From 5f7aa45aabf4acd2240563a5ac1ef23215bc662a Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Thu, 21 Dec 2017 10:44:00 +1000
Subject: [PATCH] [needs-docs][processing] Add methods to show algorithm dialog

Adds processing.createAlgorithmDialog and
processing.execAlgorithmDialog. These methods can be used
to create and execute algorithm dialogs for a specified algorithm,
optionally pre-populated with a given set of (non-default) parameter
values.
---
 python/plugins/processing/tools/general.py | 53 ++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/python/plugins/processing/tools/general.py b/python/plugins/processing/tools/general.py
index 7ff4388b9b44..366ccadd230b 100644
--- a/python/plugins/processing/tools/general.py
+++ b/python/plugins/processing/tools/general.py
@@ -38,6 +38,8 @@
                        QgsProject)
 from processing.core.Processing import Processing
 from processing.gui.Postprocessing import handleAlgorithmResults
+from processing.gui.AlgorithmDialog import AlgorithmDialog
+from qgis.utils import iface
 
 
 def algorithmHelp(id):
@@ -105,3 +107,54 @@ def runAndLoadResults(algOrName, parameters, feedback=None, context=None):
                 parameters[param.name()] = p
 
     return Processing.runAlgorithm(alg, parameters=parameters, onFinish=handleAlgorithmResults, feedback=feedback, context=context)
+
+
+def createAlgorithmDialog(algOrName, parameters={}):
+    """Creates and returns an algorithm dialog for the specified algorithm, prepopulated
+    with a given set of parameters. It is the caller's responsibility to execute
+    and delete this dialog.
+    """
+    if isinstance(algOrName, QgsProcessingAlgorithm):
+        alg = algOrName
+    else:
+        alg = QgsApplication.processingRegistry().createAlgorithmById(algOrName)
+
+    if alg is None:
+        return False
+
+    dlg = alg.createCustomParametersWidget(iface.mainWindow())
+
+    if not dlg:
+        dlg = AlgorithmDialog(alg)
+
+    dlg.setParameters(parameters)
+
+    return dlg
+
+
+def execAlgorithmDialog(algOrName, parameters={}):
+    """Executes an algorithm dialog for the specified algorithm, prepopulated
+    with a given set of parameters.
+
+    Returns the algorithm's results.
+    """
+    dlg = createAlgorithmDialog(algOrName, parameters)
+    if dlg is None:
+        return {}
+
+    canvas = iface.mapCanvas()
+    prevMapTool = canvas.mapTool()
+    dlg.show()
+    dlg.exec_()
+    if canvas.mapTool() != prevMapTool:
+        try:
+            canvas.mapTool().reset()
+        except:
+            pass
+        canvas.setMapTool(prevMapTool)
+
+    results = dlg.results()
+    # have to manually delete the dialog - otherwise it's owned by the
+    # iface mainWindow and never deleted
+    dlg.deleteLater()
+    return results