backwards compatibility aliases can be used in the wxPython namespace

[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.txt file like
usual to see info about the not so major changes and other things that
have been added to wxPython.



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

The import-startup-bootstrap process employed by wxPython was changed
such that wxWindows 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 bene 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.

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=ID_EXIT)
     
I hope to be able to remove the need for using IDs even for menu
events too...

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.  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 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 bu changing the
name to DrawRectabgleXY, 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::

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

Then you can just simplify it like this::

    dc.DrawRectangle(p, s)




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.  [[TODO: update the
BUILD.*.txt files too!]]

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.  [[TODO:  Install
these headers on Linux...]]

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




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 keyworkd args with wxSizer Add, Insert, or
Prepend 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 wxSize or a
2-integer sequence instead of separate width and height parameters.

The wxGridBagSizer 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.



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, the "internal" module names have changed, but
you shouldn't have been using them anyway so it shouldn't bother
you. ;-)

The wxPython.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.