Qt import library - creating a QML function

[teh_raab]

Hi All,

Im probably being really dumb and staring right at the issue but can't see the solution.. I've written an import library that we use for various Qt 4.8 QML applications. I have various objects that i can instantiate inside QML without any problem e.g.

Logger {
	id: write;
	name: "Main.qml";
	Component.onCompleted: {
		log("log started");
	}
}

Logger {
	id: write;
	name: "Main.qml";
	Component.onCompleted: {
		log("log started");
	}
}

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and as expected, have access to this "Logger" components "log" method e.g.

MouseArea {
	anchors.fill: parent;
	onClicked: {
		write.log("Mouse area clicked)
		console.log(convert.time_ms_to_sec(-1));
		console.log(convert.time_ms_to_sec(15000));
	}
}

MouseArea {
	anchors.fill: parent;
	onClicked: {
		write.log("Mouse area clicked)
		console.log(convert.time_ms_to_sec(-1));
		console.log(convert.time_ms_to_sec(15000));
	}
}

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This all works fine. My problem is that i now want to create some global functions inside my import library that can be called from anywhere without having to instantiate an object in every QML file. For example, i made a test function that converts milliseconds to seconds, but in order to use it i have to declare my "Conversion" object in each QML file, like..

Conversion {
	id: convert;
}
 
MouseArea {
	anchors.fill: parent;
	onClicked: {
		console.log(convert.time_ms_to_sec(15000));
	}
}

Conversion {
	id: convert;
}

MouseArea {
	anchors.fill: parent;
	onClicked: {
		console.log(convert.time_ms_to_sec(15000));
	}
}

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Is there a way of doing this without having to declare the "Conversion {}"?!? I want to be able to simply call convert.time_ms_to_sec(<val>) in any script that has my import.

Thanks in advanced,

Raab.

[wysota]

You can make your plugin provide attached properties to objects or you can make it expose a global object using QQmlExtensionPlugin::initializeEngine() (or QDeclarativeExtensionPlugin::initializeEngine() if using Qt4). The latter would work similar to Math or Array objects in JavaScript.

[teh_raab]

Thanks QDeclarativeExtensionPlugin sounds exactly like what i'm after. I'll give it a bash.

[teh_raab]

So i had another look at the code (had to run after i sent previous reply so only just got back to looking at it).. I was already using the QDeclarativeExtensionPlugin. I just don't seem to be able to pin down the syntax. Here is what i have so far.

qmldir

plugin testplugin lib

plugin testplugin lib

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testplugin.pro

TEMPLATE = lib
CONFIG += qt plugin
QT += declarative
 
DESTDIR = lib
OBJECTS_DIR = tmp
MOC_DIR = tmp
 
HEADERS += conversions.h \
		   testplugin.h
 
SOURCES += conversions.cpp \
		   testplugin.cpp

TEMPLATE = lib
CONFIG += qt plugin
QT += declarative

DESTDIR = lib
OBJECTS_DIR = tmp
MOC_DIR = tmp

HEADERS += conversions.h \
		   testplugin.h

SOURCES += conversions.cpp \
		   testplugin.cpp

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conversions.h

#ifndef CONVERSIONS_H
#define CONVERSIONS_H
 
#include <QDeclarativeItem>
 
class Conversions : public QDeclarativeItem
{
    Q_OBJECT
 
public:
    Conversions(QDeclarativeItem *parent = 0);
 
    Q_INVOKABLE int time_ms_to_sec(int val);
};
#endif

#ifndef CONVERSIONS_H
#define CONVERSIONS_H

#include <QDeclarativeItem>

class Conversions : public QDeclarativeItem
{
    Q_OBJECT

public:
    Conversions(QDeclarativeItem *parent = 0);

    Q_INVOKABLE int time_ms_to_sec(int val);
};
#endif

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testplugin.h

#ifndef TESTPLUGIN_H
#define TESTPLUGIN_H
 
#include <QDeclarativeExtensionPlugin>
 
class TestPlugin : public QDeclarativeExtensionPlugin
{
    Q_OBJECT
public:
    void registerTypes(const char *uri);
};
#endif

#ifndef TESTPLUGIN_H
#define TESTPLUGIN_H

#include <QDeclarativeExtensionPlugin>

class TestPlugin : public QDeclarativeExtensionPlugin
{
    Q_OBJECT
public:
    void registerTypes(const char *uri);
};
#endif

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conversions.cpp

#include "conversions.h"
 
