PleasantUI

Repositories: Original (Onebeld) · Fork (ghudulf)

PleasantUI is a cross-platform UI theme and control library for Avalonia, inspired by Microsoft Fluent Design, Google Material Design and the WinUI/UWP visual language. It completely re-styles every standard Avalonia control and adds a suite of custom controls, a multi-theme engine with custom theme support, a reactive localization system, and a custom window chrome — all AOT-compatible with no rd.xml required.

The project has been in active development since 2021, originally as part of the Regul and Regul Save Cleaner projects.

🏛️ Philosophy

The philosophy is to provide the user with a pleasant experience in using applications built on this library. This library isn't intended to be compared to other design principles or other UI libraries. If the interface looks good, then this library is doing its job.

This library may also contain elements from other design principles or UI libraries if it makes the interface pleasant enough (but with due attribution, of course).

✨ Features

Complete control theming

Every standard Avalonia control is receiving a complete overhaul: rounded corners, multi-layered fills, smooth transitions on hover and click, and accent color integration:

Control	Control	Control
Button (+ AppBar, Accent, Danger variants)	CheckBox	RadioButton
ToggleButton / ToggleSwitch	RepeatButton / ButtonSpinner	Slider
TextBox / AutoCompleteBox	NumericUpDown	ComboBox / DropDownButton
Calendar / CalendarDatePicker / TimePicker	DataGrid	ListBox / TreeView
Expander	TabControl / TabItem	ScrollBar / ScrollViewer
ProgressBar	Menu / ContextMenu	ToolTip
Carousel	Separator	NotificationCard

Custom Pleasant controls

Controls built from scratch that go beyond what Avalonia ships:

Control	Description	Demo
PleasantWindow	Custom window chrome with a Fluent title bar, subtitle, custom icon/title content, optional blur, content-extends-into-titlebar, and macOS caption override	None
NavigationView / NavigationViewItem	Collapsible side navigation panel, similar to WinUI NavigationView	None
PleasantTabView / PleasantTabItem	Chromium-style tab strip with add/close buttons and scrollable tab bar	None
ContentDialog	Modal overlay dialog with bottom button panel and smooth scroll content area	None
PleasantSnackbar	Temporary non-intrusive notification bar
ProgressRing	Circular progress indicator — both determinate and indeterminate with animated arc
OptionsDisplayItem	Settings-style row with header, description, icon, action button slot, navigation chevron, and expandable content
InformationBlock	Compact pill-shaped label combining an icon and a value
MarkedTextBox / MarkedNumericUpDown	Input controls with inline label/unit markers	None
RippleEffect	Material-style ripple click feedback
PleasantMiniWindow	Lightweight floating window	None
Timeline	Displays a list of events in chronological order along a vertical axis. Supports four layout modes, custom icons, and five severity types.
InstallWizard	A multi-step installation wizard with a sidebar step list, progress bar, and Back / Next / Cancel navigation.
PleasantMenu	A customizable flyout menu with a title, optional info badges, a grid of large icon buttons, and a footer bar with small utility buttons.
PathPicker	Combines a read-only TextBox with a browse button. Supports OpenFile, SaveFile, and OpenFolder modes, optional multi-select, file-type filters, and two-way binding on the selected path text.
PopConfirm	Wraps any trigger control and shows a small popup with a header, body, and Confirm / Cancel buttons before executing a command.

Theme engine

• Built-in themes: Light, Dark, Mint, Strawberry, Ice, Sunny, Spruce, Cherry, Cave, Lunar
• System mode — follows the OS light/dark preference automatically
• Custom themes — create, edit, export, import, and persist your own color palettes via the built-in ThemeEditorWindow
• Accent color follows the OS accent or can be overridden per-user; light/dark variants and gradient pairs are generated automatically
• Settings are persisted to disk automatically on desktop; mobile apps can save manually

Localization system

• Localizer singleton backed by .NET ResourceManager — add any number of .resx resource files
• {Localize Key} AXAML markup extension binds reactively — switching language updates every bound string instantly without reloading views
• Localizer.TrDefault(key, fallback) for safe lookups that fall back to a raw string instead of an error message
• LocalizationChanged event for view models and code-behind to react to language switches
• A localization key analyzer is included. You won't miss any unused keys in your applications!

