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1\section{\class{wxPaintEvent}}\label{wxpaintevent}
2
3A paint event is sent when a window's contents needs to be repainted.
4
5Please notice that in general it is impossible to change the drawing of a
6standard control (such as \helpref{wxButton}{wxbutton}) and so you shouldn't
7attempt to handle paint events for them as even if it might work on some
8platforms, this is inherently not portable and won't work everywhere.
9
10\wxheading{Derived from}
11
12\helpref{wxEvent}{wxevent}\\
13\helpref{wxObject}{wxobject}
14
15\wxheading{Include files}
16
17<wx/event.h>
18
19\wxheading{Library}
20
21\helpref{wxCore}{librarieslist}
22
23\wxheading{Event table macros}
24
25To process a paint event, use this event handler macro to direct input to a member
26function that takes a wxPaintEvent argument.
27
28\twocolwidtha{7cm}
29\begin{twocollist}\itemsep=0pt
30\twocolitem{{\bf EVT\_PAINT(func)}}{Process a wxEVT\_PAINT event.}
31\end{twocollist}%
32
33\wxheading{See also}
34
35%\helpref{wxWindow::OnPaint}{wxwindowonpaint},
36\helpref{Event handling overview}{eventhandlingoverview}
37
38\wxheading{Remarks}
39
40Note that In a paint event handler, the application must {\it always} create a \helpref{wxPaintDC}{wxpaintdc} object,
41even if you do not use it. Otherwise, under MS Windows, refreshing for this and other windows will go wrong.
42
43For example:
44
45\small{%
46\begin{verbatim}
47 void MyWindow::OnPaint(wxPaintEvent& event)
48 {
49 wxPaintDC dc(this);
50
51 DrawMyDocument(dc);
52 }
53\end{verbatim}
54}%
55
56You can optimize painting by retrieving the rectangles
57that have been damaged and only repainting these. The rectangles are in
58terms of the client area, and are unscrolled, so you will need to do
59some calculations using the current view position to obtain logical,
60scrolled units.
61
62Here is an example of using the \helpref{wxRegionIterator}{wxregioniterator} class:
63
64{\small%
65\begin{verbatim}
66// Called when window needs to be repainted.
67void MyWindow::OnPaint(wxPaintEvent& event)
68{
69 wxPaintDC dc(this);
70
71 // Find Out where the window is scrolled to
72 int vbX,vbY; // Top left corner of client
73 GetViewStart(&vbX,&vbY);
74
75 int vX,vY,vW,vH; // Dimensions of client area in pixels
76 wxRegionIterator upd(GetUpdateRegion()); // get the update rect list
77
78 while (upd)
79 {
80 vX = upd.GetX();
81 vY = upd.GetY();
82 vW = upd.GetW();
83 vH = upd.GetH();
84
85 // Alternatively we can do this:
86 // wxRect rect(upd.GetRect());
87
88 // Repaint this rectangle
89 ...some code...
90
91 upd ++ ;
92 }
93}
94\end{verbatim}
95}%
96
97
98\latexignore{\rtfignore{\wxheading{Members}}}
99
100\membersection{wxPaintEvent::wxPaintEvent}\label{wxpainteventctor}
101
102\func{}{wxPaintEvent}{\param{int }{id = 0}}
103
104Constructor.
105