QGIS API Documentation 3.43.0-Master (6c62b930b02)
qgsgrouplayerrenderer.cpp
Go to the documentation of this file.
1/***************************************************************************
2 qgsgrouplayerrenderer.cpp
3 ----------------
4 Date : September 2021
5 Copyright : (C) 2021 by Nyall Dawson
6 Email : nyall dot dawson at gmail dot com
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
19#include "qgsgrouplayer.h"
20#include "qgsfeedback.h"
21#include "qgspainteffect.h"
22#include "qgsrendercontext.h"
23#include "qgslogger.h"
24#include <optional>
25
27 : QgsMapLayerRenderer( layer->id(), &context )
28 , mFeedback( std::make_unique< QgsFeedback >() )
29 , mLayerOpacity( layer->opacity() )
30{
31 const QList< QgsMapLayer * > layers = layer->childLayers();
32 const QgsCoordinateReferenceSystem destinationCrs = context.coordinateTransform().destinationCrs();
33 for ( QgsMapLayer *childLayer : layers )
34 {
35 // we have to temporarily set the context's crs and extent to the correct one for the child layer, BEFORE creating the
36 // child layer's renderer
37 QgsCoordinateTransform layerToDestTransform( childLayer->crs(), destinationCrs, context.transformContext() );
38 layerToDestTransform.setBallparkTransformsAreAppropriate( true );
39 context.setCoordinateTransform( layerToDestTransform );
40 try
41 {
42 const QgsRectangle extentInChildLayerCrs = layerToDestTransform.transformBoundingBox( context.mapExtent(), Qgis::TransformDirection::Reverse );
43 context.setExtent( extentInChildLayerCrs );
44 }
45 catch ( QgsCsException & )
46 {
47 QgsDebugError( QStringLiteral( "Error transforming extent of %1 to destination CRS" ).arg( childLayer->id() ) );
48 continue;
49 }
50
51 mChildRenderers.emplace_back( childLayer->createMapRenderer( context ) );
52 mRendererCompositionModes.emplace_back( childLayer->blendMode() );
53 mRendererOpacity.emplace_back( childLayer->type() != Qgis::LayerType::Raster ? childLayer->opacity() : 1.0 );
54 mTransforms.emplace_back( layerToDestTransform );
55 }
56
57 mPaintEffect.reset( layer->paintEffect() && layer->paintEffect()->enabled() ? layer->paintEffect()->clone() : nullptr );
58
59 mForceRasterRender = layer->blendMode() != QPainter::CompositionMode_SourceOver;
60}
61
63
65{
66 return mFeedback.get();
67}
68
70{
71 QgsRenderContext &context = *renderContext();
72
73 context.painter()->save();
74 if ( mPaintEffect )
75 {
76 mPaintEffect->begin( context );
77 }
78
79 const QgsCoordinateReferenceSystem destinationCrs = context.coordinateTransform().destinationCrs();
80 bool canceled = false;
81 int i = 0;
82 for ( const std::unique_ptr< QgsMapLayerRenderer > &renderer : std::as_const( mChildRenderers ) )
83 {
84 if ( mFeedback->isCanceled() )
85 {
86 canceled = true;
87 break;
88 }
89
90 context.setCoordinateTransform( mTransforms[i] );
91
92 // don't need to catch exceptions here -- it would have already been caught in the QgsGroupLayerRenderer constructor!
93 const QgsRectangle extentInChildLayerCrs = mTransforms[i].transformBoundingBox( context.mapExtent(), Qgis::TransformDirection::Reverse );
94 context.setExtent( extentInChildLayerCrs );
95
96 QImage image;
98 {
99 context.painter()->setCompositionMode( mRendererCompositionModes[i] );
100 }
101
102 QPainter *prevPainter = context.painter();
103 std::unique_ptr< QPainter > imagePainter;
104 if ( renderer->forceRasterRender() )
105 {
106 image = QImage( context.deviceOutputSize(), context.imageFormat() );
107 image.setDevicePixelRatio( static_cast<qreal>( context.devicePixelRatio() ) );
108 image.fill( 0 );
109 imagePainter = std::make_unique< QPainter >( &image );
110
111 context.setPainterFlagsUsingContext( imagePainter.get() );
112 context.setPainter( imagePainter.get() );
113 }
114 renderer->render();
115
116 if ( imagePainter )
117 {
118 imagePainter->end();
119 context.setPainter( prevPainter );
120
121 context.painter()->setOpacity( mRendererOpacity[i] );
122 context.painter()->drawImage( 0, 0, image );
123 context.painter()->setOpacity( 1.0 );
124 }
125 context.painter()->setCompositionMode( QPainter::CompositionMode_SourceOver );
126 i++;
127 }
128
129 if ( mPaintEffect )
130 {
131 mPaintEffect->end( context );
132 }
133
134 context.painter()->restore();
135
136 return !canceled;
137}
138
140{
141 switch ( renderContext()->rasterizedRenderingPolicy() )
142 {
145 break;
146
148 return false;
149 }
150
151 if ( mForceRasterRender || !qgsDoubleNear( mLayerOpacity, 1.0 ) )
152 return true;
153
154 for ( QPainter::CompositionMode mode : mRendererCompositionModes )
155 {
156 if ( mode != QPainter::CompositionMode_SourceOver )
157 return true;
158 }
159
160 return false;
161}
@ Default
Allow raster-based rendering in situations where it is required for correct rendering or where it wil...
