the special-value text
If set, the spin box will display this text instead of a numeric value whenever the current value is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.
For example, if your spin box allows the user to choose a scale factor (or zoom level) for displaying an image, and your application is able to automatically choose one that will enable the image to fit completely within the display window, you can set up the spin box like this:
widgets/spinboxes/window.cpp zoomSpinBox setValue
The user will then be able to choose a scale from 1% to 1000% or select "Auto" to leave it up to the application to choose. Your code must then interpret the spin box value of 0 as a request from the user to scale the image to fit inside the window.
All values are displayed with the prefix and suffix (if set), except for the special value, which only shows the special value text. This special text is passed in the QSpinBox::valueChanged() signal that passes a QString.
To turn off the special-value text display, call this function with an empty string. The default is no special-value text, i.e. the numeric value is shown as usual.
If no special-value text is set, specialValueText() returns an empty string.