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General description

Description

This tool is a fundamental component of the Viewer tool. It provides a drawing area (or ``canvas'') on which Viewerdisplaydata tools can draw themselves. Multiple Viewerdisplaypanel tools can be placed on the screen, and each can have multiple Viewerdisplaydata tools registered to draw themselves. In this way, for example, multiple views of the same data can be simultaneously displayed, and contour Viewerdisplaydata tools can be drawn ``on top'' of raster Viewerdisplaydata tools, for example. Exact copies of Viewerdisplaypanel tools can be written to X11 Pixmap files, and high-quality PostScript representations of Viewerdisplaypanel tools can be saved and printed.

Viewerdisplaypanel tools can be adorned with various graphical user interface components, including a ``controlbox'' which allows the user to select controls like zooming and colormap fiddling, and a ``tapedeck'' which enables the user to manually or automatically move through data having more than two (non-redundant) axes.

Three points related to the registration of Viewerdisplaydata tools on Viewerdisplaypanel tools are worth making here:

1.

The order of registration of Viewerdisplaydata tools on a specific Viewerdisplaypanel tool is important. The maximum area of sky, or position-velocity space, or of whatever coordinate system is being used, is determined solely by the first registered Viewerdisplaydata tool. All other Viewerdisplaydata tools registered for display on a particular Viewerdisplaypanel tool simply draw those parts of their data which ought to be visible on the Viewerdisplaypanel tool. A consequence of this is that the zoom setting of the Viewerdisplaypanel tool must be reset to the full view whenever the first registered Viewerdisplaydata tool is removed, replaced, or re-read. Independent of the order in which Viewerdisplaydata tools are registered on a given Viewerdisplaypanel tool, the raster-type Viewerdisplaydata tools are always drawn first, followed by contours, and lastly axis labels.

2.

Axis labels are drawn by Viewerdisplaydata tools, and only by the first registered Viewerdisplaydata tool. In the Viewer tool, axis labelling information belongs to the Viewerdisplaydata tools rather than to the Viewerdisplaypanel tools, which is commonly seen in other applications. This is because the only entity which knows exactly how to draw the axis labels for a particular piece of data is the Viewerdisplaydata tool which draws the data itself. Control over the appearance of axis labels is therefore available via the individual Viewerdisplaydata tools.

3.

Registering a specific Viewerdisplaydata tool on more than one Viewerdisplaypanel tool can reduce display efficiency. The drawings made of data by a Viewerdisplaydata tool are cached, so that they only need to be recalculated under various circumstances, such as the settings for the Viewerdisplaydata tool changing, or the size of the Viewerdisplaypanel tool on which they are drawing changing. The caching will in general fail to operate efficiently if a Viewerdisplaydata tool is registered on more than Viewerdisplaypanel tool. This is best avoided by making another Viewerdisplaydata tool from the same dataset, and registering this second tool on the second Viewerdisplaypanel tool.

Additional to the tool functions described for the Viewerdisplaypanel tool, this tool also possesses the tool functions described in the Viewerstandardgui interface documentation. Note that some functions may not be documented and therefore shouldn't be used unless you really know what you are doing.