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Fix native Windows maximize for the Avalonia main window #4749

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Merged
Gabriel Dufresne (GabrielDuf) merged 2 commits into from
May 12, 2026
+139 −134
Merged

Fix native Windows maximize for the Avalonia main window #4749

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7f7fd6d
Work around for the avalonia issue with Drag and Drop resizing
GabrielDuf May 11, 2026
c09367f
Fix fullscreen on macos
GabrielDuf May 11, 2026
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10 changes: 5 additions & 5 deletions src/UniGetUI.Avalonia/UniGetUI.Avalonia.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -70,17 +70,17 @@
</Target>

<ItemGroup>
<PackageReference Include="Avalonia" Version="12.0.0-rc1" />
<PackageReference Include="Avalonia.Controls.DataGrid" Version="12.0.0-rc1" />
<PackageReference Include="Avalonia.Desktop" Version="12.0.0-rc1" />
<PackageReference Include="Avalonia.Themes.Fluent" Version="12.0.0-rc1" />
<PackageReference Include="Avalonia" Version="12.0.3" />
<PackageReference Include="Avalonia.Controls.DataGrid" Version="12.0.0" />
<PackageReference Include="Avalonia.Desktop" Version="12.0.3" />
<PackageReference Include="Avalonia.Themes.Fluent" Version="12.0.3" />
<PackageReference Include="Devolutions.AvaloniaTheme.DevExpress" Version="2026.3.13" />
<PackageReference Include="Devolutions.AvaloniaTheme.MacOS" Version="2026.3.13" />
<PackageReference Include="Devolutions.AvaloniaTheme.Linux" Version="2026.3.11" />
<PackageReference Include="AvaloniaUI.DiagnosticsSupport" Version="2.2.0-beta3" Condition="'$(EnableAvaloniaDiagnostics)' == 'true'" />
<PackageReference Include="CommunityToolkit.Mvvm" Version="8.*" />
<PackageReference Include="Octokit" Version="14.0.0" />
<PackageReference Include="Avalonia.Controls.WebView" Version="12.0.0-rc1" />
<PackageReference Include="Avalonia.Controls.WebView" Version="12.0.0" />
<PackageReference Include="Tmds.DBus.Protocol" Version="0.92.0" />
</ItemGroup>

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263 changes: 134 additions & 129 deletions src/UniGetUI.Avalonia/Views/MainWindow.axaml.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Data;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Layout;
Expand Down Expand Up @@ -39,19 +40,24 @@ public enum PageType

public partial class MainWindow : Window
{
private const int SW_RESTORE = 9;
// Workaround for Avalonia 12 issue #21160 / #21212: BorderOnly + ExtendClientArea
// strips WS_CAPTION / WS_THICKFRAME, which makes DWM disable Aero Snap drag-to-top,
// Win+Up, and the maximize/minimize/restore animations. Re-add those bits on every
// style change. WM_GETMINMAXINFO is also overridden because Avalonia's default values
// on the primary monitor make Aero Snap maximize to the current window size (no-op).
// Targeted upstream fix in Avalonia 12.1.
private const uint WM_STYLECHANGING = 0x007C;
private const uint WM_GETMINMAXINFO = 0x0024;
private const int GWL_STYLE = -16;
private const uint WS_CAPTION = 0x00C00000;
private const uint WS_THICKFRAME = 0x00040000;
private const uint WS_MINIMIZEBOX = 0x00020000;
private const uint WS_MAXIMIZEBOX = 0x00010000;
private const uint MONITOR_DEFAULTTONEAREST = 2;
private const int SM_CXSIZEFRAME = 32;
private const int SM_CYSIZEFRAME = 33;
private const int SM_CXPADDEDBORDER = 92;
private const uint SWP_NOZORDER = 0x0004;
private const uint SWP_NOACTIVATE = 0x0010;
private const uint SWP_FRAMECHANGED = 0x0020;

private bool _focusSidebarSelectionOnNextPageChange;
private TrayService? _trayService;
private bool _allowClose;
private NativeMethods.RECT? _windowsRestoreBoundsBeforeManualMaximize;

public enum RuntimeNotificationLevel
{
Expand Down Expand Up @@ -79,6 +85,27 @@ public MainWindow()
_trayService.UpdateStatus();
}

protected override void OnOpened(EventArgs e)
{
base.OnOpened(e);
if (!OperatingSystem.IsWindows())
return;

