Acorn Arcade forums: Programming: Mouse border SWI
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Mouse border SWI |
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(15:10 2/2/2001)
Phlamethrower (16:42 2/2/2001)
andrew (18:17 2/2/2001)
Phlamethrower (11:55 3/2/2001)
andrew (14:12 3/2/2001)
Phlamethrower (13:58 15/6/2002)
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andrew |
Message #4731, posted at 15:10, 2/2/2001 |
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I was trying to use the OS Word 21,1 call to set the mouse limits relative to an origin of 320,240 in MODE 28. I think it needs 2's complement values split into two bytes though. Is there a reference on how to work these out and can anybody say whether I'm on the right lines here? regards, Andrew |
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Phlamethrower |
Message #4732, posted at 16:42, 2/2/2001, in reply to message #4731 |
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According to the PRM's (You should really get a copy, or at least the Strong Help manuals), R1 is a pointer to a parameter block: R1+0 = 1
R1+1 = LSB of left coordinate
R1+2 = MSB of left coordinate
R1+3 = LSB of bottom coordinate
R1+4 = MSB of bottom coordinate
R1+5 = LSB of right coordinate
R1+6 = MSB of right coordinate
R1+7 = LSB of top coordinate
R1+8 = MSB of top coordinate All are treated as signed 16-bit values, relative to the screen origin at the time of the call. |
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andrew |
Message #4733, posted at 18:17, 2/2/2001, in reply to message #4732 |
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Thanks very much for the help Jeffrey but the only reason I mention that I might need to find out anout 2's complement is that the example in the PRMs, which have got, as I understand shows these numbers being represented.
This is why I think my code didn't work. |
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Phlamethrower |
Message #4734, posted at 11:55, 3/2/2001, in reply to message #4733 |
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You mean the infinite box example? Those are just the largest positive and negative numbers you can get, so the fact that they add up to make -1 has nothing to do with it. Without seeing your code (Or bothering to have a fiddle with the command myself) I can't really help you. I'll probably have a fiddle in an hour or two when I get to work on XSpr. |
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andrew |
Message #4735, posted at 14:12, 3/2/2001, in reply to message #4734 |
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What I'm wondering is, how do these numbers represent negative values? I'm assuming it's the two's complement system.
I've found another ay to set the bundaries I want for the mouse-driven code I was doing but I'll have another look at the call myself anyway. |
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Phlamethrower |
Message #4736, posted at 13:58, 15/6/2002, in reply to message #4735 |
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I've had a fiddle with the call, and it seems to work based on OS units. About the negatives - now that I've reminded myself what two's complement actually is (I know quite a few things but can't quite link them together sometimes  ), yes that is the system it uses. |
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Acorn Arcade forums: Programming: Mouse border SWI |
