info-mac@uw-beaver (01/24/85)
From: Randy Schulz <lcc.randy@UCLA-LOCUS.ARPA>
The window manager documentation states that unless the global location
paintWhite is cleared, InvalRect() or InvalRgn() -ing part of your
window should cause the invalidated rectangle to be automatically
painted white before it gets redrawn. Though I'm sure the manual is
correct, my recent experience leads me to disbelieve this. When I need
to move an object on the screen, I InvalRect() the area it currently
occupies. If I do not also call EraseRect() on the same rectangle, the
old image is not erased before (or after) the newly placed one is drawn
in response to the update event. Can I assume that I do not need to
erase any part of the screen before I draw in response to an update
event? If so, why might it be that I don't appear to get the update
region erased automatically? I am properly calling BeginUpdate()
before I redraw the window and EndUpdate() immediately afterwards.
Any help will be appreciated.
Randy Schulz
Locus Computing Corp.
lcc!randy@ucla-cs
trwrb!lcc!randy
{trwspp,ucivax}!ucla-va!ucla-cs!lcc!randy
{ihnp4,randvax,sdcrdcf,ucbvax}!ucla-cs!lcc!randyinfo-mac@uw-beaver (01/25/85)
From: kato.SV@XEROX.ARPA AHA! I KNOW THAT ONE! The word from APPLE (Rosenstein%Apple@CSNET.ARPA, I think) [ lsr@apple... -jma ] said that the documentation is WRONG! paintWhite is only looked at by PaintOne(?) and that's only called when one window uncovers another. This one puzzled me for a long time because I thought the same as you, "I'm sure the manual is correct...". IT AIN'T!! Kato.sv@Xerox.ARPA