docs/latex/wx/upduievt.tex

   1 \section{\class{wxUpdateUIEvent}}\label{wxupdateuievent}
   2
   3 This class is used for pseudo-events which are called by wxWidgets
   4 to give an application the chance to update various user interface elements.
   5
   6 \wxheading{Derived from}
   7
   8 \helpref{wxCommandEvent}{wxcommandevent}\\
   9 \helpref{wxEvent}{wxevent}\\
  10 \helpref{wxObject}{wxobject}
  11
  12 \wxheading{Include files}
  13
  14 <wx/event.h>
  15
  16 \wxheading{Library}
  17
  18 \helpref{wxCore}{librarieslist}
  19
  20 \wxheading{Event table macros}
  21
  22 To process an update event, use these event handler macros to direct input to member
  23 functions that take a wxUpdateUIEvent argument.
  24
  25 \twocolwidtha{7cm}
  26 \begin{twocollist}\itemsep=0pt
  27 \twocolitem{{\bf EVT\_UPDATE\_UI(id, func)}}{Process a wxEVT\_UPDATE\_UI event for the command with the given id.}
  28 \twocolitem{{\bf EVT\_UPDATE\_UI\_RANGE(id1, id2, func)}}{Process a wxEVT\_UPDATE\_UI event for any command with id included in the given range.}
  29 \end{twocollist}
  30
  31 \wxheading{Remarks}
  32
  33 Without update UI events, an application has to work hard to check/uncheck, enable/disable,
  34 show/hide, and set the text for elements such as menu items and toolbar buttons.
  35 The code for doing this has to be mixed up with the code that is invoked when
  36 an action is invoked for a menu item or button.
  37
  38 With update UI events, you define an event handler to look at the state of
  39 the application and change UI elements accordingly. wxWidgets will call your
  40 member functions in idle time, so you don't have to worry where to call this code.
  41 In addition to being a clearer and more declarative method, it also means you
  42 don't have to worry whether you're updating a toolbar or menubar identifier.
  43 The same handler can update a menu item and toolbar button, if the identifier is the same.
  44
  45 Instead of directly manipulating the menu or button, you call functions in the event
  46 object, such as \helpref{wxUpdateUIEvent::Check}{wxupdateuieventcheck}. wxWidgets
  47 will determine whether such a call has been made, and which UI element to update.
  48
  49 These events will work for popup menus as well as menubars. Just before a menu is popped
  50 up, \helpref{wxMenu::UpdateUI}{wxmenuupdateui} is called to process any UI events for
  51 the window that owns the menu.
  52
  53 If you find that the overhead of UI update processing is affecting
  54 your application, you can do one or both of the following:
  55
  56 \begin{enumerate}
  57 \item Call \helpref{wxUpdateUIEvent::SetMode}{wxupdateuieventsetmode} with
  58 a value of wxUPDATE\_UI\_PROCESS\_SPECIFIED, and set the extra style
  59 wxWS\_EX\_PROCESS\_UI\_UPDATES for every window that should receive update events.
  60 No other windows will receive update events.
  61 \item Call \helpref{wxUpdateUIEvent::SetUpdateInterval}{wxupdateuieventsetupdateinterval} with
  62 a millisecond value to set the delay between updates. You may need
  63 to call \helpref{wxWindow::UpdateWindowUI}{wxwindowupdatewindowui} at critical
  64 points, for example when a dialog is about to be shown, in case the user
  65 sees a slight delay before windows are updated.
  66 \end{enumerate}
  67
  68 Note that although events are sent in idle time, defining a wxIdleEvent
  69 handler for a window does not affect this because the events are sent from \helpref{wxWindow::OnInternalIdle}{wxwindowoninternalidle}
  70 which is {\bf always} called in idle time.
  71
  72 wxWidgets tries to optimize update events on some platforms. On Windows
  73 and GTK+, events for menubar items are only sent when the menu is about
  74 to be shown, and not in idle time.
