Linking VBL interrups under the system

[Photon]

Hm. I'm doing a bootblock where I

1. Start my own copper
2. Start a Vblank interrupt which fades a logo in, WHILE
3. I load sectors with Exec/DoIo()

Problem is, DoIo seems to need the system's Vblank int on to load, because if I just set my own int, the logo fades in nicely, but nothing is loaded.

If I don't set my fade int, tracks load nicely.


I tried putting a JMP at the end of my int that jumps to the old system interrupt address (JUST AS AN EXPERIMENT, OK? ), and then the tracks load nicely, but my fade interrupt routine is never heard from again. I guess the system sets the Vblank interrupt address back.

Anyway I have a big hunch that using jumps is hardly the correct way of "adding" a small routine to the system Vblank.

So my question is: how do I add my little fade routine to the system vblank interrupt structure? Just inserting a little JSR into the 'chain' (preferably last)would do.

[Photon]

DOH!

Problem solved, just a stupid bug. (So stupid I won't tell you what it was. Never code when you're tired )

Found the bug AFTER I managed to find out how to chain ints on my own, of course.

Anyway here's the code to add an extra subroutine on the system Vblank chain:

AddInt:	move.l 4.w,a6
	lea IntStruct(PC),a1
	moveq #5,d0		;Interrupt number 0-15. 5=INTB_VERTB
	jsr -$a8(a6)		;AddIntServer
;---------------------------------
IntStruct:
.Node:
.succ:	dc.l 0
.pred:	dc.l 0
.type:	dc.b 2		;node type. 2=NT_INTERRUPT
.pri:	dc.b -60	;priority, -60=Low
.name:	dc.l MyName
.Data:	dc.l 0		;int. data ptr
.Code:	dc.l MyInt	;int. routine address. set d0=0 and rts at end of it
MyName:	dc.b "PhotonsInt",0
EVEN
;---------------------------------
MyInt:
	movem.l d1-a6,-(SP)    ;a1 points to interrupt data 
	;-----int code------
	movem.l (SP)+,d1-a6
	moveq #0,d0
	RTS

Note that this is how you do it under the controlled circumstances of the bootblock on an A500. To use it for a system utility or something you would allocate memory for the interrupt routine and structure, and clean up after yourself when you're done, i.e. RemIntServer() and deallocate memory. Use includes instead of the typed constants here on anything above Kick 1.3.