From ecae50f1d388e2eaabc9f6365b2f47a70c53a0cd Mon Sep 17 00:00:00 2001
From: Matthias Kuhn <matthias@opengis.ch>
Date: Thu, 1 Mar 2018 08:04:18 -0500
Subject: [PATCH] Allow processing plugins to load their own parameters

---
 .../core/processing/qgsprocessingprovider.sip.in | 11 +++++++++++
 src/core/processing/qgsprocessingparameters.cpp  | 16 ++++++++++++++++
 src/core/processing/qgsprocessingprovider.cpp    |  7 +++++++
 src/core/processing/qgsprocessingprovider.h      | 11 +++++++++++
 4 files changed, 45 insertions(+)

diff --git a/python/core/processing/qgsprocessingprovider.sip.in b/python/core/processing/qgsprocessingprovider.sip.in
index fb4b9ce5fdd..6f9a861ca44 100644
--- a/python/core/processing/qgsprocessingprovider.sip.in
+++ b/python/core/processing/qgsprocessingprovider.sip.in
@@ -204,6 +204,17 @@ Returns the matching algorithm by ``name``, or a None if no matching
 algorithm is contained by this provider.
 
 .. seealso:: :py:func:`algorithms`
+%End
+
+    virtual QgsProcessingParameterDefinition *createParameter( const QString &type, const QString &name ) /Factory/;
+%Docstring
+Returns a new parameter from of the given type and name.
+This should be reimplemented by providers that implement custom types.
+If the provider does not implement the parameter with ``type``, a None will be returned.
+
+By default, this returns a None.
+
+.. versionadded:: 3.2
 %End
 
   signals:
diff --git a/src/core/processing/qgsprocessingparameters.cpp b/src/core/processing/qgsprocessingparameters.cpp
index 5da5e71f9a5..9fef8916723 100644
--- a/src/core/processing/qgsprocessingparameters.cpp
+++ b/src/core/processing/qgsprocessingparameters.cpp
@@ -25,6 +25,7 @@
 #include "qgssettings.h"
 #include "qgsvectorfilewriter.h"
 #include "qgsreferencedgeometry.h"
+#include "qgsprocessingregistry.h"
 #include <functional>
 
 bool QgsProcessingParameters::isDynamic( const QVariantMap &parameters, const QString &name )
@@ -1079,6 +1080,21 @@ QgsProcessingParameterDefinition *QgsProcessingParameters::parameterFromVariantM
     def.reset( new QgsProcessingParameterFolderDestination( name ) );
   else if ( type == QgsProcessingParameterBand::typeName() )
     def.reset( new QgsProcessingParameterBand( name ) );
+  else
+  {
+    const QList<QgsProcessingProvider *> providers = QgsApplication::instance()->processingRegistry()->providers();
+
+    for ( QgsProcessingProvider *provider : providers )
+    {
+      QgsProcessingParameterDefinition *param = provider->createParameter( type, name );
+
+      if ( param )
+      {
+        def.reset( param );
+        break;
+      }
+    }
+  }
 
   if ( !def )
     return nullptr;
diff --git a/src/core/processing/qgsprocessingprovider.cpp b/src/core/processing/qgsprocessingprovider.cpp
index d50ab04cf6f..ac650a7b88e 100644
--- a/src/core/processing/qgsprocessingprovider.cpp
+++ b/src/core/processing/qgsprocessingprovider.cpp
@@ -74,6 +74,13 @@ const QgsProcessingAlgorithm *QgsProcessingProvider::algorithm( const QString &n
   return mAlgorithms.value( name );
 }
 
+QgsProcessingParameterDefinition *QgsProcessingProvider::createParameter( const QString &type, const QString &name )
+{
+  Q_UNUSED( type )
+  Q_UNUSED( name )
+  return nullptr;
+}
+
 bool QgsProcessingProvider::addAlgorithm( QgsProcessingAlgorithm *algorithm )
 {
   if ( !algorithm )
diff --git a/src/core/processing/qgsprocessingprovider.h b/src/core/processing/qgsprocessingprovider.h
index d66f299b8a6..e5ff6375a6d 100644
--- a/src/core/processing/qgsprocessingprovider.h
+++ b/src/core/processing/qgsprocessingprovider.h
@@ -203,6 +203,17 @@ class CORE_EXPORT QgsProcessingProvider : public QObject
      */
     const QgsProcessingAlgorithm *algorithm( const QString &name ) const;
 
+    /**
+     * Returns a new parameter from of the given type and name.
+     * This should be reimplemented by providers that implement custom types.
+     * If the provider does not implement the parameter with \a type, a nullptr will be returned.
+     *
+     * By default, this returns a nullptr.
+     *
+     * \since QGIS 3.2
+     */
+    virtual QgsProcessingParameterDefinition *createParameter( const QString &type, const QString &name ) SIP_FACTORY;
+
   signals:
 
     /**