QML fit screen on all resolutions - qt

Question

Hi all I have problem with my QML code.
I made mistake and I went to put certain size to elements and now I have problem when putting app on other devices.
I will paste you my code where I have width and height so you can change it to show me how to work with dynamic resizeing.
I need to say that I am calling qml file from qt with this code:
QDeclarativeView *view= new QDeclarativeView;
ui->setupUi(this);
setCentralWidget(view);
QDeclarativeContext *ctxt = view->rootContext();
ctxt->setContextProperty("funkcije",this);
ctxt->setContextProperty("myModel", QVariant::fromValue(MainWindow::dataList));
view->setSource(QUrl("qrc:/gui.qml"));
view->setResizeMode(QDeclarativeView::SizeRootObjectToView);
showFullScreen();
And here goes my QML code:
Rectangle {
id:window
width: 602
height: 1000
anchors.fill: parent
radius: 0
.....
ListView {
id: listview1
x: 0
y: 219
// width: 574
// height: 967
width: window.width
height: window.height
visible: true
keyNavigationWraps: false
boundsBehavior: Flickable.DragAndOvershootBounds
opacity: 1
maximumFlickVelocity: 2500
anchors.leftMargin: 0
highlightMoveSpeed: 489
contentWidth: 0
preferredHighlightEnd: 2
spacing: 5
highlightRangeMode: ListView.NoHighlightRange
snapMode: ListView.SnapToItem
anchors.bottomMargin: 0
anchors.rightMargin: 0
anchors.topMargin: 219
anchors.fill: parent
model: myModel
delegate:Component {
//id: contactDelegate
Item {
id:it;
property variant myData: model
width: 574; height: 220
Column {
id:col
x: 12
y: 0
width: 561
height: 164
smooth: true
anchors.rightMargin: 0
anchors.bottomMargin: 7
anchors.leftMargin: 13
anchors.topMargin: 7
anchors.fill: parent
spacing: 15
......
highlight: Rectangle
{
width: 600
height: 222
color:"black"; radius: 5; opacity: 0.7
focus: true
}
}
Rectangle {
id: rectangle1
x: 0
y: 0
width: 602
height: 219
......
//dodaj korisnika
Flipable {
id: flipable
x: 6
y: 32
width: 173
height: 179
.......
MouseArea {
x: 10
y: 9
width: 146
height: 150
anchors.rightMargin: 7
anchors.leftMargin: 10
anchors.topMargin: 9
anchors.bottomMargin: 9
hoverEnabled: false
anchors.fill: parent
........
//Brisanje korisnika
Flipable {
id: flipable1
x: 408
y: 32
width: 175
height: 179
.......
MouseArea {
x: 7
y: 9
width: 153
height: 151
anchors.rightMargin: 8
anchors.leftMargin: 7
anchors.topMargin: 9
anchors.bottomMargin: 8
hoverEnabled: false
anchors.fill: parent
.......
//promjeni korisnika
Flipable {
id: flipable2
x: 208
y: 32
width: 176
height: 179
.......
MouseArea {
x: 7
y: 9
width: 73
height: 76
anchors.rightMargin: 7
anchors.leftMargin: 7
anchors.topMargin: 9
anchors.bottomMargin: 9
hoverEnabled: false
anchors.fill: parent
.......
Text {
id: text1
x: 200
y: 212
font.pixelSize: 12
opacity: 0
}
Rectangle {
id: rectangle2
x: 259
y: 510
width: 200
height: 200
color: "#ffffff"
opacity: 0
}
TextInput {
id: text_input1
x: 331
y: 233
width: 80
height: 20
font.pixelSize: 12
opacity: 0
}
Text {
id: text2
x: 136
y: 228
font.pixelSize: 12
opacity: 0
}
Text {
id: text3
x: 152
y: 314
font.pixelSize: 12
opacity: 0
}
Rectangle {
id: rectangle3
x: 256
y: 293
width: 200
height: 200
color: "#ffffff"
opacity: 0
}
Rectangle {
id: rectangle4
x: 339
y: 787
width: 200
height: 200
color: "#ffffff"
opacity: 0
}
Rectangle {
id: rectangle5
x: 270
y: 456
width: 200
height: 200
color: "#ffffff"
opacity: 0
}
TextInput {
id: text_input2
x: 269
y: 316
width: 80
height: 20
font.pixelSize: 12
opacity: 0
}
TextInput {
id: text_input3
x: 269
y: 401
width: 80
height: 20
font.pixelSize: 12
opacity: 0
}
TextInput {
id: text_input4
x: 269
y: 495
width: 80
height: 20
font.pixelSize: 12
opacity: 0
}
TextInput {
id: text_input5
x: 143
y: 465
width: 80
height: 20
text: qsTr("text")
font.pixelSize: 12
opacity: 0
}
states: [
State {
name: "State1"
PropertyChanges {
target: listview1
x: 0
y: 1049
width: 574
height: 967
visible: false
anchors.topMargin: 1049
anchors.rightMargin: 0
anchors.bottomMargin: 0
anchors.leftMargin: 0
}
PropertyChanges {
target: rectangle1
x: 0
y: 0
width: 602
height: 253
visible: true
}
PropertyChanges {
target: text1
x: 187
y: 253
width: 247
height: 71
color: "#c48d17"
text: qsTr("Unesite novog korisnika")
styleColor: "#e61717"
style: "Raised"
font.pixelSize: 31
font.family: "Lucida Handwriting"
verticalAlignment: "AlignVCenter"
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: rectangle2
x: 251
y: 353
width: 258
height: 42
color: "#777e79"
radius: 15
smooth: true
opacity: 1
}
PropertyChanges {
target: text_input1
x: 251
y: 360
width: 258
height: 29
font.pixelSize: 17
font.family: "Lucida Handwriting"
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: text2
x: 127
y: 362
width: 101
height: 25
color: "#fd0606"
text: qsTr("Ime")
style: "Raised"
font.family: "Lucida Handwriting"
font.pixelSize: 22
verticalAlignment: "AlignVCenter"
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: text3
x: 119
y: 519
color: "#f70606"
text: qsTr("Prezime")
style: "Raised"
font.pixelSize: 20
font.family: "Lucida Handwriting"
verticalAlignment: "AlignVCenter"
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: rectangle3
x: 251
y: 514
width: 258
height: 40
color: "#777e79"
radius: 15
opacity: 1
}
PropertyChanges {
target: rectangle4
x: 251
y: 669
width: 258
height: 38
color: "#777e79"
radius: 15
opacity: 1
}
PropertyChanges {
target: rectangle5
x: 251
y: 823
width: 258
height: 36
color: "#777e79"
radius: 15
opacity: 1
}
PropertyChanges {
target: text_input2
x: 251
y: 519
width: 258
height: 29
font.family: "Lucida Handwriting"
font.pixelSize: 17
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: text_input3
x: 251
y: 674
width: 258
height: 29
horizontalAlignment: "AlignHCenter"
font.pixelSize: 17
font.family: "Lucida Handwriting"
opacity: 1
}
PropertyChanges {
target: text_input4
x: 251
y: 827
width: 258
height: 29
font.family: "Lucida Handwriting"
font.pixelSize: 17
horizontalAlignment: "AlignHCenter"
opacity: 1
}
PropertyChanges {
target: text4
x: 127
y: 669
width: 85
height: 31
color: "#f70606"
text: qsTr("Broj")
style: "Raised"
font.family: "Lucida Handwriting"
font.pixelSize: 20
horizontalAlignment: "AlignHCenter"
verticalAlignment: "AlignVCenter"
opacity: 1
}
]
}
I have put all the code with width and height so you can see what I have done wrong. And please if someone can say me how to make it dynamically fill.

