Add a cancel button for algorithms which support cancelation

python/core/processing/qgsprocessingalgorithm.sip

@@ -28,6 +28,7 @@ class QgsProcessingAlgorithm
       FlagHideFromToolbox,
       FlagHideFromModeler,
       FlagSupportsBatch,
+      FlagCanCancel,
       FlagDeprecated,
     };
     typedef QFlags<QgsProcessingAlgorithm::Flag> Flags;
@@ -128,6 +129,7 @@ class QgsProcessingAlgorithm
     virtual Flags flags() const;
 %Docstring
  Returns the flags indicating how and when the algorithm operates and should be exposed to users.
+ Default flags are FlagSupportsBatch and FlagCanCancel.
  :rtype: Flags
 %End
 

python/plugins/processing/gui/AlgorithmDialog.py

@@ -36,7 +36,8 @@ from qgis.core import (QgsProject,
                        QgsProcessingParameterDefinition,
                        QgsProcessingOutputVectorLayer,
                        QgsProcessingFeatureSinkDefinition,
-                       QgsProcessingParameterFeatureSink)
+                       QgsProcessingParameterFeatureSink,
+                       QgsProcessingAlgorithm)
 from qgis.gui import QgsMessageBar
 from qgis.utils import iface
 
@@ -229,7 +230,9 @@ class AlgorithmDialog(AlgorithmDialogBase):
                 #command = self.alg.getAsCommand()
                 #if command:
                 #    ProcessingLog.addToLog(command)
+                self.buttonCancel.setEnabled(self.alg.flags() & QgsProcessingAlgorithm.FlagCanCancel)
                 result = executeAlgorithm(self.alg, parameters, context, self.feedback)
+                self.buttonCancel.setEnabled(False)
                 self.finish(result, context)
                 #TODO
                 #else:

python/plugins/processing/gui/AlgorithmDialogBase.py

@@ -84,6 +84,7 @@ class AlgorithmDialogBase(BASE, WIDGET):
 
         self.feedback = AlgorithmDialogFeedback(self)
         self.feedback.progressChanged.connect(self.setPercentage)
+        self.buttonCancel.clicked.connect(self.feedback.cancel)
 
         self.settings = QgsSettings()
         self.restoreGeometry(self.settings.value("/Processing/dialogBase", QByteArray()))
@@ -96,6 +97,8 @@ class AlgorithmDialogBase(BASE, WIDGET):
         self.btnRun = self.buttonBox.button(QDialogButtonBox.Ok)
         self.btnRun.setText(self.tr('Run'))
 
+        self.buttonCancel.setEnabled(False)
+
         self.btnClose = self.buttonBox.button(QDialogButtonBox.Close)
 
         self.setWindowTitle(self.alg.displayName())

python/plugins/processing/ui/DlgAlgorithmBase.ui

@@ -29,7 +29,16 @@
          <property name="spacing">
           <number>2</number>
          </property>
-         <property name="margin">
+         <property name="leftMargin">
+          <number>0</number>
+         </property>
+         <property name="topMargin">
+          <number>0</number>
+         </property>
+         <property name="rightMargin">
+          <number>0</number>
+         </property>
+         <property name="bottomMargin">
           <number>0</number>
          </property>
         </layout>
@@ -42,7 +51,16 @@
          <property name="spacing">
           <number>2</number>
          </property>
-         <property name="margin">
+         <property name="leftMargin">
+          <number>0</number>
+         </property>
+         <property name="topMargin">
+          <number>0</number>
+         </property>
+         <property name="rightMargin">
+          <number>0</number>
+         </property>
+         <property name="bottomMargin">
           <number>0</number>
          </property>
          <item>
@@ -62,7 +80,16 @@
          <property name="spacing">
           <number>0</number>
          </property>
-         <property name="margin">
+         <property name="leftMargin">
+          <number>0</number>
+         </property>
+         <property name="topMargin">
+          <number>0</number>
+         </property>
+         <property name="rightMargin">
+          <number>0</number>
+         </property>
+         <property name="bottomMargin">
           <number>0</number>
          </property>
          <item>
@@ -104,11 +131,25 @@
     </widget>
    </item>
    <item>
-    <widget class="QProgressBar" name="progressBar">
+    <layout class="QHBoxLayout" name="horizontalLayout_3">
-     <property name="value">
+     <property name="topMargin">
       <number>0</number>
      </property>
-    </widget>
+     <item>
+      <widget class="QProgressBar" name="progressBar">
+       <property name="value">
+        <number>0</number>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QPushButton" name="buttonCancel">
+       <property name="text">
+        <string>Cancel</string>
+       </property>
+      </widget>
+     </item>
+    </layout>
    </item>
    <item>
     <widget class="QDialogButtonBox" name="buttonBox">

src/core/processing/qgsprocessingalgorithm.cpp

@@ -64,7 +64,7 @@ QString QgsProcessingAlgorithm::svgIconPath() const
 
 QgsProcessingAlgorithm::Flags QgsProcessingAlgorithm::flags() const
 {
-  return FlagSupportsBatch;
+  return FlagSupportsBatch | FlagCanCancel;
 }
 
 bool QgsProcessingAlgorithm::canExecute( QString * ) const

src/core/processing/qgsprocessingalgorithm.h

@@ -48,6 +48,7 @@ class CORE_EXPORT QgsProcessingAlgorithm
       FlagHideFromToolbox = 1 << 1, //!< Algorithm should be hidden from the toolbox
       FlagHideFromModeler = 1 << 2, //!< Algorithm should be hidden from the modeler
       FlagSupportsBatch = 1 << 3,  //!< Algorithm supports batch mode
+      FlagCanCancel = 1 << 4, //!< Algorithm can be canceled
       FlagDeprecated = FlagHideFromToolbox | FlagHideFromModeler, //!< Algorithm is deprecated
     };
     Q_DECLARE_FLAGS( Flags, Flag )
@@ -140,6 +141,7 @@ class CORE_EXPORT QgsProcessingAlgorithm
 
     /**
      * Returns the flags indicating how and when the algorithm operates and should be exposed to users.
+     * Default flags are FlagSupportsBatch and FlagCanCancel.
      */
     virtual Flags flags() const;