fluentpyside 0.1.4

FluentWinUI3 QML style for PySide6 — one-liner to add the Fluent theme

FluentPySide

fluentpyside packages the FluentWinUI3 Qt Quick Controls style so any Qt / PySide6 application can add the FluentWinUI3 theme easily. The goal is to make it simple to enable the Fluent theme without bundling the full PySide6 runtime into your application. For minimal, bloat-free builds prefer installing PySide6-Essentials on the target system rather than packaging compiled plugin binaries inside this package.

⚠️ IMPORTANT — Read this before using

This library is a QML visual theme only. It styles Qt Quick Controls 2 components (Button, TextField, CheckBox, etc.) to look like Windows 11's Fluent Design. It does NOT provide:

• A Python widget library (it does NOT touch QtWidgets — no QPushButton, QLabel, etc.)
• Custom QML components — you use the standard Qt Quick Controls 2 API, this library just changes how they look

For colors and design tokens, use the Fluent singleton (available after calling fluentpyside.apply()):

Rectangle {
    color: Fluent.cardBackground
    radius: Fluent.radiusMedium
    Label {
        text: "Hello"
        color: Fluent.textPrimary
        font.pixelSize: Fluent.fontBodySize
        font.family: Fluent.fontFamily
    }
}

Quick Start

pip install PySide6-Essentials   # recommended — provides the runtime plugins
pip install fluentpyside

import fluentpyside
fluentpyside.apply()

That's it. apply() registers the FluentWinUI3 QML import path and sets the QtQuickControls2 style to FluentWinUI3. After that, any standard Qt Quick Controls 2 component in your QML will be rendered with the Fluent theme automatically.

How it works

You write standard QML using the normal Qt Quick Controls 2 imports. The fluentpyside.apply() call sets the style, so every component automatically gets the Fluent look — you don't import anything special, you don't reference any theme object, you just write normal QML.

# main.py
from PySide6.QtGui import QGuiApplication
from PySide6.QtQml import QQmlApplicationEngine
import fluentpyside

app = QGuiApplication([])
engine = QQmlApplicationEngine()

# ONE line — this is all you need
fluentpyside.apply()

engine.load("main.qml")
app.exec()

// main.qml
// NOTE: Only standard Qt imports — NO Fluent-specific import needed
import QtQuick
import QtQuick.Controls
import QtQuick.Layouts

ApplicationWindow {
    visible: true
    width: 400
    height: 300
    title: "FluentWinUI3 Demo"

    ColumnLayout {
        anchors.fill: parent
        anchors.margins: 16
        spacing: 12

        Label {
            text: "FluentWinUI3 Theme"
            font.pixelSize: 20
            font.bold: true
        }

        TextField {
            placeholderText: "Type something..."
            Layout.fillWidth: true
        }

        Button {
            text: "Click me"
            onClicked: console.log("Button clicked!")
        }

        CheckBox {
            text: "Enable feature"
        }

        Switch {
            text: "Dark mode toggle"
        }

        ProgressBar {
            value: 0.6
            Layout.fillWidth: true
        }

        ComboBox {
            model: ["Option 1", "Option 2", "Option 3"]
            Layout.fillWidth: true
        }

        Item { Layout.fillHeight: true }
    }
}

Available styled components

These standard Qt Quick Controls 2 components get Fluent styling automatically when fluentpyside.apply() is called:

Component	Notes
ApplicationWindow	Main window container
Button	Standard push button
RoundButton	Circular/pill-shaped button
DelayButton	Button that activates after holding
ToolButton	Toolbar button
TextField	Single-line text input
TextArea	Multi-line text input
SearchField	Text input with search icon (Qt 6.10+)
SpinBox	Numeric input with up/down arrows
ComboBox	Dropdown selector
CheckBox	Checkbox with label
CheckDelegate	Checkbox in a list item
RadioButton	Radio button with label
RadioDelegate	Radio button in a list item
Switch	Toggle switch
SwitchDelegate	Toggle switch in a list item
Slider	Horizontal slider
RangeSlider	Two-handle slider
ProgressBar	Linear progress indicator
BusyIndicator	Spinning loading indicator
PageIndicator	Dot-style page indicator
GroupBox	Labeled container frame
Frame	Container frame
ScrollView	Scrollable area (falls back to system)
TabBar / TabButton	Tab navigation
ToolBar	Toolbar container
ToolSeparator	Separator for toolbars
MenuBar / MenuBarItem	Top menu bar
Menu / MenuItem / MenuSeparator	Dropdown menus
Dialog / DialogButtonBox	Modal dialogs
Popup	Generic popup container
ToolTip	Hover tooltip
ItemDelegate	Clickable list item
SwipeDelegate	Swipeable list item

