QwtSymbol¶

class qwt.symbol.QwtSymbol(*args)[source]¶

A class for drawing symbols

Symbol styles:

QwtSymbol.NoSymbol: No Style. The symbol cannot be drawn.

QwtSymbol.Ellipse: Ellipse or circle

QwtSymbol.Rect: Rectangle

QwtSymbol.Diamond: Diamond

QwtSymbol.Triangle: Triangle pointing upwards

QwtSymbol.DTriangle: Triangle pointing downwards

QwtSymbol.UTriangle: Triangle pointing upwards

QwtSymbol.LTriangle: Triangle pointing left

QwtSymbol.RTriangle: Triangle pointing right

QwtSymbol.Cross: Cross (+)

QwtSymbol.XCross: Diagonal cross (X)

QwtSymbol.HLine: Horizontal line

QwtSymbol.VLine: Vertical line

QwtSymbol.Star1: X combined with +

QwtSymbol.Star2: Six-pointed star

QwtSymbol.Hexagon: Hexagon
QwtSymbol.Path: The symbol is represented by a painter path, where the origin (0, 0) of the path coordinate system is mapped to the position of the symbol

..seealso:
:py:meth:`setPath()`, :py:meth:`path()`
QwtSymbol.Pixmap: The symbol is represented by a pixmap. The pixmap is centered or aligned to its pin point.

..seealso:
:py:meth:`setPinPoint()`
QwtSymbol.Graphic: The symbol is represented by a graphic. The graphic is centered or aligned to its pin point.

..seealso:
:py:meth:`setPinPoint()`
QwtSymbol.SvgDocument: The symbol is represented by a SVG graphic. The graphic is centered or aligned to its pin point.

..seealso:
:py:meth:`setPinPoint()`
QwtSymbol.UserStyle: Styles >= QwtSymbol.UserStyle are reserved for derived classes of QwtSymbol that overload drawSymbols() with additional application specific symbol types.

Cache policies:

Depending on the render engine and the complexity of the symbol shape it might be faster to render the symbol to a pixmap and to paint this pixmap.

F.e. the raster paint engine is a pure software renderer where in cache mode a draw operation usually ends in raster operation with the the backing store, that are usually faster, than the algorithms for rendering polygons. But the opposite can be expected for graphic pipelines that can make use of hardware acceleration.

The default setting is AutoCache

..seealso:
:py:meth:`setCachePolicy()`, :py:meth:`cachePolicy()`
Note

The policy has no effect, when the symbol is painted to a vector graphics format (PDF, SVG).

Warning

Since Qt 4.8 raster is the default backend on X11

Valid cache policies:

QwtSymbol.NoCache: Don’t use a pixmap cache

QwtSymbol.Cache: Always use a pixmap cache

QwtSymbol.AutoCache: Use a cache when the symbol is rendered with the software renderer (QPaintEngine.Raster)

class QwtSymbol([style=QwtSymbol.NoSymbol])¶

The symbol is constructed with gray interior, black outline with zero width, no size and style ‘NoSymbol’.

Parameters:: style (int) – Symbol Style

class QwtSymbol(style, brush, pen, size)

Parameters:

style (int) – Symbol Style
brush (QBrush) – Brush to fill the interior
pen (QPen) – Outline pen
size (QSize) – Size

class QwtSymbol(path, brush, pen)

Parameters:

path (QPainterPath) – Painter path
brush (QBrush) – Brush to fill the interior
pen (QPen) – Outline pen

Style¶: alias of int

classmethod make(style=None, brush=None, pen=None, size=None, path=None, pixmap=None, graphic=None, svgdocument=None, pinpoint=None)[source]¶

Create and setup a new QwtSymbol object (convenience function).

Parameters:

style (int or None) – Symbol Style
brush (QBrush or None) – Brush to fill the interior
pen (QPen or None) – Outline pen
size (QSize or None) – Size
path (QPainterPath or None) – Painter path
path – Painter path
pixmap (QPixmap or None) – Pixmap as symbol
graphic (qwt.graphic.QwtGraphic or None) – Graphic
svgdocument – SVG icon as symbol

setCachePolicy(policy)[source]¶

Change the cache policy

The default policy is AutoCache

Parameters:: policy (int) – Cache policy

See also

cachePolicy()

cachePolicy()[source]¶

Returns:: Cache policy

See also

setCachePolicy()

setPath(path)[source]¶

Set a painter path as symbol

The symbol is represented by a painter path, where the origin (0, 0) of the path coordinate system is mapped to the position of the symbol.

When the symbol has valid size the painter path gets scaled to fit into the size. Otherwise the symbol size depends on the bounding rectangle of the path.