// Install the hook so future style-change attempts by Avalonia can't re-strip our bits.
Win32Properties.AddWndProcHookCallback(this, OnWindowsWndProc);

// The initial strip already happened during Show() (before this hook could catch it),
// so manually OR our bits back into the current style. DWM picks them up immediately
// and starts honouring Aero Snap / Win+Up / native maximize animations again.
if (TryGetPlatformHandle()?.Handle is { } handle && handle != 0)
{
nint current = NativeMethods.GetWindowLongPtr(handle, GWL_STYLE);
nint updated = (nint)((nuint)current | WS_CAPTION | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX);
if (updated != current)
NativeMethods.SetWindowLongPtr(handle, GWL_STYLE, updated);
}
}

protected override void OnClosing(WindowClosingEventArgs e)
{
if (!_allowClose && !Settings.Get(Settings.K.DisableSystemTray))
Expand Down Expand Up @@ -169,6 +196,34 @@ private void SetupTitleBar()
// Traffic lights sit on the left → keep the 65 px HamburgerPanel margin.
ExtendClientAreaToDecorationsHint = true;
ExtendClientAreaTitleBarHeightHint = -1;

// In fullscreen the native title bar is hidden and WindowDecorationMargin
// collapses to 0, which would clip the search box and hamburger. Use a fixed
// title bar height in that state, and drop the traffic-light reservation
// since the traffic lights aren't shown either.
this.GetObservable(WindowStateProperty).Subscribe(state =>
{
if (state == WindowState.FullScreen)
{
TitleBarGrid.ClearValue(HeightProperty);
TitleBarGrid.Height = 44;
MainContentGrid.ClearValue(MarginProperty);
MainContentGrid.Margin = new Thickness(0, 44, 0, 0);
HamburgerPanel.Margin = new Thickness(10, 0, 8, 0);
}
else
{
TitleBarGrid.Bind(HeightProperty, new Binding("WindowDecorationMargin.Top")
{
RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor) { AncestorType = typeof(Window) },
});
MainContentGrid.Bind(MarginProperty, new Binding("WindowDecorationMargin")
{
RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor) { AncestorType = typeof(Window) },
});
HamburgerPanel.Margin = new Thickness(65, 0, 8, 0);
}
});
}
else if (OperatingSystem.IsWindows())
{
Expand All @@ -182,7 +237,7 @@ private void SetupTitleBar()
MainContentGrid.Margin = new Thickness(0, 44, 0, 0);
this.GetObservable(WindowStateProperty).Subscribe(state =>
{
UpdateMaximizeButtonState(state == WindowState.Maximized || _windowsRestoreBoundsBeforeManualMaximize is not null);
UpdateMaximizeButtonState(state == WindowState.Maximized);
});
}
else if (OperatingSystem.IsLinux())
Expand Down Expand Up @@ -301,12 +356,6 @@ private void MinimizeButton_Click(object? sender, RoutedEventArgs e)

private void MaximizeButton_Click(object? sender, RoutedEventArgs e)
{
if (OperatingSystem.IsWindows() && TryGetNativeWindowHandle() is { } handle)
{
ToggleWindowsManualMaximize(handle);
return;
}

