Default image from QRC resource, but customized image from filesystem?

bitbang

Or, put another way, how to check file existence in QML?
It easy to bind the image source property to a either a qrc: or filesystem path; but how to make it use the qrc: if and only if the file in the filesystem is missing?

This is to allow users to customize an image, whose source defaults to a qrc: path unless they upload an alternative file.

I'm aware Googling suggests resorting to C++ for this, but I'm unable to find an example.

SGaist

Hi,

How can your users select the custom image ?

fcarney

QFileInfo can check for the existence of a file. You could have it verify a path and add a command to qml via setContextObject. This would allow you to add utility commands to qml.

bitbang

@SGaist
In my specific case, users upload files externally trough ssh prior to application launch.
I was wondering about an hypotetic File object:

Image {
    File {
        id: file
        source:  "file:///bitmaps/custom.png"
    }
    source:  file.exists ? file.source : "qrc:///bitmaps/default.png"
}

bitbang

@fcarney
First steps in C++-QML integration. So if I understand correctly:

Create a QObject with two properties, QString source and bool exists
In code (via signal/slot), when source changes, set exists accordingly via QFileInfo
Expose the object to QML via setContextObject

I will give it a try, thank you!
Cannot figure out why I was'nt able to find a ready-made code snippet, checking files seems a common need to me.
I'm learning the declarative approach coming from an imperative background: am I doing something wrong or in a non-QML way?

fcarney

I would create a slot function called:

bool fileExists(QString path){}

The setContextObject will place functions on the object in the QML namespace. So you will be able to call fileExists from QML.

ODБOï

hi,
this seems to work also

 Image {
        source: "file:///c:/Users/user/Pictures/img.png"
        onStatusChanged : if(status == Image.Error) source = "qrc:///img.png"                   
    }

fcarney

@LeLev
Wow, that is a really nice way to check that. Thanks!

bitbang

@LeLev @fcarney
Thank you! This solves my problem!