GDI+ refreshing problem

[torels]

Hi there... How can I prevent a part of a gdi+ graphic from being erased when it gets out of the screen or has a window ontop of it ?

thanks in advance

[Richard Robertson]

You'll have to use a double buffer system. Otherwise you just lose it if you don't hold on to it yourself.

[monoceres]

Hi!

You can't stop it from happening but when it does happen windows send you a message called WM_PAINT. This mean you use GUIRegisterMsg() to know when you need to redraw your graphic. The easiest way to fix this is to draw all your stuff into an memory bitmap and then draw that bitmap into the screen everytime you need to redraw or show something new to the user (aka double buffering).

Here's an example, that also registers WM_PAINT, try dragging it outside the screen

#include <GDIPlus.au3>
#include <WindowsConstants.au3>

$hwnd=GUICreate("Test!",400,300)
GUISetState()

_GDIPlus_Startup()
$graphics=_GDIPlus_GraphicsCreateFromHWND($hwnd)
$bitmap=_GDIPlus_BitmapCreateFromGraphics(400,300,$graphics)
$backbuffer=_GDIPlus_ImageGetGraphicsContext($bitmap)
$brush=_GDIPlus_BrushCreateSolid(0xFFFFFF00)

_GDIPlus_GraphicsClear($backbuffer)
_GDIPlus_GraphicsFillEllipse($backbuffer,10,10,380,280,$brush)
_GDIPlus_GraphicsDrawImageRect($graphics,$bitmap,0,0,400,300)
GUIRegisterMsg($WM_PAINT,"_ReDraw")

Do
Until GUIGetMsg()=-3

Func _ReDraw()
    _GDIPlus_GraphicsDrawImageRect($graphics,$bitmap,0,0,400,300)
EndFunc

[torels]

Thanks Monoceres