceString() .

swap(other)
Parameters:

other – QGlyphRun

Swaps this glyph run instance with other. This function is very fast and never fails.

underline()
Return type:

bool

Returns true if this QGlyphRun should be painted with an underline decoration.