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1 \chapter{Porting from wxWindows 1.xx}\label{porting}
2
3 This addendum gives guidelines and tips for porting applications from
4 version 1.xx of wxWindows to version 2.0.
5
6 The first section offers tips for writing 1.xx applications in a way to
7 minimize porting time. The following sections detail the changes and
8 how you can modify your application to be 2.0-compliant.
9
10 You may be worrying that porting to 2.0 will be a lot of work,
11 particularly if you have only recently started using 1.xx. In fact,
12 the wxWindows 2.0 API has far more in common with 1.xx than it has differences.
13 The main challenges are using the new event system, doing without the default
14 panel item layout, and the lack of automatic labels in some controls.
15
16 Please don't be freaked out by the jump to 2.0! For one thing, 1.xx is still available
17 and will be supported by the user community for some time. And when you have
18 changed to 2.0, we hope that you will appreciate the benefits in terms
19 of greater flexibility, better user interface aesthetics, improved C++ conformance,
20 improved compilation speed, and many other enhancements. The revised architecture
21 of 2.0 will ensure that wxWindows can continue to evolve for the foreseeable
22 future.
23
24 {\it Please note that this document is a work in progress.}
25
26 \section{Preparing for version 2.0}\label{portingpreparing}
27
28 Even before compiling with version 2.0, there's also a lot you can do right now to make porting
29 relatively simple. Here are a few tips.
30
31 \begin{itemize}
32 \item {\bf Use constraints or .wxr resources} for layout, rather than the default layout scheme.
33 Constraints should be the same in 2.0, and resources will be translated.
34 \item {\bf Use separate wxMessage items} instead of labels for wxText, wxMultiText,
35 wxChoice, wxComboBox. These labels will disappear in 2.0. Use separate
36 wxMessages whether you're creating controls programmatically or using
37 the dialog editor. The future dialog editor will be able to translate
38 from old to new more accurately if labels are separated out.
39 \item {\bf Parameterise functions that use wxDC} or derivatives, i.e. make the wxDC
40 an argument to all functions that do drawing. Minimise the use of
41 wxWindow::GetDC and definitely don't store wxDCs long-term
42 because in 2.0, you can't use GetDC() and wxDCs are not persistent.
43 You will use wxClientDC, wxPaintDC stack objects instead. Minimising
44 the use of GetDC() will ensure that there are very few places you
45 have to change drawing code for 2.0.
46 \item {\bf Don't set GDI objects} (wxPen, wxBrush etc.) in windows or wxCanvasDCs before they're
47 needed (e.g. in constructors) - do so within your drawing routine instead. In
48 2.0, these settings will only take effect between the construction and destruction
49 of temporary wxClient/PaintDC objects.
50 \item {\bf Don't rely} on arguments to wxDC functions being floating point - they will
51 be 32-bit integers in 2.0.
52 \item {\bf Don't use the wxCanvas member functions} that duplicate wxDC functions, such as SetPen and DrawLine, since
53 they are going.
54 \item {\bf Using member callbacks} called from global callback functions will make the transition
55 easier - see the FAQ
56 for some notes on using member functions for callbacks. wxWindows 2.0 will banish global
57 callback functions (and OnMenuCommand), and nearly all event handling will be done by functions taking a single event argument.
58 So in future you will have code like:
59
60 {\small\begin{verbatim}
61 void MyFrame::OnOK(wxCommandEvent& event)
62 {
63 ...
64 }
65 \end{verbatim}
66 }%
67
68 You may find that writing the extra code to call a member function isn't worth it at this stage,
69 but the option is there.
70 \item {\bf Use wxString wherever possible.} 2.0 replaces char * with wxString
71 in most cases, and if you use wxString to receive strings returned from
72 wxWindows functions (except when you need to save the pointer if deallocation is required), there should
73 be no conversion problems later on.
74 \item Be aware that under Windows, {\bf font sizes will change} to match standard Windows
75 font sizes (for example, a 12-point font will appear bigger than before). Write your application
76 to be flexible where fonts are concerned.
77 Don't rely on fonts being similarly-sized across platforms, as they were (by chance) between
78 Windows and X under wxWindows 1.66. Yes, this is not easy... but I think it is better to conform to the
79 standards of each platform, and currently the size difference makes it difficult to
80 conform to Windows UI standards. You may eventually wish to build in a global 'fudge-factor' to compensate
81 for size differences. The old font sizing will still be available via wx\_setup.h, so do not panic...
