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Starbase Graphics

On Hewlett-Packard computers under the HP-UX operating system, Scheme supports graphics through the Starbase graphics library. Note that the default distribution of Scheme for HP computers does not include support for Starbase -- you must rebuild the microcode to get this support.

variable+: starbase-graphics-device-type

This is the device type for Starbase graphics devices. A Starbase device is opened as follows:

(make-graphics-device 'starbase device-name driver-name)

where device-name and driver-name are strings that are used as the device and driver arguments to the Starbase gopen call. The device is opened with kind OUTDEV and mode 0. The device is initialized to have a mapping mode of DISTORT, and a line color index of 1.

operation+: starbase-graphics-device write-image-file filename invert?

This operation writes an image of the Starbase device's display in the file specified by filename. The image is formatted to print on an HP Laserjet printer. Normally pixels with a color index of 0 are not drawn by the printer, and all other pixels are; this results in the background being white and the foreground being black in the printed image. If invert? is not #f, this is reversed: the background is printed as black and the foreground is not printed.

operation+: starbase-graphics-device color-map-size

Returns, as an exact non-negative integer, the number of entries in the color map for the device.

operation+: starbase-graphics-device define-color color-index red green blue

Defines the color associated with the color-map index color-index. Color-index must be an exact non-negative integer strictly less than the number of entries in the color map. Red, green, and blue must be real numbers in the range 0 to 1 inclusive, which define the color to be put in the map.

operation+: starbase-graphics-device set-line-color color-index

Changes the foreground color used in graphics operations for this device. Color-index must be an exact non-negative integer strictly less than the number of entries in the color map. Graphics drawn after this operation is invoked will appear in this new color.

The text drawn by a Starbase device is controlled by the following characteristics:

Aspect

The aspect of a character is its height-to-width ratio, a real number. By default, this has the value 1.

Height

The height of a character in virtual device coordinates, a real number. This is measured along the "up vector", which is defined by the slant of the character. By default, the height is .1.

Rotation

The rotation of a character defines the direction in which the characters are drawn. It is specified as a real number in degrees, but only 4 values have any meaning: 0, 90, 180, and 270. 0 draws left-to-right with upright characters; 90 draws top-to-bottom with characters on their right side; 180 draws right-to-left with upside-down characters; 270 draws bottom-to-top with characters on their left side. The default rotation is 0.

Slant

The slant of a character defines the "up vector"; it is a real number which is the tangent of the angle between the character's "vertical" (defined by the rotation), and the "up vector", measured clockwise. The default slant is 0.

operation+: starbase-graphics-device text-aspect

operation+: starbase-graphics-device text-height

operation+: starbase-graphics-device text-rotation

operation+: starbase-graphics-device text-slant

These operations return the current values of the text characteristics.

operation+: starbase-graphics-device set-text-aspect aspect

operation+: starbase-graphics-device set-text-height height

operation+: starbase-graphics-device set-text-rotation rotation

operation+: starbase-graphics-device set-text-slant slant

These operations alter the current values of the text characteristics. They have no effect on text drawn prior to their invocation.

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