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Comment on "Things Developers Should Know About Leopard"
by Jesper — Sep 22
Question: if I want to show a picture of dimensions greater than 2^16 x 2^16 pixels, does anything Leopard make it easier, now that it is 64-bit? ("Show" == render a downsampled version, zoom in/out, scroll around in higher res versions, etc.)

64-bit does one thing: it makes it possible to have a larger *memory* space than 4 GB. With 32-bit, you'd have to have a memory window that you'd move around "over" that data, loading it in as you go.

Such capabilities have been available for the G5 in executables that just link with the standard system library (lower than even Core Foundation). In 10.5, it's available for Intel 64-bit processors (Xeon and Core 2 Duo), and it's also available for Core Foundation, Cocoa and most of the non-UI bits of Carbon.

If you previously had a window in a (32-bit) UI application communicating with a 64-bit application managing the data access, and the 32-bit application only handled showing the pixel data the 64-bit app threw at it, and the 64-bit app handled scaling, then you wouldn't see a difference in speed. But for almost any other situation involving such a large image, it'll be faster and you'll be able to write just the one, 64-bit app.

How would one write a OSX GUI app that targets both Tiger and Leopard?

One would write a Tiger version.
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