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12\input psbox.tex
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14\parindent=0pt
15\title{Guide to porting applications from wxWindows 1.xx to 2.0}
16\author{Julian Smart}
17\date{October 1997}
18\makeindex
19\begin{document}
20\maketitle
21\pagestyle{fancyplain}
22\bibliographystyle{plain}
23\setheader{{\it CONTENTS}}{}{}{}{}{{\it CONTENTS}}
24\setfooter{\thepage}{}{}{}{}{\thepage}%
25\pagenumbering{roman}
26\tableofcontents
27%
28\chapter{About this document}\label{about}
29\pagenumbering{arabic}%
30\setheader{{\it Porting guide}}{}{}{}{}{{\it Porting guide}}%
31\setfooter{\thepage}{}{}{}{}{\thepage}%
32
33This document gives guidelines and tips for porting applications from
34version 1.xx of wxWindows to version 2.0.
35
36The first section offers tips for writing 1.xx applications in a way to
37minimize porting time. The following sections detail the changes and
38how you can modify your application to be 2.0-compliant.
39
40You may be worrying that porting to 2.0 will be a lot of work,
41particularly if you have only recently started using 1.xx. In fact,
42the wxWindows 2.0 API has far more in common with 1.xx than it has differences.
43With backward compatibility mode on, much of the conversion can be
44done gradually. The main challenges are doing without the default
45panel item layout, and the lack of automatic labels in some controls.
46However, if you already use resource files (.wxr), or application-specific positioning,
47or constraints, then even this will be quite painless.
48
49So please don't be freaked out by the jump to 2.0! For one thing, 1.xx is still available
50and will be supported by the user community for some time. And when you have
51changed to 2.0, we hope that you will appreciate the benefits in terms
52of greater flexibility, better user interface aesthetics, improved C++ conformance,
53improved compilation speed, and many other enhancements. The revised architecture
54of 2.0 will ensure that wxWindows can continue to evolve for the forseeable
55future.
56
57{\it Please note that this document is a work in progress.}
58
59\chapter{Preparing for version 2.0}\label{preparing}
60
61Even before compiling with version 2.0, there's also a lot you can do right now to make porting
62relatively simple. Here are a few tips.
63
64\begin{itemize}
65\item {\bf Use constraints or .wxr resources} for layout, rather than the default layout scheme.
66Constraints should be the same in 2.0, and resources will be translated.
67\item {\bf Use separate wxMessage items} instead of labels for wxText, wxMultiText,
68wxChoice, wxComboBox. These labels will disappear in 2.0. Use separate
69wxMessages whether you're creating controls programmatically or using
70the dialog editor. The future dialog editor will be able to translate
71from old to new more accurately if labels are separated out.
72\item {\bf Parameterise functions that use wxDC} or derivatives, i.e. make the wxDC
73an argument to all functions that do drawing. Minimise the use of
74wxWindow::GetDC and definitely don't store wxDCs long-term
75because in 2.0, you can't use GetDC() and wxDCs are not persistent.
76You will use wxClientDC, wxPaintDC stack objects instead. Minimising
77the use of GetDC() will ensure that there are very few places you
78have to change drawing code for 2.0.
79\item {\bf Don't set GDI objects} (wxPen, wxBrush etc.) in windows or wxCanvasDCs before they're
80needed (e.g. in constructors) - do so within your drawing routine instead. In
812.0, these settings will only take effect between the construction and destruction
82of temporary wxClient/PaintDC objects.
83\item {\bf Don't rely} on arguments to wxDC functions being floating point - they will
84be 32-bit integers in 2.0.
85\item {\bf Don't use the wxCanvas member functions} that duplicate wxDC functions, such as SetPen and DrawLine, since
86they are going.
87\item {\bf Using member callbacks} called from global callback functions will make the transition
88easier - see the FAQ
89for some notes on using member functions for callbacks. wxWindows 2.0 will banish global
90callback functions (and OnMenuCommand), and nearly all event handling will be done by functions taking a single event argument.
91So in future you will have code like:
92
93{\small\begin{verbatim}
94void MyFrame::OnOK(wxCommandEvent& event)
95{
96 ...
97}
98\end{verbatim}
99}%
100
101You may find that writing the extra code to call a member function isn't worth it at this stage,
102but the option is there.
