Let's assume I have a component like this:
Rectangle {
id: rec1
Rectangle {
id: rec
x:10;y:100; height:100;
color: 'red'
anchors {
left: parent.left
right: parent.right
}
Loader {
id:loader
width: parent.width
sourceComponent: comp
}
}
Component {
id: comp
Rectangle {
anchors {
left: parent.left
leftMargin: 1 // this line
right: parent.right
}
height:img.height
Image {
id: img
source: '/myimage.png'
width: parent.width
fillMode: Image.PreserveAspectFit
}
}
}
}
the console reports:
QML Image: Binding loop detected for property "width"
But if I change the comp leftMargin to leftMargin: 0 (not 1), everything is ok
Is this a bug or some feature I am missing?
In my opinion you made a typo:
width:100; height:100;
...
anchors {
left: parent.left
right: parent.right
}
By doing this you:
Explicitly set your rectangles width (to 100).
Do explicitly anchoring of left side to parents left side (if this is only one anchoring operation -- it is Ok) and then -- do anchoring of right side to parent's right side (so you are implicitly defining your rectangle's width).
It is contradiction. Try to solve it (for example, by removing right anchoring) and re-run your application.
Related
I have a QML ListView, and I'm trying to dynamically add elements to it. I want the background rectangle to also scale dynamically as elements are added/removed from the ListView. Right now I get a binding loop, and I understand what they are but I can't figure out where it's coming from. I played around changing the code a bit and I was able to get rid of the binding loop one time but then the ListView couldn't be scrolled. Anyone have any ideas?
import QtQuick 2.15
import QtQuick.Window 2.0
Window {
visible: true
width: 800
height: 800
Rectangle {
id: listContainer
height: childrenRect.height
width: parent.width
color: "transparent"
anchors {
top: parent.top
topMargin: 30
left: parent.left
leftMargin: 45
}
ListView {
anchors.top: parent.top
anchors.left: parent.left
anchors.right: parent.right
model: myModel
height: childrenRect.height
header:
Text {
z: 2
height: 50
text: "HEADER"
color: "black"
}
delegate: Component {
Item {
Text {
id: userName;
text: name;
color: "black";
font.pixelSize: 50
anchors {
left: parent.left
leftMargin: 20
}
}
Rectangle {
height: 1
color: 'black'
width: listContainer.width
anchors {
left: userName.left
top: userName.top
topMargin: - 12
leftMargin: -15
}
}
}
}
spacing: 80
}
}
ListModel {
id: myModel
}
/* Fill the model with default values on startup */
Component.onCompleted: {
for (var i = 0; i < 100; i++) {
myModel.append({
name: "Big Animal : " + i
})
}
}
}
EDIT: As suggested by #Aditya, the binding loop can be removed by having a static ListView height, but I don't want it to be that way. I'm using the rectangle as a background for the ListView and I want it to scale according to the ListView. For example, if I only add two elements, I want the rectangle to also scale for those two elements and not cover the entire screen. This causes a problem:
import QtQuick 2.15
import QtQuick.Window 2.0
Window {
visible: true
width: 800
height: 800
Rectangle {
id: listContainer
height: childrenRect.height
width: parent.width
color: "yellow"
anchors {
top: parent.top
topMargin: 30
left: parent.left
leftMargin: 45
}
ListView {
anchors.top: parent.top
anchors.left: parent.left
anchors.right: parent.right
model: myModel
height: 800//childrenRect.height
header:
Text {
z: 2
height: 50
text: "HEADER"
color: "black"
}
delegate: Component {
Item {
Text {
id: userName;
text: name;
color: "black";
font.pixelSize: 50
anchors {
left: parent.left
leftMargin: 20
}
}
Rectangle {
height: 1
color: 'black'
width: listContainer.width
anchors {
left: userName.left
top: userName.top
topMargin: - 12
leftMargin: -15
}
}
}
}
spacing: 80
}
}
ListModel {
id: myModel
}
/* Fill the model with default values on startup */
Component.onCompleted: {
for (var i = 0; i < 2; i++) {
myModel.append({
name: "Big Animal : " + i
})
}
}
}
I also tried separating the header from ListView into a different component and anchoring the listview below it and that worked. The only problem was it could not be scrolled with the listview. Worst case, I could make a scrolling animation for it but that seems like an inefficient solution and I'd like to know why this doesn't work.
