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Suggestion
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Resolution: Moved
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Not Evaluated
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None
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5.9.4
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None
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Windows 10, Chrome
Hi,
I am using the qwebchannel.js provided in the Qt examples and connecting an existing Qt application to a web-page like it is done for the 'Qt WebChannel Standalone' example. I found several problems when documenting basic use cases:
1) returning a custom QObject* as a property
The qtwebchannel.js doesn't wrap the property as a QObject, so I propose to change the code as follow:
this.propertyUpdate = function(signals, propertyMap) { // update property cache for (var propertyIndex in propertyMap) { var propertyValue = propertyMap[propertyIndex]; object.__propertyCache__[propertyIndex] = this.unwrapQObject(propertyValue); } … }
2) in some cases we would like to retrieve the result of a slot synchronously so I propose to wrap the slot invocation in a Promise when there is no callback so that client code may use 'await'
function addMethod(methodData) {
...
if (callback) {
webChannel.exec({
"type": QWebChannelMessageTypes.invokeMethod,
"object": object.__id__,
"method": methodIdx,
"args": args
}, function (response) {
if (response !== undefined) {
var result = object.unwrapQObject(response);
(callback)(result);
}
});
} else {
var promise = new Promise(function (resolve, reject) {
webChannel.exec({
"type": QWebChannelMessageTypes.invokeMethod,
"object": object.__id__,
"method": methodIdx,
"args": args
}, function (response) {
if (response !== undefined) {
var result = object.unwrapQObject(response);
resolve(result);
} else {
resolve();
}
});
});
return promise;
}
}
3) Passing a QObject as argument of a slot in a script
Assuming the QObject 'o' is already exposed to the scripting side, as a property of another QObject for ex. Calling slot(o) fails with the following error message "Cannot not convert non-object argument xxx to QObject*.", even though the QObject was published to javascript by Qt without problem. (all its properties, slots, can be seen in Chrome/Inspect)
This is because QMetaObjectPublisher looks for a value for the "id" field on the Json data provided from javascript and doesn't find it. In fact it is not symetrical with what qwebchannel.js is doing: the script fills a '_id_' field instead.
To test I modified the qwebchannel.js as follow:
function QObject(name, data, webChannel)
{
this.__id__ = name;
this.id = name; // CC: QMetaObjectPublisher looks for KEY_ID = "id" when calling unwrapObject(value.toObject()[KEY_ID].toString());
...