Check for errors after unicode conversions

[wxWidgets.git] / wxPython / docs / MigrationGuide.txt

============================
wxPython 2.5 Migration Guide
============================

This document will help explain some of the major changes in wxPython
2.5 and let you know what you need to do to adapt your programs to
those changes.  Be sure to also check in the CHANGES_ file like
usual to see info about the not so major changes and other things that
have been added to wxPython.

.. _CHANGES: CHANGES.html


wxName Change
-------------

The **wxWindows** project and library is now known as
**wxWidgets**.  Please see here_ for more details.

.. _here: http://www.wxwidgets.org/name.htm

This won't really affect wxPython all that much, other than the fact
that the wxwindows.org domain name will be changing to wxwidgets.org,
so mail list, CVS, and etc. addresses will be changing.  We're going
to try and smooth the transition as much as possible, but I wanted you
all to be aware of this change if you run into any issues.



Module Initialization
---------------------

The import-startup-bootstrap process employed by wxPython was changed
such that wxWidgets and the underlying gui toolkit are **not**
initialized until the wx.App object is created (but before wx.App.OnInit
is called.)  This was required because of some changes that were made
to the C++ wxApp class.

There are both benefits and potential problems with this change.  The
benefits are that you can import wxPython without requiring access to
a GUI (for checking version numbers, etc.) and that in a
multi-threaded environment the thread that creates the app object will
now be the GUI thread instead of the one that imports wxPython.  Some
potential problems are that the C++ side of the "stock-objects"
(wx.BLUE_PEN, wx.TheColourDatabase, etc.) are not initialized until
the wx.App object is created, so you should not use them until after
you have created your wx.App object.  If you do then an exception will
be raised telling you that the C++ object has not been initialized
yet.

Also, you will probably not be able to do any kind of GUI or bitmap
operation unless you first have created an app object, (even on
Windows where most anything was possible before.)



SWIG 1.3
--------

wxPython is now using SWIG 1.3.x from CVS (with several of my own
customizations added that I hope to get folded back into the main SWIG
distribution.)  This has some far reaching ramifications:

    All classes derive from object and so all are now "new-style
    classes"

    Public data members of the C++ classes are wrapped as Python
    properties using property() instead of using __getattr__/__setattr__
    like before.  Normally you shouldn't notice any difference, but if
    you were previously doing something with __getattr__/__setattr__
    in derived classes then you may have to adjust things.

    Static C++ methods are wrapped using the staticmethod()
    feature of Python and so are accessible as ClassName.MethodName
    as expected.  They are still available as top level functions
    ClassName_MethodName as before.

    The relationship between the wxFoo and wxFooPtr classes have
    changed for the better.  Specifically, all instances that you see
    will be wxFoo even if they are created internally using wxFooPtr,
    because wxFooPtr.__init__ will change the instance's __class__ as
    part of the initialization.  If you have any code that checks
    class type using something like isinstance(obj, wxFooPtr) you will
    need to change it to isinstance(obj, wxFoo).

    

Binding Events
--------------

All of the EVT_* functions are now instances of the wx.PyEventBinder
class.  They have a __call__ method so they can still be used as
functions like before, but making them instances adds some
flexibility that I expect to take advantave of in the future.

wx.EvtHandler (the base class for wx.Window) now has a Bind method that
makes binding events to windows a little easier.  Here is its
definition and docstring::

        def Bind(self, event, handler, source=None, id=wxID_ANY, id2=wxID_ANY):
            """
            Bind an event to an event handler.

              event     One of the EVT_* objects that specifies the
                        type of event to bind.

              handler   A callable object to be invoked when the event
                        is delivered to self.  Pass None to disconnect an
                        event handler.

              source    Sometimes the event originates from a different window
                        than self, but you still want to catch it in self.  (For
                        example, a button event delivered to a frame.)  By
                        passing the source of the event, the event handling
                        system is able to differentiate between the same event
                        type from different controls.

              id,id2    Used for menu IDs or for event types that require a
                        range of IDs

            """