NOT styled (will fall back to system/default Qt style)

Component	Reason
Dial	Not implemented by upstream FluentWinUI3
Drawer	Not implemented by upstream FluentWinUI3
SplitView	Not implemented by upstream FluentWinUI3
StackView	Not implemented by upstream FluentWinUI3
SwipeView	Not implemented by upstream FluentWinUI3
TreeView	Not implemented by upstream FluentWinUI3
Tumbler	Not implemented by upstream FluentWinUI3
Label	Plain text — no styling needed, uses default

Fluent Design Tokens

After calling fluentpyside.apply(), a Fluent singleton is available in your QML with WinUI 3 design tokens. All colors automatically switch between light and dark mode based on the system preference (Fluent.isDark).

Example usage

import QtQuick
import QtQuick.Controls

ApplicationWindow {
    visible: true; width: 600; height: 400

    Rectangle {
        anchors.fill: parent
        color: Fluent.background

        ColumnLayout {
            anchors.centerIn: parent

            Label {
                text: "Welcome"
                color: Fluent.textPrimary
                font.pixelSize: Fluent.fontTitleSize
                font.family: Fluent.fontFamily
            }

            Button {
                text: "Accent Button"
                Layout.alignment: Qt.AlignHCenter
            }

            Rectangle {
                width: 200; height: 4
                radius: Fluent.radiusSmall
                color: Fluent.accent
                Layout.alignment: Qt.AlignHCenter
            }
        }
    }
}

Available properties

Surface Colors

Property	Light	Dark
Fluent.background	#f3f3f3	#202020
Fluent.backgroundSecondary	#e5e5e5	#1c1c1c
Fluent.backgroundTertiary	#f9f9f9	#282828
Fluent.cardBackground	#ffffff	#2d2d2d
Fluent.cardBackgroundSecondary	#f6f6f6	#383838
Fluent.popupBackground	#ffffff	#2d2d2d
Fluent.layerBackground	#e8e8e8	#2c2c2c
Fluent.layerAltBackground	#f6f6f6	#383838

Text Colors

Property	Light	Dark
Fluent.textPrimary	#1a1a1a	#ffffff
Fluent.textSecondary	#616161	#9d9d9d
Fluent.textTertiary	#8a8a8a	#7a7a7a
Fluent.textDisabled	#a0a0a0	#5d5d5d
Fluent.textOnAccent	#ffffff	#003d7a

Accent Colors

Property	Light	Dark
Fluent.accent	#005fb8	#60cdff
Fluent.accentHover	#004c95	#7dd6ff
Fluent.accentPressed	#003d7a	#005a9e
Fluent.accentSelected	#c7e0f4	#003d7a
Fluent.accentDisabled	#a0a0a0	#3d7a9e
Fluent.accentFocusOuter	#005fb8	#60cdff

Control Colors

Property	Light	Dark
Fluent.controlBackground	#ffffff	#3d3d3d
Fluent.controlBackgroundHover	#f0f0f0	#484848
Fluent.controlBackgroundPressed	#e5e5e5	#3d3d3d
Fluent.controlBackgroundDisabled	#f9f9f9	#282828
Fluent.controlStrongBackground	#005fb8	#60cdff
Fluent.controlStrongForeground	#ffffff	#003d7a
Fluent.controlAltBackground	#f6f6f6	#383838
Fluent.controlAltBackgroundTransparentHover	#00000005	#ffffff0a
Fluent.controlAltBackgroundTransparentPressed	#0000000f	#ffffff14

Input / Text Field Colors

Property	Light	Dark
Fluent.inputBackground	#ffffff	#2d2d2d
Fluent.inputBackgroundHover	#f0f0f0	#383838
Fluent.inputBorder	#9d9d9d	#5d5d5d
Fluent.inputBorderHover	#7a7a7a	#7a7a7a
Fluent.inputBorderFocus	#005fb8	#60cdff
Fluent.inputPlaceholderForeground	#8a8a8a	#7a7a7a
Fluent.inputForeground	#1a1a1a	#ffffff

