In-progress work on trying to get a robust inputhook setup.

This is proving to be pretty hard and will require some changes to end-user
code  in the long run.  It's simply impossible.

docs/examples/core/switchgui.py

@@ -0,0 +1,57 b''
+"""Test the new %gui command.  Run this in ipython as
+
+%run switchgui [backend]
+
+where the optional backend can be one of:  qt4, gtk, tk, wx.
+"""
+
+import sys
+import time
+
+import IPython.core.ipapi as ipapi
+ip = ipapi.get()
+
+from  IPython.lib import inputhook
+
+try:
+    backend = sys.argv[1]
+    #a = ip.magic('gui -a %s' % backend)
+    #a = ip.magic('gui %s' % backend)
+except IndexError:
+    backend = 'qt'
+
+backends = dict(wx='wxagg', qt='qt4agg', gtk='gtkagg', tk='tkagg')
+
+import matplotlib
+matplotlib.use(backends[backend])
+#matplotlib.interactive(True)
+
+import matplotlib
+from matplotlib import pyplot as plt, mlab, pylab
+import numpy as np
+
+from numpy import *
+from matplotlib.pyplot import *
+
+x = np.linspace(0,pi,100)
+
+print "A plot has been created"
+line, = plot(x,sin(2*x))
+plt.show()
+inputhook.spin_qt4()
+
+#raw_input("Press Enter to continue")
+
+print "I will now count until 10, please hit Ctrl-C before I'm done..."
+print "IPython should stop counting and return to the prompt without crashing."
+print
+line_x = line.get_data()[0]
+for i in range(1,51):
+    print i, 
+    sys.stdout.flush()
+    line.set_data(line_x,sin(x*i))
+    plt.title('i=%d' % i)
+    #plt.show()
+    plt.draw()
+    inputhook.spin_qt4()
+    #time.sleep(0.04)

IPython/lib/inputhook.py

@@ -22,6 +22,18 b' import sys'
 # Code
 #-----------------------------------------------------------------------------
 
+def appstart_qt4():
+    from PyQt4 import QtCore, QtGui
+    
+    app = QtCore.QCoreApplication.instance()
+    print 'qtapp:', app
+    if app is not None:
+        if current_gui() == 'qt4':
+            pass
+        else:
+            app.exec_()
+    
+
 class _DummyMainloop(object):
     """A special manager to hijack GUI mainloops that is mostly a no-op.
 
@@ -34,6 +46,12 b' class _DummyMainloop(object):'
         
         
     def __call__(self, *args, **kw):
+        force = kw.pop('force', False)
+        force = False
+        if force:
+            #print 'forced spin'  # dbg
+            self.ml(*args, **kw)
+            
         if self.ihm.current_gui() == self.gui_type:
             pass
         else:
@@ -45,14 +63,15 b' def spin_qt4():'
 
     app = QtCore.QCoreApplication.instance()    
     if (app is not None) and (app.thread() == QtCore.QThread.currentThread()):
-        timer = QtCore.QTimer()
-        QtCore.QObject.connect(timer,
-                               QtCore.SIGNAL('timeout()'),
-                               app, 
-                               QtCore.SLOT('quit()'))
-        timer.start(100)
-        QtCore.QCoreApplication.exec_()
-        timer.stop()
+        ## timer = QtCore.QTimer()
+        ## QtCore.QObject.connect(timer,
+        ##                        QtCore.SIGNAL('timeout()'),
+        ##                        app, 
+        ##                        QtCore.SLOT('quit()'))
+        ## timer.start(100)
+        #QtCore.QCoreApplication.exec_(force=True)
+        QtCore.QCoreApplication.processEvents(QtCore.QEventLoop.AllEvents)
+        ##timer.stop()
 
 
 def spin_wx():
@@ -241,7 +260,7 b' class InputHookManager(object):'
         except AttributeError:
             pass
         self._current_gui = 'qt4'
-        self._hijack_qt4()
+        #self._hijack_qt4()
         if app:
             from PyQt4 import QtGui
             app = QtCore.QCoreApplication.instance()

docs/examples/core/gui-qt.py

@@ -34,4 +34,9 b" if __name__ == '__main__':"
     sw = SimpleWindow()
     sw.show()
 
+    try:
+        import IPython.lib.inputhook as i; i.appstart_qt4()
+    except ImportError:
     app.exec_()
+    
+    #import time; time.sleep(10)