Position and Acceleration

After an up-down control is created, you can change the control's current position, minimum position, and maximum position by sending messages. You can also change the radix base used to display the current position in the buddy window and the rate at which the current position changes when the up or down arrow is clicked.

To retrieve the current position of an up-down control, use the UDM_GETPOS message. For an up-down control with a buddy window, the current position is the number in the buddy window's caption. Because the caption may have changed (for example, the user may have edited the text of an edit control), the up-down control retrieves the current caption and updates its current position accordingly.

The buddy window's caption may be either a decimal or hexadecimal string, depending on the radix base (that is, either base 10 or 16) of the up-down control. You can set the radix base by using the UDM_SETBASE message and retrieve the radix base by using the UDM_GETBASE message.

The UDM_SETPOS message sets the current position of a buddy window. Note that, unlike a scroll bar, an up-down control automatically changes its current position when the up and down arrows are clicked. An application, therefore, does not need to set the current position when processing the WM_VSCROLL or WM_HSCROLL message.

You can change the minimum and maximum positions of an up-down control by using the UDM_SETRANGE message. The maximum position may be less than the minimum, and in that case clicking the up arrow decreases the current position. To put it another way, up means moving towards the maximum position. To retrieve the minimum and maximum positions for an up-down control, use the UDM_GETRANGE message.

You can control the rate at which the position changes when the user holds down an arrow button by setting the up-down control's acceleration. The acceleration is defined by an array of UDACCEL structures. Each structure specifies a time interval and the number of units by which to increment or decrement at the end of that interval. To set the acceleration, use the UDM_SETACCEL message. To retrieve acceleration information, use the UDM_GETACCEL message.

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