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