Trouble with toolbar layout

[MScottM]

I have an ApplicationWindow with a toolbar, and inside the toolbar I'm using a RowLayout to try and place some comboboxes. No matter what I try, the comboboxes end up on top of each other.

main.qml:

ApplicationWindow {
    id: root
    visible: true
    color: "black"
    minimumHeight: 600
    minimumWidth: 875
    width: Screen.width * 0.8
    height: Screen.height * 0.8
    title: qsTr("Main GUI")    

    toolBar: ToolBar {
        id: toolbar
        style: MyToolBarStyle {}

    RowLayout {
        
            ComboBox {
                id: cboEnginesPage
                style: MyEnginesComboBoxStyle{}

            } // combobox

            ComboBox {
                id: cboGaugeAlignment
                x: cboEnginesPage.width
                style: MyGaugeAlignmentComboBoxStyle{}

            }//ComboBox
        }//RowLayout
    } // toolbar

// Other layouts down here

}

MyToolBarStyle:

import QtQuick 2.9
import QtQuick.Controls 1.0
import QtQuick.Controls.Styles 1.4


ToolBarStyle {
    id: styleToolBar
        padding {
            left: 8
            right: 8
            top: 3
            bottom: 3
        }
        background: Rectangle {
            //implicitWidth: 100
            implicitHeight: 40
            border.color: "#999"
            gradient: Gradient {
                GradientStop { position: 0 ; color: "#fff" }
                GradientStop { position: 1 ; color: "#555" }
            }
        }
    }

I don't know if the styling of the ComboBoxes is interfering with things? Here is code from one of them:

import QtQuick 2.6
import QtQuick.Controls 2.1

ComboBox {
    id: needleControl
    model: ["Gauges Normal ", "Needles Up "]

    delegate: ItemDelegate {
        width: needleControl.width
        contentItem: Text {
            text: modelData
            color: "#0e0e0e"
            font: needleControl.font
            elide: Text.ElideRight
            verticalAlignment: Text.AlignVCenter
        }
        highlighted: needleControl.highlightedIndex === index
    }

    indicator: Canvas {
        id: canvas
        x: needleControl.width - width - needleControl.rightPadding
        y: needleControl.topPadding + (needleControl.availableHeight - height) / 2
        width: 12
        height: 8
        contextType: "2d"

        Connections {
            target: needleControl
            onPressedChanged: canvas.requestPaint()
        }

        Connections {
            target: needleControl
            onActivated: setNeedlesUp()

        function setNeedlesUp() {
            if (needleControl.currentText==="Gauges Normal ") {
                needlesUp = false
            }
            if (needleControl.currentText==="Needles Up ") {
                needlesUp = true
            }
        }//function
    }

        onPaint: {
            context.reset();
            context.moveTo(0, 0);
            context.lineTo(width, 0);
            context.lineTo(width / 2, height);
            context.closePath();
            context.fillStyle = needleControl.pressed ? "#a3a3a3" : "#000000";
            context.fill();
        }
    }

    contentItem: Text {
        leftPadding: 8
        rightPadding: needleControl.indicator.width + needleControl.spacing

        text: needleControl.displayText
        font: needleControl.font
        color: needleControl.pressed ? "#a3a3a3" : "#000000"
        verticalAlignment: Text.AlignVCenter
        elide: Text.ElideRight
    }

    background: Rectangle {
        implicitWidth: 120
        implicitHeight: 40
        border.color: needleControl.pressed ? "#a3a3a3" : "#000000"
        border.width: needleControl.visualFocus ? 2 : 1
        radius: 2
    }

    popup: Popup {
        y: needleControl.height - 1
        width: needleControl.width
        implicitHeight: contentItem.implicitHeight
        padding: 1

        contentItem: ListView {
            clip: true
            implicitHeight: contentHeight
            model: needleControl.popup.visible ? needleControl.delegateModel : null
            currentIndex: needleControl.highlightedIndex

            ScrollIndicator.vertical: ScrollIndicator { }
        }

        background: Rectangle {
            border.color: "#000000"
            radius: 2
        }
    }
}

At run-time, I also get these errors related to the combobox styling:

QML debugging is enabled. Only use this in a safe environment.
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:462:21: Unable to assign [undefined] to int
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:456: TypeError: Cannot read property 'dropDownButtonWidth' of null
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:462:21: Unable to assign [undefined] to int
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:456: TypeError: Cannot read property 'dropDownButtonWidth' of null
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:584: TypeError: Cannot read property 'height' of null
file:///C:/Qt/5.11.2/mingw53_32/qml/QtQuick/Controls/ComboBox.qml:584: TypeError: Cannot read property 'height' of null

Any help is appreciated - I've been banging my head against this one for half the day.

-Scott