CNumSpinCtrl - a simple numeric spin control

• Download demo project - 23 Kb
• Download source - 4 Kb

Introduction

When I needed a numeric spin control, I searched both CodeGuru and CodeProject. Surprisingly I only found one article by T. VU KHAC on CodeGuru, but as it turned out his CNumSpinCtrl could only be used in pair with CNumEdit which was too restrictive for my purposes. So I ended up writing my own numeric spin control.

CNumSpinCtrl allows you to work with non-integer numbers quite easily. It provides methods to set up value range, increment, and current position. It also lets you format the output value either by specifying number of decimal places or by providing your own formatting string.

Usage

Using the control is not much different from using CSpinButtonCtrl. You would subclass a dialog item or create the control dynamically. Then all you need to do is to set up range and position and, if necessary, the output formatting. Here’s an example from the demo project:

BOOL CCNumSpinCtrlDemoDlg::OnInitDialog()
{
        CDialog::OnInitDialog();
        
        m_spinValue.SetDecimalPlaces (3);
        m_spinValue.SetTrimTrailingZeros (FALSE);
        m_spinValue.SetRangeAndDelta (0.1, 1.0, 0.05);
        m_spinValue.SetPos (0.5);
...

There one thing to watch out however - style. Make sure you uncheck the "Set buddy integer" style or, if you are creating control dynamically, do not add UDS_SETBUDDYINT style. Otherwise the Windows automatically resets buddy's value to some integer when user clicks up/down arrows.

Formatting

There are two ways to format the output value: by specifying a number of decimal places or by providing a formatting string. With the first method you will specify number of decimal places with a call to SetDecimalPlaces function. Passing -1 to this function will turn off rounding to decimal places (the value will be output with "%g" format string). You can also specify whether you want to trim any trailing zeros with a call to SetTrimTrailingZeros. With a second method you simply provide your own formatting string, which later will be used with CString’s Format function. Example:

SetFormatString ("%.2e")

Remarks

Be sure to set appropriate formatting settings. If your formatting settings are inadequate for the current range and increment, the text in the buddy control may not change at all. For example, if you set the increment to be 0.005, but the number of decimal places only to 1, the value in buddy control will not change when a user clicks on up and down arrows. This is because the control does not keep the current value internally. The value is obtained from the buddy control before it is incremented or decremented. Then it is formatted and passed back to the buddy control. So the formatting settings are quite important.

Revisions