Add background and font colour to a button with material design - qt

Question

I am trying to design a login form with a material design on Qt which should look something like this:
However I can't figure out how to add colour to the button in QML and change the font colour of the button text. This is what I have got so far:
import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
Item {
property alias login: login
Pane {
id: pane
x: 144
y: 117
width: 353
height: 246
clip: false
font.strikeout: false
background: Rectangle {
color: "#ffffff"
}
ColumnLayout {
id: columnLayout
x: 139
y: -158
anchors.fill: parent
TextField {
id: username
Layout.fillWidth: true
placeholderText: qsTr("Username")
}
TextField {
id: password
Layout.fillWidth: true
placeholderText: qsTr("Password")
}
Button {
id: login
text: qsTr("Login")
spacing: -2
font.capitalization: Font.MixedCase
Layout.fillWidth: true
highlighted: false
// background: Rectangle {
// implicitWidth: 100
// implicitHeight: 40
// color: button.down ? "#d6d6d6" : "#f6f6f6"
// border.color: "#26282a"
// border.width: 1
// radius: 4
// }
}
}
}
}
As you can see (in the commented code) I tried to add colour using Rectangle with the background property but this removes the button features like shadow, highlight, darken on click and so on. Is there a simple way to accomplish this?
For reference here is the output of my code:

Answer 1

In order to theme a Material controls, you have to use the Material attached properties
In your case you want to use Material.background :
import QtQuick.Controls.Material 2.2
// ...
Button {
id: login
text: qsTr("Login")
Layout.fillWidth: true
Material.background: Material.Indigo
Material.foreground: "white"
}
Note that buttons should have upercased text, according to the material guidelines.

Answer 2

If you want to have a design that complies with the Google Materials design guidelines, the easiest way, is to use
QtQuick.Controls.Materials
To use them, it is sufficent to use any of the methods described here to activate them in your application. To try it out, I'd reccomend the command line argument. Just start your application with
-style material
If you want to have it fixed in your code, put it in the main.cpp:
QQuickStyle::setStyle("Material");
Note that the -style options is the very same option defined here for widgets and desktop os styles. Despite this quick styles and widget styles are totally different things and you cannot apply the former to the latter and vice versa. Widget
If now you already use the Material-style, but are not contempt with it and desire to change some of the definitions for selected controls, you can import
import QtQuick.Controls.Materials 2.x
where you need to adapt x to the most recent version installed. 0 is the right one for Qt5.7
Then you can alter specific aspects like
import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Controls.Material 2.0
ApplicationWindow {
id: mainWindow
width: 800
height: 600
visible: true
Button {
id: login
text: qsTr("LOGIN")
Material.background: Material.Orange // Change the background
}
}
If you don't want to use the Material and only want to change a specific color of the Control you need to understand why it is not that easy to do, without messing it up.
I tried to add colour using Rectangle with the background property but this removes the button features like shadow, highlight, darken on click and so on. Is there a simple way to accomplish this?
You can't just change the color of the background, as there is not the color. There are various colors that are applied for different states. The expression might look like this:
color: (control.down ? 'darkgrey' : 'lightgrey')
So if you change the color to orange like this:
color: 'orange'
you messed up, as now the other state is not considered anymore.
Additionally, of course, you can't change the color of the background like background.color: 'green' from the beginning, as QML does not know about the property background.color. It expects an Item there, which has no color and the Rectangle is only created later. So what you need to do is
Be cautious to not override states
Wait until the property is available
example.qml
Button {
id: login
text: qsTr("LOGIN")
Binding {
target: login
property: "background.color"
value: 'red'
when: !login.pressed // Here comes the state
}
}

Answer 3

You can simply highlight a Button to make the button colorize its background in a style-independent way. The Material style fills the background with the accent color and makes the text light:
Button {
text: qsTr("Login")
highlighted: true
}
A highlighted Button is by far more efficient than a customized button. Customization should be done only if necessary. It is just a visual highlight. There can be multiple highlighted buttons. Highlighting a Button does not affect focus.