[python-win32] Starting a GUI app from AddIn server

[Johannes Brunen]

Hi,

I'm facing the following problem:

I have written an AddIn server which is called from a GUI application.
After some action in the GUI app the function 
DoSomething of class CmdEvtHandlerStartApp is called. This works pretty
fine.

class AddInBase:
    """
    Base class for CADdy++ AddIns.
    """
    _com_interfaces_  = ['ICADdyAddIn']
    _public_methods_  = []
    _reg_clsctx_      = pythoncom.CLSCTX_INPROC_SERVER
    _reg_policy_spec_ = "win32com.server.policy.EventHandlerPolicy"
    _typelib_guid_    = '{9C3BB401-114D-11D4-AC72-00105A4925FC}'
    ....

class AddIn(AddInBase):
    _reg_clsid_  = '{FC76E6CC-B0C8-4233-AFFA-45594501A4F0}'
    _reg_progid_ = 'CADdyAddIn.PythonGui0'

    def __init__(self):
        AddInBase.__init__(self)

    def OnInit(self, theCADdy):
        NewCmd = self.AddCmd(NewPool, "StartGuiApplication",
constants.CMD_NOBREAK, CmdEvtHandlerStartApp)

class CmdEvtHandlerStartApp(CmdEvtHandlerBase):
    def OnExecute(self, cmd, data, cmdStr):
        self.DoSomething()
        
    def DoSomething(self):
        ....

Now, I would like to start a separate wxPython GUI app/dialog
(wxAppGui0) from the DoSomething call which 
should run asynchronously to the main GUI app. The following
requirements should be met:
	1. The app/dialog should always stay on top of the main GUI app
	2. The app/dialog should not appear on the window taskbar
	3. The main GUI should not be affected by the app/dialog
	4. I need some communication between the AddIn class and the
app/dialog

I tried the following with varying success:
a) Idee: Use a separate thread for the app/dialog and use proper locking
for data exchange between the threads.
    def DoSomething(self):
        import threading
        import wxAppGui0
        thread = threading.Thread(target = wxAppGui0.main)
        thread.start()

=> 	This seems to work fine for a first call to the DoSomething
function. But after closing the wxAppGui0 app/dialog it is 
	impossible to restart the app/dialog by a new call to function
DoSomething. Inside wxPython the call to the embedded
	function CreateWindowEx failed:
		File
"C:\Programme\Python\Lib\site-packages\wx-2.6-msw-ansi\wx\_controls.py",
line 79, in __init__
    		newobj = _controls_.new_Button(*args, **kwargs)
		PyAssertionError: C++ assertion "wxAssertFailure" failed
in ..\..\src\msw\control.cpp(162): 
			CreateWindowEx("BUTTON", flags=56010000,
ex=00000000) failed
	This problem only appears if I have set the wxFrame style to
wx.FRAME_NO_TASKBAR. Is there anything I could do
	in order to use this case? Is this the recommended way to go?
Are there any additionl flaws with this design?

b) Idee: Create a completly separate process for the app/dialog and
setup some communication infrastructure.
    def DoSomething(self):
        cmd =
r'C:\Development\Learn\Python\COM\Test\Lesson3\wxAppGui0.pyw'
        import win32process
        procHandle, threadHandle, procId, threadId  =
win32process.CreateProcess(
            None, # appName
            'pythonw.exe ' + cmd,
            None, # process security
            None, # thread security
            0, # inherit handles
            win32process.NORMAL_PRIORITY_CLASS,
            None, # new environment
            None, # Current directory
            win32process.STARTUPINFO(), # startup info
            )

=>	For this scenario I have to build additional communication
infrastructure (COM or pipes). I would like to avoid additional
	registering of a wxAppGui0 COM server. Another problem is that I
do have to explicitly specify the wxAppGui0.pyw path.

For a) and b), additionally, I don't know how to force the app/dialog
always to be on top of the GUI app. How can I enforce
this requirement? Can I somehow tell wxPython to use my GUI application
as it's parent?

Could someone recommend a design for the above use case? I don't have
much experiences in the field. 

Best

Johannes




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