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27 February 1999
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Site
of the week
vbAccelerator was the featured site of the week at DevX's VB Zone,
the web-site of the VBPJ magazine.
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Newsletter
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You can now get notification of vbAccelerator's highly regular site updates
through the Newsletter, produced in association with the VB Toolshed and Goffredo's Visual
Basic Source Code Library. Find out about it and sign up in the
Partners section.
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Man Changes Programming Language Shock!
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Also, at DevX, on 18 January,
Bruce McKinney, author of Hardcore Visual Basic (probably the best VB coding book on sale),
announced in an article
that he was no longer going to write any more editions. At
the same time he heretically announced that he would be doing future programming
in Delphi because "VB makes the easy things easier; Delphi makes the hard things
easier". There are a couple of upsides to this:
- Hardcore Visual Basic is now effectively a free product. The entire text of the
book is available at MSDN and in the VB6 Help file (Bruce M says, not verified by me) and now
for the first time you can also download all the source code for free also. This is a good thing.
Go get it!
Source code for both VB5 and a revised VB6 version is provided.
- If you're interested in VB, its problems, and some ideas of things to ask Microsoft for
in VB7, then there is a
lot of reading to be had!
vbAccelerator is not about to follow this lead. Obviously it would be far too difficult
for a start (changing the domain name, redoing all the logos...) More seriously, VB
still hasn't let me down yet. Yes, there are some issues with the VB language and a
lack of support for many features we really should have. But there are plenty of
workarounds and other times its good to have a the challenge :) One issue you can't
help but agree with is the way VB6 has broken VB5 code without there being any real
justification (for example, UserControls calling the Resize and ReadProperties events
in the opposite order...). vbAccelerator is starting a new series of articles next
month considering some of these issues. The initial articles are going to cover
Implementing interfaces rather than using events and Can you
create a control with a Toolbar style collection interface (and have it work)?
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An Unpleasant Issue With the With Statement
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The With statement in VB is a nice language feature which can make
code easier to write and maintain. However, there's a big catch to it, pointed out in an article by
Dave Jewell in the UK magazine PC Pro.
When you use With to refer to an object, VB will call the COM AddRef
method on the object. Only when the End With statement is reached is COM's
Release method called. This means that if you're code breaks out of a With...End With
statement block for any reason, VB will have taken out a permanent reference on that
object. Objects cannot clear up properly unless there are no outstanding references
on them or when your executable terminates! This code fragment shows how you can get into
serious difficulties with this:
Dim c As cWorker
Dim fResult As Double
On Error Goto ErrorHandler
Set c = MainObject.Worker(1)
With c
.Iterations = 1000
.InitialValue = 3
.ProgressLabel = lblStatus
.DoProcess
fResult = .Value
End With
ErrorHandler:
LogError 2501,"Processing Failed: " & Err.Description
If for any reason the code raises an error during the With block above, the
object c will never terminate whilst your project is running. It will
just float somewhere around in memory until the project completes because of the
outstanding reference. You can try to set c to nothing in the error handler,
but this still won't terminate the object because the With block has taken out
another reference on it!
Although this 'feature' is mentionned somewhere in the VB documentation
it isn't particularly well known.
The conclusion is that if you're using With...End With you better be
very careful...
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VB Source Book Project
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This project aims to build a new
freeware VB source code library to rival the expensive commercial versions out there.
There are currently some 2000 source code snippets, controls, DLLs and some complete VB
sites in the library.
Send an email (VBSource@aztech.enta.net) if you'd like to help with
testing some of the snippets.
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10 January 1999
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Version 2 of Icon Menu and Owner Draw Combo List controls
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The January 1999 release of vbAccelerator brings with it major new versions of two
of the highest profile controls on the site: the
Icon Menu Control and the
Owner-Draw Combo and List Box Control.
The Icon Menu Control gains many new features with this release: the ability to insert
or remove menu items, making the control much easier to use, the ability to track menu
items which have had the VB .Visible property set to False and also it is now
capable of working in MDI projects with multiple child menus.
The Owner-Draw Combo and List Box control has not changed so much, but the changes that
have been made approach the state-of-the-art in hardcore VB coding. The previous
release of this control worked in most SDI applications, but it had a hacked
implementation of focus which caused it to fail on MDI forms, and it sometimes
caused GPFs. The new version overrides VB's implementation of focus for ActiveX controls
by modifying the control's vtable to ensure absolutely correct focus implementation.
