TWidgetSet.RedrawWindow function

Declaration

function RedrawWindow(Wnd: HWND; lprcUpdate: PRECT; hrgnUpdate: HRGN; 
 flags: UINT): Boolean; virtual

Arguments

Function result

Description

All invalidated parts of a window, which deserve an update, are collected in the update region. When this region is not empty, WM_ERASEBKGND, WM_PAINT and WM_NCPAINT messages are sent to the window, as soon as the application is (almost) idle. RedrawWindow can be used to force an immediate redraw instead.

WM_ERASEBKGND is optional, erases the background before painting. WM_NCPAINT paints the non-client areas (borders, caption...), without assistance by user code.

When neither lprcUpdate nor hrgnUpdate are specified, the whole client area of the window is affected. Otherwise the region takes precedence over the rectangle.

Flags specify how the window is invalidated or validated, and when repainting occurs. Flags other than RDW_ERASE may not be supported by all platforms.

To invalidate specify RDW_INVALIDATE, and optionally one of:

RDW_ERASE

Forces a WM_ERASEBKGND message before painting.

RDW_FRAME

Also redraws the window frame, as covered by the update region.

RDW_INTERNALPAINT

Force WM_PAINT even if the update region is empty.

Validation is not implemented for all platforms. To validate, specify RDW_VALIDATE and optionally one of the following:

RDW_NOERASE

Suppress all pending WM_ERASEBKGND messages.

RDW_NOFRAME

Suppress all pending WM_NCPAINT messages.

RDW_NOINTERNALPAINT

Suppress all pending internal WM_PAINT messages.

These flags specify when repainting will occur:

RDW_ERASENOW

Send WM_ERASEBKGND messages before returning.

RDW_UPDATENOW

Send WM_PAINT messages before returning.

The handling of child windows normally depends on the WS_CLIPCHILDREN window style flag. Clipped child windows are not normally affected by RedrawWindow. These flags override:

RDW_ALLCHILDREN

Include all child windows.

RDW_NOCHILDREN

Exclude all child windows.

See also

• InvalidateRect
• InvalidateRgn