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{Event table macros} 20 21To process a paint event, use this event handler macro to direct input to a member 22function that takes a wxPaintEvent argument. 23 24\twocolwidtha{7cm} 25\begin{twocollist}\itemsep=0pt 26\twocolitem{{\bf EVT\_PAINT(func)}}{Process a wxEVT\_PAINT event.} 27\end{twocollist}% 28 29\wxheading{See also} 30 31%\helpref{wxWindow::OnPaint}{wxwindowonpaint}, 32\helpref{Event handling overview}{eventhandlingoverview} 33 34\wxheading{Remarks} 35 36Note that In a paint event handler, the application must {\it always} create a \helpref{wxPaintDC}{wxpaintdc} object, 37even if you do not use it. Otherwise, under MS Windows, refreshing for this and other windows will go wrong. 38 39For example: 40 41\small{% 42\begin{verbatim} 43 void MyWindow::OnPaint(wxPaintEvent& event) 44 { 45 wxPaintDC dc(this); 46 47 DrawMyDocument(dc); 48 } 49\end{verbatim} 50}% 51 52You can optimize painting by retrieving the rectangles 53that have been damaged and only repainting these. The rectangles are in 54terms of the client area, and are unscrolled, so you will need to do 55some calculations using the current view position to obtain logical, 56scrolled units. 57 58Here is an example of using the \helpref{wxRegionIterator}{wxregioniterator} class: 59 60{\small% 61\begin{verbatim} 62// Called when window needs to be repainted. 63void MyWindow::OnPaint(wxPaintEvent& event) 64{ 65 wxPaintDC dc(this); 66 67 // Find Out where the window is scrolled to 68 int vbX,vbY; // Top left corner of client 69 GetViewStart(&vbX,&vbY); 70 71 int vX,vY,vW,vH; // Dimensions of client area in pixels 72 wxRegionIterator upd(GetUpdateRegion()); // get the update rect list 73 74 while (upd) 75 { 76 vX = upd.GetX(); 77 vY = upd.GetY(); 78 vW = upd.GetW(); 79 vH = upd.GetH(); 80 81 // Alternatively we can do this: 82 // wxRect rect(upd.GetRect()); 83 84 // Repaint this rectangle 85 ...some code... 86 87 upd ++ ; 88 } 89} 90\end{verbatim} 91}% 92 93 94\latexignore{\rtfignore{\wxheading{Members}}} 95 96\membersection{wxPaintEvent::wxPaintEvent}\label{wxpainteventctor} 97 98\func{}{wxPaintEvent}{\param{int }{id = 0}} 99 100Constructor. 101 102