QGIS API Documentation  3.21.0-Master (5b68dc587e)
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QgsTextRenderer Class Reference

Handles rendering text using rich formatting options, including drop shadows, buffers and background shapes. More...

#include <qgstextrenderer.h>

Public Types

enum  DrawMode { Rect = 0 , Point , Label }
 Draw mode to calculate width and height. More...
 
enum  HAlignment { AlignLeft = 0 , AlignCenter , AlignRight , AlignJustify }
 Horizontal alignment. More...
 
enum  TextPart { Text = 0 , Buffer , Background , Shadow }
 Components of text. More...
 
enum  VAlignment { AlignTop = 0 , AlignVCenter , AlignBottom }
 Vertical alignment. More...
 

Static Public Member Functions

static HAlignment convertQtHAlignment (Qt::Alignment alignment)
 Converts a Qt horizontal alignment flag to a QgsTextRenderer::HAlignment value. More...
 
static VAlignment convertQtVAlignment (Qt::Alignment alignment)
 Converts a Qt vertical alignment flag to a QgsTextRenderer::VAlignment value. More...
 
static Q_DECL_DEPRECATED void drawPart (const QRectF &rect, double rotation, HAlignment alignment, const QStringList &textLines, QgsRenderContext &context, const QgsTextFormat &format, TextPart part, bool drawAsOutlines=true)
 Draws a single component of rendered text using the specified settings. More...
 
static Q_DECL_DEPRECATED void drawPart (QPointF origin, double rotation, HAlignment alignment, const QStringList &textLines, QgsRenderContext &context, const QgsTextFormat &format, TextPart part, bool drawAsOutlines=true)
 Draws a single component of rendered text using the specified settings. More...
 
static void drawText (const QRectF &rect, double rotation, HAlignment alignment, const QStringList &textLines, QgsRenderContext &context, const QgsTextFormat &format, bool drawAsOutlines=true, VAlignment vAlignment=AlignTop)
 Draws text within a rectangle using the specified settings. More...
 
static void drawText (QPointF point, double rotation, HAlignment alignment, const QStringList &textLines, QgsRenderContext &context, const QgsTextFormat &format, bool drawAsOutlines=true)
 Draws text at a point origin using the specified settings. More...
 
static QFontMetricsF fontMetrics (QgsRenderContext &context, const QgsTextFormat &format, double scaleFactor=1.0)
 Returns the font metrics for the given text format, when rendered in the specified render context. More...
 
static int sizeToPixel (double size, const QgsRenderContext &c, QgsUnitTypes::RenderUnit unit, const QgsMapUnitScale &mapUnitScale=QgsMapUnitScale())
 Calculates pixel size (considering output size should be in pixel or map units, scale factors and optionally oversampling) More...
 
static double textHeight (const QgsRenderContext &context, const QgsTextFormat &format, const QStringList &textLines, DrawMode mode=Point, QFontMetricsF *fontMetrics=nullptr)
 Returns the height of a text based on a given format. More...
 
static double textHeight (const QgsRenderContext &context, const QgsTextFormat &format, QChar character, bool includeEffects=false)
 Returns the height of a character when rendered with the specified text format. More...
 
static double textWidth (const QgsRenderContext &context, const QgsTextFormat &format, const QStringList &textLines, QFontMetricsF *fontMetrics=nullptr)
 Returns the width of a text based on a given format. More...
 

Static Public Attributes

static constexpr double FONT_WORKAROUND_SCALE = 10
 Scale factor for upscaling font sizes and downscaling destination painter devices. More...
 

Friends

class QgsLabelPreview
 
class QgsVectorLayerLabelProvider
 

Detailed Description

Handles rendering text using rich formatting options, including drop shadows, buffers and background shapes.

Since
QGIS 3.0

Definition at line 36 of file qgstextrenderer.h.

Member Enumeration Documentation

◆ DrawMode

Draw mode to calculate width and height.

Enumerator
Rect 

Text within rectangle draw mode.

Point 

Text at point of origin draw mode.

Label 

Label-specific draw mode.

Definition at line 41 of file qgstextrenderer.h.

◆ HAlignment

Horizontal alignment.

Enumerator
AlignLeft 

Left align.

AlignCenter 

Center align.

AlignRight 

Right align.

AlignJustify 

Justify align.

Definition at line 58 of file qgstextrenderer.h.

◆ TextPart

Components of text.

Enumerator
Text 

Text component.

Buffer 

Buffer component.

