DISPLAY: start or stop automatic display of observations

This page is part of the ING document INS-DAS-24: client-server interface for control of cameras

Purpose: control the automatic display of raw observations and processed data.

Actors: udas_display client; udas_camera server; ds9 or saotng image-display.

Outline: the client switches on the display of images; the camera server then sends each image to the display as the image becomes available. Later, the client turns off the display and the server stops sending the images.

Normal course of events:

Client invokes the DISPLAY action on the camera server with these arguments:

Argument1: keyword "input" denoting raw images.
Argument2: keyword "on".

Server validates the command.
Server returns good status for the action to the client.
Client exits in good order.
Each time a raw image becomes available, the camera server sends it to the display.
Later, the client is run again and invokes the DISPLAY action with these arguments:

Argument1: keyword "input" or "output" denoting raw or processed images respectively.
Argument2: keyword "off".

Server validates the command.
Server returns good status for the action to the client.
Server stops sending raw images to the display.

Variations:

In steps 4 and 5, the keyword is "output" instead of "input". Server displays processed data instead of raw data.
Client turns on both the display for both raw and processed images. Server displays both kinds separately, into separate image displays.
Client tries to turn the display on when it is already on or off when it already off. Server handles these commands normally, leaves the display in the requested state, and reports no error.
In step 5, two or more new images are ready for display before the display becomes ready to accept a new image. Server displays only the most-recent image and ignores the others.
For either the raw or the processed images, server cannot contact the appropriate display programme. Server carries on, and tries to make contact again when the next image becomes ready for display, such that the display cycle "picks up" if the display programme is later started up. No errors are reported.