103\item {\bf Use wxString wherever possible.} 2.0 will replace char * with wxString
104in most cases, and if you use wxString to receive strings returned from
105wxWindows functions (except when you need to save the pointer if deallocation is required), there should
106be no conversion problems later on.
107\item Be aware that under Windows, {\bf font sizes will change} to match standard Windows
108font sizes (for example, a 12-point font will appear bigger than before). Write your application
109to be flexible where fonts are concerned.
110Don't rely on fonts being similarly-sized across platforms, as they were (by chance) between
111Windows and X under wxWindows 1.66. Yes, this is not easy... but I think it's better to conform to the
112standards of each platform, and currently the size difference makes it difficult to
113conform to Windows UI standards. You may eventually wish to build in a global 'fudge-factor' to compensate
114for size differences. The old font sizing will still be available via wx\_setup.h, so do not panic...
115\item {\bf Consider dropping wxForm usage}: an alternative is to be found in utils/wxprop.
116wxPropertyFormView can be used in a wxForm-like way, except that you specify a pre-constructed panel
117or dialog; or you can use a wxPropertyListView to show attributes in a scrolling list - you don't even need
118to lay panel items out.
119
120Because wxForm uses a number of features to be dropped in wxWindows 2.0, it cannot be
121supported in the future, at least in its present state.
122\item {\bf When creating a wxListBox}, put the wxLB\_SINGLE, wxLB\_MULTIPLE, wxLB\_EXTENDED styles in the window style parameter, and put
123zero in the {\it multiple} parameter. The {\it multiple} parameter will be removed in 2.0.
124\item {\bf For MDI applications}, don't reply on MDI being run-time-switchable in the way that the
125MDI sample is. In wxWindows 2.0, MDI functionality is separated into distinct classes.
126\end{itemize}
127
128\chapter{The new event system}\label{eventsystem}
129
130The way that events are handled has been radically changed in wxWindows 2.0. Please
131read the topic `Event handling overview' in the wxWindows 2.0 manual for background
132on this.
133
134\section{Callbacks}
135
136Instead of callbacks for panel items, menu command events, control commands and other events are directed to
137the originating window, or an ancestor, or an event handler that has been plugged into the window
138or its ancestor. Event handlers always have one argument, a derivative of wxEvent.
139
140For menubar commands, the {\bf OnMenuCommand} member function will be replaced by a series of separate member functions,
141each of which responds to a particular command. You need to add these (non-virtual) functions to your
142frame class, add a DECLARE\_EVENT\_TABLE entry to the class, and then add an event table to
143your implementation file, as a BEGIN\_EVENT\_TABLE and END\_EVENT\_TABLE block. The
144individual event mapping macros will be of the form:
145
146\begin{verbatim}
147BEGIN_EVENT_TABLE(MyFrame, wxFrame)
148 EVT_MENU(MYAPP_NEW, MyFrame::OnNew)
149 EVT_MENU(wxID_EXIT, MyFrame::OnExit)
150END_EVENT_TABLE()
151\end{verbatim}
152
153Control commands, such as button commands, can be routed to a derived button class,
154the parent window, or even the frame. Here, you use a function of the form EVT\_BUTTON(id, func).
155Similar macros exist for other control commands.
156
157\section{Other events}
158
159To intercept other events, you used to override virtual functions, such as OnSize. Now, while you can use
160the OnSize name for such event handlers (or any other name of your choice), it has only a single argument
161(wxSizeEvent) and must again be `mapped' using the EVT\_SIZE macro. The same goes for all other events,
162including OnClose (although in fact you can still use the old, virtual form of OnClose for the time being).
163
164\chapter{Class hierarchy}\label{classhierarchy}
165
166The class hierarchy has changed somewhat. wxToolBar and wxButtonBar
167classes have been split into several classes, and are derived from wxControl (which was
168called wxItem). wxPanel derives from wxWindow instead of from wxCanvas, which has
169disappeared in favour of wxScrolledWindow (since all windows are now effectively canvases
170which can be drawn into). The status bar has become a class in its own right, wxStatusBar.
171
172There are new MDI classes so that wxFrame does not have to be overloaded with this
173functionality.
174
175There are new device context classes, with wxPanelDC and wxCanvasDC disappearing.
176See \helpref{Device contexts and painting}{dc}.