You are probably also biting yourself with the Item as the top-level in the delegate, since that doesn't give any implicit size, which the ListView uses to calculate the scrolling needs. You can simply use Text directly as the delegate (you don't need the Component either) and put the line/rectangle inside. If doing so you can use the contentHeight property of ListView to size the background.
Furthermore, I would suggest to have the ListView as the top level and do any styling secondary, with which I mean, put the background Rectangle inside.
import QtQuick 2.12
import QtQuick.Window 2.12
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
ListView {
id: listView
model: 3
anchors.fill: parent
Rectangle { //background
color: "yellow"
z: -1
width: listView.width
height: listView.contentHeight
}
delegate: Text {
text: "name" + index
color: "black";
font.pixelSize: 50
leftPadding: 20
Rectangle {
height: 1
color: 'black'
width: listView.width
y: - 12
x: -15
}
}
spacing: 80
}
}
Btw, if you are going to put the ListView in some RowLayout or something, you probably also want implicitHeight: contentHeight in the ListView.
The binding loop is originating from the ListView's height: childrenRect.height statement. It looks like the ListView needs to be a fixed height, or at least not dependent on childrenRect. It is most likely how the ListView element knows that the view should be scrollable to view elements below.
It really depends on what you're trying to achieve with setting the height to match childrenRect, but in my case, ListView height is changing based on the children (per your desire presumably). With a 100 items the height came out to be 7970. With 5 items in the model, the result was 350. You can check this by adding a debug or console.log() with onHeightChanged However, as a result of this scaling, the ListView is assumed to be big enough to view the entire data set regardless of the window parent container size.
You do not need to scale the ListView height to match the contents; that is what it is built for. It allows scrolling because the contents are too big to be shown within its limited height.
I was able to achieve get rid of the binding loop and be able to scroll by simply changing the statement to a static value, which is the parent height of 800 as an example:
Window {
visible: true
width: 800
height: 800
Rectangle {
id: listContainer
height: childrenRect.height
width: parent.width
color: "transparent"
anchors {
top: parent.top
topMargin: 30
left: parent.left
leftMargin: 45
}
ListView {
anchors.top: parent.top
anchors.left: parent.left
anchors.right: parent.right
model: myModel
height: 800//childrenRect.height
header:
Text {
z: 2
height: 50
text: "HEADER"
color: "black"
}
delegate: Component {
Item {
Text {
id: userName;
text: name;
color: "black";
font.pixelSize: 50
anchors {
left: parent.left
leftMargin: 20
}
}
Rectangle {
height: 1
color: 'black'
width: listContainer.width
anchors {
left: userName.left
top: userName.top
topMargin: - 12
leftMargin: -15
}
}
}
}
spacing: 80
}
}
ListModel {
id: myModel
}
/* Fill the model with default values on startup */
Component.onCompleted: {
for (var i = 0; i < 100; i++) {
myModel.append({
name: "Big Animal : " + i
})
}
}
}
Edit:
I feel like you're trying to just secure a background for a scalable ListView. Having a static background as a container works but not very well for modern unser interfaces - any bounce effects or such will not move the rectangle. You could achieve this by anchoring the rectangle to the ListView element but it is a very roundabout way. Instead, you could just set a rectangle to style each element of the ListView delegate instead.
delegate: Component {
Item {
Rectangle{
width: listContainer.width
height: userName.height+13
//add 13 to adjust for margin set below
anchors {
left: userName.left
top: userName.top
topMargin: - 12
leftMargin: -15
//just copying from the other rectangle below
}
gradient: Gradient {
//I am just using gradient here for a better understanding of spacing. You could use color.
GradientStop { position: 0.0; color: "aqua" }
GradientStop { position: 1.0; color: "green" }
}
}
Text {
id: userName;
text: name;
color: "black";
font.pixelSize: 50
anchors {
left: parent.left
leftMargin: 20
}
}
Rectangle {
height: 1
color: 'black'
width: listContainer.width
anchors {
left: userName.left
top: userName.top
topMargin: - 12
leftMargin: -15
}
}
}
}
This will make sure that the rectangle background behind the ListView will look like it is scrolling with the items. In reality we have broken one rectangle into multiple and just set each element with one. You can also use this type of styling to achieve alternate colors in your list for example.
