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Re: Deleting and erasing lines [message #10578 is a reply to message #10484]

Thu, 11 December 1997 00:00

hegde
Messages: 17
Registered: December 1995

Junior Member

David Fanning (davidf@dfanning.com) wrote:
: Andrew A. Baker (andy.baker@bristol.ac.uk) writes:

: > The best method that I know from other programming endeavours is to use
: > XOR (exclusive-OR), so that the colour drawn depends on the colour
: > already there and reversal (i.e. erasing the line) is then a trivial
: > process. I don't need a line of one colour only, so is there a way of
: > doing non-absolute colours? Or is there a better way?

: The XOR method is fast and easy. It just doesn't look all
: that great normally. The reason is that it will only work

In addition to this, if you use XOR mode the line will be visible all the time.
If you don't need a line of "one colour only", I would suggest XOR mode.
Else if you are specific about the line color,

1) keep the entire image in a pixmap and copy it to window each time after
before drawing the line.

OR
2) copy the image enclosed in the line's bounding rectangle to pixmap and copy
it back before drawing the line.

-M. Hegde

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[Message index]

		Deleting and erasing lines By: Andrew A. Baker on Thu, 11 December 1997 00:00
		Re: Deleting and erasing lines By: Andrew A. Baker on Fri, 12 December 1997 00:00
		Re: Deleting and erasing lines By: hegde on Thu, 11 December 1997 00:00

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