Some examples of its use::

     self.Bind(wx.EVT_SIZE,   self.OnSize)
     self.Bind(wx.EVT_BUTTON, self.OnButtonClick, theButton)
     self.Bind(wx.EVT_MENU,   self.OnExit, id=wx.ID_EXIT)


The wx.Menu methods that add items to a wx.Menu have been modified
such that they return a reference to the wx.MenuItem that was created.
Additionally menu items and toolbar items have been modified to
automatically generate a new ID if -1 is given, similar to using -1
with window classess.  This means that you can create menu or toolbar
items and event bindings without having to predefine a unique menu ID,
although you still can use IDs just like before if you want.  For
example, these are all equivallent other than their specific ID
values::

  1.
    item = menu.Append(-1, "E&xit", "Terminate the App")
    self.Bind(wx.EVT_MENU, self.OnExit, item)

  2. 
    item = menu.Append(wx.ID_EXIT, "E&xit", "Terminate the App")
    self.Bind(wx.EVT_MENU, self.OnExit, item)

  3. 
    menu.Append(wx.ID_EXIT, "E&xit", "Terminate the App")
    self.Bind(wx.EVT_MENU, self.OnExit, id=wx.ID_EXIT)

     
If you create your own custom event types and EVT_* functions, and you
want to be able to use them with the Bind method above then you should
change your EVT_* to be an instance of wxPyEventBinder instead of a
function.  For example, if you used to have something like this::

    myCustomEventType = wxNewEventType()
    def EVT_MY_CUSTOM_EVENT(win, id, func):
        win.Connect(id, -1, myCustomEventType, func)


Change it like so::

    myCustomEventType = wx.NewEventType()
    EVT_MY_CUSTOM_EVENT = wx.PyEventBinder(myCustomEventType, 1)

The second parameter is an integer in [0, 1, 2] that specifies the
number of IDs that are needed to be passed to Connect.





The wx Namespace
----------------

The second phase of the wx Namespace Transition has begun.  That means
that the real names of the classes and other symbols do not have the
'wx' prefix and the modules are located in a Python package named
wx.  There is still a Python package named wxPython with modules
that have the names with the wx prefix for backwards compatibility.
Instead of dynamically changing the names at module load time like in
2.4, the compatibility modules are generated at build time and contain
assignment statements like this::

    wxWindow = wx.core.Window

Don't let the "core" in the name bother you.  That and some other
modules are implementation details, and everything that was in the
wxPython.wx module before will still be in the wx package namespace
after this change.  So from your code you would use it as wx.Window.

A few notes about how all of this was accomplished might be
interesting...  SWIG is now run twice for each module that it is
generating code for.  The first time it outputs an XML representaion
of the parse tree, which can be up to 20MB and 300K lines in size!
That XML is then run through a little Python script that creates a
file full of SWIG %rename directives that take the wx off of the
names, and also generates the Python compatibility file described
above that puts the wx back on the names.  SWIG is then run a second
time to generate the C++ code to implement the extension module, and
uses the %rename directives that were generated in the first step.

Not every name is handled correctly (but the bulk of them are) and so
some work has to be done by hand, especially for the reverse-renamers.
So expect a few flaws here and there until everything gets sorted out.

In summary, the wx package and names without the "wx" prefix are now
the official form of the wxPython classes.  For example::

    import wx

    class MyFrame(wx.Frame):
        def __init__(self, parent, title):
	    wx.Frame.__init__(self, parent, -1, title)
	    p = wx.Panel(self, -1)
	    b = wx.Button(p, -1, "Do It", (10,10))
	    self.Bind(wx.EVT_BUTTON, self.JustDoIt, b)

	def JustDoIt(self, evt):
	    print "It's done!"

    app = wx.PySimpleApp()
    f = MyFrame(None, "What's up?")
    f.Show()
    app.MainLoop()

You shouldn't need to migrate all your modules over to use the new
package and names right away as there are modules in place that try to
provide as much backwards compatibility of the names as possible.  If
you rewrote the above sample using "from wxPython.wx import * ", the
old wxNames, and the old style of event binding it will still work
just fine.




