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发信人: Mice (梦), 信区: Programming
标  题: 消息 WM_SETREDRAW   的应用
发信站: 紫丁香 (Mon Sep 22 11:47:27 1997)

                简介�:

   本文从Ask Dr.GUI.#1摘录，介绍了当对列表框同时进行
较多的插入或删除时，如何避免因列表框的过多重画而闪烁。
其中涉及到消息 WM_SETREDRAW ；并且，该消息对所以的
Windows标准Control均起作用�

               正文：
   Using WM_SETREDRAW to Prevent List Box Flashing

Dear Dr. GUI:
   Do you know a method I can use to modify a list box
string without having to use LB_DELETESTRING and then
LB_INSERTSTRING? Deleting and insertin  g causes an
unpleasant repaint of the entire list box, not to mention
the "jump" that takes place between the delete and the
insert messages.

Dr. GUI replies:

   Although Microsoft Windows has no atomic call that
deletes and inserts a string in a list box, you can
prevent the list box from jumping around when you modify
its contents. Take a look at the WM_SETREDRAW message.
Sending this message to the list box with a FALSE value
in wParam prevents the control from updating when you
make changes. Passing a TRUE value reenables these
updates. After you reenable updates, you have to force
the control to redraw. In other words, follow these
steps:

SendMessage(hWndListbox, WM_SETREDRAW, FALSE, 0) ;

/* Modify the control content here. */
SendMessage(hWndListbox, WM_SETREDRAW, TRUE, 0) ;

InvalidateRect(hWndListbox, NULL, FALSE) ;

UpdateWindow(hWndListbox) ;

   By the way, WM_SETREDRAW works on all standard controls,
not only on list boxes.
--

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