GetDCEx
The GetDCEx
function retrieves the handle of a display device (DC) context for the
specified window. The display device context can be used in subsequent GDI
functions to draw in the client area.
This function
is an extension to the GetDC
function that gives an application more control over how and whether clipping
occurs in the client area.
HDC
GetDCEx(
|
HWND hWnd, |
// handle of window |
|
HRGN hrgnClip, |
// handle of clip region |
|
DWORD flags |
// device-context creation flags |
|
); |
|
Parameters
hWnd
Identifies
the window where drawing will occur.
hrgnClip
Specifies a
clipping region that may be combined with the visible region of the client
window.
flags
Specifies how
the device context is created. This parameter can be a combination of the
following values:
|
Value |
Meaning |
|
DCX_WINDOW |
Returns a
device context corresponding to the window rectangle rather than the client
rectangle. |
|
DCX_CACHE |
Returns a
device context from the cache, rather than the OWNDC or CLASSDC window.
Essentially overrides CS_OWNDC and CS_CLASSDC. |
|
DCX_PARENTCLIP |
Uses the
visible region of the parent window. The parent s WS_CLIPCHILDREN and
CS_PARENTDC style bits are ignored. The device context origin is set to the
upper-left corner of the window identified by hWnd. |
|
DCX_CLIPSIBLINGS |
Excludes
the visible regions of all sibling windows above the window identified by hWnd. |
|
DCX_CLIPCHILDREN |
Excludes
the visible regions of all child windows below the window identified by hWnd. |
|
DCX_NORESETATTRS |
Does not
reset the attributes of this device context to the default attributes when
this device context is released. |
|
DCX_LOCKWINDOWUPDATE |
Allows
drawing even if there is a LockWindowUpdate6BBZ47 call in effect that would otherwise
exclude this window. Used for drawing during tracking. |
|
DCX_EXCLUDERGN |
The
clipping region identified by hrgnClip is excluded from the visible
region of the returned device context. |
|
DCX_INTERSECTRGN |
The
clipping region identified by hrgnClip is intersected with the visible
region of the returned device context. |
|
DCX_VALIDATE |
When
specified with DCX_INTERSECTUPDATE, causes the device context to be
completely validated. Using this function with both DCX_INTERSECTUPDATE and
DCX_VALIDATE is identical to using the BeginPaint function. |
Return Values
If the
function succeeds, the return value is the handle of the device context for the
given window.
If the
function fails, the return value is NULL. An invalid value for the hWnd
parameter will cause the function to fail.
Remarks
Unless the
display device context belongs to a window class, the ReleaseDC function
must be called to release the device context after painting. Because only five
common device contexts are available at any given time, failure to release a
device context can prevent other applications from accessing a device context.
A device
context belonging to the window s class is returned by the GetDC
function if CS_CLASSDC, CS_OWNDC or CS_PARENTDC was specified as a style in the
WNDCLASS structure when the class was registered.
See Also