QgsClipper class

A class to trim lines and polygons to within a rectangular region.

Contents

The functions in this class are likely to be called from within a render loop and hence need to as CPU efficient as possible. The main purpose of the functions in this class are to trim lines and polygons to lie within a rectangular region. This is necessary for drawing items to an X11 display which have a limit on the magnitude of the screen coordinates (+/- 32768, i.e. 16 bit integer).

Public types

enum Boundary { XMax, XMin, YMax, YMin }
A handy way to refer to the four boundaries.

Public static variables

static const double MAX_X
Maximum X-coordinate of the rectangular box used for clipping.
static const double MAX_Y
Maximum Y-coordinate of the rectangular box used for clipping.
static const double MIN_X
Minimum X-coordinate of the rectangular box used for clipping.
static const double MIN_Y
Minimum Y-coordinate of the rectangular box used for clipping.

Public static functions

static auto clippedLine(const QgsCurve& curve, const QgsRectangle& clipExtent) -> QPolygonF
Takes a linestring and clips it to clipExtent.
static void trimFeature(QVector<double>& x, QVector<double>& y, bool shapeOpen)
Trims the given feature to a rectangular box.

Function documentation

static QPolygonF QgsClipper::clippedLine(const QgsCurve& curve, const QgsRectangle& clipExtent)

Takes a linestring and clips it to clipExtent.

Parameters
curve the linestring
clipExtent clipping bounds
Returns clipped line coordinates

static void QgsClipper::trimFeature(QVector<double>& x, QVector<double>& y, bool shapeOpen)

Trims the given feature to a rectangular box.

Returns the trimmed feature in x and y. The shapeOpen parameter determines whether the function treats the points as a closed shape (polygon), or as an open shape (linestring).