FlClash/plugins/window/README.md

window

Desktop window control for FlClash on Linux, macOS and Windows. Written for FlClash; it replaced the window_manager fork, and its platform code derives from that plugin (see LICENSE).

Dart API

desktopWindow is the singleton DesktopWindow. Every call is a method on the window method channel; events arrive on the same channel as onEvent with a name argument and are delivered to WindowListeners as WindowEvents.

Coordinates and sizes cross the channel in logical pixels on every platform. Windows converts with the window's own DPI.

Every native handler validates its arguments and answers a missing or mistyped argument with a PlatformException whose code is bad_args. A call the platform cannot honor answers with code unsupported. Native code never crashes on channel input.

Method channel contract

Arguments are a Map<String, Object?>; - means no arguments. Void methods return null.

Method	Arguments	Returns	Notes
ensureInitialized	-	null	Binds the plugin to the Flutter view's window and leaves it hidden. Every other method requires it.
show	inactive: bool	null	inactive shows without taking focus.
hide	-	null
isVisible	-	bool
focus	-	null
close	-	null	Runs the close path; with preventClose set only the close event fires.
setPreventClose	value: bool	null
isMaximized	-	bool
maximize	-	null
unmaximize	-	null
isMinimized	-	bool
minimize	-	null
restore	-	null
isFullScreen	-	bool
setFullScreen	value: bool	null
getBounds	-	{x, y, width, height} doubles	Logical pixels, top-left origin on every platform.
setBounds	x?, y?, width?, height?: double	null	Absent x/y keeps the position, absent size keeps the size. Never changes z-order or focus.
isPositionSupported	-	bool	false on Wayland, where the compositor owns placement.
setMinimumSize	width, height: double	null
isAlwaysOnTop / setAlwaysOnTop	value: bool	bool / null
setTitleBarStyle	style: "normal" | "hidden", windowButtonVisibility: bool	null	Hidden keeps the system frame, border and resize edges; only the caption goes.
setSkipTaskbar	value: bool	null	macOS switches the activation policy.
setRoundedCorners	value: bool	null	Windows 11 corner preference; no-op elsewhere.
isEffectSupported	effect: String	bool	See effects below. False for anything setEffect would silently not draw.
setEffect	effect: String, tint: int? ARGB, brightness: "light" | "dark" | null	null	unsupported error when isEffectSupported is false. brightness picks the light or dark material; null follows the system.
startDragging	-	null	Begins a window move from the current pointer press.

Events

onEvent carries name, one of:

close, focus, blur, show, hide, maximize, unmaximize, minimize, restore, geometry-changed, enter-full-screen, leave-full-screen, should-terminate, activate.

• geometry-changed fires once the window's position or size has settled, whether the user or setBounds changed it. Each platform coalesces the raw notifications for 150 ms (Windows WM_WINDOWPOSCHANGED, macOS did-move and did-resize, Linux configure-event) and reports the final geometry. It is not suppressed while maximized or full screen; Dart decides what to keep.
• show and hide follow the window's visibility changes: Windows reports WM_SHOWWINDOW, Linux the GTK show/hide signals, and macOS a show or hide call that changed isVisible.
• close fires when the user or close asks to close; with preventClose the window stays open and Dart decides.
• enter-full-screen and leave-full-screen are raised by the platform's full-screen transition; on Windows the plugin emulates full screen and raises them itself from setFullScreen.
• should-terminate (macOS) is forwarded by the application delegate from applicationShouldTerminate.
• activate is raised by the runner when another launch, or a Dock reopen, asks the running instance to show its window. Nothing is shown natively.

Window style

Each platform keeps one style record and reapplies it as a whole whenever any part changes, so the settings never fight each other:

• titleBarStyle, windowButtonVisibility
• roundedCorners (Windows)
• effect, effectTint, effectBrightness (Windows, macOS)

On Windows that record owns DwmExtendFrameIntoClientArea, the DWM window attributes (including immersive dark mode, which the system backdrops and the frame border follow) and SetWindowCompositionAttribute; on macOS it owns isOpaque, backgroundColor, titlebarAppearsTransparent and the effect view, whose appearance is the requested brightness; on Linux the header bar and decoration state.

Effects

effect is one of none, transparent, blur, acrylic, mica. Linux supports only none: no desktop-neutral blur protocol exists for GTK 3, and a transparent window without blur is not a useful effect.

