MGHGRGLAXIS_

MGHGRGLAXIS__DEFINE

Class Name

MGHgrGLaxis

Purpose

This class implements an axis with optional labelling in the gaps
between the major tick marks ("GL" = gaps labelled).
An MGHgrGLaxis intercepts calls to the superclass's Draw method,
at which point it fiddles around to put the gap labels in the
right places & hide the tick labels. So it is called every time
the axis is drawn (which is more often than you might think)
nevertheless the run-time penalty does not seem to be
significant. Subclassing Draw is necessary because some of the
information needed to draw the gap labels is not known until draw
time.

Superclasses

MGHgrAxis.

Properties

The following properties (ie keywords to the Init, GetProperty &
SetProperty methods) are supported in addition to those inherited
from MGHgrAxis:
LABEL_GAPS (Init, Get, Set)
This property determines whether the gaps and/or tick marks are
labelled. Valid values are:
0 - Label tick marks and not gaps, just like MGHgrAxis. This
is the default
1 - Label gaps and not tick marks.
2 - Label gaps and tick marks. This is intended mainly for
debugging.
GAPTEXT (Get)
A string array containing the gap labels, as calculated last
time the axis was drawn.
The following properties are inherited from MGHgrAxis with
additional functionality
TICKFORMAT, TICKFRMTDATA (Init, Get, Set)
If LABEL_GAPS is set to 1 or 2 then these are used for
formatting the gap labels as well as the tick labels.
Another note:
MINOR (Init, Get, Set)
This behaves in exactly the same way as in MGHgrAxis, but
normally if gaps are labelled one would set it to 0.

To Do

Make GAPTEXT a settable property? Do most of the gap-text
calculations when relevant properties are changed, not when the axis
is drawn?
###########################################################################
This software is provided subject to the following conditions:
1. NIWA makes no representations or warranties regarding the
accuracy of the software, the use to which the software may
be put or the results to be obtained from the use of the
software. Accordingly NIWA accepts no liability for any loss
or damage (whether direct of indirect) incurred by any person
through the use of or reliance on the software.
2. NIWA is to be acknowledged as the original author of the
software where the software is used or presented in any form.
###########################################################################

Modification History

Mark Hadfield, 1998-06:
Written.
Mark Hadfield, 2000-05:
Changed method of suppressing the tick-mark labels in the Draw
method. Previously it was done by retrieving the axis's TICKTEXT
object, then setting its STRINGS property to a vector of blank
strings. This was found not to work for vector-output devices,
introduced in IDL 5.3. So, now the tick mark labels are
suppressed by setting the axis's NOTEXT property.
Mark Hadfield, 2000-07:
Code for labelling gaps was overhauled, so that now the gap
labels can be calculated dynamically from corresponding axis
values & optionally formatted with the TICKFORMAT and
TICKFRMTDATA properties.
Mark Hadfield, 2001-11:
- Updated for IDL 5.5.
- Added support for TICKUNITS--only "years" is supported now but
adding the remainder would be trivial.
Mark Hadfield, 2002-04:
- This class was made a subclass of MGHgrMSAxis, not MGHgrAxis.
- Added a boolean value to the class structure to record whether
the gap-text object should be protected from being recreated
at every redraw.
Mark Hadfield, 2004-07:
- Modified to be consistent with the new axis classes. Now
inherits from MGHgrAxis, which includes the master-slave
functionality previously in MGHgrMSAxis.
- GAPTEXT now a string property, as are TITLE and TICKTEXT,
inherited from MGHgrAxis. The associated IDLgrText objects
are handled behind the scenes.
- Supports property sheets.
- IDL 6.0 logical syntax.