The following code defines a symbol drawing an arrow:

from qtpy.QtGui import QApplication, QPen, QPainterPath, QTransform
from qtpy.QtCore import Qt, QPointF
from qwt import QwtPlot, QwtPlotCurve, QwtSymbol
import numpy as np

app = QApplication([])

# --- Construct custom symbol ---

path = QPainterPath()
path.moveTo(0, 8)
path.lineTo(0, 5)
path.lineTo(-3, 5)
path.lineTo(0, 0)
path.lineTo(3, 5)
path.lineTo(0, 5)

transform = QTransform()
transform.rotate(-30.0)
path = transform.map(path)

pen = QPen(Qt.black, 2 );
pen.setJoinStyle(Qt.MiterJoin)

symbol = QwtSymbol()
symbol.setPen(pen)
symbol.setBrush(Qt.red)
symbol.setPath(path)
symbol.setPinPoint(QPointF(0., 0.))
symbol.setSize(10, 14)

# --- Test it within a simple plot ---

curve = QwtPlotCurve()
curve_pen = QPen(Qt.blue)
curve_pen.setStyle(Qt.DotLine)
curve.setPen(curve_pen)
curve.setSymbol(symbol)
x = np.linspace(0, 10, 10)
curve.setData(x, np.sin(x))

plot = QwtPlot()
curve.attach(plot)
plot.resize(600, 300)
plot.replot()
plot.show()

app.exec_()

Parameters:: path (QPainterPath) – Painter path

See also

path(), setSize()

path()[source]¶

Returns:: Painter path for displaying the symbol

See also

setPath()

setPixmap(pixmap)[source]¶

Set a pixmap as symbol

Parameters:: pixmap (QPixmap) – Pixmap

See also

pixmap(), setGraphic()

Note

The style() is set to QwtSymbol.Pixmap

Note

brush() and pen() have no effect

pixmap()[source]¶

Returns:: Assigned pixmap

See also

setPixmap()

setGraphic(graphic)[source]¶

Set a graphic as symbol

Parameters:: graphic (qwt.graphic.QwtGraphic) – Graphic

See also

graphic(), setPixmap()

Note

The style() is set to QwtSymbol.Graphic

Note

brush() and pen() have no effect

graphic()[source]¶

Returns:: Assigned graphic

See also

setGraphic()

setSvgDocument(svgDocument)[source]¶

Set a SVG icon as symbol

Parameters:: svgDocument – SVG icon

See also

setGraphic(), setPixmap()

Note

The style() is set to QwtSymbol.SvgDocument

Note

brush() and pen() have no effect

setSize(*args)[source]¶

Specify the symbol’s size

setSize(width[, height=-1])[source]

Parameters:

width (int) – Width
height (int) – Height

setSize(size)[source]

Parameters:: size (QSize) – Size

See also

size()

size()[source]¶

Returns:: Size

See also

setSize()

setBrush(brush)[source]¶

Assign a brush

The brush is used to draw the interior of the symbol.

Parameters:: brush (QBrush) – Brush

See also

brush()

brush()[source]¶

Returns:: Brush

See also

setBrush()

setPen(*args)[source]¶

Build and/or assign a pen, depending on the arguments.

setPen(color, width, style)[source]

Build and assign a pen

In Qt5 the default pen width is 1.0 ( 0.0 in Qt4 ) what makes it non cosmetic (see QPen.isCosmetic()). This method signature has been introduced to hide this incompatibility.

Parameters:

color (QColor) – Pen color
width (float) – Pen width
style (Qt.PenStyle) – Pen style

setPen(pen)[source]

Assign a pen

Parameters:: pen (QPen) – New pen

See also

pen(), brush()

pen()[source]¶

Returns:: Pen

See also

setPen(), brush()

setColor(color)[source]¶

Set the color of the symbol

Change the color of the brush for symbol types with a filled area. For all other symbol types the color will be assigned to the pen.

Parameters:: color (QColor) – Color

setPinPoint(pos, enable=True)[source]¶

Set and enable a pin point

The position of a complex symbol is not always aligned to its center ( f.e an arrow, where the peak points to a position ). The pin point defines the position inside of a Pixmap, Graphic, SvgDocument or PainterPath symbol where the represented point has to be aligned to.

Parameters:: pos (QPointF) – Position
Enable bool enable:: En/Disable the pin point alignment

See also

pinPoint(), setPinPointEnabled()

pinPoint()[source]¶

Returns:: Pin point

See also

setPinPoint(), setPinPointEnabled()

setPinPointEnabled(on)[source]¶

En/Disable the pin point alignment

Parameters:: on (bool) – Enabled, when on is true

See also

setPinPoint(), isPinPointEnabled()

isPinPointEnabled()[source]¶

Returns:: True, when the pin point translation is enabled

See also

setPinPoint(), setPinPointEnabled()

drawSymbols(painter, points)[source]¶

Render an array of symbols

Painting several symbols is more effective than drawing symbols one by one, as a couple of layout calculations and setting of pen/brush can be done once for the complete array.

Parameters:

painter (QPainter) – Painter
points (QPolygonF) – Positions of the symbols in screen coordinates

drawSymbol(painter, point_or_rect)[source]¶

Draw the symbol into a rectangle

The symbol is painted centered and scaled into the target rectangle. It is always painted uncached and the pin point is ignored.

This method is primarily intended for drawing a symbol to the legend.

Parameters:

painter (QPainter) – Painter
point_or_rect (QPointF or QPoint or QRectF) – Position or target rectangle of the symbol in screen coordinates

renderSymbols(painter, points)[source]¶

Render the symbol to series of points

Parameters:

painter (QPainter) – Painter
point_or_rect – Positions of the symbols

boundingRect()[source]¶

Calculate the bounding rectangle for a symbol at position (0,0).

Returns:: Bounding rectangle

invalidateCache()[source]¶

Invalidate the cached symbol pixmap

The symbol invalidates its cache, whenever an attribute is changed that has an effect ob how to display a symbol. In case of derived classes with individual styles (>= QwtSymbol.UserStyle) it might be necessary to call invalidateCache() for attributes that are relevant for this style.

See also

setCachePolicy(), drawSymbols()

setStyle(style)[source]¶

Specify the symbol style