[processing] make location of GRASS 6 help files configurable

This prevents errors when algorithm help requested and there is no
access to the Internet (e.g. closed networks)

python/plugins/processing/algs/grass/GrassAlgorithm.py

@@ -96,9 +96,15 @@ def getIcon(self):
             self._icon = QIcon(os.path.join(pluginPath, 'images', 'grass.svg'))
         return self._icon
 
-
     def help(self):
-        return False, 'http://grass.osgeo.org/grass64/manuals/' + self.grassName + '.html'
+        helpPath = GrassUtils.grassHelpPath()
+        if helpPath == '':
+            return False, None
+
+        if os.path.exists(helpPath):
+            return False, QUrl.fromLocalFile(os.path.join(helpPath, '{}.html'.format(self.grassName))).toString()
+        else:
+            return False, helpPath + '{}.html'.format(self.grass7Name)
 
     def getParameterDescriptions(self):
         descs = {}
@@ -162,7 +168,7 @@ def defineCharacteristicsFromFile(self):
                     elif isinstance(output, OutputVector):
                         vectorOutputs += 1
                     if isinstance(output, OutputHTML):
-                        self.addOutput(OutputFile("rawoutput", output.description + 
+                        self.addOutput(OutputFile("rawoutput", output.description +
                                                   " (raw output)", "txt"))
                 line = lines.readline().strip('\n').strip()
             except Exception as e:

python/plugins/processing/algs/grass/GrassAlgorithmProvider.py

@@ -63,6 +63,11 @@ def initializeSettings(self):
         ProcessingConfig.addSetting(Setting(self.getDescription(),
                                             GrassUtils.GRASS_LOG_CONSOLE,
                                             self.tr('Log console output'), False))
+        ProcessingConfig.addSetting(Setting(
+            self.getDescription(),
+            GrassUtils.GRASS_HELP_PATH,
+            self.tr('Location of GRASS docs'),
+            GrassUtils.grassHelpPath()))
 
     def unload(self):
         AlgorithmProvider.unload(self)
@@ -71,6 +76,7 @@ def unload(self):
             ProcessingConfig.removeSetting(GrassUtils.GRASS_WIN_SHELL)
         ProcessingConfig.removeSetting(GrassUtils.GRASS_LOG_COMMANDS)
         ProcessingConfig.removeSetting(GrassUtils.GRASS_LOG_CONSOLE)
+        ProcessingConfig.removeSetting(GrassUtils.GRASS_HELP_PATH)
 
     def createAlgsList(self):
         self.preloadedAlgs = []

python/plugins/processing/algs/grass/GrassUtils.py

@@ -50,6 +50,7 @@ class GrassUtils:
     GRASS_WIN_SHELL = 'GRASS_WIN_SHELL'
     GRASS_LOG_COMMANDS = 'GRASS_LOG_COMMANDS'
     GRASS_LOG_CONSOLE = 'GRASS_LOG_CONSOLE'
+    GRASS_HELP_PATH = 'GRASS_HELP_PATH'
 
     sessionRunning = False
     sessionLayers = {}
@@ -412,3 +413,27 @@ def tr(string, context=''):
         if context == '':
             context = 'GrassUtils'
         return QCoreApplication.translate(context, string)
+
+    @staticmethod
+    def grassHelpPath():
+        helpPath = ProcessingConfig.getSetting(GrassUtils.GRASS_HELP_PATH)
+
+        if helpPath is None:
+            if isWindows():
+                localPath = os.path.join(Grass7Utils.grassPath(), 'docs/html')
+                if os.path.exists(localPath):
+                    helpPath = os.path.abspath(localPath)
+            elif isMac():
+                localPath = '/Applications/GRASS-6.4.app/Contents/MacOS/docs/html'
+                if os.path.exists(localPath):
+                    helpPath = os.path.abspath(localPath)
+            else:
+                searchPaths = ['/usr/share/doc/grass-doc/html',
+                               '/opt/grass/docs/html',
+                               '/usr/share/doc/grass/docs/html']
+                for path in searchPaths:
+                    if os.path.exists(path):
+                        helpPath = os.path.abspath(path)
+                        break
+
+        return helpPath if helpPath is not None else 'http://grass.osgeo.org/grass64/manuals/'