F0O@psuvm.psu.edu (06/19/91)
HI!
In TPW, in the Windows Programmers Guide, step 6: Automatically re-
displaying graphics, I notice they use procedures:
TMyWindow.WMLButtonDown
TMyWindow.MouseMove
TMyWindow.Paint
Why isn't the Paint method called WMPaint? That's what the actual
Windows message is called. I used a WMPaint method in one of my programs
and it worked ok. What's going on here folks?
Thanks in Advance
[Tim]dmurdoch@watstat.waterloo.edu (Duncan Murdoch) (06/20/91)
In article <91170.083555F0O@psuvm.psu.edu> F0O@psuvm.psu.edu writes: > > HI! > > In TPW, in the Windows Programmers Guide, step 6: Automatically re- >displaying graphics, I notice they use procedures: > TMyWindow.WMLButtonDown > TMyWindow.MouseMove > TMyWindow.Paint > > Why isn't the Paint method called WMPaint? That's what the actual >Windows message is called. I used a WMPaint method in one of my programs As I read the online docs on the two, Paint is a procedure to paint the window, while WMPaint is a procedure to service the WMPaint message. The distinction is that WMPaint calls BeginView, Paint, then EndView to communicate with the scrollers. Duncan Murdoch dmurdoch@watstat.waterloo.edu
chard@borland.com (Richard Nelson) (06/21/91)
In article <1991Jun19.201012.29349@maytag.waterloo.edu> dmurdoch@watstat.waterloo.edu (Duncan Murdoch) writes: >> In TPW, in the Windows Programmers Guide, step 6: Automatically re- >>displaying graphics, I notice they use procedures: >> TMyWindow.WMLButtonDown >> TMyWindow.MouseMove >> TMyWindow.Paint >> >> Why isn't the Paint method called WMPaint? That's what the actual >>Windows message is called. I used a WMPaint method in one of my programs > >As I read the online docs on the two, Paint is a procedure to paint the >window, while WMPaint is a procedure to service the WMPaint message. The >distinction is that WMPaint calls BeginView, Paint, then EndView to >communicate with the scrollers. That's basically it. The reason you'd normally override Paint instead of WMPaint is that rewriting WMPaint would require assigning a display context, adjusting the scroller, etc. WMPaint will handle all of that in a standard way, then call Paint. Once Paint is called, you've already got a DC (PaintDC), so it's quite easy to just write the painting parts and not have to worry about all the "administrative overhead." Hence the designations in the docs: WMPaint is "Override: Seldom," while Paint is "Override: Often." The alternate answer, of course, is that I suppose you might want to call Paint in response to something other than a wm_Paint message (though I can't think of a reason off the top of my head). There are a number of places in ObjectWindows where a message-response method simply calls another method, precisely because you might want to have other ways of producing the same response (such as with a menu command). Thus, you might have a message-response method WMFoo and a command- response method CMFoo that both produce the same action, calling a method Foo. Hope this helps some. -- ======================================================================= Richard Nelson, Languages Development Unit, Borland International Internet: chard@borland.com | MCIMail: RNELSON/BORLAND Had this been Borland's opinion, I would have written it in a manual.