New wx.DC Methods
-----------------

Many of the Draw methods of wx.DC have alternate forms in C++ that take
wxPoint or wxSize parameters (let's call these *Type A*) instead of
the individual x, y, width, height, etc. parameters (and we'll call
these *Type B*).  In the rest of the library I normally made the *Type
A* forms of the methods be the default method with the "normal" name,
and had renamed the *Type B* forms of the methods to some similar
name.  For example in wx.Window we have these Python methods::

    SetSize(size)               # Type A
    SetSizeWH(width, height)    # Type B


For various reasons the new *Type A* methods in wx.DC were never added
and the existing *Type B* methods were never renamed.  Now that lots
of other things are also changing in wxPython it has been decided that
it is a good time to also do the method renaming in wx.DC too in order
to be consistent with the rest of the library.  The methods in wx.DC
that are affected are listed here::

    FloodFillXY(x, y, colour, style = wx.FLOOD_SURFACE)
    FloodFill(point, colour,  style = wx.FLOOD_SURFACE)

    GetPixelXY(x, y)
    GetPixel(point)

    DrawLineXY(x1, y1, x2, y2)
    DrawLine(point1, point2)

    CrossHairXY(x, y)
    CrossHair(point)

    DrawArcXY(x1, y1, x2, y2, xc, yc)
    DrawArc(point1, point2, center)

    DrawCheckMarkXY(x, y, width, height)
    DrawCheckMark(rect)

    DrawEllipticArcXY(x, y, w, h, start_angle, end_angle)
    DrawEllipticArc(point, size, start_angle, end_angle)

    DrawPointXY(x, y)
    DrawPoint(point)

    DrawRectangleXY(x, y, width, height)
    DrawRectangle(point, size)
    DrawRectangleRect(rect)

    DrawRoundedRectangleXY(x, y, width, height, radius)
    DrawRoundedRectangle(point, size, radius)
    DrawRoundedRectangleRect(rect, radius)

    DrawCircleXY(x, y, radius)
    DrawCircle(point, radius)

    DrawEllipseXY(x, y, width, height)
    DrawEllipse(point, size)
    DrawEllipseRect(rect)

    DrawIconXY(icon, x, y)
    DrawIcon(icon, point)

    DrawBitmapXY(bmp, x, y, useMask = FALSE)
    DrawBitmap(bmp, point, useMask = FALSE)

    DrawTextXY(text, x, y)
    DrawText(text, point)

    DrawRotatedTextXY(text, x, y, angle)
    DrawRotatedText(text, point, angle)

    
    BlitXY(xdest, ydest, width, height, sourceDC, xsrc, ysrc,
           rop = wxCOPY, useMask = FALSE, xsrcMask = -1, ysrcMask = -1)
    Blit(destPt, size, sourceDC, srcPt,
         rop = wxCOPY, useMask = FALSE, srcPtMask = wx.DefaultPosition)

    SetClippingRegionXY(x, y, width, height)
    SetClippingRegion(point, size)
    SetClippingRect(rect)
    SetClippingRegionAsRegion(region);

	
If you have code that draws on a DC and you are using the new wx
namespace then you **will** get errors because of these changes, but
it should be easy to fix the code.  You can either change the name of
the *Type B* method called to the names shown above, or just add
parentheses around the parameters as needed to turn them into tuples
and let the SWIG typemaps turn them into the wx.Point or wx.Size
object that is expected.  Then you will be calling the new *Type A*
method.  For example, if you had this code before::

    dc.DrawRectangle(x, y, width, height)

You could either continue to use the *Type B* method by changing the
name to DrawRectangleXY, or just change it to the new *Type A* by
adding some parentheses like this::

    dc.DrawRectangle((x, y), (width, height))

Or if you were already using a point and size like this::

    dc.DrawRectangle(p.x, p.y, s.width, s.height)

Then you can just simplify it like this::

    dc.DrawRectangle(p, s)

Now before you start yelling and screaming at me for breaking all your
code, take note that up above I said, "...using the new wx namespace..."
That's because if you are still importing from wxPython.wx then there
are some classes defined there with Draw and etc. methods that have
2.4 compatible signatures.  However if/when the old wxPython.wx
namespace is removed then these classes will be removed too so you
should plan on migrating to the new namespace and new DC Draw methods
before that time.