Conversions::Conversions(QDeclarativeItem *parent)
    : QDeclarativeItem(parent)
{
    // need to disable this flag to draw inside a QDeclarativeItem
    setFlag(QGraphicsItem::ItemHasNoContents, false);
}
 
 
int Conversions::time_ms_to_sec(int val = -1) {
    if(val == -1) {
        return -1;
    }
    else {
        return (val / 1000);
    }
}

#include "conversions.h"

Conversions::Conversions(QDeclarativeItem *parent)
    : QDeclarativeItem(parent)
{
    // need to disable this flag to draw inside a QDeclarativeItem
    setFlag(QGraphicsItem::ItemHasNoContents, false);
}


int Conversions::time_ms_to_sec(int val = -1) {
    if(val == -1) {
        return -1;
    }
    else {
        return (val / 1000);
    }
}

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testplugin.cpp

#include "testplugin.h"
#include "conversions.h"
#include <qdeclarative.h>
 
void TestPlugin::registerTypes(const char *uri)
{
    qmlRegisterType<Conversions>(uri, 1, 0, "Conversions");
}
 
Q_EXPORT_PLUGIN2(testplugin, TestPlugin);

#include "testplugin.h"
#include "conversions.h"
#include <qdeclarative.h>

void TestPlugin::registerTypes(const char *uri)
{
    qmlRegisterType<Conversions>(uri, 1, 0, "Conversions");
}

Q_EXPORT_PLUGIN2(testplugin, TestPlugin);

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And here is the QML -> I run this QML directly from QtCreater viewer. I have placed comments on line that is failing which shows what im trying to achieve.

Main.qml

import QtQuick 1.0
import TestPlugin 1.0
 
Item {
	width: 100; height: 100
 
	Conversions {
		id: convv
		Component.onCompleted: {
			console.log("Test 1: " + convv.time_ms_to_sec(1000)); //Works ok
			console.log("Test 2: " + time_ms_to_sec(2000)); //Works ok
		}
	}
 
	MouseArea {
		anchors.fill: parent;
		onClicked: {
			console.log("Test 3: " + convv.time_ms_to_sec(3000)); //Works ok
			console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
		}
	}
}

import QtQuick 1.0
import TestPlugin 1.0

Item {
	width: 100; height: 100

	Conversions {
		id: convv
		Component.onCompleted: {
			console.log("Test 1: " + convv.time_ms_to_sec(1000)); //Works ok
			console.log("Test 2: " + time_ms_to_sec(2000)); //Works ok
		}
	}

	MouseArea {
		anchors.fill: parent;
		onClicked: {
			console.log("Test 3: " + convv.time_ms_to_sec(3000)); //Works ok
			console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
		}
	}
}

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My final goal being..

Main.qml

import QtQuick 1.0
import TestPlugin 1.0
 
Item {
	width: 100; height: 100
 
	MouseArea {
		anchors.fill: parent;
		onClicked: {
			console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
		}
	}
}

import QtQuick 1.0
import TestPlugin 1.0

Item {
	width: 100; height: 100

	MouseArea {
		anchors.fill: parent;
		onClicked: {
			console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
		}
	}
}

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I have seen references to "setContextProperty" but not sure if this is required for what im after, or if so how to use it.

Thanks again,

Rob.

[wysota]

Hmm... I even told you what function you were to reimplement

class Conversions : public QObject {
  Q_OBJECT
public:
  Conversions(QObject *parent = 0) : QObject(parent) {}
public slots:
  int time_ms_to_sec(int val = -1) {
    return val == -1 ? -1 : (val / 1000);
  }
};
 
void TestPlugin::initializeEngine(QDeclarativeEngine *engine, const char *url) {
  engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));
}

class Conversions : public QObject {
  Q_OBJECT
public:
  Conversions(QObject *parent = 0) : QObject(parent) {}
public slots:
  int time_ms_to_sec(int val = -1) {
    return val == -1 ? -1 : (val / 1000);
  }
};

void TestPlugin::initializeEngine(QDeclarativeEngine *engine, const char *url) {
  engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));
}

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[teh_raab]

You Sir, are a legend It was pretty much what i had but could not work out the issue..

I had to change

engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));

engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));

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to be..

engine->rootContext()->setContextProperty("_conversions", new Conversions(engine));

engine->rootContext()->setContextProperty("_conversions", new Conversions(engine));

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I could then call from QML -> "_conversions.time_ms_to_sec(4000)". Im assuming thats because i already have "Conversions" as a registered type ("qmlRegisterType<Conversions>(uri, 1, 0, "Conversions");")!

Thanks once again.

[wysota]

The question is why you registered "Conversions". What is the point of doing that? How does your "Conversions" type differ from "Conversion"?

[teh_raab]

It shouldnt. That was just the original implementation that i wanted kept in until i got the above working. It has since been removed.