please dont rip this site Prev Next

WM_MOUSEWHEEL Overview  Group

The WM_MOUSEWHEEL message is sent to the focus window when the mouse wheel is rotated. The DefWindowProc function propagates the message to the window’s parent. There should be no internal forwarding of the message, since DefWindowProc propagates it up the parent chain until it finds a window that processes it.

WM_MOUSEWHEEL

fwKeys = LOWORD(wParam);    // key flags

zDelta = (short) HIWORD(wParam);    // wheel rotation

xPos = (short) LOWORD(lParam);    // horizontal position of pointer

yPos = (short) HIWORD(lParam);    // vertical position of pointer

Parameters

fwKeys
Value of the low-order word of wParam. Indicates whether various virtual keys are down. This parameter can be any combination of the following values:

Value

Description

MK_CONTROL

Set if the CTRL key is down.

MK_LBUTTON

Set if the left mouse button is down.

MK_MBUTTON

Set if the middle mouse button is down.

MK_RBUTTON

Set if the right mouse button is down.

MK_SHIFT

Set if the SHIFT key is down.

zDelta
The value of the high-order word of wParam. Indicates the distance that the wheel is rotated, expressed in multiples or divisions of WHEEL_DELTA, which is 120. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user.
xPos
Value of the low-order word of lParam. Specifies the x-coordinate of the pointer, relative to the upper-left corner of the screen.
yPos
Value of the high-order word of lParam. Specifies the y-coordinate of the pointer, relative to the upper-left corner of the screen.

Remarks

The zDelta parameter will be a multiple of WHEEL_DELTA, which is set at 120. This is the threshold for action to be taken, and one such action (for example, scrolling one increment) should occur for each delta.

The delta was set to 120 to allow Microsoft or other vendors to build finer-resolution wheels in the future, including perhaps a freely-rotating wheel with no notches. The expectation is that such a device would send more messages per rotation, but with a smaller value in each message. To support this possibility, you should either add the incoming delta values until WHEEL_DELTA is reached (so for a given delta-rotation you get the same response), or scroll partial lines in response to the more frequent messages. You could also choose your scroll granularity and accumulate deltas until it is reached.

See Also

GetSystemMetrics, mouse_event, SystemParametersInfo 


file: /Techref/os/win/api/win32/mess/src/msg25_28.htm, 4KB, , updated: 2000/4/7 11:20, local time: 2024/11/14 06:25,
TOP NEW HELP FIND: 
44.210.149.218:LOG IN

 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF="http://www.piclist.com/techref/os/win/api/win32/mess/src/msg25_28.htm"> WM_MOUSEWHEEL</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2024 contributors:
o List host: MIT, Site host massmind.org, Top posters @none found
- Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
 

Welcome to www.piclist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .