Investigating MacPaint's Source Code

https://ztoz.blog/posts/macpaint-source-code/

by zdw • 1 year ago

87 16 1 year ago

My wife has been working on a pixel accurate recreation of MacPaint on the web, and one of the things that I've learned from on-and-off helping with it was just how much of the magic in it is actually just handled by QuickDraw.

Also, the text styling has a lot more complexity than you would expect.

jwstarr• 1 year ago

By "pixel accurate", do you mean the user interface or the rendering? Is she able to leverage the HTML 2D Canvas API or does she have to go lower level than that?

allthreespies• 1 year ago

I’m using a buffer pool and raw bitmaps with calls to drawImage - the canvas api doesn’t play very well with trying to do things in a pixel perfect way.

I’ve gone on a lot of rabbit holes digging into original source code and dev manuals for this project, hopefully one day I’ll write some of it up somewhere. I think what’s been interesting is iterating towards the most elegant solutions has often meant ending up with pretty similar approaches to what Atkinson originally used.

userbinator3• 1 year ago

MSPaint (which I wish MS would officially open-source) heavily relies on GDI too.

gblargg• 1 year ago

QuickDraw's regions always impressed me. They could cover an arbitrary area, and most operations could be masked to a region. This was important for updating a window behind another efficiently, just mask to the visible portion and draw its contents normally.

JKCalhoun2• 1 year ago

Me as well.

As I recall, regions were essentially something akin to an array of run-length-encodings for each scan line (where, additionally, there was a sentinel or some way to indicate the next n rows are the same as the previous). The fun part is then writing a set of routines to union, difference, etc. pairs of these RLE region objects (and here I use the word 'object' loosely).

userbinator3• 1 year ago

Something felt a little "off" about the text of this article, but this fragment raised the most suspicion:

demonstrate mechanical empathy with the 68k platform

garbagewoman• 1 year ago

Suspicion of what?

userbinator3• 1 year ago

Doesn't sound like something a native nor non-native English speaker would write.

astrange• 1 year ago

Correct phrase is "mechanical sympathy" but I think this is an intentional joke.

ghusbands• 1 year ago

What are you trying to imply? That is was written entirely by LLMs or such? It has none of the usual tells. Or perhaps that an LLM was used to help? Yeah, that is possible, but not problematic.

I think it is mostly just a somewhat dry, academic style.

peterbmarks• 1 year ago

Bill Atkinson unfortunately has been diagnosed with Pancreatic cancer. https://daringfireball.net/linked/2024/11/13/atkinson-prayer... I'm sure everyone wishes him well.

JKCalhoun2• 1 year ago

Atkinson writes QuickDraw, then writes an app, MacPaint, that essentially uses every aspect of it, then has Susan Kare using MacPaint. What a fantastic feedback loop for readying a framework before shipping.

Contrast this with the "I Don't Know How To Count That Low" meme.

Investigating MacPaint's Source Code

Related Stories