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82 lines
3.6 KiB
Markdown
82 lines
3.6 KiB
Markdown
# Example (JKQTPlotter): Plotting Arrows {#JKQTPlotterGeometricArrows}
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This project shows the capabilities of JKQTPlotter to also draw arrows as geometric elements, using JKQTPGeoArrow. The arrow head/tail are defined by the enum values in JKQTPLineDecoratorStyle.
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The source code of the main application can be found in [`geo_arrows.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/geo_arrows/geo_arrows.cpp). First a plot is generated. Then several types of arrows are plotted onto the JKQtPlotter.
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## Different types of arrows
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A first table shows all available arrow tips in different sizes.
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```.cpp
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for (size_t i=0; i<static_cast<size_t>(JKQTPLineDecoratorCount); i++) {
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auto const decor=static_cast<JKQTPLineDecoratorStyle>(i);
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plot.addGraph(a=new JKQTPGeoArrow(&plot, 0.1, arr_y, 0.3, arr_y+0.05, decor, JKQTPNoDecorator));
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a->setStyle(QColor("red"), 0.2);
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plot.addGraph(a=new JKQTPGeoArrow(&plot, 0.4, arr_y, 0.6, arr_y+0.05, decor, JKQTPNoDecorator));
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a->setStyle(QColor("red"), 0.5);
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plot.addGraph(a=new JKQTPGeoArrow(&plot, 0.7, arr_y, 0.9, arr_y+0.05, decor, JKQTPNoDecorator));
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a->setStyle(QColor("red"), 1);
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plot.addGraph(a=new JKQTPGeoArrow(&plot, 1.0, arr_y, 1.3, arr_y+0.05, decor, JKQTPNoDecorator));
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a->setStyle(QColor("red"), 2);
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plot.addGraph(a=new JKQTPGeoArrow(&plot, 1.4, arr_y, 1.7, arr_y+0.05, decor, JKQTPNoDecorator));
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a->setStyle(QColor("red"), 3);
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plot.addGraph(new JKQTPGeoText(&plot, a->getX2()+0.05, a->getY2(), "\\verb{"+JKQTPLineDecoratorStyle2String(decor)+"}", 12, a->getLineColor()));
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arr_y+=arr_deltay;
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}
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```
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Here is the resulting table:
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Note how the head-size scales with the line-width, but not linearly, but rather sub-linearly, so the tips do not grow too strongly.
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Also note that all arrows end at the designated line-end (here indicated by dashed grey lines), even circles and rectangle:
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## Classes with support for arrows
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You can use JKQTPGeoArrow and JKQTPGeoLine to draw arrows (JKQTPGeoArrow is just a convenience class that enables arrows by default, otherwise it is equal to JKQTPGeoLine).
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In addition, also other classes can show line-decorators:
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- JKQTPGeoLine
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- JKQTPGeoPolyLines
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- JKQTPGeoInfiniteLine
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.
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Here is an example of how to actiavate them for a JKQTPGeoPolyLines:
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```.cpp
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QVector<QPointF> points; points<<QPointF(3, 0.6)<<QPointF(4, 0.5)<<QPointF(3, 1.2)<<QPointF(4, 1.0);
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JKQTPGeoPolyLines* polyLine=new JKQTPGeoPolyLines(&plot, points);
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polyLine->setHeadDecoratorStyle(JKQTPFilledDoubleArrow);
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polyLine->setTailDecoratorStyle(JKQTPCircleDecorator);
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plot.addGraph(polyLine);
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```
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Here is the result:
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For the class JKQTPGeoInfiniteLine the start can be decorated with an arrow (only if two_sided==false!):
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```.cpp
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JKQTPGeoInfiniteLine* infLine=new JKQTPGeoInfiniteLine(&plot, 1.5, 0.2, 1, 0.25);
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infLine->setHeadDecoratorStyle(JKQTPFilledDoubleArrow);
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plot.addGraph(infLine);
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```
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Here is the result:
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## Screenshot
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The result of the complete example looks like this:
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