I try to make a neat game for AGA Amigas using the OS functions and encountered a (minor) problem:
I tried to make the display NTSC friendly, too, and need some more lines to display the full graphics. It is no problem to open a max overscan screen, BUT this one (without using the overscan prefs of the workbench) wonīt fit on a NTSC tv, some portion of the display will reach over upper bounds of the possible display.
(I should mention that the game should start from disk right after switching the machine on, so the Workbench wouldnīt be loaded at this time -> no overscan prefs loaded, too)
I searched in the RKMs for some hint on how IPrefs sets the preferences overscan values but canīt find anything about it (besides the information about the prefs file format, which isnīt of much help for this purpose). I only stumbled across the ViewPort structure and the associated copperlist, which could be changed and made up with RethinkDisplay() and related functions. Nonetheless, it didnīt give me a clue on how to change the display start, scanlines and end :(
Anybody here who is able to help me with this? Would be appretiated!
try on http://utilitybase.com, i think you will have help from it. (i am got all answers on all my questions regarding any amiga coding, which i try to put here with no lack).
I solved it, finally. Somebody should have written down to the RKMs, that the display clip region, if chosen >OSCAN_MAX, may lead to very unexpected results ;) So, I use OSCAN_MAX as max value now (lost some lines nonetheless) for NTSC lowres by giving the appropriate SA_DClip attribute to OpenScreenTags().
