Name: Trace Hook
Hook Pointer Block Address: 9BA8
Hook Enable BCALL: 4FF3
Hook Disable BCALL: 4FF6
Hook Call BCALL: 4FF9
Hook Active Flag: 0, (iy + 36h)
This hook allows you to change the actions that happen when tracing a graph.
Using the Hook
These different values, passed in a, determines what the hook should do.
- 0: Unknown what this is used for, but it's called between the a=1 and a=4 hookcalls.
- b: contains the function that will be graphed y1=01 .. y0=0A or x1=01.. x6=06 or r1=01 .. r6=06 or u=01 .. w=03.
- 1: The trace cursor will move.
- Zero flag: clear to abort the move.
- 2: The trace cursor wants to move outside the screen and thus the graph will be (partially) redrawn.
- 3: The trace cursor blinks.
- Zero flag: Clear to stop the blinking
- 4: The trace cursor is (re)drawn
- Zero flag: Clear to abort the drawing of the cursor. (The blinking pixel in the middle will still blink at the position the cursor wasn't drawn)
This documentation is probably incomplete.