Effect	Windows	macOS
none	default frame	opaque window
transparent	transparent gradient accent	clear window
blur	ACCENT_ENABLE_BLURBEHIND	NSVisualEffectView .sidebar, behind-window blending, follows the window's active state
acrylic	ACCENT_ENABLE_ACRYLICBLURBEHIND (Windows 10 1803+)	NSVisualEffectView .fullScreenUI
mica	DWMSBT_MAINWINDOW on Windows 11	unsupported

The accent effects leave the DWM frame margins at zero: Windows fills a frame extended into the client area with an opaque material that covers them. mica extends the whole frame, which the system backdrop needs, and the Windows 10 top border below extends the top. The accent effects go through SetWindowCompositionAttribute, so isEffectSupported is false for them on a user32 without it rather than reporting an effect that draws nothing.

With titleBarStyle: hidden on Windows, WM_NCCALCSIZE takes the frame insets from AdjustWindowRectExForDpi and keeps the client rect at the window's top edge, plus the frame height when maximized so the taskbar stays uncovered. Windows 11 draws the top border into a non-client strip one physical pixel tall left there. Windows 10 draws the whole caption over any strip shorter than one (Windows Terminal's NonClientIslandWindow records the same), so it gets no strip. Instead, while no accent effect is on, WindowStyle::Apply extends the DWM frame over the whole caption height and WindowController keeps a row of client area one physical pixel tall above the Flutter view, paints it black in WM_PAINT (alpha 0 to DWM, which shows the frame's border through it) and answers WM_NCHITTEST with HTTOP for it. The plugin therefore positions the view itself on WM_SIZE and after every frame change; the runner's own placement only runs before ensureInitialized. The row is gone while maximized or full screen, where there is no border to show, and while an accent effect is on.

The Flutter content must paint a translucent background for anything but none to be visible.

On macOS the plugin follows macos_window_utils, which flutter_acrylic uses: ensureInitialized installs a host view controller whose view is the NSVisualEffectView and hosts the Flutter view controller as a child, so the effect view is the Flutter view's superview for the life of the window. Placing the effect view beneath the Flutter view as a sibling breaks input: AppKit hands an unhandled mouseDown from a non-opaque view to the sibling below it before the view controller, so Flutter never receives clicks. none and transparent mask the material out with an empty maskImage and leave the view inactive instead of swapping view controllers.

Lifecycle

The engine reports AppLifecycleState from its own view of the window. Where that view keeps an unseen window rendering, the plugin sends hidden on flutter/lifecycle itself:

• Linux: Wayland has no minimized state, so GTK never sets ICONIFIED after minimize and the engine reports only the focus loss, as inactive. When the window loses focus within 500 ms of minimize, the plugin sends hidden from a window-state-event handler connected after the engine's. A compositor that ignores the request, such as sway, leaves the focus where it is, and a restore from the compositor focuses the window, which the engine reports as resumed. A minimize the compositor starts itself, such as Super+H, still reads as inactive.
• macOS: on activation the engine resumes if any window in NSApp.windows is visible, and the status item's window always is. After every activation change the plugin sends hidden while its own window is not visible. A window that comes back without another activation change would then wait for an occlusion notification, which macOS does not always post, so after show or a deminiaturize the plugin sends resumed or inactive itself.

On Windows the engine counts the Flutter view as a window of its own that hides only once it is sized to zero. Hiding the top-level window never resizes the view, and neither does minimizing it, because the plugin consumes that WM_SIZE. The plugin has no handle to the engine, so the runner passes the top-level window's WM_SHOWWINDOW and WM_SIZE to the engine for the view through WindowPluginForwardVisibility (see Runner hooks).

Unused contract surface

The application drives only none, blur and acrylic, always passes windowButtonVisibility: true, and calls setRoundedCorners for Windows alone. transparent, mica, hidden caption buttons and the macOS setRoundedCorners no-op stay in the contract so every platform answers the same table; they have no application caller today.

Runner hooks

• Windows: WindowPluginFindRunningWindow() and WindowPluginActivateWindow(HWND) from window/window_plugin_c_api.h, and WindowPluginForwardVisibility(controller, message, wparam, lparam) from window/window_plugin_runner.h, which the top-level window procedure calls before HandleTopLevelWindowProc. That header is inline because it calls flutter::FlutterEngine, which only the app's C++ wrapper implements; the plugin DLL cannot use it.
• Linux: window_plugin_activate() from window/window_plugin.h.
• macOS: WindowPlugin.instance?.handleShouldTerminate(), WindowPlugin.instance?.handleReopen(), and NSWindow.hiddenWindowAtLaunch() for MainFlutterWindow.order(_:relativeTo:).