tandy put their sound chip on the 1A interrupt?

[lethal_guitar@mastodon.social]

@foone it's the most efficient way to render images in planar EGA/VGA video modes. So clearly that's what you need to use for a game that's mostly static screens

[foone@digipres.club]

@lethal_guitar yeah. I guess it's faster to draw, but given that it's static scenes... The disk access is gonna take longer!

[foone@digipres.club]

it allocates a 1024 byte buffer, then makes a pointer to the end of it, minus -0x42?

why would you need a link to the end of a new, freshly cleared buffer, minus 62?

[foone@digipres.club]

I think the memory allocation system here is that every malloc returns 2 extra bytes, which is a pointer to the previous block.
unless it's an odd number, in which case it's a free block. and pointer to the previous block, once you make it even again

[foone@digipres.club]

I hate dealing with the internals of memory allocation systems. I prefer to leave that to smarter people than me

[foone@digipres.club]

You see this little About dialog box? Guess how many times the DrawText function is called?

Once! and just to draw "Where in the World is Carmen Sandiego?".
The rest of the text is draw elsewhere, and I have no idea why.

[foone@digipres.club]

correction: it calls it once to draw "Where in the World is Carmen Sandiego?" but that's unrelated to the one on screen WHAT?

[foone@digipres.club]

Ahh, it's using a different version of the DrawFont call: DrawFontN

[foone@digipres.club]

the only problem with using Ghidra to hack children's games instead of, like, Serious Things like firmwares or malware or whatever, is sometimes you have to make a label named NUM_MOUNTAIN_CLIMBING_HINTS

[foone@digipres.club]

(the number of mountain climbing hints is 3, by the way)

[foone@digipres.club]

I think I accidentally hacked my debugger

[foone@digipres.club]

It has a surprisingly robust UI engine. I swapped from BoldFont to SmalFont and the menu adapted perfectly.

[foone@digipres.club]

The game loads the BoldFont first, then the SmallFont, then the NormalFont.

Annoyingly this isn't how they're laid out in memory:
It's SmallFont, then BoldFont, then NormalFont

[foone@digipres.club]

Weirdly, swapping the NormalFont for the SmallFont causes the printer text to be VERTICAL, for reasons I do not remotely understand!

[plan_a_to_y@furry.engineer]

@foone I dunno why but that gives me a "subtle thing that's wrong which leads into things turning to horror" vibe.

"Where in the world is Carmen Sandiego?"
she's right behind you
run.

[foone@digipres.club]

font_alloc = malloc(local_a);
if (font_alloc == (void *)0x0) {
font_alloc = (void *)0x0;
}

Ahh yes. remember, if you get a null pointer back from malloc(), make sure to set that variable to NULL so it won't be left as... NULL?

[foone@digipres.club]

@Plan_A_to_Y the last thing a young ACME sleuth hears is a chuckle and "nothing personal, kid"

[foone@digipres.club]

The three fonts

[viraptor@cyberplace.social]

@foone inlined helper that optimises out to a null?

[foone@digipres.club]

@viraptor probably. or a macro and a poor optimizer.