  75
  76 \wxheading{See also}
  77
  78 \helpref{Event handling overview}{eventhandlingoverview}
  79
  80 \latexignore{\rtfignore{\wxheading{Members}}}
  81
  82 \membersection{wxUpdateUIEvent::wxUpdateUIEvent}\label{wxupdateuieventctor}
  83
  84 \func{}{wxUpdateUIEvent}{\param{wxWindowID }{commandId = 0}}
  85
  86 Constructor.
  87
  88 \membersection{wxUpdateUIEvent::CanUpdate}\label{wxupdateuieventcanupdate}
  89
  90 \func{static bool}{CanUpdate}{\param{wxWindow*}{ window}}
  91
  92 Returns {\tt true} if it is appropriate to update (send UI update events to)
  93 this window.
  94
  95 This function looks at the mode used (see \helpref{wxUpdateUIEvent::SetMode}{wxupdateuieventsetmode}),
  96 the wxWS\_EX\_PROCESS\_UI\_UPDATES flag in {\it window},
  97 the time update events were last sent in idle time, and
  98 the update interval, to determine whether events should be sent to
  99 this window now. By default this will always return {\tt true} because
 100 the update mode is initially wxUPDATE\_UI\_PROCESS\_ALL and
 101 the interval is set to 0; so update events will be sent as
 102 often as possible. You can reduce the frequency that events
 103 are sent by changing the mode and/or setting an update interval.
 104
 105 \wxheading{See also}
 106
 107 \helpref{wxUpdateUIEvent::ResetUpdateTime}{wxupdateuieventresetupdatetime},
 108 \helpref{wxUpdateUIEvent::SetUpdateInterval}{wxupdateuieventsetupdateinterval},
 109 \helpref{wxUpdateUIEvent::SetMode}{wxupdateuieventsetmode}
 110
 111 \membersection{wxUpdateUIEvent::Check}\label{wxupdateuieventcheck}
 112
 113 \func{void}{Check}{\param{bool}{ check}}
 114
 115 Check or uncheck the UI element.
 116
 117 \membersection{wxUpdateUIEvent::Enable}\label{wxupdateuieventenable}
 118
 119 \func{void}{Enable}{\param{bool}{ enable}}
 120
 121 Enable or disable the UI element.
 122
 123 \membersection{wxUpdateUIEvent::Show}\label{wxupdateuieventshow}
 124
 125 \func{void}{Show}{\param{bool}{ show}}
 126
 127 Show or hide the UI element.
 128
 129 \membersection{wxUpdateUIEvent::GetChecked}\label{wxupdateuieventgetchecked}
 130
 131 \constfunc{bool}{GetChecked}{\void}
 132
 133 Returns true if the UI element should be checked.
 134
 135 \membersection{wxUpdateUIEvent::GetEnabled}\label{wxupdateuieventgetenabled}
 136
 137 \constfunc{bool}{GetEnabled}{\void}
 138
 139 Returns true if the UI element should be enabled.
 140
 141 \membersection{wxUpdateUIEvent::GetShown}\label{wxupdateuieventgetshown}
 142
 143 \constfunc{bool}{GetShown}{\void}
 144
 145 Returns true if the UI element should be shown.
 146
 147 \membersection{wxUpdateUIEvent::GetSetChecked}\label{wxupdateuieventgetsetchecked}
 148
 149 \constfunc{bool}{GetSetChecked}{\void}
 150
 151 Returns true if the application has called \helpref{wxUpdateUIEvent::Check}{wxupdateuieventcheck}. For wxWidgets internal use only.
 152
 153 \membersection{wxUpdateUIEvent::GetSetEnabled}\label{wxupdateuieventgetsetenabled}
 154
 155 \constfunc{bool}{GetSetEnabled}{\void}
 156
 157 Returns true if the application has called \helpref{wxUpdateUIEvent::Enable}{wxupdateuieventenable}. For wxWidgets internal use only.
 158
 159 \membersection{wxUpdateUIEvent::GetSetShown}\label{wxupdateuieventgetsetshown}
 160
 161 \constfunc{bool}{GetSetShown}{\void}
 162
 163 Returns true if the application has called \helpref{wxUpdateUIEvent::Show}{wxupdateuieventshow}. For wxWidgets internal use only.