WindowState = WindowState == WindowState.Maximized
? WindowState.Normal
: WindowState.Maximized;
Expand All @@ -323,121 +372,64 @@ private void UpdateMaximizeButtonState(bool isMaximized)
CoreTools.Translate(isMaximized ? "Restore" : "Maximize"));
}

private nint? TryGetNativeWindowHandle()
private static nint OnWindowsWndProc(nint hWnd, uint msg, nint wParam, nint lParam, ref bool handled)
{
var handle = TryGetPlatformHandle()?.Handle ?? 0;
return handle == 0 ? null : handle;
}

private void ToggleWindowsManualMaximize(nint handle)
{
if (_windowsRestoreBoundsBeforeManualMaximize is { } restoreBounds)
{
if (SetWindowsWindowBounds(handle, restoreBounds))
// Intercept SetWindowLong(GWL_STYLE, ...) attempts and OR our required bits back into
// the new style before Windows accepts the change. lParam points to a STYLESTRUCT
// whose styleNew member is the proposed new style. We modify it in place and let the
// chain continue (no handled=true) so Avalonia / DefWindowProc still process the
// (now-corrected) message.
if (msg == WM_STYLECHANGING && wParam.ToInt64() == GWL_STYLE)
{
var ss = Marshal.PtrToStructure<NativeMethods.STYLESTRUCT>(lParam);
uint preserved = ss.styleNew | WS_CAPTION | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX;
if (preserved != ss.styleNew)
{
_windowsRestoreBoundsBeforeManualMaximize = null;
UpdateMaximizeButtonState(false);
ss.styleNew = preserved;
Marshal.StructureToPtr(ss, lParam, false);
}
return;
}

if (NativeMethods.IsZoomed(handle))
{
_ = NativeMethods.ShowWindow(handle, SW_RESTORE);
UpdateMaximizeButtonState(false);
return;
}

if (!NativeMethods.GetWindowRect(handle, out NativeMethods.RECT currentBounds))
{
Logger.Warn("Could not get the window bounds before maximizing.");
return;
}

var monitor = NativeMethods.MonitorFromWindow(handle, MONITOR_DEFAULTTONEAREST);
if (monitor == 0)
{
Logger.Warn("Could not find a monitor for the window before maximizing.");
return;
}

var monitorInfo = new NativeMethods.MONITORINFO
{
cbSize = Marshal.SizeOf<NativeMethods.MONITORINFO>(),
};
if (!NativeMethods.GetMonitorInfo(monitor, ref monitorInfo))
{
Logger.Warn("Could not get monitor bounds before maximizing.");
return;
}

if (SetWindowsWindowBounds(handle, GetMaximizedWindowBounds(handle, monitorInfo.rcWork)))
{
_windowsRestoreBoundsBeforeManualMaximize = currentBounds;
UpdateMaximizeButtonState(true);
// Override the max-size / max-position Avalonia would otherwise provide. On the
// primary monitor (where the taskbar lives) Avalonia's defaults can leave ptMaxSize
// equal to the current window size, so Aero Snap drag-to-top "maximizes" to the same
// bounds and the window appears not to resize. We always report the current monitor's
// work area, which is what Windows actually uses for native maximize.
// handled = true so Avalonia's own WM_GETMINMAXINFO handler can't run after us and
// overwrite the values we just set.
if (msg == WM_GETMINMAXINFO)
{
nint monitor = NativeMethods.MonitorFromWindow(hWnd, MONITOR_DEFAULTTONEAREST);
if (monitor != 0)
{
var mi = new NativeMethods.MONITORINFO { cbSize = Marshal.SizeOf<NativeMethods.MONITORINFO>() };
if (NativeMethods.GetMonitorInfo(monitor, ref mi))
{
var mmi = Marshal.PtrToStructure<NativeMethods.MINMAXINFO>(lParam);
mmi.ptMaxPosition.X = mi.rcWork.Left - mi.rcMonitor.Left;
mmi.ptMaxPosition.Y = mi.rcWork.Top - mi.rcMonitor.Top;
mmi.ptMaxSize.X = mi.rcWork.Right - mi.rcWork.Left;
mmi.ptMaxSize.Y = mi.rcWork.Bottom - mi.rcWork.Top;
if (mmi.ptMaxTrackSize.X < mmi.ptMaxSize.X) mmi.ptMaxTrackSize.X = mmi.ptMaxSize.X;
if (mmi.ptMaxTrackSize.Y < mmi.ptMaxSize.Y) mmi.ptMaxTrackSize.Y = mmi.ptMaxSize.Y;
Marshal.StructureToPtr(mmi, lParam, false);
handled = true;
return 0;
}
}
}
return 0;
}

