QGIS API Documentation  3.23.0-Master (eb871beae0)
qgstolerance.cpp
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1 /***************************************************************************
2  qgstolerance.cpp - wrapper for tolerance handling
3  ----------------------
4  begin : March 2009
5  copyright : (C) 2009 by Richard Kostecky
6  email : csf.kostej at gmail dot com
7  ***************************************************************************
8  * *
9  * This program is free software; you can redistribute it and/or modify *
10  * it under the terms of the GNU General Public License as published by *
11  * the Free Software Foundation; either version 2 of the License, or *
12  * (at your option) any later version. *
13  * *
14  ***************************************************************************/
15 
16 #include "qgstolerance.h"
17 #include "qgsmapsettings.h"
18 #include "qgssettingsregistrycore.h"
19 #include "qgspointxy.h"
20 
21 #include <QPoint>
22 #include <cmath>
23 
24 
25 // return ratio [mu/lu] between map units and layer units
26 // this is of course only an approximation
27 double _ratioMU2LU( const QgsMapSettings &mapSettings, QgsMapLayer *layer )
28 {
29  const double distMU = mapSettings.mapUnitsPerPixel();
30  const QgsPointXY ptMapCenterMU = mapSettings.visibleExtent().center();
31  const QgsPointXY ptMapCenterRightMU( ptMapCenterMU.x() + distMU, ptMapCenterMU.y() );
32  const QgsPointXY ptMapCenterLU = mapSettings.mapToLayerCoordinates( layer, ptMapCenterMU );
33  const QgsPointXY ptMapCenterRightLU = mapSettings.mapToLayerCoordinates( layer, ptMapCenterRightMU );
34  const double distLU = std::sqrt( ptMapCenterLU.sqrDist( ptMapCenterRightLU ) );
35  const double ratio = distMU / distLU;
36  return ratio;
37 }
38 
39 double QgsTolerance::toleranceInProjectUnits( double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, QgsTolerance::UnitType units )
40 {
41  // converts to map units
42  if ( units == ProjectUnits )
43  return tolerance;
44  else if ( units == Pixels )
45  return tolerance * mapSettings.mapUnitsPerPixel();
46  else // units == LayerUnits
47  {
48  // [mu] = [lu] * [mu/lu]
49  return tolerance * _ratioMU2LU( mapSettings, layer );
50  }
51 }
52 
53 
54 double QgsTolerance::toleranceInMapUnits( double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, QgsTolerance::UnitType units )
55 {
56  // converts to layer units
57  if ( units == LayerUnits )
58  {
59  return tolerance;
60  }
61  else if ( units == Pixels )
62  {
63  const double layerUnitsPerPixel = computeMapUnitPerPixel( layer, mapSettings );
64  return tolerance * layerUnitsPerPixel;
65  }
66  else // ProjectUnits
67  {
68  // [lu] = [mu] / [mu/lu]
69  return tolerance / _ratioMU2LU( mapSettings, layer );
70  }
71 }
72 
74 {
75  const double tolerance = QgsSettingsRegistryCore::settingsDigitizingSearchRadiusVertexEdit.value();
76  UnitType units = QgsSettingsRegistryCore::settingsDigitizingSearchRadiusVertexEditUnit.value();
77  if ( units == LayerUnits )
78  units = ProjectUnits;
79  return toleranceInProjectUnits( tolerance, nullptr, mapSettings, units );
80 }
81 
82 double QgsTolerance::vertexSearchRadius( QgsMapLayer *layer, const QgsMapSettings &mapSettings )
83 {
84  const double tolerance = QgsSettingsRegistryCore::settingsDigitizingSearchRadiusVertexEdit.value();
85  const UnitType units = QgsSettingsRegistryCore::settingsDigitizingSearchRadiusVertexEditUnit.value();
86  return toleranceInMapUnits( tolerance, layer, mapSettings, units );
87 }
88 
89 double QgsTolerance::defaultTolerance( QgsMapLayer *layer, const QgsMapSettings &mapSettings )