 164
 165 \membersection{wxUpdateUIEvent::GetSetText}\label{wxupdateuieventgetsettext}
 166
 167 \constfunc{bool}{GetSetText}{\void}
 168
 169 Returns true if the application has called \helpref{wxUpdateUIEvent::SetText}{wxupdateuieventsettext}. For wxWidgets internal use only.
 170
 171 \membersection{wxUpdateUIEvent::GetText}\label{wxupdateuieventgettext}
 172
 173 \constfunc{wxString}{GetText}{\void}
 174
 175 Returns the text that should be set for the UI element.
 176
 177 \membersection{wxUpdateUIEvent::GetMode}\label{wxupdateuieventgetmode}
 178
 179 \func{static wxUpdateUIMode}{GetMode}{\void}
 180
 181 Static function returning a value specifying how wxWidgets
 182 will send update events: to all windows, or only to those which specify that they
 183 will process the events.
 184
 185 See \helpref{wxUpdateUIEvent::SetMode}{wxupdateuieventsetmode}.
 186
 187 \membersection{wxUpdateUIEvent::GetUpdateInterval}\label{wxupdateuieventgetupdateinterval}
 188
 189 \func{static long}{GetUpdateInterval}{\void}
 190
 191 Returns the current interval between updates in milliseconds.
 192 -1 disables updates, 0 updates as frequently as possible.
 193
 194 See \helpref{wxUpdateUIEvent::SetUpdateInterval}{wxupdateuieventsetupdateinterval}.
 195
 196 \membersection{wxUpdateUIEvent::ResetUpdateTime}\label{wxupdateuieventresetupdatetime}
 197
 198 \func{static void}{ResetUpdateTime}{\void}
 199
 200 Used internally to reset the last-updated time to the
 201 current time. It is assumed that update events are
 202 normally sent in idle time, so this is called at the end of
 203 idle processing.
 204
 205 \wxheading{See also}
 206
 207 \helpref{wxUpdateUIEvent::CanUpdate}{wxupdateuieventcanupdate},
 208 \helpref{wxUpdateUIEvent::SetUpdateInterval}{wxupdateuieventsetupdateinterval},
 209 \helpref{wxUpdateUIEvent::SetMode}{wxupdateuieventsetmode}
 210
 211 \membersection{wxUpdateUIEvent::SetMode}\label{wxupdateuieventsetmode}
 212
 213 \func{static void}{SetMode}{\param{wxUpdateUIMode }{mode}}
 214
 215 Specify how wxWidgets will send update events: to
 216 all windows, or only to those which specify that they
 217 will process the events.
 218
 219 {\it mode} may be one of the following values.
 220 The default is wxUPDATE\_UI\_PROCESS\_ALL.
 221
 222 \begin{verbatim}
 223 enum wxUpdateUIMode
 224 {
 225         // Send UI update events to all windows
 226     wxUPDATE_UI_PROCESS_ALL,
 227
 228         // Send UI update events to windows that have
 229         // the wxWS_EX_PROCESS_UI_UPDATES flag specified
 230     wxUPDATE_UI_PROCESS_SPECIFIED
 231 };
 232 \end{verbatim}
 233
 234 \membersection{wxUpdateUIEvent::SetText}\label{wxupdateuieventsettext}
 235
 236 \func{void}{SetText}{\param{const wxString\&}{ text}}
 237
 238 Sets the text for this UI element.
 239
 240 \membersection{wxUpdateUIEvent::SetUpdateInterval}\label{wxupdateuieventsetupdateinterval}
 241
 242 \func{static void}{SetUpdateInterval}{\param{long }{updateInterval}}
 243
 244 Sets the interval between updates in milliseconds.
 245 Set to -1 to disable updates, or to 0 to update as frequently as possible.
 246 The default is 0.
 247
 248 Use this to reduce the overhead of UI update events if your application
 249 has a lot of windows. If you set the value to -1 or greater than 0,
 250 you may also need to call \helpref{wxWindow::UpdateWindowUI}{wxwindowupdatewindowui}
 251 at appropriate points in your application, such as when a dialog
 252 is about to be shown.
 253