docs/doxygen/overviews/customwidgets.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        customwidgets.h
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // Licence:     wxWindows licence
   6 /////////////////////////////////////////////////////////////////////////////
   7
   8 /**
   9
  10 @page overview_customwidgets Creating a Custom Widget
  11
  12 @tableofcontents
  13
  14 Typically combining the existing @ref group_class_ctrl controls in wxDialogs
  15 and wxFrames is sufficient to fullfill any GUI design. Using the wxWidgets
  16 standard controls makes your GUI looks native on all ports and is obviously
  17 easier and faster.
  18
  19 However there are situations where you need to show some particular kind of
  20 data which is not suited to any existing control. In these cases rather than
  21 hacking an existing control for something it has not been conceived for, it's
  22 better to write a new widget.
  23
  24
  25
  26 @section overview_customwidgets_how Writing a Custom Widget
  27
  28 There are at least two very different ways to implement a new widget.
  29
  30 The first is to build it upon wxWidgets existing classes, thus deriving it from
  31 wxControl or wxWindow. In this way you'll get a @b generic widget. This method
  32 has the advantage that writing a single implementation works on all ports; the
  33 disadvantage is that it the widget will look the same on all platforms, and
  34 thus it may not integrate well with the native look and feel.
  35
  36 The second method is to build it directly upon the native toolkits of the
  37 platforms you want to support (e.g. GTK+, Carbon and GDI). In this way you'll
  38 get a @b native widget. This method in fact has the advantage of a native look
  39 and feel but requires different implementations and thus more work.
  40
  41 In both cases you'll want to better explore some hot topics like:
  42 - @ref overview_windowsizing
  43 - @ref overview_events_custom to implement your custom widget's events.
  44
  45 You will probably need also to gain some familiarity with the wxWidgets
  46 sources, since you'll need to interface with some undocumented wxWidgets
  47 internal mechanisms.
  48
  49
  50
  51 @subsection overview_customwidgets_how_generic Writing a Generic Widget
  52
  53 Generic widgets are typically derived from wxControl or wxWindow.
  54 They are easy to write. The typical "template" is as follows:
  55
  56 @code
  57 enum MySpecialWidgetStyles
  58 {
  59     SWS_LOOK_CRAZY = 1,
  60     SWS_LOOK_SERIOUS = 2,
  61     SWS_SHOW_BUTTON = 4,
  62
  63     SWS_DEFAULT_STYLE = (SWS_SHOW_BUTTON|SWS_LOOK_SERIOUS)
  64 };
  65
  66 class MySpecialWidget : public wxControl
  67 {
  68 public:
  69     MySpecialWidget() { Init(); }
  70
  71     MySpecialWidget(wxWindow *parent,
  72                     wxWindowID winid,
  73                     const wxString& label,
  74                     const wxPoint& pos = wxDefaultPosition,
  75                     const wxSize& size = wxDefaultSize,
  76                     long style = SWS_DEFAULT_STYLE,
  77                     const wxValidator& val = wxDefaultValidator,
  78                     const wxString& name = "MySpecialWidget")
  79     {
  80         Init();
  81
  82         Create(parent, winid, label, pos, size, style, val, name);
  83     }
  84
  85     bool Create(wxWindow *parent,
  86                 wxWindowID winid,
  87                 const wxString& label,
  88                 const wxPoint& pos = wxDefaultPosition,
  89                 const wxSize& size = wxDefaultSize,
  90                 long style = SWS_DEFAULT_STYLE,
  91                 const wxValidator& val = wxDefaultValidator,
  92                 const wxString& name = wxCollapsiblePaneNameStr);
  93
  94     // accessors...
  95
  96 protected:
  97
  98     void Init() {
  99         // init widget's internals...
 100     }
 101
 102     virtual wxSize DoGetBestSize() const {
 103         // we need to calculate and return the best size of the widget...
 104     }
 105
 106     void OnPaint(wxPaintEvent&) {
 107         // draw the widget on a wxDC...
 108     }
 109
 110 private:
 111     DECLARE_DYNAMIC_CLASS(MySpecialWidget)
 112     DECLARE_EVENT_TABLE()
 113 };
 114 @endcode
 115
 116
 117
 118 @subsection overview_customwidgets_how_native Writing a Native Widget
 119
 120 Writing a native widget is typically more difficult as it requires you to know
 121 the APIs of the platforms you want to support. See @ref page_port_nativedocs
 122 for links to the documentation manuals of the various toolkits.
 123
 124 The organization used by wxWidgets consists in:
 125 - declaring the common interface of the control in a generic header, using
 126   the 'Base' postfix; e.g. MySpecialWidgetBase.
 127   See for example the wxWidgets' @c "wx/button.h" file.
 128
 129 - declaring the real widget class inheriting from the Base version in
 130   platform-specific headers; see for example the wxWidgets' @c "wx/gtk/button.h" file.
 131
 132 - separating the different implementations in different source files, putting
 133   all common stuff in a separate source.
 134   See for example the wxWidgets' @c "src/common/btncmn.cpp", @c "src/gtk/button.cpp"
 135   and @c "src/msw/button.cpp" files.
 136
 137 */