PAYNE@latlog.UUCP (02/11/88)
I have a query about the use of XCopyArea: When trying to use XCopyArea to scroll the contents of a window I do the following: Scroll-left: I use XCopyArea to move an area the full size of the window from x=0 to x=-100 (say). This moves the image to the left and generates a graphics expose event for the portion on the right because it has no information to write to that portion of the screen - this is good. Scroll-right: This time I use XCopyArea to move an area the full size of the screen from x=-100 to x=0. What seems to happen is that the source origin gets changed to be 0(?) so that the image is not moved. If I copy an area smaller than the full window size then I do not get a graphics expose event so I can not find out what part of the screen I need to refresh. 1) Firstly, is this behaviour right, and if so is there a good reason why the source origin is truncated (or whatever) ? 2) I realize that this is not perhaps how you envisaged XCopyArea to be used(?) but given that the scroll-left works just fine in this case is there a way of getting identical behaviour when I do a scroll-right? 3) Alternatively am I doing something wrong? Thanks in advance. Julian Payne, European Silicon Structures (ES2 ). (payne@latlog.uucp)
asw@vax-d.rutherford.ac.UK (Antony Williams) (02/12/88)
You would be much better off to calculate the area to be drawn yourself.
A round trip to the server to get the exposure event will cause a delay
in the window update. The scrolled part will appear first, then the
remainder will be drawn some time later. Better to XCopyArea
entirely within the window, and compute the rectangle which has
come into view.
Tony
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Tony Williams |Informatics Division
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