Packages

Package	Description
PleasantUI	Core theme, all control styles, Pleasant controls, theme engine, localization
PleasantUI.ToolKit	MessageBox, ThemeEditorWindow, color picker utilities
PleasantUI.MaterialIcons	Material Design icon geometry library for use with PathIcon
PleasantUI.DataGrid	Fluent-styled DataGrid extension

📖 Documentation

Detailed reference docs for each control are in the docs/ folder:

Doc	Controls
PleasantWindow	PleasantWindow, IPleasantSplashScreen
PleasantMiniWindow	PleasantMiniWindow
PleasantTitleBar	PleasantTitleBar
PleasantCaptionButtons	PleasantCaptionButtons
NavigationView	NavigationView, NavigationViewItem
PleasantTabView	PleasantTabView, PleasantTabItem
ContentDialog	ContentDialog
MessageBox	MessageBox (ToolKit)
PleasantDialog	PleasantDialog (ToolKit)
CrashReportDialog	CrashReportDialog
StepDialog	StepDialog
PleasantSnackbar	PleasantSnackbar
ProgressRing	ProgressRing
OptionsDisplayItem	OptionsDisplayItem
InformationBlock	InformationBlock
Timeline	Timeline, TimelineItem
InstallWizard	InstallWizard, WizardStep
PathPicker	PathPicker
PopConfirm	PopConfirm
PleasantMenu	PleasantMenu, PleasantMenuItem, PleasantMenuFooterItem
PleasantMenuFlyout	PleasantMenuFlyout
PleasantFlyout	PleasantFlyout
PinCode	PinCode
SelectionList	SelectionList, SelectionListItem
RippleEffect	RippleEffect
SmoothScrollViewer	SmoothScrollViewer
MarkedInputs	MarkedTextBox, MarkedNumericUpDown
MarkedTextBox	MarkedTextBox
MarkedNumericUpDown	MarkedNumericUpDown
PleasantDatePicker	PleasantDatePicker
PleasantBorder	PleasantBorder
BackdropBlurBorder	BackdropBlurBorder
ShadowBorder	ShadowBorder
PleasantTrayPopup	PleasantTrayPopup, StatusItem
DataGrid	PleasantUI.DataGrid package
PropertyGrid	PropertyGrid, PropertyRow
CommandBar	CommandBar, CommandBarButton, CommandBarToggleButton
BreadcrumbBar	BreadcrumbBar, BreadcrumbBarItem
PleasantDrawer	PleasantDrawer
DashboardCard	DashboardCard
DownloadPanel	DownloadPanel
LogViewerPanel	LogViewerPanel
TerminalPanel	TerminalPanel
TreeViewPanel	TreeViewPanel, TreeViewSection
ItemListPanel	ItemListPanel
VirtualizingWrapPanel	VirtualizingWrapPanel
PleasantView	PleasantView
PleasantSplashScreen	PleasantSplashScreen
ModalWindowHost	ModalWindowHost
ThemePreviewVariantScope	ThemePreviewVariantScope
Localization	Localizer, {Localize} markup extension
Theme Engine	PleasantTheme, custom themes, color tokens

🚀 Getting Started

Install

Package List (Avalonia 12)

Published on NuGet:

<PackageReference Include="PleasantUI" Version="5.3.0" />
<PackageReference Include="PleasantUI.DataGrid" Version="5.3.0" />
<PackageReference Include="PleasantUI.MaterialIcons" Version="5.3.0" />
<PackageReference Include="PleasantUI.ToolKit" Version="5.3.0" />

Add the theme

In your App.axaml, add PleasantTheme to your styles:

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="YourApp.App">
    <Application.Styles>
        <PleasantTheme />
    </Application.Styles>
</Application>

