A pane with a sliding marker, which allows the user to control a numerical value within a specified range.
capi
range-pane
titled-object
simple-pane
:print-function |
A function of two arguments, or a format string. |
:show-value-p |
A generalized boolean. |
:start-point |
A keyword. |
:tick-frequency |
An integer, a ratio or the keyword :default . |
slider-print-function
slider-show-value-p
slider-start-point
slider-tick-frequency
The class slider
allows the user to enter a number by moving a marker on a sliding scale to the desired value.
show-value-p determines whether the slider displays the current value, on Microsoft Windows and GTK+. The default value is t
. show-value-p is ignored on Cocoa.
start-point specifies which end of the slider is the start point in the range. The values allowed depend on the orientation of the slider. For horizontal sliders, start-point can take these values:
:left |
The start point is on the left. |
:right |
The start point is on the right. |
:default |
The start point is at the default side (the left). |
For vertical sliders, start-point can take these values:
:top |
The start point is at the top. |
:bottom |
The start point is at the bottom. |
:default |
The start point is at the default position, which is the top on Microsoft Windows and Motif, and the bottom on Cocoa. |
tick-frequency specifies the spacing of tick marks drawn on the slider. If tick-frequency is :default
, then the slider may or may not draw tick marks according the OS conventions. If tick-frequency is 0, then no tick marks are drawn. If tick-frequency is a ratio 1/N for integer N>1, then tick marks are drawn to divide the slider range into N sections. Otherwise tick-frequency should be an integer greater than 1 which specifies the spacing of tick marks in units between start and end. The default value of tick-frequency is :default
.
print-function, when supplied, should be a function with signature:
print-function pane value => result
where pane is the slider pane, value is its current value, and result is a string or nil
. When the slider pane displays the current value, it calls print-function and displays the value as result, unless that is nil
, in which case the value is printed normally.
As a special case, print-function can also be a string, which is used as the format string in a call to format with one additional argument, the value, that is:
(format nil print-function value)
and the result of this call to format is displayed.
:print-function
is not implemented on Motif.:print-function
has no effect on Cocoa because the slider pane never displays the value.slider
without a print-function but set it later, initially you should supply a print-function that always returns nil
, for example:
(make-instance 'capi:slider :start 10 :end 34 :print-function 'false)
slider
are always integers that increase linearly as the slider moves.slider
is displayed (when show-value-p is true) in a tooltip that is visible only while the user moves the marker with a mouse.
In LispWorks 6.0 and earlier versions, ticks are drawn as if tick-frequency is :default
.
Given the default start and end of 0 and 100, this gives ticks at 0, 25, 50, 75 and 100:
(make-instance 'slider :tick-frequency 25)
while this gives ticks at 0, 20, 40, 60, 80 and 100:
(make-instance 'slider :tick-frequency 1/5)
This example illustrates the use of print-function to display fractional and non-linear values ranges:
(example-edit-file "capi/elements/slider-print-function")
CAPI User Guide and Reference Manual (Unix version) - 01 Dec 2021 19:32:42