The source code is written in 6502 assmebler. In order to compile the source code you need the ADE2 Assembler ROM. Given I wrote this over 30 years ago I don't remember the instructions required to get this to compile using ADE2. The good news is that it is already in compiled binary state. Just download the TTXTED.SSD file and mount that in your BBC emulator.
Quickest way to enter the Mode 7 graphic editor:
- From main menu select G
- Press CTRL + S and that will embed the Teletext colour code in all rows on column 1
- Use the cursor key to move the dot whilst pressing the spacebar to plot
Press CTRL + H for instructions
It is not very clear at first what you need to do but there is a pattern here:
If you plot a point somewhere near the middle of the screen and then move the dot to the left about a quarter way across and then press CTRL + C it'll draw a circle.
Press CTRL + P for parameter page
I'll add more instructions along with screen dumps when I have more time