Background 

Background shape.

Shadow 

Drop shadow.

Definition at line 49 of file qgstextrenderer.h.

◆ VAlignment

Vertical alignment.

Since
QGIS 3.16
Enumerator
AlignTop 

Align to top.

AlignVCenter 

Center align.

AlignBottom 

Align to bottom.

Definition at line 78 of file qgstextrenderer.h.

Member Function Documentation

◆ convertQtHAlignment()

QgsTextRenderer::HAlignment QgsTextRenderer::convertQtHAlignment ( Qt::Alignment  alignment)
static

Converts a Qt horizontal alignment flag to a QgsTextRenderer::HAlignment value.

See also
convertQtVAlignment()
Since
QGIS 3.16

Definition at line 45 of file qgstextrenderer.cpp.

◆ convertQtVAlignment()

QgsTextRenderer::VAlignment QgsTextRenderer::convertQtVAlignment ( Qt::Alignment  alignment)
static

Converts a Qt vertical alignment flag to a QgsTextRenderer::VAlignment value.

See also
convertQtHAlignment()
Since
QGIS 3.16

Definition at line 60 of file qgstextrenderer.cpp.

◆ drawPart() [1/2]

void QgsTextRenderer::drawPart ( const QRectF &  rect,
double  rotation,
HAlignment  alignment,
const QStringList &  textLines,
QgsRenderContext context,
const QgsTextFormat format,
QgsTextRenderer::TextPart  part,
bool  drawAsOutlines = true 
)
static

Draws a single component of rendered text using the specified settings.

Parameters
rectdestination rectangle for text
rotationtext rotation
alignmenthorizontal alignment
textLineslist of lines of text to draw
contextrender context
formattext format
partcomponent of text to draw. Note that Shadow parts cannot be drawn individually and instead are drawn with their associated part (e.g., drawn together with the text or background parts)
drawAsOutlinesset to false to render text as text. This allows outputs to formats like SVG to maintain text as text objects, but at the cost of degraded rendering and may result in side effects like misaligned text buffers. This setting is deprecated and has no effect as of QGIS 3.4.3 and the text format should be set using QgsRenderContext::setTextRenderFormat() instead.
Deprecated:
Private API only, will be removed in 4.0

Definition at line 147 of file qgstextrenderer.cpp.

◆ drawPart() [2/2]

void QgsTextRenderer::drawPart ( QPointF  origin,
double  rotation,
QgsTextRenderer::HAlignment  alignment,
const QStringList &  textLines,
QgsRenderContext context,
const QgsTextFormat format,
QgsTextRenderer::TextPart  part,
bool  drawAsOutlines = true 
)
static

Draws a single component of rendered text using the specified settings.

Parameters
originorigin for start of text. Y coordinate will be used as baseline.
rotationtext rotation
alignmenthorizontal alignment
textLineslist of lines of text to draw
contextrender context
formattext format
partcomponent of text to draw. Note that Shadow parts cannot be drawn individually and instead are drawn with their associated part (e.g., drawn together with the text or background parts)
drawAsOutlinesset to false to render text as text. This allows outputs to formats like SVG to maintain text as text objects, but at the cost of degraded rendering and may result in side effects like misaligned text buffers. This setting is deprecated and has no effect as of QGIS 3.4.3 and the text format should be set using QgsRenderContext::setTextRenderFormat() instead.
Deprecated:
Private API only, will be removed in 4.0

Definition at line 217 of file qgstextrenderer.cpp.

◆ drawText() [1/2]

void QgsTextRenderer::drawText ( const QRectF &  rect,
double  rotation,
QgsTextRenderer::HAlignment  alignment,
const QStringList &  textLines,
QgsRenderContext context,
const QgsTextFormat format,
bool  drawAsOutlines = true,
VAlignment  vAlignment = AlignTop 
)
static

Draws text within a rectangle using the specified settings.

Parameters
rectdestination rectangle for text
rotationtext rotation
alignmenthorizontal alignment
textLineslist of lines of text to draw
contextrender context
formattext format
drawAsOutlinesset to false to render text as text. This allows outputs to formats like SVG to maintain text as text objects, but at the cost of degraded rendering and may result in side effects like misaligned text buffers. This setting is deprecated and has no effect as of QGIS 3.4.3 and the text format should be set using QgsRenderContext::setTextRenderFormat() instead.
vAlignmentvertical alignment (since QGIS 3.16)

Definition at line 80 of file qgstextrenderer.cpp.