I have a ListView in my qml file, but when I am overscrolling it, it gets stuck for a several seconds and then flicks back. Does anyone know what can be the reason of that delay before flicking back?
Also, it's only freezes, when the text inside my delegates is on Russian language. On english it works fine
Upd:
There is nothing specific, but minimal, reproducible example:
ListView {
id: list
anchors {
right: parent.right
top: parent.top
}
height: parent.height
width: 502
interactive: height < contentHeight
spacing: 24
currentIndex: -1
footer: Item {
height: 100
}
delegate: Item {
anchors {
left: list.contentItem.left
right: list.contentItem.right
leftMargin: 40
rightMargin: 40
}
implicitHeight: Math.max(image.height, description.implicitHeight)
// Some other code
}
ScrollBar.vertical: OknaGui.ScrollBar { id: scrollBar } // Just a scrollbar
}
This might not be the proper solution, but you can disable overscroll at all with boundsBehavior: Flickable.StopAtBounds
I am attempting to make a PDF viewer inside of a Flickable in QML. To do this I use the Poppler library to render my PDFPages to images. When I zoom, I re-scale the size of the image, causing the content Height and Width to change.
My question is, when I zoom out to the point where the image width is less than the Flickable width, the image is shoved to the left. Similarly, if I flip the orientation and the height of the image becomes less than the FlickArea height, the image is locked to the top. Is there any good way to center the image in the FlickArea window?
For the purposes of making this example simpler I replaced my PDF image with a Rectangle.
//Flickable qml snippet
Flickable
{
id: flickArea
anchors.fill: parent
anchors.centerIn: parent
focus: true
contentWidth: testRect.width
contentHeight: testRect.height
clip: true
Rectangle
{
id: testRect
color: "red"
width: 2550 * zoom
height: 3300 * zoom
property double zoom: 1.0;
}
}
//zoom button snippet
Item
{
id: zoomContainer
width: 80
height: zoomColumn.childrenRect.height
z: 2
anchors
{
right: parent.right
bottom: parent.bottom
rightMargin: 10
bottomMargin: 10
}
Column
{
id: zoomColumn
width: parent.width
spacing: 5
anchors
{
right: parent.right
}
Button
{
id: zoomInButton
height: 75
width: parent.width
text: '+'
onClicked: {
testRect.zoom += 0.1
console.log(testRect.zoom)
}
}
Button
{
id: zoomOutButton
height: 75
width: parent.width
text: '-'
onClicked: {
testRect.zoom -= 0.1
console.log(testRect.zoom)
}
}
}
}
Try something like this:
Flickable
{
id: flickArea
anchors.fill: parent
// anchors.centerIn: parent // redundant code
focus: true
contentWidth: wrapper.width
contentHeight: wrapper.height
clip: true
Item
{
id: wrapper
width: Math.max(flickArea.width, testRect.width)
height: Math.max(flickArea.height, testRect.height)
Rectangle
{
id: testRect
color: "red"
anchors.centerIn: parent // centered in wrapper
width: 2550 * zoom
height: 3300 * zoom
property double zoom: 1.0;
}
}
}
I am using Row to layout some buttons on a Rectangle which is my custom toolbar implementation. The problem is no matter what I do, the components are always aligned from the left. I would like them to be aligned with the center of the row and flowing outwards towards the edges. The code looks as follows:
Rectangle {
id: toolbar
color: "green"
anchors.left: parent.left
anchors.right: parent.right
anchors.bottom: parent.bottom
height: 100
Row
{
anchors.fill: parent
anchors.horizontalCenter: parent.horizontalCenter
spacing: 60
ToolButton {
height: parent.height
Image {
anchors.verticalCenter: parent.verticalCenter
source: "../images/image.png"
}
}
ToolButton {
height: parent.height
Image {
anchors.verticalCenter: parent.verticalCenter
source: "../images/image.png"
}
}
}
}
My buttons are always laid out starting from the left side of the row. Rather I would like to have them laid out relative to the center of the toolbar. I thought specifying this line anchors.horizontalCenter: parent.horizontalCenter should achieve that but no matter what I try, the components are laid out from the left boundary.
If you set your Row's alignments to center in the parent object and then make the Row's width adjust to the childrenRect's width then you can have items expand from the center of the object. Note: you may need to set the widths of the ToolButton's in order for the childrenRect to have it's width value populated.