Answer 1

It's unfortunately tricky to get perfect, as it's likely that as the screen size shrinks you might actually want the buttons to be bigger and to drop content from the screen to ensure the user can access and read everything ok.
But the general approach is actually to set a scale factor in the C++ side:
ctxt->setContextProperty("scale", /* put calculated scale factor here */);
And then on the QML side, use that everyone to scale all the objects:
Rectangle {
id:window
width: 602 * scale
height: 1000 * scale
That way you can adjust the scale variable to change everything's size. Having said that, many people end up with different QML files depending on the platform size though.

Answer 2

I recommend you read the Scalability page in the current Qt (4.8) documentation: it is on exactly this topic.
It recommends these techniques (I'm quoting the page here), and then supplies much more detail.
Create separate top-level layout definitions for each form factor.
Keep the layouts small and let components scale relative to their
immediate parent.
Define device independent measurements, such as dp (device
independent pixels), and use these to scale components and for layout
measurement.
Define layouts in a proportional way using the built-in layout
features of QML.
Update 2014-11-18 This and video article looks very useful indeed:
Supporting Multiple Screen Sizes & Screen Densities with Qt and V-Play
Update 2017-01-24 There is an updated Qt 5.8 version of the Scalability page mentioned above.

Answer 3

Changing the device, you are actually changing the screen pixel density. If you have a device with low quality display it will have lower number of pixels per inch or pixels per centimeter than a device with high quality display.
Understanding this we can easily devise a method to scale our content according to the pixel density. For example in my case I have a laptop on which I use Qt creator. It has pixel density of 4. But my android phone is of high quality which has density of 16(4 times more than my Laptop). It means if an item has a width 'X' and height 'Y' when displaying on my Laptop, on my phone it will appear with a width 'X'/4 and height 'Y'/4 . Thus I have to scale height and width by 4.
Now, How to implement this? In QML we have a property "pixelDensity" under object Screen which will give you the pixel density of the screen where you are running your application. Dividing this by the screen density of screen where you tested your application will give you the scale factor. So now you don't need to worry about other devices you have just find the pixel density of screen you are currently working on.
Following code works perfectly for me.
property int default_pix_density: 4 //pixel density of my current screen
property int scale_factor: Screen.pixelDensity/default_pix_density
Rectangle
{
width: 50*scale_factor
height: 20*scale_factor
}