Border / Divider

Property	Light	Dark
Fluent.border	#d1d1d1	#3d3d3d
Fluent.borderStrong	#9d9d9d	#5d5d5d
Fluent.borderDisabled	#e5e5e5	#2d2d2d
Fluent.divider	#d1d1d1	#3d3d3d
Fluent.dividerStrong	#9d9d9d	#5d5d5d

Status Colors

Property	Light	Dark
Fluent.success	#0f7b0f	#6ccb5f
Fluent.caution	#9d5d00	#fcb900
Fluent.warning	#ff8c00	#ffb900
Fluent.critical	#c42b1c	#ff99a4
Fluent.informational	#005fb8	#60cdff

Typography

Property	Value
Fluent.fontFamily	"Segoe UI Variable"
Fluent.fontCaptionSize	12
Fluent.fontBodySize	14
Fluent.fontBodyStrongSize	14
Fluent.fontBodyLargeSize	16
Fluent.fontSubtitleSize	20
Fluent.fontTitleSize	28
Fluent.fontTitleLargeSize	40
Fluent.fontDisplaySize	68

Spacing

Property	Value
Fluent.spacingXXS	2
Fluent.spacingXS	4
Fluent.spacingS	8
Fluent.spacingM	12
Fluent.spacingL	16
Fluent.spacingXL	20
Fluent.spacingXXL	24

Radius

Property	Value
Fluent.radiusSmall	4
Fluent.radiusMedium	8
Fluent.radiusLarge	12
Fluent.radiusXLarge	16
Fluent.radiusCircle	9999

Requirements

• Python 3.8+
• PySide6-Essentials (recommended) or PySide6 — provides the Qt runtime plugins needed at runtime. This package only ships the QML styling files (no compiled plugin binaries), keeping the wheel small and cross-platform.

Public API reference

fluentpyside.apply() -> str

One-liner to enable the FluentWinUI3 theme. Call this before loading any QML. Returns the path used for the style.

import fluentpyside
fluentpyside.apply()  # call BEFORE engine.load()

fluentpyside.set_style(engine=None, path=None) -> str

Lower-level API if you need fine-grained control. Sets the QML import path and Qt Quick Controls 2 style.

engine = QQmlApplicationEngine()
style_path = fluentpyside.set_style(engine=engine)
engine.load("main.qml")

fluentpyside.install_assets(target_dir)

Copy the FluentWinUI3 QML tree into a target project directory. Useful for vendoring the theme files.

python -m fluentpyside --install /path/to/your/project

fluentpyside.find_installed_style() -> Optional[Path]

Search for the FluentWinUI3 style in the installed PySide6 package. Returns None if not found.

fluentpyside.default_style_path() -> Path

Return the package-local style path (inside the fluentpyside wheel).

Common mistakes

❌ "ReferenceError: Fluent is not defined"

Make sure you call fluentpyside.apply() before loading your QML. The Fluent singleton is only available after the style is applied:

engine = QQmlApplicationEngine()
fluentpyside.apply()  # ✅ Fluent singleton is now available
engine.load("main.qml")

❌ Using Qt Widgets instead of Qt Quick

This library styles Qt Quick Controls 2 (QML) only. It does nothing for classic Qt Widgets:

# ❌ These are Qt Widgets — NOT styled by fluentpyside
from PySide6.QtWidgets import QPushButton, QLabel, QMainWindow

# ✅ Use QML with PySide6 — this IS styled
from PySide6.QtQml import QQmlApplicationEngine

❌ Calling apply() after loading QML

fluentpyside.apply() must be called before engine.load():

engine = QQmlApplicationEngine()
fluentpyside.apply()  # ✅ BEFORE
engine.load("main.qml")

# NOT:
# engine.load("main.qml")  # ❌ too late
# fluentpyside.apply()

❌ Forgetting PySide6-Essentials

This package only ships QML files. You need PySide6 installed for the runtime:

pip install PySide6-Essentials  # or PySide6 (full)
pip install fluentpyside

Updating the theme in a project

If you want to copy the FluentWinUI3 QML tree into a target project manually:

python tools/update_theme.py /path/to/your/project

This copies FluentWinUI3/ into /path/to/your/project/QtQuick/Controls/FluentWinUI3/ so you can add the project root as a QML import path.

License

• Wrapper: MIT License (file LICENSE)
• Upstream QML assets: copied from the locally installed PySide6 / PySide6-Essentials package. Follow Qt/PySide licensing when redistributing.