XeO3: Bloody bugs!!!

I've been writing the cache code, and its simple enough, but theres a bug in it, and I can't for the life of me find it!! So I thought I'd post it here to see if anyones got any ideas. I suspect I've just been looking at it too much; not that that helps me of course! Anyway, its a simple linked list but the indexes are all +1 so that 0 specifies the end of the list. To offset this I simply subtract 1 from the address to the links which allows the normal use again. Anyway, heres to code....

        ;
        ; Y = rotation index
        ; Temp+16 = pointer to the raw sprite info with an 
        ;           8 byte cache index table
        ;
        lda  (Temp+16),y       ; get cache index using the current rotation index
        tay                    ; into the sprite cache index list
        ldx  Cache_Next-1,y    ; If we are last, then do nothing!!!
        beq  Skip_MoveToEnd
        lda  Cache_Prev-1,y    ; get the PREV from our current cache block
        sta  Cache_Prev-1,x    ; and store in the NEXT's Prev
  
        ; We've now unlinked from the NEXT item, unlink from PREV item
    
        tax                    ; and set the PREV of our new one to the OLD last.
        beq  !We_are_First
        lda  Cache_Next-1,y
        sta  Cache_Next-1,x
        bne  !SkipFirst
 
!We_are_First:
        ldx  Cache_Next-1,y
        stx  FirstCache
        lda  #$00
        sta  Cache_Prev-1,x
  
!SkipFirst:
        ; Now link the cache block to the end
        lda  #0
        sta  Cache_Next-1,y     ; get the PREV from our current cache block
        lax  LastCache
        sta  Cache_Prev,y       ; Set the LAST entry as our prev.
        tya
        sta  Cache_Next-1,x     ; and set the last entry's NEXT as our new item
        sta  LastCache          ; now set thr NEW last as the new item.
Skip_MoveToEnd:  

So.... There you go! If you spot anything, let me know - while I've still got hair!

XeO3: Microcoding

I've spent a very pleasent day slowly shifting through the sprite source and doing some micro optimisations; that is removing unneeded instructions and the odd cycle here and there. It'll have no huge impact, but it might help compensate for when I do the cache linking everyframe. The idea (as Ive said before) is when a frame from the cache is used, I remove it from the linked list, and add it to the bottom again (the end). This keeps used ones in the list, and unused ones drift to the top.

So, now I've dont this, I'll go and put the code in to actually use the cache properly and see how it all holds together.

XeO3: Working Lunch!

The great thing about owning my own laptop is I can put the code onto it and bring it into work so I can play with it at lunchtime - fab! So, I've made the change where by I now no longer have a bitmask marking the rotations that have been cached, I now just use the cache index value directly and if its 0, then its not cached. This works great, and frees up 167 bytes (space for 4 more sprites!) Not that you really seed a speed up, but I know its a little quicker, so thats nice.

The next thing to do is to try and finally make the cache work the way its supposed to! This simply means keeping commonly used rotations in there, and letting ones I don't use much drift to the top of the free list - I hope to do that later tonight.

XeO3: Sprite time...

So I'm sitting here fixing the damage I did while debugging last night, and it occurs to me that Im wasting time and memory with my sprite system - again; although not much of either this time.....

I currently store a bitmask to tell me if a rotation is cached, and an index which points to it - like this

     db   BitMask      ; 1 bit per rotation. In MCM mode, ever other bit is unused.
     db   Rotation1_Index
     db   Rotation2_Index
     db   Rotation3_Index
     db   Rotation4_Index
     db   Rotation5_Index
     db   Rotation6_Index
     db   Rotation7_Index
     db   Rotation8_Index
     ds   32           ; Raw Sprite Graphic

Now, before I changed everything to indexes, the bitmask made sense, as it was quicker to check than the address. But now.... All I need to do is load the rotation index data and see if its 0. This will save 167 bytes, and all the time I spend masking the rotation flags. It will also help me speed up the cache itself - a little.

Classic retro music on a HUGE scale....

This has to be seen (and heard) to be believed.... Not only does it look pretty cool, but its actually playing music! Click HERE to see it... Theres a tune in there I recognise, but cant place....yet.....

While we're at it... heres another scary image....

Edit: TETRIS!!! Thats it!!!

XeO3: Success!!!

At last!!! Found the little ******!!!!

After a really painful debug session with Yape (he really needs to make his debugger more usable!!!) I finally tracked the problem down to..........The player ship sprite! Yep... nothing to do with the cache at all - well, not really. It was the sprite rendering that fried the memory, but that was only because the player ship pointers had been nuked! Funny....Im sure this was the same bad bug as last time...I wonder if the fix got lost, I'll have to check my source control logs... Anyway, the fix was just 3 lines!

          lda   PlayerAnims
          ldx   #0
          jsr   SetSpriteShape

So...there we go... Crappy nights work, but worth it in the end. I'm thinking about releasing the current minus4, as its debugger is much nicer than anything else out there, and really helps.

Edit: Yep...it appears I only half fixed this the last time. I was drawing a bad sprite last time, and now it just killed it dead! Oh well...all fixed.

XeO3: Problems....problems................problems

Still no advance on this graphics corruption and crash; I spent all of last night looking through code and playing with Minus4 to try and replicate the bug there, all with no luck. I still think it's to do with the new sprite cache initialisation code because if I run it once only, it seems to be fine. Problem is, the code looks okay to me, which means I'll have to step through all 137 sprite slots being initialised.

You know in a way, this restores my faith in development. When I started this, I had come to the conclusion that either I'd just gotten way better than when I was doing this stuff profesionally, or things were just not that hard now. But this shows that really nasty bugs can still rear their ugly heads, and are still a fag to track down. Thats not to say that its not easier over all - if I hadn't improved in the 18 years I've been doing this for a living, I'd be really worried!

XeO3: Damn bugs.......

I'm still trying to find this bug, and without much luck. I thought I'd found it earlier, but no joy. I'm fairly sure its something to do with the new cache, but I just can't track it down. If I could get it to do the same in Minus4, I could debug it properly, but it runs okay there; that leads me to think its hitting an undocumented opcode that yape and a real Plus4 won't do, but that Minus 4 does do. When adding the codes, I just added them all....I didnt really stop to think that it might not work on the actual machine. I hope to build a new version of Minus4 tomorrow without the undocumented op's - or rather without all the extra ones XeO3 doesn't use.

RetroEdit: reliving the past....

I was busy building a shed today, so I didn't get much done, but I did have a look trough the source of RetroEdit and wasn thinking that it needs cleaned up a bit. I started to write this right back when I was only just starting to use C#, and it shows. I currently use it day-to-day at work so I know a lot more about it, and I can make it much nicer inside. So I may try and clean uo the code before extending it in the near future - like putting editing in for example.....

XeO3: damn.....damn........................damn....

Just proves you should never say "finished" on anything.... After assuming I'd fixed all bugs, a real topper comes along and kicks me on my arse! After a couple of restarts (and this varies!) it looks like theres MAJOR corruption going on, and its killing all the graphics. The game itself looks like its playing away fine, but graphics (sprites, backgrounds and everything else) looks like they've been tosted by something. I can't get this to happen in Minus4, only Yape and on a real machine, so it looks like it'll be a bugger to find.

Damn.....damn..................................damn.