Axis Widget Class
Overview
An Axis widget can be used to provide horizontal or vertical annotation for one
or more widgets. The Axis widget can display an axis line, major and minor tick
marks, major and minor tick mark labels, auxiliary annotation and a title
label. The annotation and tick marks can be scrolled when the associated widget
is scrolled.
The displayable range of tick mark labels is defined by the starting and ending
values of the Axis widget. The displayable size of the Axis widget is defined
by its virtual length in pixels. The range of numbers displayed at a given time
is defined by the virtual position in pixels and the width (horizontal Axis) or
height (vertical Axis) in pixels of the widget window.
Using the Axis Widget with the Grid Class
The Grid class already provides one level of vertical and horizontal annotation
(labeled tick marks). The Axis widget can be used when additional levels of
annotation are required. The Grid class provides a set of constraint resources
to position Axis children.
Creating an Axis Widget
An application creates an Axis widget as a child of a Grid widget. The Grid
widget class defines constraint resources used to position the Axis widget.
Graphic Attributes
The appearance of an Axis widget can be customized extensively. Resources are
provided to set the appearance (solid or 3D), the size and color of the axis
line and tick marks. The annotation label font, color and orientation can also
be set using the widget resources.
Scale
The Axis widget can use a linear or logarithmic scale. Other non-linear scales
can be displayed by specifying an array of annotation labels and user defined
locations using the auxiliary set of resources.
Axis Thumb
The thumb of a scrolled Axis widget is the visible part of the Axis, and thus
the thumb size is equal to the width (horizontal Axis) or the height (vertical
Axis) of the Axis window. The thumb size is always less than or equal to the
virtual length of the Axis widget.
Floating Point Resources
The Axis widget defines floating point resources such as XmNminorIncrement and
XmNmajorIncrement. The Xt library does not support floating point resources,
and thus, those resources must be passed as an address rather than a value.
Floating point resources can also be retrieved using the XtGetValues function.
Similar to the function XtSetValues, you must specify the address of the
floating point value in the XtSetArg or XtVaGetValues call. The floating point
value returned is equal to constant XintUNDEFINED_FLOAT if the value of the
resource is not defined.
Axis Widget Appearance
Below are two examples of the visual appearance of the Axis widget. The first
example uses a linear scale, the second a logarithmic scale.
Figure 4: Linear Axis.
Figure 5: Logarithmic Axis.