private static NativeMethods.RECT GetMaximizedWindowBounds(nint handle, NativeMethods.RECT workArea)
{
uint dpi = NativeMethods.GetDpiForWindow(handle);
if (dpi == 0)
dpi = NativeMethods.GetDpiForSystem();

int frameX = NativeMethods.GetSystemMetricsForDpi(SM_CXSIZEFRAME, dpi)
+ NativeMethods.GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi);
int frameY = NativeMethods.GetSystemMetricsForDpi(SM_CYSIZEFRAME, dpi)
+ NativeMethods.GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi);

frameX = Math.Max(frameX, 8);
frameY = Math.Max(frameY, 8);

return new NativeMethods.RECT
{
Left = workArea.Left - frameX,
Top = workArea.Top - frameY,
Right = workArea.Right + frameX,
Bottom = workArea.Bottom + frameY,
};
}

private static bool SetWindowsWindowBounds(nint handle, NativeMethods.RECT bounds)
{
bool result = NativeMethods.SetWindowPos(
handle,
0,
bounds.Left,
bounds.Top,
bounds.Right - bounds.Left,
bounds.Bottom - bounds.Top,
SWP_NOZORDER | SWP_NOACTIVATE | SWP_FRAMECHANGED);
if (!result)
Logger.Warn($"Could not set window bounds. Win32 error: {Marshal.GetLastWin32Error()}");
return result;
}

// P/Invokes compile on any platform; they are only called from code paths guarded by
// OperatingSystem.IsWindows(), so non-Windows targets never invoke user32.dll at runtime.
private static class NativeMethods
{
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool IsZoomed(nint hWnd);
[DllImport("user32.dll", EntryPoint = "GetWindowLongPtrW", SetLastError = true)]
public static extern nint GetWindowLongPtr(nint hWnd, int nIndex);

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool ShowWindow(nint hWnd, int nCmdShow);

[DllImport("user32.dll")]
public static extern uint GetDpiForWindow(nint hwnd);

[DllImport("user32.dll")]
public static extern uint GetDpiForSystem();

[DllImport("user32.dll")]
public static extern int GetSystemMetricsForDpi(int nIndex, uint dpi);

[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool GetWindowRect(nint hWnd, out RECT lpRect);
[DllImport("user32.dll", EntryPoint = "SetWindowLongPtrW", SetLastError = true)]
public static extern nint SetWindowLongPtr(nint hWnd, int nIndex, nint dwNewLong);

[DllImport("user32.dll")]
public static extern nint MonitorFromWindow(nint hwnd, uint dwFlags);
Expand All @@ -446,16 +438,29 @@ private static class NativeMethods
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool GetMonitorInfo(nint hMonitor, ref MONITORINFO lpmi);

[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool SetWindowPos(
nint hWnd,
nint hWndInsertAfter,
int X,
int Y,
int cx,
int cy,
uint uFlags);
[StructLayout(LayoutKind.Sequential)]
public struct STYLESTRUCT
{
public uint styleOld;
public uint styleNew;
}

[StructLayout(LayoutKind.Sequential)]
public struct POINT
{
public int X;
public int Y;
}

[StructLayout(LayoutKind.Sequential)]
public struct MINMAXINFO
{
public POINT ptReserved;
public POINT ptMaxSize;
public POINT ptMaxPosition;
public POINT ptMinTrackSize;
public POINT ptMaxTrackSize;
}

[StructLayout(LayoutKind.Sequential)]
public struct RECT
Expand Down
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