Underscanned screen?

[Samurai_Crow]

Is it possible to get OpenScreenTags() to yield narrow screens? I'm trying to mirror a 2 bitplane interleaved screen 64 pixels across and use the rest of the width as display dma.

[meynaf]

You can open screens with almost any size. If it refuses to use the dimensions you set, try using SA_DClip entry in your tag list.

Be awared, though, that :
1) Low res screens narrower than 64 pixels will not display properly (seems fixed in OS 3.1).
2) If you open a screen that's only one line high, the system will crash.
3) Vertically centered screens may show other screens behind unless exclusive flag is set, and this is V39+.

But... i'm not sure what you mean by using the rest as display dma.

[Samurai_Crow]

I mean using the bordersprite bit to feed a screen into an AGA sprite to mirror its content. The bottom row will be set to all zeros so the sprite will end properly. The rest of the pixels horizontally will be regular display.

[meynaf]

Still not very clear for me i'm afraid.
You say you want a narrow screen but after you say the rest of the horizontal pixels will be displayed normally - so at the end it isn't a narrow screen...

Please be more specific.
What is the exact display you want to setup ? Where will the sprite, the 64-bit wide screen, and the normal display be ?
And what is the ultimate goal ?

[Samurai_Crow]

I'm doing a vertical split screen. 64 pixels of sprite and 256 pixels of display stacked horizontally from each other.

[meynaf]

So all you want is to add 64 pixels of sprite at the left of a 256 pixels wide screen ?

[Samurai_Crow]

For now, yes. To build on it more, I would like to add sidescrolling to the 256 pixel screen.

[meynaf]

Then you can simply open a 256-pixel wide screen, then activate border sprites, and put your sprite at the left on the screen.
Or maybe this fails for some reason ?

That said, scrolling Intuition screens isn't something really straightforward imo, so you might be better off by just writing your own copperlist.

[Samurai_Crow]

I will figure out the guru number first, then track the bug from there. It's an 80000003 unrecoverable alert.
EDIT
It turns out the reason why the first instruction in my code was failing was that the standard libraries weren't opening in the startup code. I'm coding this in AmigaE and using OPT OSVERSION=39 at the top for Kickstart 3.0 as a minimum. I'll probably bump it up to 40 later on for the bugfixes in Kick3.1 but the fact that it failed suggests a bug in the compiler. That's disturbing.

[Samurai_Crow]

Update: I've gotten it working now. There were a couple of problems with my code but OpenScreenTags will indeed open a 256x240 screen. Soon I'll have to release a demo of the underscanned screen using a 64-pixel wide HUD using an AGA sprite.