[Scummvm-tracker] [ScummVM :: Bugs] #16246: AGI: DDP: F1 help screen is rendered incorrectly in the Amiga version

[ScummVM :: Bugs]

#16246: AGI: DDP: F1 help screen is rendered incorrectly in the Amiga version
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Reporter:  Thelypody  |       Owner:  (none)
    Type:  defect     |      Status:  new
Priority:  normal     |   Component:  Engine: AGI
 Version:             |  Resolution:
Keywords:             |        Game:
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Comment (by sluicebox):

 Confirmed, the Amiga background should indeed be white.

 Video:
 https://archive.org/details/Amiga_500_Longplay_149_Donald_Ducks_Playground/Amiga_500_Longplay_149_Donald_Ducks_Playground.mkv?start=64

 The discrepancy seems to be in how we clear the screen. Script 31
 intializes the help screen like this:


 {{{
 text.screen();             # enter text mode
 set.text.attribute(0, 15); # black text on white background
 clear.lines(0, 24, 15);    # clear lines 0-24
 }}}

 The third parameter is the color (white) but the AGI interpreter ignores
 this in text mode and is hard-coded to use black, at least in the DOS
 interpreter. Apparently the Amiga version does something different. Maybe
 it uses the color parameter, maybe it uses the background from
 `set.text.attribute`, or maybe it's hard-coded to use white instead of
 black.

 I scanned my AGI corpus, and this is the only script that calls
 `clear.lines` in text mode with a non-zero color, so this could be the
 only screen ever affected.

 We'll have to do some tests on the Amiga interpreter to see what the
 correct behavior is. If I can get this running in an emulator, I can
 hopefully patch the game script to pass different color values to
 `clear.lines` and see how it responds. (Or if someone wants to disassemble
 the Amiga interpreter in the meantime, go for it!) Either way... may take
 a while =)
-- 
Ticket URL: <https://bugs.scummvm.org/ticket/16246#comment:1>
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