WxWidgets lesson 13 wxMemoryDC uses cached DC rendering
Description
Using wxMemoryDC rendering, you can reduce flicker, and when the rendering is complete, paste the content onto the target DC, where wxBitmap is needed as the canvas. The effect is equivalent to using wxBufferedPaintDC, but wxBufferedPaintDC is limited to use in OnPaint functions
Code
WxRect rect = GetClientRect ()
Int width = rect.GetWidth ()
Int height = rect.GetHeight ()
WxMemoryDC memDC
WxBitmap bitmap (width, height)
MemDC.SelectObject (bitmap)
MemDC.SetBackground (* wxWHITE_BRUSH)
MemDC.Clear ()
MemDC.SetPen (* wxRED_PEN)
MemDC.SetBrush (* wxRED_BRUSH)
MemDC.DrawRectangle ((wxRect (0,10, width, 100))
WxClientDC destDC (this)
DestDC.Blit (0,0
Bitmap.GetWidth (), bitmap.GetHeight ()
& memDC
0, 0
WxCOPY
True)
MemDC.SelectObject (wxNullBitmap)
A reminder
By default, the memDC background is black
WxScreenDC screen device environment
Description
WxScreenDC supports drawing graphics outside the program window and rendering in other DC, aiming at the client area of the program, not the screen. In order to map points to the screen, you need to use the ClientToScreen function to convert coordinates.
Code
WxPoint pt = ClientToScreen (GetPosition ())
Pt.x = pt.x + GetSize () .GetWidth ()
Pt.y = pt.y + GetSize () .GetHeight ()
WxSize size (100,100)
WxRect rect (pt, size)
WxScreenDC dc
Dc.SetPen (wxPen (* wxLIGHT_GREY, 2, wxSOLID))
/ / dc.SetBrush (* wxTRANSPARENT_BRUSH)
Dc.SetBrush (wxBrush (* wxBLACK))
Dc.DrawRectangle (rect)
WxClientDC wxPaintDC
Description
WxClientDC allows access to the device environment handle in the client area outside the OnPaint event, and you can see from the erase background event that wxPaintDC is in the OnPaint event
Device environment handle for internal access to the client area
Here we need to explain the client area: for a control, the size of the client area is the size of the control itself. If you customize the OnPaint event, it is only rendered within the control area. For windows, the client area does not include the title bar, menu bar, status bar and toolbars, and certainly does not include borders (this is important for dragging borders to zoom in at any time)
