QML performance on sliders - performance

Question

Hmm.. I have 22 of these slider elements placed via a Repeater in my app.. Moving a slider is quite jitter-y and jerky, and that is on the nvidia gpu on my laptop. This was smoother on integrated graphics.. Is there anything plainly obvious I could improve? I'm fairly new to Qt, so this is a puzzle for me..
import QtQuick 2.0
import QtQuick.Controls 2.2
Item {
height: 4*82
width: 82
Rectangle {
height: 4*82
width: 83.55
color: "#0a0a0a"
border.color: "#80cccccc"
Rectangle {
width: 83.55
height: 22
color: "#0a0a0a"
border.color: "#80cccccc"
y:parent.y -22
Label {
x:parent.x+parent.width/2 - width/2
y:5
id: name
text: qsTr("MASTER EFX SP")
color: slider.value > 0 ? "#6eaf71" : "#3c3c3c"
font.pixelSize: 10
}
}
}
Slider {
id: slider
from: 0
to: 255
value: 0
orientation: Qt.Vertical
height: (4*82)-32
width: 83.55
y: 16
stepSize: 1.0
handle: Item {
y: parent.topPadding + parent.visualPosition * (parent.availableHeight - 50)
x: parent.leftPadding + parent.availableWidth / 2 - 30 / 2
Rectangle {
color: parent.parent.pressed || parent.parent.value > 0? "#901fdcf5" : "#90ffffff"
border.color: parent.parent.pressed || parent.parent.value > 0? "#1fdcf5" : "gray"
width: 30
height: 50
radius: 2
}
Rectangle {
color: parent.parent.pressed || parent.parent.value > 0? "#80000831" : "#4e4e4e"
width: 30
height: 2
y: 50/2-2
}
}
background: Rectangle {
x: parent.leftPadding + (horizontal ? 0 : (parent.availableWidth - width) / 2)
y: parent.topPadding + (horizontal ? (parent.availableHeight - height) / 2 : 0)
implicitWidth: horizontal ? 200 : 6
implicitHeight: horizontal ? 6 : 200
width: horizontal ? parent.availableWidth : implicitWidth
height: horizontal ? implicitHeight : parent.availableHeight
radius: 0
border.color: "#3c3c3c"
color: "#3c3c3c"
scale: horizontal && parent.mirrored ? -1 : 1
readonly property bool horizontal: parent.orientation === Qt.Horizontal
}
}
}

Answer 1

First, try to understand what's wrong - it might not be the sliders after all.
use Gammaray to open your Qml application and examine the graphics stack.
From the code that you pasted, the only thing I could think that migth cause an issue is the radius property, as it's the only expensive thing your code is doing.
Also, try to update the library imports to the latest qt version, you are using a really old one and new ones also migth improve performance.