Rectangle {
id: toolbar
color: "green"
anchors.left: parent.left
anchors.right: parent.right
anchors.bottom: parent.bottom
height: 100
Row
{
anchors{
horizontalCenter: parent.horizontalCenter
verticalCenter: parent.verticalCenter
}
height: parent.height
width: childrenRect.width
spacing: 60
ToolButton {
height: parent.height
width: 50
Image {
anchors.verticalCenter: parent.verticalCenter
source: "../images/image.png"
}
}
ToolButton {
height: parent.height
width: 50
Image {
anchors.verticalCenter: parent.verticalCenter
source: "../images/image.png"
}
}
}
}
You've set anchors.fill: parent on the Row so it will of course fill its parent. Instead, you should remove this, and only set height: parent.height on the Row.
Documentation citation:
since a Row automatically positions its children horizontally, a child item within a Row should not set its x position or horizontally anchor itself using the left, right, anchors.horizontalCenter, fill or centerIn anchors. If you need to perform these actions, consider positioning the items without the use of a Row.
Row is only for positioning it`s children horizontally. Without any 'flows' or centering. It is for automatic positioning in a row which let you exclude defines of anchors and margins inside item when you need to perform that simple task.
But if you need something more complicated, you need to do it with anchors and margins manually. For example. Centering items and spreading them from center to the edges might look like this:
import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.0
Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
Rectangle {
id: toolbar
color: "green"
anchors.centerIn: parent
height: 100
width: parent.width
Rectangle {
id: toolbutton1
height: parent.height
anchors {
right: toolbutton2.left
margins: 20
}
width: 100
color: "blue"
}
Rectangle {
id: toolbutton2
height: parent.height
anchors {
right: parent.horizontalCenter
margins: 10
}
width: 100
color: "magenta"
}
Rectangle {
id: toolbutton3
height: parent.height
anchors {
left: parent.horizontalCenter
margins: 10
}
width: 100
color: "red"
}
Rectangle {
id: toolbutton4
height: parent.height
anchors {
left: toolbutton3.right
margins: 20
}
width: 100
color: "yellow"
}
}
}
I need to share equally the horizontal space between all "buttons" in my Row.
I use this code with a Repeater.
Component {
id: buttonComponent
Rectangle {
height: buttonRow.height
width: buttonRow.width / buttonsRepeater.count
color: "#FFDDDD"
Text {
anchors.centerIn: parent
text: model.text
}
}
}
Rectangle {
color: "#DDDDDD"
id: buttonBar
height: 30
anchors {
bottom: parent.bottom
left: parent.left
right: parent.right
}
Row {
id: buttonRow
anchors.fill: parent
Repeater {
id: buttonsRepeater
model: buttonsModel
delegate: buttonComponent
}
}
}
Now, I like to compute the ideal width of the Row such that all my button texts appear correctly.
How can I get this ideal width?
If you don't want to use QtQuick.Layouts as they are not really ready yet, you can use this :
Rectangle {
id: buttonBar;
color: "#DDDDDD";
height: 30;
width: (buttonColumn.width + 20 + buttonRow.spacing) * buttonsRepeater.count;
anchors {
bottom: parent.bottom;
left: parent.left;
}
Column {
id: buttonColumn;
visible: false;
Repeater {
model: buttonsModel;
delegate: Text {
text: model.text;
}
}
}
Row {
id: buttonRow;
anchors.fill: parent;
property real itemWidth : ((width + spacing) / buttonsRepeater.count) - spacing;
Repeater {
id: buttonsRepeater;
model: buttonsModel;
delegate: Component {
id: buttonDelegate;
Rectangle {
height: parent.height;
width: parent.itemWidth;
color: "#FFDDDD";
border.width: 1;
Text {
anchors.centerIn: parent;
text: model.text;
}
}
}
}
}
}
I just used a hidden Column to easily compute max width of Text elements, and added a little padding in the bar width to avoid unspaced text.
The minimum width of a button itself is the implicitWidth property of its Text element.
One solution to your problem might be to add code in the Component.onCompleted handler, i.e. code that is executed after the repeater has created its items, and then sum up these implicitWidth properties of each of the repeater's item (which you can get by using its itemAt(index) function).
These kinds of dynamic layout is a bit cumbersome in QML still, which will get much better in Qt 5.1 with the introduction of Qt Quick Layouts