avoid needless list construction

[lilass.git] / gui.py

diff --git a/gui.py b/gui.py
index 155226b3939fff4598786870baa61b3aedf13396..c0697614408a251d396077159ff3d41edb1ce55e 100644 (file)
--- a/gui.py
+++ b/gui.py
@@ -18,36 +18,92 @@
 # This file abstracts GUI stuff away, so that the actual dsl.py does not have to deal with it
 import sys
 
-# frontend detectors
-def qtAvailable():
-       try:
-               import PyQt4
-               return True
-       except ImportError:
-               return False
+'''
+This module implements two functions:
+
+def error(message):
+       This function displays the error message to the user in some appropriate fassion
 
-def zenityAvailable():
-       return True # FIXME
+def setup(internalResolutions, externalResolutions):
+       Both arguments are lists of (width, height) tuples of resolutions. You can use dsl.res2user to obtain a user-readable representation of a resolution tuple.
+       The user should be asked about his display setup preferences.
+       The function returns None if the user cancelled, and an instance of dsl.ScreenSetup otherwise.
+'''
+import subprocess, collections
 
-# actual frontend
-if qtAvailable():
-       from PyQt4 import QtGui
-       from qt_dialogue import PositionSelection
-       app = QtGui.QApplication(sys.argv)
+# Qt frontend
+class QtFrontend:
+       def __init__(self):
+               from PyQt4 import QtGui
+               self.app = QtGui.QApplication(sys.argv)
+               print("Qt loaded")
        
-       def error(message):
-               '''Displays a fatal error to the user'''
+       def error(self, message):
+               from PyQt4 import QtGui
                QtGui.QMessageBox.critical(None, 'Fatal error', message)
        
-       def setup(internalResolutions, externalResolutions):
-               '''Returns a ScreenSetup instance, or None if the user canceled'''
+       def setup(self, internalResolutions, externalResolutions):
+               from qt_dialogue import PositionSelection
                return PositionSelection(internalResolutions, externalResolutions).run()
-elif zenityAvailable():
-       import subprocess
-       from zenity_dialogue import run as setup # this provides the setup function
        
+       @staticmethod
+       def isAvailable():
+               try:
+                       import PyQt4
+                       return True
+               except ImportError:
+                       return False
+
+
+# Zenity frontend
+class ZenityFrontend:
        def error(message):
                '''Displays a fatal error to the user'''
                subprocess.check_call(["zenity", "--error", "--text="+message])
-else:
-       print >> sys.stderr, 'No GUI frontend available, please make sure PyQt4 or Zenity is installed'
+       
+       def setup(self, internalResolutions, externalResolutions):
+               from zenity_dialogue import run
+               run(internalResolutions, externalResolutions)
+       
+       @staticmethod
+       def isAvailable():
+               try:
+                       from dsl import processOutputIt
+                       processOutputIt("zenity", "--version")
+                       return True
+               except Exception:
+                       return False
+
+
+# CLI frontend
+class CLIFrontend:
+       def error(self, message):
+               print(message, file=sys.stderr)
+       
+       def setup(self, internalResolutions, externalResolutions):
+               raise Exception("Choosing the setup interactively is not supported with the CLI frontend")
+       
+       @staticmethod
+       def isAvailable():
+               return True
+
+# list of available frontends
+frontends = collections.OrderedDict()
+frontends["qt"] = QtFrontend
+frontends["zenity"] = ZenityFrontend
+frontends["cli"] = CLIFrontend
+
+# get a frontend
+def getFrontend(name = None):
+       # by name
+       if name is not None:
+               if name in frontends:
+                       if frontends[name].isAvailable():
+                               return frontends[name]() # call constructor
+               # frontend not found or not available
+               raise Exception("Frontend %s not found or not available" % name)
+       # auto-detect
+       for frontend in frontends.values():
+               if frontend.isAvailable():
+                       return frontend() # call constructor
+       raise Exception("No frontend is available - this should not happen")