help with blitz basic displayadjust
 

hi! i have a problem understanding the displayadjust command on blitz basic

in my proggy i have a bitmap of 512 pixels, but i want to display only 256 of it

so displayadjust is my option

here a snippet of code (for aga machines)


BitMap 2,512,256,8
LoadBitMap 2,"title1.iff",0
.......
InitCopList 0,44,256,$10018,8,256,0
DisplayAdjust 0,-8,16,-16,32,-32
.......
DisplayBitMap 0,2,0,0 ; show the title bitmap

but from the screenshot i have ,the image is 1 pxl left
see the red line on the left
why?

also i cannot understand the fetch parameter on displayadjust, nor the others too :D ehehehe i've experimented a lot :D

http://imageshack.us/a/img21/5623/012jfz.png

The best help you could have about BlitzBasic will be found in this forum:

http://www.amiforce.de/board.php?boa...n1a93pp4clrfag

I'd like help with this command and unfortunately the forum AlfaRomeo recommended seems to be dead.

Anyone? :)

The Amiforce.de forum was moved to amiblitz.de some time ago, but there too seems to be all but dead unfortunately.

The DisplayAdjust command is a little bit like voodoo to me, but it's really just setting some registers (so it's the finer points of using the display hardware registers that are the real voodoo). From what I understand, the command adjusts the standard values, so entering 0 for a register leaves it at the default value for a given display setup.

The registers are explained here:

DDFStart and DDFStop
DIWStrt and DIWStop

The fetch width parameter I'm not so sure about, but I suspect it's just the number of bytes to adjust the overall fetch by. For example, with a display window start adjust of +16 and a stop adjust of 0, that makes the display 16 pixels narrower, or two bytes of fetching per row, requiring the fetch width parameter to be -2.