Flags on onKeyDown?

Jim

@chris fullmer said:

I don't quite understand what that means. What is bitwise?

Think in binary, then compare them column for column. It's a logical, bit-to-bit comparison.


5 in binary is 101
6 in binary is 110

5 & 6 is; logical AND each column (bit position)

    Columns
________________
|  1  |  0  |  1   <- decimal 5
| and | and | and
|  1  |  1  |  0   <- decimal 6
=================
   1     0     0 

so 101 & 110 = 100 <- decimal 4

The masks are constants, which are set to some convenient values:


# I just made these up
001 = CONSTRAIN_MASK
010 = ALT_MASK
100 = COPY_MASK

So if the flag is decimal value 7:


111  <- decimal 7

In order to check the CONSTRAIN_MASK, you logical AND the CONSTRAIN_MASK with the flag value:


    111  <- flag value decimal 7
  & 001  <- contain mask constant
   ======
    001 <- CONSTRAIN_MASK set true

or in real ruby as Thomas wrote;

contrain_key_down = ((flags & CONSTRAIN_MODIFIER_MASK) == CONSTRAIN_MODIFIER_MASK)
copy_key_down = ((flags & COPY_MODIFIER_MASK) == COPY_MODIFIER_MASK)
alt_key_down = ((flags & ALT_MODIFIER_MASK) == ALT_MODIFIER_MASK)

Although Adam B might know a clever way to decode them all in one elegant statement.