Difference between revisions of "Drawing on a panel with a DC"
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* Catch the wxEVT_ERASE_BACKGROUND event | * Catch the wxEVT_ERASE_BACKGROUND event | ||
* See this : http://docs.wxwidgets.org/stable/wx_wxwindow.html#wxwindowsetbackgroundstyle | * See this : http://docs.wxwidgets.org/stable/wx_wxwindow.html#wxwindowsetbackgroundstyle | ||
+ | |||
+ | For all details, see article [[Flicker-Free Drawing]] |
Revision as of 20:21, 21 January 2009
If you want to do drawing using software rendering on a panel, this code snippet should get you started :
#include "wx/wx.h"
#include "wx/sizer.h"
class BasicDrawPane : public wxPanel
{
public:
BasicDrawPane(wxFrame* parent);
void paintEvent(wxPaintEvent& evt);
void paintNow();
void render(wxDC& dc);
// some useful events
/*
void mouseMoved(wxMouseEvent& event);
void mouseDown(wxMouseEvent& event);
void mouseWheelMoved(wxMouseEvent& event);
void mouseReleased(wxMouseEvent& event);
void rightClick(wxMouseEvent& event);
void mouseLeftWindow(wxMouseEvent& event);
void keyPressed(wxKeyEvent& event);
void keyReleased(wxKeyEvent& event);
*/
DECLARE_EVENT_TABLE()
};
class MyApp: public wxApp
{
bool OnInit();
wxFrame *frame;
BasicDrawPane * drawPane;
public:
};
IMPLEMENT_APP(MyApp)
bool MyApp::OnInit()
{
wxBoxSizer* sizer = new wxBoxSizer(wxHORIZONTAL);
frame = new wxFrame((wxFrame *)NULL, -1, wxT("Hello wxDC"), wxPoint(50,50), wxSize(800,600));
drawPane = new BasicDrawPane( (wxFrame*) frame );
sizer->Add(drawPane, 1, wxEXPAND);
frame->SetSizer(sizer);
frame->SetAutoLayout(true);
frame->Show();
return true;
}
BEGIN_EVENT_TABLE(BasicDrawPane, wxPanel)
// some useful events
/*
EVT_MOTION(BasicDrawPane::mouseMoved)
EVT_LEFT_DOWN(BasicDrawPane::mouseDown)
EVT_LEFT_UP(BasicDrawPane::mouseReleased)
EVT_RIGHT_DOWN(BasicDrawPane::rightClick)
EVT_LEAVE_WINDOW(BasicDrawPane::mouseLeftWindow)
EVT_KEY_DOWN(BasicDrawPane::keyPressed)
EVT_KEY_UP(BasicDrawPane::keyReleased)
EVT_MOUSEWHEEL(BasicDrawPane::mouseWheelMoved)
*/
// catch paint events
EVT_PAINT(BasicDrawPane::paintEvent)
END_EVENT_TABLE()
// some useful events
/*
void BasicDrawPane::mouseMoved(wxMouseEvent& event) {}
void BasicDrawPane::mouseDown(wxMouseEvent& event) {}
void BasicDrawPane::mouseWheelMoved(wxMouseEvent& event) {}
void BasicDrawPane::mouseReleased(wxMouseEvent& event) {}
void BasicDrawPane::rightClick(wxMouseEvent& event) {}
void BasicDrawPane::mouseLeftWindow(wxMouseEvent& event) {}
void BasicDrawPane::keyPressed(wxKeyEvent& event) {}
void BasicDrawPane::keyReleased(wxKeyEvent& event) {}
*/
BasicDrawPane::BasicDrawPane(wxFrame* parent) :
wxPanel(parent)
{
}
/*
* Called by the system of by wxWidgets when the panel needs
* to be redrawn. You can also trigger this call by
* calling Refresh()/Update().
*/
void BasicDrawPane::paintEvent(wxPaintEvent& evt)
{
wxPaintDC dc(this);
render(dc);
}
/*
* Alternatively, you can use a clientDC to paint on the panel
* at any time. Using this generally does not free you from
* catching paint events, since it is possible that e.g. the window
* manager throws away your drawing when the window comes to the
* background, and expects you will redraw it when the window comes
* back (by sending a paint event).
*/
void BasicDrawPane::paintNow()
{
wxClientDC dc(this);
render(dc);
}
/*
* Here we do the actual rendering. I put it in a separate
* method so that it can work no matter what type of DC
* (e.g. wxPaintDC or wxClientDC) is used.
*/
void BasicDrawPane::render(wxDC& dc)
{
// draw some text
dc.DrawText(wxT("Testing"), 40, 60);
// draw a circle
dc.SetBrush(*wxGREEN_BRUSH); // green filling
dc.SetPen( wxPen( wxColor(255,0,0), 5 ) ); // 5-pixels-thick red outline
dc.DrawCircle( wxPoint(200,100), 25 /* radius */ );
// draw a rectangle
dc.SetBrush(*wxBLUE_BRUSH); // blue filling
dc.SetPen( wxPen( wxColor(255,175,175), 10 ) ); // 10-pixels-thick pink outline
dc.DrawRectangle( 300, 100, 400, 200 );
// draw a line
dc.SetPen( wxPen( wxColor(0,0,0), 3 ) ); // black line, 3 pixels thick
dc.DrawLine( 300, 100, 700, 300 ); // draw line across the rectangle
// Look at the wxDC docs to learn how to draw other stuff
}
To avoid flickering :
- Try bufferred DCs, they are necessary on some platforms. wxAutoBufferedPaintDC might help you.
- Catch the wxEVT_ERASE_BACKGROUND event
- See this : http://docs.wxwidgets.org/stable/wx_wxwindow.html#wxwindowsetbackgroundstyle
For all details, see article Flicker-Free Drawing