82 \item {\bf Consider dropping wxForm usage}:
83 wxPropertyFormView can be used in a wxForm-like way, except that you specify a pre-constructed panel
84 or dialog; or you can use a wxPropertyListView to show attributes in a scrolling list - you don't even need
85 to lay panel items out.
86
87 Because wxForm uses a number of features to be dropped in wxWindows 2.0, it cannot be
88 supported in the future, at least in its present state.
89 \item {\bf When creating a wxListBox}, put the wxLB\_SINGLE, wxLB\_MULTIPLE, wxLB\_EXTENDED styles in the window style parameter, and put
90 zero in the {\it multiple} parameter. The {\it multiple} parameter will be removed in 2.0.
91 \item {\bf For MDI applications}, don't reply on MDI being run-time-switchable in the way that the
92 MDI sample is. In wxWindows 2.0, MDI functionality is separated into distinct classes.
93 \end{itemize}
94
95 \section{The new event system}\label{portingeventsystem}
96
97 The way that events are handled has been radically changed in wxWindows 2.0. Please
98 read the topic `Event handling overview' in the wxWindows 2.0 manual for background
99 on this.
100
101 \subsection{Callbacks}
102
103 Instead of callbacks for panel items, menu command events, control commands and other events are directed to
104 the originating window, or an ancestor, or an event handler that has been plugged into the window
105 or its ancestor. Event handlers always have one argument, a derivative of wxEvent.
106
107 For menubar commands, the {\bf OnMenuCommand} member function will be replaced by a series of separate member functions,
108 each of which responds to a particular command. You need to add these (non-virtual) functions to your
109 frame class, add a DECLARE\_EVENT\_TABLE entry to the class, and then add an event table to
110 your implementation file, as a BEGIN\_EVENT\_TABLE and END\_EVENT\_TABLE block. The
111 individual event mapping macros will be of the form:
112
113 \begin{verbatim}
114 BEGIN_EVENT_TABLE(MyFrame, wxFrame)
115 EVT_MENU(MYAPP_NEW, MyFrame::OnNew)
116 EVT_MENU(wxID_EXIT, MyFrame::OnExit)
117 END_EVENT_TABLE()
118 \end{verbatim}
119
120 Control commands, such as button commands, can be routed to a derived button class,
121 the parent window, or even the frame. Here, you use a function of the form EVT\_BUTTON(id, func).
122 Similar macros exist for other control commands.
123
124 \subsection{Other events}
125
126 To intercept other events, you used to override virtual functions, such as OnSize. Now, while you can use
127 the OnSize name for such event handlers (or any other name of your choice), it has only a single argument
128 (wxSizeEvent) and must again be `mapped' using the EVT\_SIZE macro. The same goes for all other events,
129 including OnClose (although in fact you can still use the old, virtual form of OnClose for the time being).
130
131 \section{Class hierarchy}\label{portingclasshierarchy}
132
133 The class hierarchy has changed somewhat. wxToolBar and wxButtonBar
134 classes have been split into several classes, and are derived from wxControl (which was
135 called wxItem). wxPanel derives from wxWindow instead of from wxCanvas, which has
136 disappeared in favour of wxScrolledWindow (since all windows are now effectively canvases
137 which can be drawn into). The status bar has become a class in its own right, wxStatusBar.
138
139 There are new MDI classes so that wxFrame does not have to be overloaded with this
140 functionality.
141
142 There are new device context classes, with wxPanelDC and wxCanvasDC disappearing.
143 See \helpref{Device contexts and painting}{portingdc}.
144
145 \section{GDI objects}\label{portinggdiobjects}
146
147 These objects - instances of classes such as wxPen, wxBrush, wxBitmap (but not wxColour) -
148 are now implemented with reference-counting. This makes assignment a very cheap operation,
149 and also means that management of the resource is largely automatic. You now pass {\it references} to
150 objects to functions such as wxDC::SetPen, not pointers, so you will need to dereference your pointers.
151 The device context does not store a copy of the pen
152 itself, but takes a copy of it (via reference counting), and the object's data gets freed up
153 when the reference count goes to zero. The application does not have to worry so much about
154 who the object belongs to: it can pass the reference, then destroy the object without
155 leaving a dangling pointer inside the device context.
