TADA!
As I mentioned to Jez off-list, the WM_HSCROLL and WM_VSCROLL messages
come with parameters that are 16-bit... but the definition of scrollbars
allows 32-bit numbers, if Get/SetScrollInfo APIs are used. Jez was
noticing these issues when scroll ranges got into the 100,000+ range, he
mentioned off-list.
So I perused the code for scrolling, and it seems that the incoming
scroll message parameters are preserved and passed to the default Scroll
event, with uses them.
There are two possible solutions. I prefer the 2nd.
1) In all the places where WM_HSCROLL and WM_VSCROLL events are received
(several .xs modules) the message parameter could be replaced by the
real 32-bit value from a GetScrollInfo call, before calling the Scroll
event.
2) In all the places where the Scroll event is processed, it should be
the user responsibility to use Get/SetScrollInfo instead. For
Win32::GUI, this means that the default Scroll event in GUI.xs should be
updated.
The reason I prefer the second is that it preserves the Windows
idoit-syncracies, which are (reasonably well) documented in MSDN; that
it is less GUI code to change, and in a more central place; and that
users should be used to using Get/SetScrollInfo in their own code
anyway, due to MSDN documentation.
Comments?
I'll start working on a patch to GUI.xs Scroll function.... along the
way, I'm looking for the off-by-one error... gotta be in there somewhere...
On approximately 9/30/2004 8:09 AM, came the following characters from
the keyboard of Jez White:
As a quick reply, I have noticed other 'issues' with scrolling,
typically when large values are used for the scroll range, I'm not sure
if it's a win32::gui thing, a windows thing or a bug- it might or might
not be related to issue you've highlighted.
Cheers,
jez.
----- Original Message ----- From: "Glenn Linderman" <[EMAIL PROTECTED]>
To: "Jez White" <[EMAIL PROTECTED]>
Cc: "Laurent ROCHER" <[EMAIL PROTECTED]>;
<perl-win32-gui-hackers@lists.sourceforge.net>
Sent: Thursday, September 30, 2004 3:57 PM
Subject: Re: [perl-win32-gui-hackers] Main Commit
Now you know I'm not really a Windows GUI expert. I'm going to look
now at updating my applications in the same manner as Laurent updated
the sample code.
But I've recently noticed something in the sample bitmap scrolling
code, which I am gratefully using in a couple of my applications,
which is more obvious when displaying Black & White line art that
extends to the very edge of the BMP, rather than full-color images,
although once you know to look for it, it can be seen with full-color
images also.
When scrolling to the complete right/bottom of a bitmap in a smaller
window, especially when scrolling via "pages" by clicking on the empty
area of the scroll bar, it becomes clear that the right-/bottom-most
column/row of pixels in the window does not get redrawn at the very
end. It is like there is an off-by-one error somewhere in the code.
Now I notice the scrolling limits are based on Win32::GUI::Width, and
that Win32::GUI::Width calculates width as Right-Left. Now I don't
know the Windows spec well enough to know if it should be Right-Left+1
-- in other words, in Right the last drawable pixel, or the first
non-drawable pixel? Of course, maybe the off-by-one error is somewhere
else instead; this possible source of the off-by-one is just
speculation on my part that I haven't yet confirmed or discarded by
reading the Windows documentation. But the scrolling bug exists,
regardless of where the off-by-one error creeps in.
On approximately 9/30/2004 12:01 AM, came the following characters
from the keyboard of Jez White:
Hi,
I've just tested the changes to the -onpaint event and it looks good:)
Cheers,
jez.
----- Original Message -----
*From:* Laurent ROCHER <mailto:[EMAIL PROTECTED]>
*To:* perl-win32-gui-hackers@lists.sourceforge.net
<mailto:perl-win32-gui-hackers@lists.sourceforge.net>
*Sent:* Wednesday, September 29, 2004 10:22 PM
*Subject:* [perl-win32-gui-hackers] Main Commit
Hi,
Changelog
- MakeFile.pl, MakeFile_m.pl
+ Use tab as space in rule for use with dmake
- GUI.pm, GUI.xs
+ Add -brush option for Win32::GUI::Class.
- GUI_Helper.cpp
+ classname_From and handle_From : Replace strlen as static
string length.
- Window.xs, GUI_MessageLoops.cpp, Samples\BitmpaScroll.pl :
+ Move Paint event in Window_onEvent.
+ Use DoEvent_Paint function like Graphic
- ToolTip.xs :
+ Add -balloon option
Laurent.
--
Glenn -- http://nevcal.com/
===========================
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The best part about procrastination is that you are never bored,
because you have all kinds of things that you should be doing.