90 {
91  const double tolerance = QgsSettingsRegistryCore::settingsDigitizingDefaultSnappingTolerance.value();
92  const UnitType units = QgsSettingsRegistryCore::settingsDigitizingDefaultSnappingToleranceUnit.value();
93  return toleranceInMapUnits( tolerance, layer, mapSettings, units );
94 }
95 
96 
97 double QgsTolerance::computeMapUnitPerPixel( QgsMapLayer *layer, const QgsMapSettings &mapSettings )
98 {
99  // the layer is projected. Find out how many pixels are in one map unit - either horizontal and vertical direction
100  // this check might not work correctly in some cases
101  // (on a large area the pixels projected around "0,0" can have different properties from the actual point)
102  const QgsPointXY p1 = toLayerCoordinates( layer, mapSettings, QPoint( 0, 1 ) );
103  const QgsPointXY p2 = toLayerCoordinates( layer, mapSettings, QPoint( 0, 2 ) );
104  const QgsPointXY p3 = toLayerCoordinates( layer, mapSettings, QPoint( 1, 0 ) );
105  const QgsPointXY p4 = toLayerCoordinates( layer, mapSettings, QPoint( 2, 0 ) );
106  const double x = p1.sqrDist( p2 );
107  const double y = p3.sqrDist( p4 );
108  if ( x > y )
109  {
110  return std::sqrt( x );
111  }
112  else
113  {
114  return std::sqrt( y );
115  }
116 }
117 
118 
119 QgsPointXY QgsTolerance::toLayerCoordinates( QgsMapLayer *layer, const QgsMapSettings &mapSettings, QPoint point )
120 {
121  const QgsPointXY pt = mapSettings.mapToPixel().toMapCoordinates( point );
122  return mapSettings.mapToLayerCoordinates( layer, pt );
123 }
Base class for all map layer types.
Definition: qgsmaplayer.h:73
The QgsMapSettings class contains configuration for rendering of the map.
double mapUnitsPerPixel() const
Returns the distance in geographical coordinates that equals to one pixel in the map.
const QgsMapToPixel & mapToPixel() const
QgsRectangle visibleExtent() const
Returns the actual extent derived from requested extent that takes output image size into account.
QgsPointXY mapToLayerCoordinates(const QgsMapLayer *layer, QgsPointXY point) const
transform point coordinates from output CRS to layer's CRS
QgsPointXY toMapCoordinates(int x, int y) const
Transforms device coordinates to map (world) coordinates.
A class to represent a 2D point.
Definition: qgspointxy.h:59
double sqrDist(double x, double y) const SIP_HOLDGIL
Returns the squared distance between this point a specified x, y coordinate.
Definition: qgspointxy.h:190
double y
Definition: qgspointxy.h:63
Q_GADGET double x
Definition: qgspointxy.h:62
QgsPointXY center() const SIP_HOLDGIL
Returns the center point of the rectangle.
Definition: qgsrectangle.h:251
static double toleranceInMapUnits(double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, UnitType units=LayerUnits)
Static function to translate tolerance value into layer units.
static double vertexSearchRadius(const QgsMapSettings &mapSettings)
Static function to get vertex tolerance value.
static double defaultTolerance(QgsMapLayer *layer, const QgsMapSettings &mapSettings)
Static function to get default tolerance value for a layer.
static double toleranceInProjectUnits(double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, QgsTolerance::UnitType units)
Static function to translate tolerance value into map units.
UnitType
Type of unit of tolerance value from settings.
Definition: qgstolerance.h:42
@ ProjectUnits
Map (project) units. Added in 2.8.
Definition: qgstolerance.h:48
@ Pixels
Pixels unit of tolerance.
Definition: qgstolerance.h:46
@ LayerUnits
Layer unit value.
Definition: qgstolerance.h:44
double _ratioMU2LU(const QgsMapSettings &mapSettings, QgsMapLayer *layer)