156
157 For the purposes of code migration, you can use the old style of object management - maintaining
158 pointers to GDI objects, and using the FindOrCreate... functions. However, it is preferable to
159 keep this explicit management to a minimum, instead creating objects on the fly as needed, on the stack,
160 unless this causes too much of an overhead in your application.
161
162 At a minimum, you will have to make sure that calls to SetPen, SetBrush etc. work. Also, where you pass NULL to these
163 functions, you will need to use an identifier such as wxNullPen or wxNullBrush.
164
165 \section{Dialogs and controls}\label{portingdialogscontrols}
166
167 \wxheading{Labels}
168
169 Most controls no longer have labels and values as they used to in 1.xx. Instead, labels
170 should be created separately using wxStaticText (the new name for wxMessage). This will
171 need some reworking of dialogs, unfortunately; programmatic dialog creation that doesn't
172 use constraints will be especially hard-hit. Perhaps take this opportunity to make more
173 use of dialog resources or constraints. Or consider using the wxPropertyListView class
174 which can do away with dialog layout issues altogether by presenting a list of editable
175 properties.
176
177 \wxheading{Constructors}
178
179 All window constructors have two main changes, apart from the label issue mentioned above.
180 Windows now have integer identifiers; and position and size are now passed as wxPoint and
181 wxSize objects. In addition, some windows have a wxValidator argument.
182
183 \wxheading{Show versus ShowModal}
184
185 If you have used or overridden the {\bf wxDialog::Show} function in the past, you may find
186 that modal dialogs no longer work as expected. This is because the function for modal showing
187 is now {\bf wxDialog:ShowModal}. This is part of a more fundamental change in which a
188 control may tell the dialog that it caused the dismissal of a dialog, by
189 calling {\bf wxDialog::EndModal} or {\bf wxWindow::SetReturnCode}. Using this
190 information, {\bf ShowModal} now returns the id of the control that caused dismissal,
191 giving greater feedback to the application than just TRUE or FALSE.
192
193 If you overrode or called {\bf wxDialog::Show}, use {\bf ShowModal} and test for a returned identifier,
194 commonly wxID\_OK or wxID\_CANCEL.
195
196 \wxheading{wxItem}
197
198 This is renamed wxControl.
199
200 \wxheading{wxText, wxMultiText and wxTextWindow}
201
202 These classes no longer exist and are replaced by the single class wxTextCtrl.
203 Multi-line text items are created using the wxTE\_MULTILINE style.
204
205 \wxheading{wxButton}
206
207 Bitmap buttons are now a separate class, instead of being part of wxBitmap.
208
209 \wxheading{wxMessage}
210
211 Bitmap messages are now a separate class, wxStaticBitmap, and wxMessage
212 is renamed wxStaticText.
213
214 \wxheading{wxGroupBox}
215
216 wxGroupBox is renamed wxStaticBox.
217
218 \wxheading{wxForm}
219
220 Note that wxForm is no longer supported in wxWindows 2.0. Consider using the wxPropertyFormView class
221 instead, which takes standard dialogs and panels and associates controls with property objects.
222 You may also find that the new validation method, combined with dialog resources, is easier
223 and more flexible than using wxForm.
224
225 \section{Device contexts and painting}\label{portingdc}
226
227 In wxWindows 2.0, device contexts are used for drawing into, as per 1.xx, but the way
228 they are accessed and constructed is a bit different.
229
230 You no longer use {\bf GetDC} to access device contexts for panels, dialogs and canvases.
231 Instead, you create a temporary device context, which means that any window or control can be drawn
232 into. The sort of device context you create depends on where your code is called from. If
233 painting within an {\bf OnPaint} handler, you create a wxPaintDC. If not within an {\bf OnPaint} handler,
234 you use a wxClientDC or wxWindowDC. You can still parameterise your drawing code so that it
235 doesn't have to worry about what sort of device context to create - it uses the DC it is passed
236 from other parts of the program.
237
238 You {\bf must } create a wxPaintDC if you define an OnPaint handler, even if you do not
239 actually use this device context, or painting will not work correctly under Windows.
240
241 If you used device context functions with wxPoint or wxIntPoint before, please note
242 that wxPoint now contains integer members, and there is a new class wxRealPoint. wxIntPoint
243 no longer exists.
