[processing] Polygons to line fixes

- Maintain Z/M values
- Handle curved geometries without segmentizing
- Retain null geometries

Author: nyalldawson

python/plugins/processing/algs/qgis/LinesToPolygons.py

@@ -50,6 +50,7 @@ def getIcon(self):
     def defineCharacteristics(self):
         self.name, self.i18n_name = self.trAlgorithm('Lines to polygons')
         self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+        self.tags = self.tr('line,polygon,convert')
 
         self.addParameter(ParameterVector(self.INPUT,
                                           self.tr('Input layer'),

python/plugins/processing/algs/qgis/PolygonsToLines.py

@@ -50,6 +50,7 @@ def getIcon(self):
     def defineCharacteristics(self):
         self.name, self.i18n_name = self.trAlgorithm('Polygons to lines')
         self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+        self.tags = self.tr('line,polygon,convert')
 
         self.addParameter(ParameterVector(self.INPUT,
                                           self.tr('Input layer'), [dataobjects.TYPE_VECTOR_POLYGON]))
@@ -62,36 +63,17 @@ def processAlgorithm(self, progress):
         writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
             layer.fields().toList(), QgsWkbTypes.LineString, layer.crs())
 
-        outFeat = QgsFeature()
-        inGeom = QgsGeometry()
-        outGeom = QgsGeometry()
-
         features = vector.features(layer)
         total = 100.0 / len(features)
         for current, f in enumerate(features):
-            inGeom = f.geometry()
-            attrs = f.attributes()
-            lineList = self.extractAsLine(inGeom)
-            outFeat.setAttributes(attrs)
-            for h in lineList:
-                outFeat.setGeometry(outGeom.fromPolyline(h))
-                writer.addFeature(outFeat)
+            if f.hasGeometry():
+                lines = QgsGeometry(f.geometry().geometry().boundary()).asGeometryCollection()
+                for line in lines:
+                    f.setGeometry(line)
+                    writer.addFeature(f)
+            else:
+                writer.addFeature(f)
 
             progress.setPercentage(int(current * total))
 
         del writer
-
-    def extractAsLine(self, geom):
-        multiGeom = QgsGeometry()
-        lines = []
-        if geom and geom.type() == QgsWkbTypes.PolygonGeometry:
-            if geom.isMultipart():
-                multiGeom = geom.asMultiPolygon()
-                for i in multiGeom:
-                    lines.extend(i)
-            else:
-                multiGeom = geom.asPolygon()
-                lines = multiGeom
-            return lines
-        else:
-            return []

python/plugins/processing/tests/testdata/expected/polys_to_lines.gml

@@ -37,4 +37,11 @@
       <ogr:Bfloatval>-0.123</ogr:Bfloatval>
     </ogr:polys_to_lines>
   </gml:featureMember>
+  <gml:featureMember>
+    <ogr:polys_to_lines fid="multipolys.3">
+      <ogr:Bname>Test</ogr:Bname>
+      <ogr:Bintval>3</ogr:Bintval>
+      <ogr:Bfloatval>0</ogr:Bfloatval>
+    </ogr:polys_to_lines>
+  </gml:featureMember>
 </ogr:FeatureCollection>