@ PreferVector
Prefer vector-based rendering, when the result will still be visually near-identical to a raster-base...
@ ForceVector
Always force vector-based rendering, even when the result will be visually different to a raster-base...
@ Raster
Raster layer.
@ Reverse
Reverse/inverse transform (from destination to source)
Represents a coordinate reference system (CRS).
Handles coordinate transforms between two coordinate systems.
void setBallparkTransformsAreAppropriate(bool appropriate)
Sets whether approximate "ballpark" results are appropriate for this coordinate transform.
QgsRectangle transformBoundingBox(const QgsRectangle &rectangle, Qgis::TransformDirection direction=Qgis::TransformDirection::Forward, bool handle180Crossover=false) const
Transforms a rectangle from the source CRS to the destination CRS.
QgsCoordinateReferenceSystem destinationCrs() const
Returns the destination coordinate reference system, which the transform will transform coordinates t...
Custom exception class for Coordinate Reference System related exceptions.
Base class for feedback objects to be used for cancellation of something running in a worker thread.
Definition qgsfeedback.h:44
~QgsGroupLayerRenderer() override
QgsGroupLayerRenderer(QgsGroupLayer *layer, QgsRenderContext &context)
Constructor for a QgsGroupLayerRenderer, for the specified layer.
bool forceRasterRender() const override
Returns true if the renderer must be rendered to a raster paint device (e.g.
QgsFeedback * feedback() const override
Access to feedback object of the layer renderer (may be nullptr)
bool render() override
Do the rendering (based on data stored in the class).
A map layer which consists of a set of child layers, where all component layers are rendered as a sin...
QgsPaintEffect * paintEffect() const
Returns the current paint effect for the group layer.
QList< QgsMapLayer * > childLayers() const
Returns the child layers contained by the group.
Base class for utility classes that encapsulate information necessary for rendering of map layers.
QgsRenderContext * renderContext()
Returns the render context associated with the renderer.
Base class for all map layer types.
Definition qgsmaplayer.h:77
QPainter::CompositionMode blendMode() const
Returns the current blending mode for a layer.
bool enabled() const
Returns whether the effect is enabled.
virtual QgsPaintEffect * clone() const =0
Duplicates an effect by creating a deep copy of the effect.
A rectangle specified with double values.
Contains information about the context of a rendering operation.
void setCoordinateTransform(const QgsCoordinateTransform &t)
Sets the current coordinate transform for the context.
QPainter * painter()
Returns the destination QPainter for the render operation.
void setPainterFlagsUsingContext(QPainter *painter=nullptr) const
Sets relevant flags on a destination painter, using the flags and settings currently defined for the ...
QgsCoordinateTransformContext transformContext() const
Returns the context's coordinate transform context, which stores various information regarding which ...
float devicePixelRatio() const
Returns the device pixel ratio.
QgsRectangle mapExtent() const
Returns the original extent of the map being rendered.
void setExtent(const QgsRectangle &extent)
When rendering a map layer, calling this method sets the "clipping" extent for the layer (in the laye...
Qgis::RasterizedRenderingPolicy rasterizedRenderingPolicy() const
Returns the policy controlling when rasterisation of content during renders is permitted.
void setPainter(QPainter *p)
Sets the destination QPainter for the render operation.
QSize deviceOutputSize() const
Returns the device output size of the render.
QgsCoordinateTransform coordinateTransform() const
Returns the current coordinate transform for the context.
QImage::Format imageFormat() const
Returns the QImage format which should be used for QImages created during rendering.
bool qgsDoubleNear(double a, double b, double epsilon=4 *std::numeric_limits< double >::epsilon())
Compare two doubles (but allow some difference)
Definition qgis.h:6367
#define QgsDebugError(str)
Definition qgslogger.h:40