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, 7 insertions, 7 deletions

diff --git a/src/imports/controls/fusion/ComboBox.qml b/src/imports/controls/fusion/ComboBox.qml
index 3ecb0cf2..58764809 100644
--- a/src/imports/controls/fusion/ComboBox.qml
+++ b/src/imports/controls/fusion/ComboBox.qml
@@ -34,13 +34,13 @@
 **
 ****************************************************************************/
 
-import QtQuick 2.12
-import QtQuick.Window 2.12
-import QtQuick.Templates 2.12 as T
-import QtQuick.Controls 2.12
-import QtQuick.Controls.impl 2.12
-import QtQuick.Controls.Fusion 2.12
-import QtQuick.Controls.Fusion.impl 2.12
+import QtQuick 2.14
+import QtQuick.Window 2.14
+import QtQuick.Templates 2.14 as T
+import QtQuick.Controls 2.14
+import QtQuick.Controls.impl 2.14
+import QtQuick.Controls.Fusion 2.14
+import QtQuick.Controls.Fusion.impl 2.14
 
 T.ComboBox {
     id: control