Not just this but the only other outstanding bug, which was a failure to size correctly
according to the selected font, has been fixed. The fixing in this control paves the
way to the full implementation of ComboBoxEx, TreeView and ListView controls in VB for
future releases of the site. Cool!
Oh, I can't leave it here without mentionning that the long-promised Goldfish
application is now finally release and available for download.
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7 January 1999
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http://vbaccelerator.com Doesn't Exist?
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Unfortunately vbaccelerator.com went down between 30 December and 5 January. This
was caused by a problem at InterNIC
who removed access for the domain name because they had unfortunately not worked
through their forms in time.
As you can tell, we're now back up and running, but the domain is currently "on-hold"
until InterNIC complete their bureaucracy, so there may well be another outage. Hopefully
this time it won't occur in the middle of a major holiday when there is no-one to ask
how to fix it!
Be assured, however, that vbAccelerator is not going away and I will do my utmost to
ensure 100% service.
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25 November 1998
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vbAccelerator Gets a New ISP!
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Today vbAccelerator has moved to its new address, http://vbaccelerator.com,
and is now hosted by a new service provider. The new ISP gives vbAccelerator
a much higher bandwidth and the speed is somewhat better!
(Also we're no longer getting squeezed by every other free home page
on Demon...)
To celebrate the new site, there are 14 new source code articles this month
including 2 new controls. Check it out!
My apologies to you for the sluggish and often non-existent performance at the
previous site. If you've battled with "time-out", "document contains no data",
"404 - page not found" and inability to download files, I sympathise.
Thanks to everyone who wrote in with offers of help - your offers were greatly appreciated.
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vbAccelerator versus VB6
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vbAccelerator does not yet own a copy of Visual Basic 6, so the
code originated for this site isn't available as VB6 native executables. However, there should be no
problem moving most of the code from VB5 to VB6. And since all the source code is provided
on this site you can always recompile it yourself!
Please change any OCX or DLL names before recompiling in VB6 to prevent incompatibility.
If you are feeling particularly public spirited, you could even
post me the VB6 version! (as usual, other
code, cash, cheques, cuddly toys etc will also be gratefully received :)
Here at vbAccelerator we're not too sure about VB6. There's some neat new extensions
(WebClasses, DHTML forms, UDTs in ActiveX, lightweight controls, possibly the DTD stuff) but what
happened to the all the great new hacking tools we could have had? Comparing this
release to VB5 it seems that things aren't going forward in the right way.
Where are cool new features that would really make you want to program in VB like
inheritance, proper multi-threading support, fixes to the dire collection
object, easier subclassing, proper menu and toolbar
integration, docking windows, more OLE type libraries and so on?
Some of the new VB6 features don't seem to be helpful either. The CallByName
feature is flawed because it takes the simple option and thus requires a public object.
Object persistance suffers in the same way. A potentially nice new feature is that
you can create a control at run-time. But this has the same problem as VB5 does when
you create an object that has events at runtime - you have to set up a withevents
class at design time to intercept the events! Another issue is the completely new
OCX implementations for COMCTL32.DLL. Why do we need a new incompatible OCX just to put
in a few new features? Surely this isn't because otherwise VB5 programmers
could use it? Also, the use of owner-draw in the new OCX version to create relatively
useless features such as item colouration is seriously misguided (IMHO).
Compare this to the stuff that was added in VB5 (OCXs, AddressOf, Implements,
ObjPtr, CopyMemory (?)...) and to me it seems that VB6 is a bum deal.
I'm sure I'm wrong about at least half of this. What do you think?
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19 October 1998
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A New Version of SSUBTMR.DLL
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If you've been here before, you'll probably know that SSUBTMR.DLL is the sub-classing component
at the heart of all my controls (if you haven't, check out
Subclassing Without the Crashes). The rebar/toolbar control has exposed a bug
in this component if used in combination with other Common Controls.
Read about it and make sure you download
the new version now if you're using my controls! The new version is binary compatible so
it doesn't cause any install problems.
Thanks to Jim Parzych for noting this problem.
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