OS3.x - Open a screen with 1x bandwidth

[dissident]

Again something special.

Is there a smart way to open a screen on OS3.x with the 1x bandwidth?

The only solution I know is poking in the graphics base like this:

  move.l	_GraphicsBase,a6
  move.b	#BANDWIDTH_1X,gb_MemType(a6)

And after that open the screen. But you have to disable multitasking with Forbid() to be sure that the bandwidth won't be changed.

Not very system friendly. I did some investigations in the autodocs, but did not find a way to change the bandwidth, after the screen is opened or before with a special tag. Looking in the vieport/viewport extra structure didn't help.

[dissident]

Do you have any hints for me, Thomas Richter?

[Ernst Blofeld]

Originally Posted by dissident

Do you have any hints for me, Thomas Richter?

You need to say his name three times for him to appear.

[aros-sg]

Maybe create your own screen bitmap with manually allocated planes that are misaligned (address multiple of 2, but not 4 or 8) such that only 1x is possible. And then open screen with custom bitmap (SA_Bitmap tag).

[dissident]

Originally Posted by aros-sg

Maybe create your own screen bitmap with manually allocated planes that are misaligned (address multiple of 2, but not 4 or 8) such that only 1x is possible. And then open screen with custom bitmap (SA_Bitmap tag).

Not a bad idea. I guess I have to tell what should be the purpose of this screen. It‘s part of a display downgrader to get BPL1MOD / BPL2MOD to 0 values. I doubt that the system is smart enough to detect misaligned bitmaps. There must be a reason for the global entry in the graphics base for the bandwidth.