Gnuplot display on DomTerm

Thu, 18 Aug 2016 20:45:56 -0700
DomTerm, UI

I have recently spent a lot of time on DomTerm, which is becoming a fairly decent terminal emulator. Being based on HTML5 technologies lets you do many interesting things, including embed graphics. The new qtdomterm standalone terminal emulator is especially nice; alternatively, you can also use the domterm --browser command to start a process that uses a window/tab in your default desktop browser.
The gnuplot package is a powerful graphing package. It has a command-line that lets you specify complicated functions and plots, and then give a plot command to display the resulting plot. Unfortunately, it is difficult to find a a good front-end that is usable for both command-line interaction and graphics. People usually have to specify output to either a file or an external viewer. Would that one could insert the plots directly in the REPL output stream!
The development version of gnuplot (i.e. 5.1, available from CVS) has native support for DomTerm. It has domterm as a new terminal type, which you can select explicitly (with the command set term domterm), or use by default (since gnuplot checks the DOMTERM environment variable, which is set by DomTerm).
This works by using the pre-existing svg output driver to generate SVG, but surrounding the SVG by escape sequences, and then printing the result to standard output. DomTerm recognizes the escape sequence, extracts the SVG (or more generally clean HTML) and inserts it at the cursor.
You can save the session output to an html file. Here is an example. In qtdomterm you can use the File / Save As menu item; otherwise ctrl-shift-S should work. This is a single html file, with embedded SVG; images are embedded with a data: URL. The file is actually XML (xhtml), to make it easier to process. The saved file does need to css and js (JavaScript) files to be readable, so you need to link or copy the hlib directory in the DomTerm source distribution.