Flags on onKeyDown?

fredo6

I just need to read a state of CTRL\MENU key upon the start-up of the plugin.

Did you try with the event OnMouseMove, which has a flags argument too?

BTM

@unknownuser said:

I just need to read a state of CTRL\MENU key upon the start-up of the plugin.

Did you try with the event OnMouseMove, which has a flags argument too?

… This is a bit off-topic, but on windows
` class Flagtest

def onMouseMove(flags,x,y,view)
UI.messagebox flags
end
end

Sketchup.active_model.select_tool Flagtest.new`
will come up with 0 on mouse move, if no keys are pressed. on my mac, it's 256. Any idea why?

update:
Also, onMouseMove only activates when the mouse moves in the model area, so it wouldn't activate on startup of the plugin.

Chris Fullmer

ok, I am using the "flags" parameter of the onLButtonUp method to determine ctrl, alt key status. This is my code so far. It works, but I have a feeling it could be optimized. I really don't manipulate strings very well. I nearly turned it all into an array.

` def onLButtonUp(flags, x, y, view)

flag_bin = flags.to_s(2)
flag_bin_to_add = 6 - flag_bin.length
zeros = "0"*flag_bin_to_add
adjusted_flag = (zeros + flag_bin).reverse

ctrlk = true if adjusted_flag[3,1] == "1"
altk = true if adjusted_flag[5,1] == "1"`

So I take the flag, turn it into binary as Jim showed. But a value less than 32 makes a binary with less than 6 digits in it. So if the user is holding alt, then a 6 digit binary is given. If they are holding ctrl, then only a 4 digit binary is given. So I am adding zeros to the binary string, then reversing it because I like the binary to be ordered according to the numerical representations for each key, lowest number key on the left, highest number key on the right.

Then I set my variables to be true if their binary digit is true, indicating that their key was pressed.

I hope that makes sense. Again, this seems to work great. But it feels klunky. Is there an easier way to parse the bit field?

Any optimization ideas?

Chris

ps - I tacked it onto this thread since this thread is what pointed me in the direction of how to work with the "flags" parameter.

thomthom

shift = (flags & CONSTRAIN_MODIFIER_MASK) == CONSTRAIN_MODIFIER_MASK

Use the & for bitwise comparison.

Chris Fullmer

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

thomthom

Bitwise operation - Wikipedia

(en.wikipedia.org)

thomthom

Nice little list of Ruby's operators http://www.tutorialspoint.com/ruby/ruby_operators.htm

MartinRinehart

@chris fullmer said:

flag_bin = flags.to_s(2) flag_bin_to_add = 6 - flag_bin.length zeros = "0"*flag_bin_to_add adjusted_flag = (zeros + flag_bin).reverse

Stick in a non-zero bit to the left of the flags.

Quickly: (flags | 128).to_s(2)[2..7].reverse

Slowly:

flags 
        # 00bbbbbb
flags | 128 
        # 10bbbbbb
(flags | 128).to_s(2)
        # 8-char string version
(flags | 128).to_s(2)[2..7] 
        # the 6 chars your really want

thomthom

Converting to string is very inefficient.

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.