Overriding QDir::homePath()

d2uriel

Take a look at the sources: qfilesystemengine*.cpp files.

On the other hand, this method is already portable so what do you wanna do with it?

lwcorp

I did and didn't understand a thing. It's not portable at all because it does something weird and only upon failure uses environment variables.

Please explain what it does (something with tokens).

d2uriel

Have you tested this method on different kinds of OS'? What is it returning on Windows/Linux/MacOSX?

redkite

From doc :

bq. Under Windows this function will return the directory of the current user's profile. Typically, this is:
C:/Documents and Settings/Username

bq. Under non-Windows operating systems the HOME environment variable is used if it exists, otherwise the path returned by the rootPath().

goetz

On Windows, the user directory is searched in the following order, the first method that returns a valid[1] path is used:

The value returned by GetUserProfileDirectoryW Windows API call
The value of USERPROFILE environment variable
The value of HOMEDRIVE + HOMEPATH environment variables
The value of HOME environment variable
The value of SystemDrive environment variable (no check for existence)
"C:/" (hard coded as last resort, no check for existence)

fn1. valid means the method returns a value and the directory denoted by that value does exist

lwcorp

[quote author="Volker" date="1332108047"]

The value returned by GetUserProfileDirectoryW Windows API call[/quote]
So my question is how does GetUserProfileDirectoryW work. Had I understood it, maybe I could have bypassed it.

goetz

I don't know the internals. Thats Windows API and I avoid digging into that wherever I can :-) Some Google search may get you more details. Usually that method returns "C:/Documents and Settings/USER" on Win2k/XP and "C:/Users/USER" on Vista/Win7.

lgeyer

Just to let me get this right: you want to modify the behaviour of an existing binary, you are not a developer who wants to modify its own sourcecode or application.

Well, I guess you are left with four options then, in the order of work and stress involved

recompile the binary not using QDir::homePath() or
file a bug report or a merge request which modifies the behaviour of QDir::homePath() in a way that <code>%USERPROFILE%</code> takes precedence over GetUserProfileDirectoryW or
distribute the binary with a patched set of the Qt libraries which modify the behaviour of QDir::homePath() or
hook GetUserProfileDirectoryW directly to modify its behaviour.

I'm not quite sure as of right now but I tend to say that <code>%USERPROFILE%</code> and <code>%HOME%</code> should take precedence over GetUserProfileDirectoryW just to cover cases like yours (where you want to temporarily redirect the home directory) and to get a more consistent cross-platform behaviour.

lwcorp

Would you be kind enough to submit that bug report? I don't seem to find such an option anywhere.

Had I understood GetUserProfileDirectoryW, I could have somehow bypassed it without actually modifying the code.

andre

The bugsystem is currently at https://bugreports.qt-project.org/secure/Dashboard.jspa

lwcorp

"Thanks!":https://bugreports.qt-project.org/browse/QTBUG-24907

goetz

Regarding the text in your bugreport:

bq. Various standalone portable softwares could have been forced to become portable, if only they hadn't stored their data in a path that involves QDir::homePath().

A sane Qt application doesn't use homePath() for that, but calls QDesktopServices::storageLocation() with, for example, QDesktopServices::DataLocation as argument. These methods do not use homePath() under the hood (or only as a last resort), but call SHGetFolderPath() on Windows, which is native Windows API again.

lwcorp

The OP links to at least 2 programs that do this. Well, if their authors knew what they were doing, they would have accepted an "/ini=" command line parameter in the first place.

But what advantage does SHGetFolderPath() offer? Can it easily be bypassed?

BTW:

bq. Deprecated

SHGetFolderPath function, Microsoft MSDN: http://msdn.microsoft.com/en-us/library/windows/desktop/bb762181(v=vs.85).aspx

andre

Deprecated for Vista and up, but Qt also runs on XP, where the replacement function does not exist yet.

lwcorp

Please answer:

bq. But what advantage does SHGetFolderPath() offer? Can it easily be bypassed?

goetz

[quote author="lwcorp" date="1337853314"]Please answer:

bq. But what advantage does SHGetFolderPath() offer? Can it easily be bypassed?[/quote]

Advantage: it is official API, although deprecated. But as Andre already mentioned, as long as Qt is running on XP, one will have to use it, as the replacement isn't there.

Bypassing: I don't know, as I never had a need to do this.