◆ drawText() [2/2]

void QgsTextRenderer::drawText ( QPointF  point,
double  rotation,
QgsTextRenderer::HAlignment  alignment,
const QStringList &  textLines,
QgsRenderContext context,
const QgsTextFormat format,
bool  drawAsOutlines = true 
)
static

Draws text at a point origin using the specified settings.

Parameters
pointorigin of text
rotationtext rotation
alignmenthorizontal alignment
textLineslist of lines of text to draw
contextrender context
formattext format
drawAsOutlinesset to false to render text as text. This allows outputs to formats like SVG to maintain text as text objects, but at the cost of degraded rendering and may result in side effects like misaligned text buffers. This setting is deprecated and has no effect as of QGIS 3.4.3 and the text format should be set using QgsRenderContext::setTextRenderFormat() instead.

Definition at line 103 of file qgstextrenderer.cpp.

◆ fontMetrics()

QFontMetricsF QgsTextRenderer::fontMetrics ( QgsRenderContext context,
const QgsTextFormat format,
double  scaleFactor = 1.0 
)
static

Returns the font metrics for the given text format, when rendered in the specified render context.

The font metrics will take into account all scaling required by the render context.

The optional scaleFactor argument can specify a font size scaling factor. It is recommended to set this to QgsTextRenderer::FONT_WORKAROUND_SCALE and then manually scale painter devices or calculations based on the resultant font metrics. Failure to do so will result in poor quality text rendering at small font sizes.

Since
QGIS 3.2

Definition at line 266 of file qgstextrenderer.cpp.

◆ sizeToPixel()

int QgsTextRenderer::sizeToPixel ( double  size,
const QgsRenderContext c,
QgsUnitTypes::RenderUnit  unit,
const QgsMapUnitScale mapUnitScale = QgsMapUnitScale() 
)
static

Calculates pixel size (considering output size should be in pixel or map units, scale factors and optionally oversampling)

Parameters
sizesize to convert
crendercontext
unitsize units
mapUnitScalea mapUnitScale clamper
Returns
font pixel size

Definition at line 75 of file qgstextrenderer.cpp.

◆ textHeight() [1/2]

double QgsTextRenderer::textHeight ( const QgsRenderContext context,
const QgsTextFormat format,
const QStringList &  textLines,
DrawMode  mode = Point,
QFontMetricsF *  fontMetrics = nullptr 
)
static

Returns the height of a text based on a given format.

Parameters
contextrender context
formattext format
textLineslist of lines of text to calculate width from
modedraw mode
fontMetricsfont metrics

Definition at line 602 of file qgstextrenderer.cpp.

◆ textHeight() [2/2]

double QgsTextRenderer::textHeight ( const QgsRenderContext context,
const QgsTextFormat format,
QChar  character,
bool  includeEffects = false 
)
static

Returns the height of a character when rendered with the specified text format.

Parameters
contextrender context
formattext format
charactercharacter to determine height of. If character is invalid, then the maximum character height will be returned.
includeEffectsif true, then the size of formatting effects such as buffers and shadows will be considered in the returned height. If false, then the returned size considers the character only.
Since
QGIS 3.16

Definition at line 614 of file qgstextrenderer.cpp.

◆ textWidth()

double QgsTextRenderer::textWidth ( const QgsRenderContext context,
const QgsTextFormat format,
const QStringList &  textLines,
QFontMetricsF *  fontMetrics = nullptr 
)
static

Returns the width of a text based on a given format.

Parameters
contextrender context
formattext format
textLineslist of lines of text to calculate width from
fontMetricsfont metrics

Definition at line 527 of file qgstextrenderer.cpp.

Friends And Related Function Documentation

◆ QgsLabelPreview

friend class QgsLabelPreview
friend

Definition at line 385 of file qgstextrenderer.h.

◆ QgsVectorLayerLabelProvider

friend class QgsVectorLayerLabelProvider
friend

Definition at line 384 of file qgstextrenderer.h.

Member Data Documentation

◆ FONT_WORKAROUND_SCALE

constexpr double QgsTextRenderer::FONT_WORKAROUND_SCALE = 10
staticconstexpr

Scale factor for upscaling font sizes and downscaling destination painter devices.

Using this scale factor and manually adjusting any font metric based calculations results in more stable font metrics and sizes for small font sizes.

Since
QGIS 3.16

Definition at line 240 of file qgstextrenderer.h.


The documentation for this class was generated from the following files: