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Reference for unit 'InterfaceBase' (#lcl)

TWidgetSet.RedrawWindow

Redraws (part of) a window.

Declaration

Source position: winapih.inc line 223

public function TWidgetSet.RedrawWindow(

Wnd: HWND;

lprcUpdate: PRect;

hrgnUpdate: HRGN;

flags: UINT

):Boolean; virtual;

Arguments

`Wnd`		The window to redraw.
`lprcUpdate`		The rectangle to redraw, ignored when a region is given.
`hrgnUpdate`		The region to redraw, can be zero.
`flags`		How the redraw works.

Function result

False on failure.

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.

TWidgetSet.InvalidateRect		Marks a display area for repaint.
TWidgetSet.InvalidateRgn		Marks a display area for repaint.

TWidgetSet.RedrawWindow

Declaration

Arguments

Function result

Description

See also