3 Using the Widget

If you have the TCL/GWM widget enabled it will be used when any ‘xwindows’ output is produced by a Starlink graphics program, whether the requirement is to display a colour image or a simple line plot.

The TCL/GWM widget can be invoked by the standard graphics system and can be generated with an overlay if required, in the same manner as the standard GWM ‘xwindows’ display. Those graphics programs that automatically generate a display ‘xwindows’ can use the TCL/GWM widget if it is available.

A typical TCL/GWM widget might be generated thus:

where % is the shell prompt. This will generate a widget with 128 colours allocated called xwindows

If you need an overlay plane (e.g. to plot contour maps over images) you can use the -overlay switch:

A full list of the TCL/GWM widget command switches is given in SUN/186.

3.1 The main display window

The main window of the TCL/GWM widget is by default the standard GWM ‘xwindows’ size with buttons along the bottom which activate the facilities available. Along the bottom and down the right side are the scroll bars (a widget with an overlay plane has two sets of scroll bars, the inner set for the overlay and the outer set for the main plotting surface.)

In order across the bottom, the buttons are:

Exit

Press this and the widget will exit.

Colours

Displays the Gwm Colours dialog box that allows you to manipulate the colours on the plotting surface of the widget, including the foreground, background, overlay and crosshair cursor.

Clear

Wipes the plotting surface clean.

Clear Overlay

Wipes the overlay surface clean. This button is only present if you start the TCL/GWM widget with an overlay.

Capture

Displays the Gwm JPEG dialog box that allows you to dump the current plot to a JPEG file.

Print

Displays the Gwm Print dialog box that allows you to dump the current plot to a print file in a number of formats, including PostScript.

Crosshair

Toggles the appearance of the crosshair cursor.

Help

Displays the help text. The help text is essentially the same information provided in this document.

3.2 Colour manipulation

The Gwm Colours dialog box provides a mechanism which allows you to alter the colours on the plotting surface. You can change the colours using the Red, Green and Blue sliders, and you can select which colour or pixel value to alter by selecting the appropriate button.

Checkbuttons

 

Background:

Colour (pixel value) 0 – this is the background colour of the plotting surface.

Foreground:

Colour (pixel value) 1 – this is the foreground colour of the plotting surface.

Other:

This option toggles the Pixel value slider which enables you to select any of the colours or pixel values to change, including 0 (background), 1 (foreground) and the overlay (if you have one enabled).

Overlay:

If you have generated a TCL/GWM widget with an overlay for plotting contours on an image, you can change the colour used for the overlay by selecting the Overlay button.

Crosshair:

This button allows you to modify the colour used to display the crosshair cursor. You don’t have to have the crosshair cursor enabled to set the colour.

Buttons

 

OK:

Closes the Gwm Colours dialogue box.

Help:

Displays this help text.

Sliders

 

Pixel value:

When you have the Other button selected, this slider selects which colour or pixel value is to be modified.

Red, Green, Blue:

These control the intensity of the red, green and blue colour for any given colour (pixel value) previously selected.

The Gwm Colours dialog box can be left on screen while plots are being made to the TCL/GWM widget.

3.3 Capturing the display

The Gwm JPEG dialog box allows you to dump the plot currently on the plotting surface to a named JPEG file. You can also select the image quality.

Slider

 

Image quality:

Selects the quality of the image produced in the JPEG compression. You can vary the quality from 50% to 95% with 95% being the highest quality and therefore largest file.

Checkbutton

 

Progressive:

A ‘progressive’ image is an image that, when loaded by a JPEG viewing program, will be displayed in increasing quality as the viewer program reads more of the file. This is the option to select if the JPEG image is to be used on the World Wide Web.

Entry

 

Filename:

You should type in the name of the file you want to dump into, including the file extension if you want one. JPEG files traditionally have the extension .jpg but this widget does NOT supply any default extension.

Buttons

 

OK:

Start the dump. When the dump is complete, the Gwm JPEG dialog box exits and control is returned to the GWM/TCL widget.

Cancel:

Abandons the Gwm JPEG dialog without dumping to file.

Help:

Displays the help text.

The Filename is the only entry you must fill in, there is no default filename for the dump.

When you have chosen and entered a filename, select the OK button to capture the plot and complete the dump to JPEG file.

3.4 Printing the display

The Gwm Print dialog allows you to create a print file in a specified format with a chosen filename. The file can be printed later on an appropriate printer.

Menu

 

Format:

The format menu gives a choice of various print formats: B/W (greyscale) and colour PostScript, B/W (greyscale) and colour Encapsulated PostScript, and HP InkJet.

Checkbuttons

 

As Window: / Colour:

The two checkbuttons control the background colour of the image as printed. You can chose either the background colour of the image on the plotting surface, or define the colour yourself using the ‘Colour:’ checkbutton, and selecting the required colour in the entry window below. White is the default colour.

Entry

 

Filename:

You can choose the filename to which the print image is dumped. There is no default file extension for any of the Formats – you have complete control of the full filename. The convention is that standard PostScript files are given a .ps extension and Encapsulated PostScript files are given a .eps extension. HP InkJet dump files may be given a .dat extension.

Buttons

 

OK:

Activates the print action and closes the Gwm Print dialogue box.

Cancel:

Exits from the Gwm Print dialog box without creating a print file.

Help:

Displays the help text.

To create a print file, select a format, background colour and filename, then select the OK button. The dump will be started and the control returned to the TCL/GWM widget. While the print is being captured, the Capture and Print buttons on the TCL/GWM widget are greyed out, indicating that the functions are unavailable. When the print capture and dump has completed, the buttons return to normal and it is then OK to send more plotting commands to the widget.