From f3d473cb27b16b686aee6368d5fac9b32dd968a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Germ=C3=A1n=20Carrillo?= <gcarrillo@linuxmail.org>
Date: Wed, 10 Jun 2020 22:26:50 -0500
Subject: [PATCH] Getter/setter for linking a map canvas with its QgsProject;
 link app canvases to QgsProject::instance(); rationale: using the QgsProject
 singleton is discouraged

---
 python/gui/auto_generated/qgsmapcanvas.sip.in | 15 +++++++++++++++
 src/app/qgisapp.cpp                           |  4 ++++
 src/gui/qgsmapcanvas.cpp                      | 10 ++++++++++
 src/gui/qgsmapcanvas.h                        | 19 +++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/python/gui/auto_generated/qgsmapcanvas.sip.in b/python/gui/auto_generated/qgsmapcanvas.sip.in
index 9422f5e35bd..afcd7b723c1 100644
--- a/python/gui/auto_generated/qgsmapcanvas.sip.in
+++ b/python/gui/auto_generated/qgsmapcanvas.sip.in
@@ -337,6 +337,21 @@ You don't have to call it manually, QgsMapTool takes care of it.
     QgsMapTool *mapTool();
 %Docstring
 Returns the currently active tool
+%End
+
+    void setProject( QgsProject *project );
+%Docstring
+Sets the ``project`` linked to this canvas.
+
+.. versionadded:: 3.14
+%End
+
+    QgsProject *project();
+%Docstring
+Returns the project linked to this canvas.
+The returned value may be ``None``.
+
+.. versionadded:: 3.14
 %End
 
     void setCanvasColor( const QColor &_newVal );
diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
index e0f81a91a32..01807f62b2f 100644
--- a/src/app/qgisapp.cpp
+++ b/src/app/qgisapp.cpp
@@ -940,6 +940,9 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, bool skipVersionCh
   int myGreen = settings.value( QStringLiteral( "qgis/default_canvas_color_green" ), 255 ).toInt();
   int myBlue = settings.value( QStringLiteral( "qgis/default_canvas_color_blue" ), 255 ).toInt();
   mMapCanvas->setCanvasColor( QColor( myRed, myGreen, myBlue ) );
+
+  // set project linked to main canvas
+  mMapCanvas->setProject( QgsProject::instance() );
   endProfile();
 
   // what type of project to auto-open
@@ -4481,6 +4484,7 @@ QgsMapCanvasDockWidget *QgisApp::createNewMapCanvasDock( const QString &name )
   QgsMapCanvas *mapCanvas = mapCanvasWidget->mapCanvas();
   mapCanvas->freeze( true );
   mapCanvas->setObjectName( name );
+  mapCanvas->setProject( QgsProject::instance() );
   connect( mapCanvas, &QgsMapCanvas::messageEmitted, this, &QgisApp::displayMessage );
   connect( mLayerTreeCanvasBridge, &QgsLayerTreeMapCanvasBridge::canvasLayersChanged, mapCanvas, &QgsMapCanvas::setLayers );
 
diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
index 3db39f2812f..f036886584a 100644
--- a/src/gui/qgsmapcanvas.cpp
+++ b/src/gui/qgsmapcanvas.cpp
@@ -2030,6 +2030,11 @@ void QgsMapCanvas::unsetMapTool( QgsMapTool *tool )
   }
 }
 
+void QgsMapCanvas::setProject( QgsProject *project )
+{
+  mProject = project;
+}
+
 void QgsMapCanvas::setCanvasColor( const QColor &color )
 {
   if ( canvasColor() == color )
@@ -2247,6 +2252,11 @@ QgsMapTool *QgsMapCanvas::mapTool()
   return mMapTool;
 }
 
+QgsProject *QgsMapCanvas::project()
+{
+  return mProject;
+}
+
 void QgsMapCanvas::panActionEnd( QPoint releasePoint )
 {
   // move map image and other items to standard position
diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
index 7997073e601..a870bf0e19c 100644
--- a/src/gui/qgsmapcanvas.h
+++ b/src/gui/qgsmapcanvas.h
@@ -28,6 +28,7 @@
 #include "qgscustomdrophandler.h"
 #include "qgstemporalrangeobject.h"
 #include "qgsmapcanvasinteractionblocker.h"
+#include "qgsproject.h"
 
 #include <QDomDocument>
 #include <QGraphicsView>
@@ -355,6 +356,21 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
     //! Returns the currently active tool
     QgsMapTool *mapTool();
 
+    /**
+     * Sets the \a project linked to this canvas.
+     *
+     * \since QGIS 3.14
+     */
+    void setProject( QgsProject *project );
+
+    /**
+     * Returns the project linked to this canvas.
+     * The returned value may be NULLPTR.
+     *
+     * \since QGIS 3.14
+     */
+    QgsProject *project();
+
     //! Write property of QColor bgColor.
     void setCanvasColor( const QColor &_newVal );
     //! Read property of QColor bgColor.
@@ -1112,6 +1128,9 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
     //! previous tool if current is for zooming/panning
     QgsMapTool *mLastNonZoomMapTool = nullptr;
 
+    //! Pointer to project linked to this canvas
+    QgsProject *mProject = nullptr;
+
     //! Context menu
     QMenu *mMenu = nullptr;