Merge pull request #3959 from nyalldawson/processing_port_feedback

[processing] Port feedback object to c++

doc/api_break.dox

@@ -1831,6 +1831,11 @@ Processing        {#qgis_api_break_3_0_Processing}
 
 - Algorithm providers now subclass the c++ QgsProcessingProvider class, and must be adapted to the API for QgsProcessingProvider. Specifically,
 getName() should be replaced with id(), getDescription() with name(), and getIcon with icon().
+- Algorithm's processAlgorithm method now passes a QgsProcessingFeedback object instead of the loosely defined progress parameter. Algorithms will
+need to update their use of the progress argument to utilise the QgsProcessingFeedback API.
+- Similarly, Python processing scripts no longer have access to a progress variable for reporting their progress. Instead they have a feedback
+object of type QgsProcessingFeedback, and will need to adapt their use of progress reporting to the QgsProcessingFeedback API.
+- SilentProgress was removed. Use the base QgsProcessingFeedback class instead.
 
 
 QGIS 2.4        {#qgis_api_break_2_4}

python/core/core.sip

@@ -259,6 +259,7 @@
 %Include layertree/qgslayertreeregistrybridge.sip
 %Include layertree/qgslayertreeutils.sip
 
+%Include processing/qgsprocessingfeedback.sip
 %Include processing/qgsprocessingprovider.sip
 %Include processing/qgsprocessingregistry.sip
 

python/core/processing/qgsprocessingfeedback.sip

@@ -0,0 +1,80 @@
+/**
+ * \class QgsProcessingFeedback
+ * \ingroup core
+ * Base class for providing feedback from a processing algorithm.
+ *
+ * This base class implementation silently ignores all feedback reported by algorithms.
+ * Subclasses of QgsProcessingFeedback can be used to log this feedback or report
+ * it to users via the GUI.
+ * \note added in QGIS 3.0
+ */
+class QgsProcessingFeedback : public QgsFeedback
+{
+%TypeHeaderCode
+#include <qgsprocessingfeedback.h>
+%End
+
+  public:
+
+    /**
+     * Sets the algorithm's progress. The progress
+     * argument is limited to the range 0-100 and reflects the percentage
+     * progress through the task.
+     * @see setProgressText()
+     */
+    virtual void setProgress( double progress );
+
+    /**
+     * Sets a progress report text string. This can be used in conjunction with
+     * setProgress() to provide detailed progress reports, such as "Transformed
+     * 4 of 5 layers".
+     * @see setProgress()
+     */
+    virtual void setProgressText( const QString& text );
+
+    /**
+     * Reports that the algorithm encountered an error which prevented it
+     * from successfully executing.
+     */
+    virtual void reportError( const QString& error );
+
+    /**
+     * Pushes a general informational message from the algorithm. This can
+     * be used to report feedback which is neither a status report or an
+     * error, such as "Found 47 matching features".
+     * @see pushCommandInfo()
+     * @see pushDebugInfo()
+     * @see pushConsoleInfo()
+     */
+    virtual void pushInfo( const QString& info );
+
+    /**
+     * Pushes an informational message containing a command from the algorithm.
+     * This is usually used to report commands which are executed in an external
+     * application or as subprocesses.
+     * @see pushInfo()
+     * @see pushDebugInfo()
+     * @see pushConsoleInfo()
+     */
+    virtual void pushCommandInfo( const QString& info );
+
+    /**
+     * Pushes an informational message containing debugging helpers from
+     * the algorithm.
+     * @see pushInfo()
+     * @see pushCommandInfo()
+     * @see pushConsoleInfo()
+     */
+    virtual void pushDebugInfo( const QString& info );
+
+
+    /**
+     * Pushes a console feedback message from the algorithm. This is used to
+     * report the output from executing an external command or subprocess.
+     * @see pushInfo()
+     * @see pushDebugInfo()
+     * @see pushCommandInfo()
+     */
+    virtual void pushConsoleInfo( const QString& info );
+
+};

python/plugins/processing/algs/exampleprovider/ExampleAlgorithm.py

@@ -75,7 +75,7 @@ def defineCharacteristics(self):
         self.addOutput(OutputVector(self.OUTPUT_LAYER,
                                     self.tr('Output layer with selected features')))
 
-    def processAlgorithm(self, progress):
+    def processAlgorithm(self, feedback):
         """Here is where the processing itself takes place."""
 
         # The first thing to do is retrieve the values of the parameters

python/plugins/processing/algs/gdal/GdalAlgorithm.py

@@ -56,7 +56,7 @@ def getIcon(self):
     def getCustomParametersDialog(self):
         return GdalAlgorithmDialog(self)
 
-    def processAlgorithm(self, progress):
+    def processAlgorithm(self, feedback):
         commands = self.getConsoleCommands()
         layers = dataobjects.getVectorLayers()
         supported = dataobjects.getSupportedOutputVectorLayerExtensions()
@@ -73,7 +73,7 @@ def processAlgorithm(self, progress):
                         c = re.sub('["\']{}["\']'.format(fileName), "'"