Re: How are the icons in windows explorer made

On 05.08.2009 17:03, Marc Wentink wrote:
> How does tortoiseCVS change the icons, how does it add CVS icons in the
> right lower corner of a pictogram representing the file in the windows
> explorer?
> 
> I am asking this since a customer wants something like that, and I
> thought of tortoiseCVS as a program where something similar is done.
> Sorry for the strange question, but if somebody has a hint, please let
> me know. I want to add a ‘tortoiseCVS’ like icon to a file pictogram, if
> the file is used by an application the customer is using.
> 
> Any help welcome.

If you really want to go this route:

See "Creating Icon Overlay Handlers:" (aka shell extensions)
http://msdn.microsoft.com/en-us/library/bb776858(VS.85).aspx

But there is a very important caveat:

(Quoting from msdn page above):
'''
Note   The number of different icon overlay handlers that the system can
support is limited by the amount of space available for icon overlays in
the system image list. There are currently fifteen slots allotted for icon
overlays, some of which are reserved by the system. For this reason, icon
overlay handlers should be implemented only if there are no satisfactory
alternatives.
'''

Because of the very limited number of slots, the tortoise* projects (I know
at least TortoiseHg and TortoiseSVN) share a common component, namely the
TortoiseOverlays, provided by the TortoiseSVN project.

TortoiseOverlays is available from
http://tortoisesvn.tigris.org/svn/tortoisesvn/TortoiseOverlays/
(log in as user "guest", leave password empty).

Strongly recommended read:
http://tortoisesvn.tigris.org/svn/tortoisesvn/TortoiseOverlays/version-1.0.7/Documentation.txt

Installers are in:
http://tortoisesvn.tigris.org/svn/tortoisesvn/TortoiseOverlays/version-1.0.7/bin/

Before TortoiseOverlays was used, the Tortoise* projects conflicted
with each other on the overlay handler slots.

Now, TortoiseHg and TortoiseSVN share the same slots (apologies, I've
only hacked on TortoiseHg so I don't know if TortoiseCVS is using
TortoiseOverlays as well).

And you really need to know what you do, since you will have to implement
the shell extension dll in C++, which has the potential to tear down explorer
as it is loaded in to the process space of explorer. Of course, you need
to understand COM programming, too.

(Customers tend to get highly confused if their explorer crashes.)

Also make you sure you carefully test your extension on all relevant Windows
versions: Windows XP, Windows Vista, Windows 7.

And you need to think about providing 32bit and 64bit versions
of your shell extension dll, since on the 64bit versions of Windows,
explorer is 64bit as well and thus needs a 64bit shell extension dll.

If that's not enough, you should know that explorer of vista (and Windows 7) calls
the overlay handlers on multiple threads. So your code must be multi thread
safe.

Last but not least the overlay handler shell extensions are loaded into
the address space of every application (Word, Excel, etc.!) as soon as it
fires up an open file dialog.

So you can crash (and slow down) all applications as well.

You should also make sure that your shell extension is fast enough, as
it slows down explorer (and applications open file dialog, which has a very
high potential to annoy users.

Still think this is is good idea? Good luck then :)
In other words: think twice before doing it.


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