Add valueRole API to ComboBox

This allows the user to conveniently manage data for a role associated with
the text role. A common example of this is an enum stored in a backend with
nicely formatted text displayed to the user. Before this patch, developers
would have to write code like this:

    ComboBox {
        textRole: "text"
        onActivated: backend.modifier = model[currentIndex].value
        Component.onCompleted: currentIndex = findValue(backend.modifier)
        model: [
            { value: Qt.NoModifier, text: qsTr("No modifier") },
            { value: Qt.ShiftModifier, text: qsTr("Shift") },
            { value: Qt.ControlModifier, text: qsTr("Control") }
        ]

        function findValue(value) {
            for (var i = 0; i < model.length; ++i) {
                if (model[i].value === value)
                    return i
            }
            return -1
        }
    }

With this patch, the code becomes much simpler:

    ComboBox {
        textRole: "text"
        valueRole: "value"
        onActivated: backend.modifier = currentValue
        Component.onCompleted: currentIndex = indexOfValue(backend.modifier)
        model: [
            { value: Qt.NoModifier, text: qsTr("No modifier") },
            { value: Qt.ShiftModifier, text: qsTr("Shift") },
            { value: Qt.ControlModifier, text: qsTr("Control") }
        ]
    }

[ChangeLog][Controls][ComboBox] Added valueRole, currentValue and
indexOfValue(). These allow convenient management of data for a role
associated with the text role.

Change-Id: I0ed19bd0ba9cf6b044a8113ff1a8782d43065449
Fixes: QTBUG-73491
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/imports/templates/qtquicktemplates2plugin.cpp b/src/imports/templates/qtquicktemplates2plugin.cpp
index 10f9b8dd..008293a2 100644
--- a/src/imports/templates/qtquicktemplates2plugin.cpp
+++ b/src/imports/templates/qtquicktemplates2plugin.cpp
@@ -355,6 +355,9 @@ void QtQuickTemplates2Plugin::registerTypes(const char *uri)
     qmlRegisterUncreatableType<QQuickSplitHandleAttached>(uri, 2, 13, "SplitHandle",
         QStringLiteral("SplitHandle is only available as an attached property."));
     qmlRegisterType<QQuickSplitHandleAttached>();
+
+    // QtQuick.Templates 2.14 (new types and revisions in Qt 5.14)
+    qmlRegisterType<QQuickComboBox, 14>(uri, 2, 14, "ComboBox");
 }
 
 QT_END_NAMESPACE