3 ms·

Is this similar to the Windows (since at least 3.1 I think?) BitBlt function, that takes an `op` parameter to decide how to combine the source, destination and

Is this similar to the Windows (since at least 3.1 I think?) BitBlt function, that takes an `op` parameter to decide how to combine the source, destination and mask? I remember there are names for some of the codes like BLACKNESS for producing black whatever the inputs are, COPY (or something like that) to just copy the source to the destination etc. I always thought BLACKNESS and WHITENESS had a kind of poetic ring to them. As far as I know, I think this is from Petzold, it's implemented in software but the opcode is actually converted to custom assembly inside the function when you call it, a rare example of self-modifying code in the Windows operating system.

abareplace 2y ago
Yep. BitBlt originally used complex 16-bit "operation codes" that store the binary operations in reverse Polish notation. Then, they added "operation index" that stores the same information in a byte, like in Amiga, which is shorter and more elegant. The coding is now redundant because each raster operation code contains both an operation index and an operation code. See https://devblogs.microsoft.com/oldnewthing/20180528-00/?p=98845 https://devblogs.microsoft.com/oldnewthing/20180528-00/?p=98...