Initialize correctly

Make sure AvaloniaXamlLoader.Load(this) is called in Initialize():

public partial class App : Application
{
    public override void Initialize()
    {
        AvaloniaXamlLoader.Load(this); // required
    }

    public override void OnFrameworkInitializationCompleted()
    {
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            desktop.MainWindow = new MainWindow
            {
                DataContext = new MainWindowViewModel(),
            };
        }

        base.OnFrameworkInitializationCompleted();
    }
}

Use PleasantWindow

Replace Window with PleasantWindow to get the custom Fluent title bar:

using PleasantUI.Controls;

public partial class MainWindow : PleasantWindow
{
    public MainWindow() => InitializeComponent();
}

<PleasantWindow xmlns="https://github.com/avaloniaui"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
                x:Class="YourApp.Views.MainWindow"
                Title="Avalonia Application">
</PleasantWindow>

Key PleasantWindow properties:

Property	Type	Description
TitleBarType	Classic / ClassicExtended	Title bar layout style
ExtendsContentIntoTitleBar	bool	Lets content render behind the title bar
Subtitle	string	Secondary text shown next to the title
DisplayIcon	object	Custom icon content in the title bar
DisplayTitle	object	Custom title content (e.g. a PathIcon)
EnableBlur	bool	Acrylic/blur window background
CaptionButtons	enum	Which caption buttons to show
LeftTitleBarContent	object	Content injected left of the title

🌍 Localization

Register your .resx resource managers in your Application constructor:

public App()
{
    Localizer.AddRes(new ResourceManager(typeof(Properties.Localizations.App)));
    Localizer.ChangeLang("en");
}

Use {Localize Key} in AXAML — updates live when the language changes:

<TextBlock Text="{Localize WelcomeMessage}" />
<Button Content="{Localize SaveButton}" />

Switch language at runtime:

Localizer.ChangeLang("ru");

Safe lookup with fallback in code-behind:

string title = Localizer.TrDefault("DialogTitle", "Confirm");

🔲 Button variants

<Button Content="Default" />
<Button Theme="{StaticResource AccentButtonTheme}" Content="Accent" />
<Button Theme="{StaticResource DangerButtonTheme}" Content="Danger" />
<Button Theme="{StaticResource AppBarButtonTheme}" Content="AppBar" />

📃 OptionsDisplayItem

<!-- Navigation row -->
<OptionsDisplayItem Header="Account"
                    Description="Manage your account"
                    Icon="{x:Static MaterialIcons.AccountOutline}"
                    Navigates="True" />

<!-- Row with action control -->
<OptionsDisplayItem Header="Dark mode"
                    Icon="{x:Static MaterialIcons.WeatherNight}">
    <OptionsDisplayItem.ActionButton>
        <ToggleSwitch />
    </OptionsDisplayItem.ActionButton>
</OptionsDisplayItem>

<!-- Expandable row -->
<OptionsDisplayItem Header="Advanced" Expands="True">
    <OptionsDisplayItem.Content>
        <StackPanel>
            <CheckBox Content="Enable feature X" />
        </StackPanel>
    </OptionsDisplayItem.Content>
</OptionsDisplayItem>

🖼️ Screenshots

Regul Save Cleaner

OlibKey

❤️ Credits

Main

• Avalonia under license from MIT
• Built with JetBrains Rider

Controls and Code

• Aura.UI (PieroCastillo) - NavigationView and AuraTabView under license from MIT
• ProgressRing (ymg2006) - under license from MIT
• RichTextKit (toptensoftware) - implementation of BinarySearch under license from Apache 2.0
• weather (rocksdanister) - implementation of BackdropBlurBorder under license from MIT
• Xaml.Behaviors.Interactions.Animated (Egolds) - implementation of VerticalScrollViewerAnimatedBehavior under license from MIT
• BilibiliClient (afunc233) - implementation of VirtualizingWrapPanel
• Material.Avalonia (CommunityAvalonia) - implementation of Ripple Effect under license from MIT