CGpGraphics.GetHDCmethod

Gets a handle to the device context associated with this **Graphics** object.

Syntax

FUNCTION GetHDC () AS HDC

Description

Gets a handle to the device context associated with this Graphics object.

Remarks

Each call to the GetHDC method of a Graphics object should be paired with a call to the ReleaseHDC method of that same Graphics object. Do not call any methods of the Graphics object between the calls to GetHDC and ReleaseHDC. If you attempt to call a method of the Graphics object between GetHDC and ReleaseHDC, the method will fail and will return ObjectBusy.

Any state changes you make to the device context between GetHDC and ReleaseHDC will be ignored by GDI+ and will not be reflected in rendering done by GDI+.

Example

' ======================================================================================== ' The following function uses GDI+ to draw an ellipse, then uses GDI to draw a rectangle, ' and finally uses GDI+ to draw a line. The function's one parameter is a pointer to a GDI+ ' Graphics object. The code calls the Graphics.DrawEllipse method of that Graphics object ' to draw an ellipse. Next, the code calls the Graphics.GetHDC method to obtain a handle ' to the device context associated with the Graphics object. The code draws a rectangle by ' passing the device context handle to the GDI Rectangle function. The code calls the ' Graphics.ReleaseHDC method of the Graphics object and then uses the Graphics object to ' draw a line. ' ======================================================================================== SUB Example_GetHDC (BYVAL hdc AS HDC)

' // Create a graphics object from the window device context DIM graphics AS CGpGraphics = hdc ' // Get the DPI scaling ratio DIM rxRatio AS SINGLE = graphics.GetDpiX / 96 DIM ryRatio AS SINGLE = graphics.GetDpiY / 96 ' // Set the scale transform graphics.ScaleTransform(rxRatio, ryRatio)

DIM bluePen AS CGpPen = ARGB_BLUE graphics.DrawEllipse(@bluepen, 10, 10, 100, 50) ' // GDI+

DIM hdc2 AS HDC = graphics.GetHDC

' // Make GDI calls, but don't call any methods ' // on graphics until after the call to ReleaseHDC. Rectangle(hdc2, 120 * rxRatio, 10 * rxRatio, 220 * rxRatio, 60 * rxRatio) ' // GDI graphics.ReleaseHDC(hdc)

' // Ok to call methods on graphics again. graphics.DrawLine(@bluePen, 240, 10, 340, 60)

END SUB ' ========================================================================================

Reference

• Include file CGpGraphics.inc
• Defined in AfxNova/CGpGraphics.inc:106
• Documented in Graphics/GdiPlus Classes/CGpGraphics Classes.md
• Topic: CGpGraphics Class