Building, Extending and Embedding wxPython
------------------------------------------

wxPython's setup.py script now expects to use existing libraries for
the contribs (gizmos, stc, xrc, etc.) rather than building local
copies of them.  If you build your own copies of wxPython please be
aware that you now need to also build the ogl, stc, xrc, and gizmos
libraries in addition to the main wx lib.  

The wxPython.h and other header files are now in
.../wxPython/include/wx/wxPython instead of in wxPython/src.  You
should include it via the "wx/wxPython/wxPython.h" path and add
.../wxPython/include to your list of include paths.  On OSX and
unix-like systems the wxPython headers are installed to the same place
that the wxWidgets headers are installed, so if you are building
wxPython compatible extensions on those platforms then your include
path should already be set properly.

If you are also using SWIG for your extension then you'll need to
adapt how the wxPython .i files are imported into your .i files.  See
the wxPython sources for examples.  Your modules will need to at least
``%import core.i``, and possibly others if you need the definition of
other classes.  Since you will need them to build your modules using
SWIG, the main wxPython .i files are also installed with the wxPython
headers in an i_files sibdirectory.  It should be enough to pass a
-I/pathname on the command line for SWIG to find the files.

The bulk of wxPython's setup.py has been moved to another module,
wx/build/config.py.  This module will be installed as part of wxPython
so 3rd party modules that wish to use the same setup/configuration
code can do so simply by importing this module from their own setup.py
scripts using ``import wx.build.config``. 

You no longer need to call wxClassInfo::CleanUpClasses() and
wxClassInfo::InitializeClasses() in your extensions or when embedding
wxPython. 

The usage of wxPyBeginAllowThreads and wxPyEndAllowThreads has changed
slightly.  wxPyBeginAllowThreads now returns a boolean value that must
be passed to the coresponding wxPyEndAllowThreads function call.  This
is to help do the RightThing when calls to these two functions are
nested, or if calls to external code in other extension modules that
are wrapped in the standard Py_(BEGIN|END)_ALLOW_THERADS may result in
wx event handlers being called (such as during the call to
os.startfile.)



Two (or Three!) Phase Create
----------------------------

If you use the Precreate/Create method of instantiating a window, (for
example, to set an extended style flag, or for XRC handlers) then
there is now a new method named PostCreate to help with transplanting
the brain of the prewindow instance into the derived window instance.
For example::

    class MyDialog(wx.Dialog):
        def __init__(self, parent, ID, title, pos, size, style):
            pre = wx.PreDialog()
            pre.SetExtraStyle(wx.DIALOG_EX_CONTEXTHELP)
            pre.Create(parent, ID, title, pos, size, style)
            self.PostCreate(pre)



Sizers
------

The hack allowing the old "option" keyword parameter has been removed.
If you use keyword args with w.xSizer Add, Insert, or Prepend methods
then you will need to use the ``proportion`` name instead of ``option``.

When adding a spacer to a sizer you now need to use a wx.Size or a
2-integer sequence instead of separate width and height parameters.

The wx.GridBagSizer class (very similar to the RowColSizer in the
library) has been added to C++ and wrapped for wxPython.  It can also
be used from XRC.

You should not use AddWindow, AddSizer, AddSpacer (and similar for
Insert, Prepend, and etc.) methods any longer.  Just use Add and the
wrappers will figure out what to do.


PlatformInfo
------------

Added wx.PlatformInfo which is a tuple containing strings that
describe the platform and build options of wxPython.  This lets you
know more about the build than just the __WXPORT__ value that
wx.Platform contains, such as if it is a GTK2 build.  For example,
instead of::

     if wx.Platform == "__WXGTK__":
         ...

you should do this::

    if "__WXGTK__" in wx.PlatformInfo:
         ...

and you can specifically check for a wxGTK2 build by looking for
"gtk2" in wx.PlatformInfo.  Unicode builds are also detectable this
way.  If there are any other platform/toolkit/build flags that make
sense to add to this tuple please let me know.