177
178\chapter{GDI objects}\label{gdiobjects}
179
180These objects - instances of classes such as wxPen, wxBrush, wxBitmap (but not wxColour) -
181are now implemented with reference-counting. This makes assignment a very cheap operation,
182and also means that management of the resource is largely automatic. You now pass {\it references} to
183objects to functions such as wxDC::SetPen. The device context does not store a copy of the pen
184itself, but takes a copy of it (via reference counting), and the object's data gets freed up
185when the reference count goes to zero. The application does not have to worry so much about
186who the object belongs to: it can pass the reference, then destroy the object without
187leaving a dangling pointer inside the device context.
188
189For the purposes of code migration, you can use the old style of object management - maintaining
190pointers to GDI objects, and using the FindOrCreate... functions. However, it is preferable to
191keep this explicit management to a minimum, instead creating objects on the fly as needed, on the stack,
192unless this causes too much of an overhead in your application.
193
194At a minimum, you will have to make sure that calls to SetPen, SetBrush etc. work. Some compilers
195will do the conversion from pointer to reference automatically (via a constructor in the GDI
196class) but you cannot rely on this being true for all compilers. Also, where you pass NULL to these
197functions, you will need to either cast to the appropriate reference type, or instead
198use an identifier such as wxNullPen or wxNullBrush.
199
200\chapter{Dialogs and controls}\label{dialogscontrols}
201
202\wxheading{Labels}
203
204Most controls no longer have labels and values as they used to in 1.xx. Instead, labels
205should be created separately using wxStaticText (the new name for wxMessage). This will
206need some reworking of dialogs, unfortunately; programmatic dialog creation that doesn't
207use constraints will be especially hard-hit. Perhaps take this opportunity to make more
208use of dialog resources or constraints. Or consider using the wxPropertyListView class
209which can do away with dialog layout issues altogether by presenting a list of editable
210properties.
211
212\wxheading{Constructors}
213
214All window constructors have two main changes, apart from the label issue mentioned above.
215Windows now have integer identifiers; and position and size are now passed as wxPoint and
216wxSize objects. In addition, some windows have a wxValidator argument. wxWindows 2.0 may provide
217old-style constructors in WXWIN\_COMPATIBILITY mode for limited backward compatibility.
218
219\wxheading{Show versus ShowModal}
220
221If you have used or overridden the {\bf wxDialog::Show} function in the past, you may find
222that modal dialogs no longer work as expected. This is because the function for modal showing
223is now {\bf wxDialog:ShowModal}. This is part of a more fundamental change in which a
224control may tell the dialog that it caused the dismissal of a dialog, by
225calling {\bf wxDialog::EndModal} or {\bf wxWindow::SetReturnCode}. Using this
226information, {\bf ShowModal} now returns the id of the control that caused dismissal,
227giving greater feedback to the application than just TRUE or FALSE.
228
229If you overrode or called {\bf wxDialog::Show}, use {\bf ShowModal} and test for a returned identifier,
230commonly wxID\_OK or wxID\_CANCEL.
231
232\wxheading{wxItem}
233
234This is renamed wxControl.
235
236\wxheading{wxText, wxMultiText and wxTextWindow}
237
238These classes no longer exist and are replaced by the single class wxTextCtrl.
239Multi-line text items are created using the wxTE\_MULTILINE style.
240
241\wxheading{wxButton}
242
243Bitmap buttons are now a separate class, instead of being part of wxBitmap.
244
245\wxheading{wxMessage}
246
247Bitmap messages are now a separate class, wxStaticBitmap, and wxMessage
248is renamed wxStaticText.
249
250\wxheading{wxGroupBox}
251
252wxGroupBox is renamed wxStaticBox.
253
254\wxheading{wxForm}
255
256Note that wxForm is no longer supported in wxWindows 2.0. Consider using the wxPropertyForm class
257instead, which takes standard dialogs and panels and associates controls with property objects.
258You may also find that the new validation method, combined with dialog resources, is easier
259and more flexible than using wxForm.
260
261\chapter{Device contexts and painting}\label{dc}
262
263In wxWindows 2.0, device contexts are used for drawing into, as per 1.xx, but the way
264they are accessed and constructed is a bit different.
265
266You no longer use {\bf GetDC} to access device contexts for panels, dialogs and canvases.
