Well that article was really only about changes that occurred in Windows 7. There's better information about how a programmer adds overlays here:
http://msdn.microsoft.com/en-us/library ... 85%29.aspxgrindax wrote:I don't know if that means the entire OS can only make use of 15 overlays, or if a single type of image/file can have 15 associated overlays.
From the above page, I get the impression that there is only space for 15 overlay images, and from the previous article, Windows 7 reserves 5 of them.
grindax wrote:If it's true that Windows only comes with 5, I can't imagine that installing Mozy and Dropbox (which in total use 3 or 4) has taken me over the OS limit.
The registry key will show you how many are installed. While it's possible that this limitation is part of the problem, I don't believe that's the case, and there's more to it than that.
grindax wrote:The frustrating thing about that MSDN article is that it talks about overlays winning or losing when multiple apply, but there's no indication how they take priority.
This newer link explains this better. Each handler for a program wishing to add overlays has to implement the
IShellIconOverlayIdentifier interface, which contains 3 methods.
1) IsMemberOf - Takes the path & attributes of an item and returns whether or not an overlay should be displayed.
2) GetOverlayInfo - Returns the path to the overlay image.
3) GetPriority - Which returns an number from 0 (highest) to 100 (lowest) defining the priority for this overlay.
Where it gets tricky is that the defined priority is handled by each handler, so if they all say they're the highest then the first one the shell checks wins, but to make it even more confusing it says:
The Shell has a set of internal rules that determine the priority for many cases ... GetPriority is used for those cases in which the Shell's internal rules do not apply.
Who knows what those internal rules are and how they come into play here? It seems the real purpose of this is if your handler defines multiple overlays you can then use the priorities to define which of them is more important.
grindax wrote:But somehow Windows Explorer on Windows 7 is showing the expected overlays in the 3 situations I outlined. For the Mozy files, there is no other overlay, so there shouldn't be any conflict issue. For the Dropbox .url files, somehow Windows Explorer knows that Dropbox's overlays take precedence. And for the dynamic updates of files that are being synchronised, Windows Explorer must be seeing some events that Dropbox is triggering.
Well I think the 3 cases you outlined may be entirely separate problems.
1) I have a completely unsubstantiated feeling that this is related to Mozy's implementation or registry settings more than XY.
2) I think this might be something funny in the Shell's internal rules to be honest. Perhaps, they have a rule that gives their overlays a higher priority when called from non-native controls or outside of WE.
3) I agree with your assessment. I want to take a look with process monitor to see if I can identify anything to give Don some help, but I need to find the time for that.
