Add transform context to processing context

python/core/processing/qgsprocessingcontext.sip

@@ -70,6 +70,9 @@ Returns the project in which the algorithm is being executed.
 %Docstring
 Sets the ``project`` in which the algorithm will be executed.
 
+This also automatically sets the transformContext() to match
+the project's transform context.
+
 .. seealso:: :py:func:`project()`
 %End
 
@@ -82,6 +85,23 @@ Returns the expression context.
     void setExpressionContext( const QgsExpressionContext &context );
 %Docstring
 Sets the expression ``context``.
+%End
+
+    QgsCoordinateTransformContext transformContext() const;
+%Docstring
+Returns the coordinate transform context.
+
+.. seealso:: :py:func:`setTransformContext()`
+%End
+
+    void setTransformContext( const QgsCoordinateTransformContext &context );
+%Docstring
+Sets the coordinate transform ``context``.
+
+Note that setting a project for the context will automatically set the coordinate transform
+context.
+
+.. seealso:: :py:func:`transformContext()`
 %End
 
     QgsMapLayerStore *temporaryLayerStore();

src/core/processing/qgsprocessingcontext.h

@@ -102,9 +102,18 @@ class CORE_EXPORT QgsProcessingContext
 
     /**
      * Sets the \a project in which the algorithm will be executed.
+     *
+     * This also automatically sets the transformContext() to match
+     * the project's transform context.
+     *
      * \see project()
      */
-    void setProject( QgsProject *project ) { mProject = project; }
+    void setProject( QgsProject *project )
+    {
+      mProject = project;
+      if ( mProject )
+        mTransformContext = mProject->transformContext();
+    }
 
     /**
      * Returns the expression context.
@@ -121,6 +130,22 @@ class CORE_EXPORT QgsProcessingContext
      */
     void setExpressionContext( const QgsExpressionContext &context ) { mExpressionContext = context; }
 
+    /**
+     * Returns the coordinate transform context.
+     * \see setTransformContext()
+     */
+    QgsCoordinateTransformContext transformContext() const { return mTransformContext; }
+
+    /**
+     * Sets the coordinate transform \a context.
+     *
+     * Note that setting a project for the context will automatically set the coordinate transform
+     * context.
+     *
+     * \see transformContext()
+     */
+    void setTransformContext( const QgsCoordinateTransformContext &context ) { mTransformContext = context; }
+
     /**
      * Returns a reference to the layer store used for storing temporary layers during
      * algorithm execution.
@@ -375,6 +400,7 @@ class CORE_EXPORT QgsProcessingContext
 
     QgsProcessingContext::Flags mFlags = nullptr;
     QPointer< QgsProject > mProject;
+    QgsCoordinateTransformContext mTransformContext;
     //! Temporary project owned by the context, used for storing temporarily loaded map layers
     QgsMapLayerStore tempLayerStore;
     QgsExpressionContext mExpressionContext;