QwtPlotCurve.PaintAttribute 枚举类型参考

成员变量

详细描述

Attributes to modify the drawing algorithm. The default setting enables ClipPolygons | FilterPoints

参见

setPaintAttribute(), testPaintAttribute()

在文件 QwtPlotCurve.x 第 110 行定义.

结构体成员变量说明

ClipPolygons

ClipPolygons = 0x01

Clip polygons before painting them. In situations, where points are far outside the visible area (f.e when zooming deep) this might be a substantial improvement for the painting performance

在文件 QwtPlotCurve.x 第 117 行定义.

FilterPoints

FilterPoints = 0x02

Tries to reduce the data that has to be painted, by sorting out duplicates, or paintings outside the visible area. Might have a notable impact on curves with many close points. Only a couple of very basic filtering algorithms are implemented.

在文件 QwtPlotCurve.x 第 125 行定义.

FilterPointsAggressive

FilterPointsAggressive = 0x10

More aggressive point filtering trying to filter out intermediate points, accepting minor visual differences.

Has only an effect, when drawing the curve to a paint device in integer coordinates ( f.e. all widgets on screen ) using the fact, that consecutive points are often mapped to the same x or y coordinate. Each chunk of samples mapped to the same coordinate can be reduced to 4 points ( first, min, max last ).

In the worst case the polygon to be rendered will be 4 times the width of the plot canvas.

The algorithm is very fast and effective for huge datasets, and can be used inside a replot cycle.

注解

Implemented for QwtPlotCurve::Lines only

As this algo replaces many small lines by a long one a nasty bug of the raster paint engine ( Qt 4.8, Qt 5.1 - 5.3 ) becomes more dominant. For these versions the bug can be worked around by enabling the QwtPainter::polylineSplitting() mode.

在文件 QwtPlotCurve.x 第 166 行定义.

ImageBuffer

ImageBuffer = 0x08

Render the points to a temporary image and paint the image. This is a very special optimization for Dots style, when having a huge amount of points. With a reasonable number of points QPainter::drawPoints() will be faster.

在文件 QwtPlotCurve.x 第 141 行定义.

MinimizeMemory

MinimizeMemory = 0x04

Minimize memory usage that is temporarily needed for the translated points, before they get painted. This might slow down the performance of painting

在文件 QwtPlotCurve.x 第 132 行定义.