244
245 wxMetaFile and wxMetaFileDC have been renamed to wxMetafile and wxMetafileDC.
246
247 \section{Miscellaneous}
248
249 \subsection{Strings}
250
251 wxString has replaced char* in the majority of cases. For passing strings into functions,
252 this should not normally require you to change your code if the syntax is otherwise the
253 same. This is because C++ will automatically convert a char* or const char* to a wxString by virtue
254 of appropriate wxString constructors.
255
256 However, when a wxString is returned from a function in wxWindows 2.0 where a char* was
257 returned in wxWindows 1.xx, your application will need to be changed. Usually you can
258 simplify your application's allocation and deallocation of memory for the returned string,
259 and simply assign the result to a wxString object. For example, replace this:
260
261 {\small\begin{verbatim}
262 char* s = wxFunctionThatReturnsString();
263 s = copystring(s); // Take a copy in case it is temporary
264 .... // Do something with it
265 delete[] s;
266 \end{verbatim}
267 }
268
269 with this:
270
271 {\small\begin{verbatim}
272 wxString s = wxFunctionThatReturnsString();
273 .... // Do something with it
274 \end{verbatim}
275 }
276
277 To indicate an empty return value or a problem, a function may return either the
278 empty string (``") or a null string. You can check for a null string with wxString::IsNull().
279
280 \subsection{Use of const}
281
282 The {\bf const} keyword is now used to denote constant functions that do not affect the
283 object, and for function arguments to denote that the object passed cannot be changed.
284
285 This should not affect your application except for where you are overriding virtual functions
286 which now have a different signature. If functions are not being called which were previously,
287 check whether there is a parameter mismatch (or function type mismatch) involving consts.
288
289 Try to use the {\bf const} keyword in your own code where possible.
290
291 \section{Backward compatibility}\label{portingcompat}
292
293 Some wxWindows 1.xx functionality has been left to ease the transition to 2.0. This functionality
294 (usually) only works if you compile with WXWIN\_COMPATIBILITY set to 1 in setup.h.
295
296 Mostly this defines old names to be the new names (e.g. wxRectangle is defined to be wxRect).
297
298 \section{Quick reference}\label{portingquickreference}
299
300 This section allows you to quickly find features that
301 need to be converted.
302
303 \subsection{Include files}
304
305 Use the form:
306
307 \begin{verbatim}
308 #include <wx/wx.h>
309 #include <wx/button.h>
310 \end{verbatim}
311
312 For precompiled header support, use this form:
313
314 \begin{verbatim}
315 // For compilers that support precompilation, includes "wx.h".
316 #include <wx/wxprec.h>
317
318 #ifdef __BORLANDC__
319 #pragma hdrstop
320 #endif
321
322 // Any files you want to include if not precompiling by including
323 // the whole of <wx/wx.h>
324 #ifndef WX_PRECOMP
325 #include <stdio.h>
326 #include <wx/setup.h>
327 #include <wx/bitmap.h>
328 #include <wx/brush.h>
329 #endif
330
331 // Any files you want to include regardless of precompiled headers
332 #include <wx/toolbar.h>
333 \end{verbatim}
334
335 \subsection{IPC classes}
336
337 These are now separated out into wxDDEServer/Client/Connection (Windows only) and wxTCPServer/Client/Connection
338 (Windows and Unix). Take care to use wxString for your overridden function arguments, instead of char*, as per
339 the documentation.
340
341 \subsection{MDI style frames}
342
343 MDI is now implemented as a family of separate classes, so you can't switch to MDI just by
344 using a different frame style. Please see the documentation for the MDI frame classes, and the MDI
345 sample may be helpful too.
346
347 \subsection{OnActivate}
348
349 Replace the arguments with one wxActivateEvent\& argument, make sure the function isn't virtual,
350 and add an EVT\_ACTIVATE event table entry.
351
352 \subsection{OnChar}
353
354 This is now a non-virtual function, with the same wxKeyEvent\& argument as before.
355 Add an EVT\_CHAR macro to the event table
356 for your window, and the implementation of your function will need very few changes.
357
358 \subsection{OnClose}
359
360 The old virtual function OnClose is now obsolete.
361 Add an OnCloseWindow event handler using an EVT\_CLOSE event table entry. For details
362 about window destruction, see the Windows Deletion Overview in the manual. This is a subtle
363 topic so please read it very carefully. Basically, OnCloseWindow is now responsible for
364 destroying a window with Destroy(), but the default implementation (for example for wxDialog) may not
365 destroy the window, so to be sure, always provide this event handler so it is obvious what's going on.