BTW, wx.Platform will probably be deprecated in the future.



ActiveX
-------

Lindsay Mathieson's newest wxActiveX_ class has been wrapped into a new
extension module called wx.activex.  It is very generic and dynamic
and should allow hosting of arbitray ActiveX controls within your
wxPython apps.  So far I've tested it with IE, PDF, and Flash
controls, (and there are new samples in the demo and also library
modules supporting these.)

.. _wxActiveX: http://members.optusnet.com.au/~blackpaw1/wxactivex.html

The new wx.activex module contains a bunch of code, but the most
important things to look at are ActiveXWindow and ActiveXEvent.
ActiveXWindow derives from wxWindow and the constructor accepts a
CLSID for the ActiveX Control that should be created.  (There is also
a CLSID class that can convert from a progID or a CLSID String.)  The
ActiveXWindow class simply adds methods that allow you to query some
of the TypeInfo exposed by the ActiveX object, and also to get/set
properties or call methods by name.  The Python implementation
automatically handles converting parameters and return values to/from
the types expected by the ActiveX code as specified by the TypeInfo,
(just bool, integers, floating point, strings and None/Empty so far,
but more can be handled later.)

That's pretty much all there is to the class, as I mentioned before it
is very generic and dynamic.  Very little is hard-coded and everything
that is done with the actual ActiveX control is done at runtime and
referenced by property or method name.  Since Python is such a dynamic
language this is a very good match.  I thought for a while about doing
some Python black-magic and making the specific methods/properties of
the actual ActiveX control "appear" at runtime, but then decided that
it would be better and more understandable to do it via subclassing.
So there is a utility class in wx.activex that given an existing
ActiveXWindow instance can generate a .py module containing a derived
class with real methods and properties that do the Right Thing to
reflect those calls to the real ActiveX control.  There is also a
script/tool module named genaxmodule that given a CLSID or progID and
a class name, will generate the module for you.  There are a few
examples of the output of this tool in the wx.lib package, see
iewin.py, pdfwin.py and flashwin.py.

Currently the genaxmodule tool will tweak some of the names it
generates, but this can be controled if you would like to do it
differently by deriving your own class from GernerateAXModule,
overriding some methods and then using this class from a tool like
genaxmodule.  [TODO: make specifying a new class on genaxmodule's
command-line possible.]  The current default behavior is that any
event names that start with "On" will have the "On" dropped, property
names are converted to all lower case, and if any name is a Python
keyword it will have an underscore appended to it.  GernerateAXModule
does it's best when generating the code in the new module, but it can
only be as good as the TypeInfo data available from the ActiveX
control so sometimes some tweaking will be needed.  For example, the
IE web browser control defines the Flags parameter of the Navigate2
method as required, but MSDN says it is optional.

It is intended that this new wx.activex module will replace both the
older version of Lindsay's code available in iewin.IEHtmlWindow, and
also the wx.lib.activexwraper module.  Probably the biggest
differences you'll ecounter in migrating activexwrapper-based code
(besides events working better without causing deadlocks) is that
events are no longer caught by overriding methods in your derived
class.  Instead ActiveXWindow uses the wx event system and you bind
handlers for the ActiveX events exactly the same way you do for any wx
event.  There is just one extra step needed and that is creating an
event ID from the ActiveX event name, and if you use the genaxmodule
tool then this extra step will be handled for you there.  For example,
for the StatusTextChange event in the IE web browser control, this
code is generated for you::

    wxEVT_StatusTextChange = wx.activex.RegisterActiveXEvent('StatusTextChange')
    EVT_StatusTextChange = wx.PyEventBinder(wxEVT_StatusTextChange, 1)

and you would use it in your code like this::

    self.Bind(iewin.EVT_StatusTextChange, self.UpdateStatusText, self.ie)

When the event happens and your event handler function is called the
event properties from the ActiveX control (if any) are converted to
attributes of the event object passed to the handler.  (Can you say
'event' any more times in a single sentence? ;-) ) For example the
StatusTextChange event will also send the text that should be put into
the status line as an event parameter named "Text" and you can access
it your handlers as an attribute of the event object like this::

    def UpdateStatusText(self, evt):
        self.SetStatusText(evt.Text)