267Instead, you create a temporary device context, which means that any window or control can be drawn
268into. The sort of device context you create depends on where your code is called from. If
269painting within an {\bf OnPaint} handler, you create a wxPaintDC. If not within an {\bf OnPaint} handler,
270you use a wxClientDC or wxWindowDC. You can still parameterise your drawing code so that it
271doesn't have to worry about what sort of device context to create - it uses the DC it is passed
272from other parts of the program.
273
274You {\bf must } create a wxPaintDC if you define an OnPaint handler, even if you do not
275actually use this device context, or painting will not work correctly under Windows.
276
277If you used device context functions with wxPoint or wxIntPoint before, please note
278that wxPoint now contains integer members, and there is a new class wxRealPoint. wxIntPoint
279no longer exists.
280
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281wxMetaFile and wxMetaFileDC have been renamed to wxMetafile and wxMetafileDC.
282
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283\chapter{Miscellaneous}
284
285\section{Strings}
286
287wxString has replaced char* in the majority of cases. For passing strings into functions,
288this should not normally require you to change your code if the syntax is otherwise the
289same. This is because C++ will automatically convert a char* or const char* to a wxString by virtue
290of appropriate wxString constructors.
291
292However, when a wxString is returned from a function in wxWindows 2.0 where a char* was
293returned in wxWindows 1.xx, your application will need to be changed. Usually you can
294simplify your application's allocation and deallocation of memory for the returned string,
295and simply assign the result to a wxString object. For example, replace this:
296
297{\small\begin{verbatim}
298 char* s = wxFunctionThatReturnsString();
299 s = copystring(s); // Take a copy in case it's temporary
300 .... // Do something with it
301 delete[] s;
302\end{verbatim}
303}
304
305with this:
306
307{\small\begin{verbatim}
308 wxString s = wxFunctionThatReturnsString();
309 .... // Do something with it
310\end{verbatim}
311}
312
313To indicate an empty return value or a problem, a function may return either the
314empty string (``") or a null string. You can check for a null string with wxString::IsNull().
315
316\section{Use of const}
317
318The {\bf const} keyword is now used to denote constant functions that do not affect the
319object, and for function arguments to denote that the object passed cannot be changed.
320
321This should not affect your application except for where you are overriding virtual functions
322which now have a different signature. If functions are not being called which were previously,
323check whether there is a parameter mismatch (or function type mismatch) involving consts.
324
325Try to use the {\bf const} keyword in your own code where possible.
326
327\chapter{Backward compatibility}\label{compat}
328
329Some wxWindows 1.xx functionality has been left to ease the transition to 2.0. This functionality
330(usually) only works if you compile with WXWIN\_COMPATIBILITY set to 1.
331
e2a6f233 332Mostly this defines old names to be the new names (e.g. wxRectangle is defined to be wxRect).
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333
334\chapter{Quick reference}\label{quickreference}
335
336This section allows you to quickly find features that
337need to be converted.
338
339TODO
340
341\section{OnActivate}
342
343Rename to OldOnActivate, or replace arguments with one wxActivateEvent\& argument.
344
345\wxheading{See also}
346
347\helpref{Backward compatibility}{compat}
348
349\section{OnClose}
350
351This can either remain the same as before, or you can add an OnCloseWindow event
352handler using an EVT\_CLOSE event table entry.
353
354\wxheading{See also}
355
356\helpref{Backward compatibility}{compat}
357
358\section{OnMenuCommand}
359
360Rename to OldOnMenuCommand, or replace with a series of functions, one for
361each case of your old switch statement. Create an event table for your frame
362containing EVT\_MENU macros, and insert DECLARE\_EVENT\_TABLE() in your frame class.
363
364\wxheading{See also}
365
366\helpref{Backward compatibility}{compat}
367
368\section{OnSize}
369
370Rename to OldOnSize, or replace arguments with one wxSizeEvent\& argument.
371
372\wxheading{See also}
373
374\helpref{Backward compatibility}{compat}
375
376\section{wxDialog::Show}
377
378If you used {\bf Show} to show a modal dialog, or to override the standard
379modal dialog {\bf Show}, use {\bf ShowModal} instead.
380
381\wxheading{See also}
382
383\helpref{Dialogs and controls}{dialogscontrols}
384
385\end{document}