ScrollWindowEx

This function scrolls the content of the specified windows client area.

int ScrollWindowEx( 
HWND hWnd, 
int dx, 
int dy, 
const RECT *prcScroll, 
const RECT *prcClip, 
HRGN hrgnUpdate, 
LPRECT prcUpdate, 
UINT flags ); 

Parameters

• hWnd
  Handle to the window where the client area is to be scrolled.
• dx
  Specifies the amount, in device units, of horizontal scrolling. This parameter must be a negative value to scroll to the left.
• dy
  Specifies the amount, in device units, of vertical scrolling. This parameter must be a negative value to scroll up.
• prcScroll
  Pointer to the RECT structure specifying the portion of the client area to be scrolled. If this parameter is NULL, the entire client area is scrolled.
• prcClip
  Pointer to the RECT structure containing the coordinates of the clipping rectangle. Only device bits within the clipping rectangle are affected. Bits scrolled from the outside of the rectangle to the inside are painted; bits scrolled from the inside of the rectangle to the outside are not painted.
• hrgnUpdate
  Handle to the region that is modified to hold the region invalidated by scrolling. This parameter may be NULL.
• prcUpdate
  Pointer to the RECT structure receiving the boundaries of the rectangle invalidated by scrolling. This parameter may be NULL.
• flags
  Specifies flags that control scrolling. This parameter can be one of the following values:

  Value	Description
  SW_ERASE	Erases the newly invalidated region by sending a WM_ERASEBKGND message to the window when specified with the SW_INVALIDATE flag.
  SW_INVALIDATE	Invalidates the region identified by the hrgnUpdate parameter after scrolling.
  SW_SCROLLCHILDREN	Scrolls all child windows that intersect the rectangle pointed to by the prcScroll parameter. The child windows are scrolled by the number of pixels specified by the dx and dy parameters. The system sends a WM_MOVE message to all child windows that intersect the prcScroll rectangle, even if they do not move.

Return Values

COMPLEXREGION indicates that the region consists of more than one rectangle. ERROR indicates that an error occurred. NULLREGION indicates that the region is empty. SIMPLEREGION indicates that the region is a single rectangle. To get extended error information, call GetLastError.

Remarks

Only one of the dx and dy parameters can be nonzero.

If the SW_INVALIDATE and SW_ERASE flags are not specified, ScrollWindowEx does not invalidate the area that is scrolled from. If either of these flags is set, ScrollWindowEx invalidates this area. The area is not updated until the application calls the UpdateWindow function or retrieves the WM_PAINT message from the application queue.

If the SW_SCROLLCHILDREN flag is specified, the system does not properly update the screen if part of a child window is scrolled. The part of the scrolled child window that lies outside the source rectangle is not erased and is not properly redrawn in its new destination. To move child windows that do not lie completely within the rectangle specified by prcScroll, use the DeferWindowPos function. The cursor is repositioned if the SW_SCROLLCHILDREN flag is set and the caret rectangle intersects the scroll rectangle.

If the window has the WS_CLIPCHILDREN style, the returned areas specified by hrgnUpdate and prcUpdate represent the total area of the scrolled window that must be updated, including any areas in child windows that need updating.

All input and output coordinates (for prcScroll, prcClip, prcUpdate, and hrgnUpdate) are determined as client coordinates, regardless of whether the window has the CS_OWNDC or CS_CLASSDC class style.

Requirements

Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

DeferWindowPos, GetLastError, RECT, ScrollDC, UpdateWindow

 Last updated on Tuesday, July 13, 2004

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