Usually these event object attributes should be considered read-only,
but some will be defined by the TypeInfo as output parameters.  In
those cases if you modify the event object's attribute then that value
will be returned to the ActiveX control.  For example, to prevent a
new window from being opened by the IE web browser control you can do
this in the handler for the iewin.EVT_NewWindow2 event::

    def OnNewWindow2(self, evt):
        evt.Cancel = True   

So how do you know what methods, events and properties that an ActiveX
control supports?  There is a funciton in wx.activex named GetAXInfo
that returns a printable summary of the TypeInfo from the ActiveX
instance passed in.  You can use this as an example of how to browse
the TypeInfo provided, and there is also a copy of this function's
output appended as a comment to the modules produced by the
genaxmodule tool.  Beyond that you'll need to consult the docs
provided by the makers of the ActiveX control that you are using.



Other Stuff
-----------

Instead of over a dozen separate extension modules linked together
into a single extension module, the "core" module is now just a few
extensions that are linked independently, and then merged together
later into the main namespace via Python code.

Because of the above and also because of the way the new SWIG works,
the "internal" module names have changed, but you shouldn't have been
using them anyway so it shouldn't bother you. ;-)

The help module no longer exists and the classes therein are now part
of the core module imported with wxPython.wx or the wx package.

wxPyDefaultPosition and wxPyDefaultSize are gone.  Use the
wxDefaultPosition and wxDefaultSize objects instead.

Similarly, the wxSystemSettings backwards compatibiility aliases for
GetSystemColour, GetSystemFont and GetSystemMetric have also gone into
the bit-bucket.  Use GetColour, GetFont and GetMetric instead.


The wx.NO_FULL_REPAINT_ON_RESIZE style is now the default style for
all windows.  The name still exists for compatibility, but it is set
to zero.  If you want to disable the setting (so it matches the old
default) then you need to use the new wx.FULL_REPAINT_ON_RESIZE style
flag otherwise only the freshly exposed areas of the window will be
refreshed.

wxPyTypeCast has been removed.  Since we've had the OOR (Original
Object Return) for a couple years now there should be no need to use
wxPyTypeCast at all.

If you use the old wxPython package and wxPython.wx namespace then
there are compatibility aliases for much of the above items.

The wxWave class has been renamed to wxSound, and now has a slightly
different API.

wx.TaskbarIcon works on wxGTK-based platforms now, however you have to
manage it a little bit more than you did before.  Basically, the app
will treat it like a top-level frame in that if the wx.TaskBarIcon
still exists when all the frames are closed then the app will still
not exit.  You need to ensure that the wx.TaskBarIcon is destroyed
when your last Frame is closed.  For wxPython apps it is usually
enough if your main frame object holds the only reference to the
wx.TaskBarIcon, then when the frame is closed Python reference
counting takes care of the rest.

Before Python 2.3 it was possible to pass a floating point object as a
parameter to a function that expected an integer, and the
PyArg_ParseTuple family of functions would automatically convert to
integer by truncating the fractional portion of the number.  With
Python 2.3 that behavior was deprecated and a deprecation warning is
raised when you pass a floating point value, (for example, calling
wx.DC.DrawLineXY with floats for the position and size,) and lots of
developers using wxPython had to scramble to change their code to call
int() before calling wxPython methods.  Recent changes in SWIG have
moved the conversion out of PyArg_ParseTuple to custom code that SWIG
generates.  Since the default conversion fragment was a little too
strict and didn't generate a very meaningful exception when it failed,
I decided to use a custom fragment instead, and it turned out that
it's very easy to allow floats to be converted again just like they
used to be.   So, in a nutshell, any numeric type that can be
converted to an integer is now legal to be passed to SWIG wrapped
functions in wxPython for parameters that are expecting an integer.
If the object is not already an integer then it will be asked to
convert itself to one.  A similar conversion fragment is in place for
parameters that expect floating point values.