366
367 \subsection{OnEvent}
368
369 This is now a non-virtual function, with the same wxMouseEvent\& argument as before. However
370 you may wish to rename it OnMouseEvent. Add an EVT\_MOUSE\_EVENTS macro to the event table
371 for your window, and the implementation of your function will need very few changes.
372 However, if you wish to intercept different events using different functions, you can
373 specify specific events in your event table, such as EVT\_LEFT\_DOWN.
374
375 Your OnEvent function is likely to have references to GetDC(), so make sure you create
376 a wxClientDC instead. See \helpref{Device contexts}{portingdc}.
377
378 If you are using a wxScrolledWindow (formerly wxCanvas), you should call
379 PrepareDC(dc) to set the correct translation for the current scroll position.
380
381 \subsection{OnMenuCommand}
382
383 You need to replace this virtual function with a series of non-virtual functions, one for
384 each case of your old switch statement. Each function takes a wxCommandEvent\& argument.
385 Create an event table for your frame
386 containing EVT\_MENU macros, and insert DECLARE\_EVENT\_TABLE() in your frame class, as
387 per the samples.
388
389 \subsection{OnPaint}
390
391 This is now a non-virtual function, with a wxPaintEvent\& argument.
392 Add an EVT\_PAINT macro to the event table
393 for your window.
394
395 Your function {\it must} create a wxPaintDC object, instead of using GetDC to
396 obtain the device context.
397
398 If you are using a wxScrolledWindow (formerly wxCanvas), you should call
399 PrepareDC(dc) to set the correct translation for the current scroll position.
400
401 \subsection{OnSize}
402
403 Replace the arguments with one wxSizeEvent\& argument, make it non-virtual, and add to your
404 event table using EVT\_SIZE.
405
406 \subsection{wxApp definition}
407
408 The definition of OnInit has changed. Return a bool value, not a wxFrame.
409
410 Also, do {\it not} declare a global application object. Instead, use the macros
411 DECLARE\_APP and IMPLEMENT\_APP as per the samples. Remove any occurrences of IMPLEMENT\_WXWIN\_MAIN:
412 this is subsumed in IMPLEMENT\_APP.
413
414 \subsection{wxButton}
415
416 For bitmap buttons, use wxBitmapButton.
417
418 \subsection{wxCanvas}
419
420 Change the name to wxScrolledWindow.
421
422 \subsection{wxDialogBox}
423
424 Change the name to wxDialog, and for modal dialogs, use ShowModal instead of Show.
425
426 \subsection{wxDialog::Show}
427
428 If you used {\bf Show} to show a modal dialog or to override the standard
429 modal dialog {\bf Show}, use {\bf ShowModal} instead.
430
431 \wxheading{See also}
432
433 \helpref{Dialogs and controls}{portingdialogscontrols}
434
435 \subsection{wxForm}
436
437 Sorry, this class is no longer available. Try using the wxPropertyListView or wxPropertyFormView class
438 instead, or use .wxr files and validators.
439
440 \subsection{wxPoint}
441
442 The old wxPoint is called wxRealPoint, and wxPoint now uses integers.
443
444 \subsection{wxRectangle}
445
446 This is now called wxRect.
447
448 \subsection{wxScrollBar}
449
450 The function names have changed for this class: please refer to the documentation for wxScrollBar. Instead
451 of setting properties individually, you will call SetScrollbar with several parameters.
452
453 \subsection{wxText, wxMultiText, wxTextWindow}
454
455 Change all these to wxTextCtrl. Add the window style wxTE\_MULTILINE if you
456 wish to have a multi-line text control.
457
458 \subsection{wxToolBar}
459
460 This name is an alias for the most popular form of toolbar for your platform. There is now a family
461 of toolbar classes, with for example wxToolBar95, wxToolBarMSW and wxToolBarSimple classes existing
462 under Windows 95.
463
464 Toolbar management is supported by frames, so calling wxFrame::CreateToolBar and adding tools is usually
465 enough, and the SDI or MDI frame will manage the positioning for you. The client area of the frame is the space
466 left over when the menu bar, toolbar and status bar have been taken into account.
467