ekberg@ti-csl.csc.ti.COM (02/08/90)
The protocol spec says the following > The backing-planes indicates (with bits set to 1) which bit planes of the > window hold dynamic data that must be preserved in backing-stores and during > save-unders. The backing-pixel specifies what value to use in planes not > covered by backing-planes. The server is free to save only the specified > bit planes in the backing-store or save-under and regenerate the remaining > planes with the specified pixel value. Any bits beyond the specified depth > of the window in these values are simply ignored. The question I have is: What happens when pixels are taken from the backing store? If the server had saved all planes in the backing store can it simply copy all planes back into the window? For example, if the backing planes is xF0 and the backing pixel is x75, can the server, when it saves into the backing store save all planes, and then when it restores from the backing store restore all planes? This effectively ignores the backing planes and backing pixel values. Or must the server, when it restores from the backing store restore the planes corresponding to xF0 and set the planes not covered (x0F) to x05 (x0F anded with x75)? The real issue is what does the phrase "free to save" in the protocol spec really mean? -- tom (aisle C-4Q), ekberg@csc.ti.com
rws@EXPO.LCS.MIT.EDU (Bob Scheifler) (02/08/90)
For example, if the backing planes is xF0 and the backing pixel is x75, can
the server, when it saves into the backing store save all planes, and then
when it restores from the backing store restore all planes?
Yes.
The real issue is what does the phrase "free to save" in the protocol spec
really mean?
That means it has the option of only saving the specified planes, but it is
not required to save just those planes.