Add canonical overlay-mode window support#195
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Add first-class support for "overlay" windows — borderless, always-on-top, whole-window translucent, with optional click-through and corner-locked geometry — so apps no longer need their own native window-styling hacks. - ImGuiApp.EnableOverlay / SetOverlayGeometry / DisableOverlay + IsOverlayActive - OverlayChrome: native Win32 styling via the app's own handle; safe no-op on other platforms and on backends missing the *Ptr style APIs, while still tracking logical overlay state - New OverlayCorner enum for work-area corner anchoring - ImGuiAppPerformanceSettings.OverlayFps: a dedicated overlay frame rate that bypasses focus/idle/visibility throttling (an always-on-top overlay is usually unfocused yet shows live data) - Demo, tests, and README documentation https://claude.ai/code/session_01Ngds45GjiRS3syR4uTrrvE
Reorder OverlayFps ahead of IdleTimeoutSeconds so the explanatory comments no longer immediately follow a line ending in a trailing inline comment, which dotnet format's trivia attachment flagged (IDE0055). https://claude.ai/code/session_01Ngds45GjiRS3syR4uTrrvE
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Summary
MeltdownMonitor (and apps like it) implement an "overlay mode" — a borderless, always-on-top, translucent HUD — by reaching past
ImGuiAppand hand-styling the native window with their own P/Invoke (EnumThreadWindowsto find the handle, rawuser32calls to restyle it). This PR makes that a first-class, canonical feature ofImGui.App, so consumers get always-on-top / borderless / translucency / click-through / corner-locking out of the box and never need their own native hacks.What's new
Overlay API (
ImGuiApp)EnableOverlay(float opacity = 1.0f, bool clickThrough = false)— enter overlay mode: borderless, always-on-top, whole-window translucent, optional click-through. Cheap to call every frame (the native window is only restyled when something actually changes).SetOverlayGeometry(OverlayCorner corner, int offsetX, int offsetY, int width, int height)— lock the overlay to a corner of the active monitor's work area.DisableOverlay()— restore the decorated, non-topmost, opaque window.IsOverlayActiveproperty.OverlayCornerenum.Native styling lives in an internal
OverlayChromeand usesImGuiApp's own native handle (window.Native.Win32.Hwnd) rather than enumerating thread windows. It's implemented on Windows and degrades gracefully (no-op) on other platforms and on backends that don't export the*Ptrwindow-style APIs, while still tracking the logical overlay state.Frame limiting "in context" with overlay
ImGuiAppPerformanceSettings.OverlayFps(default 30) — an always-on-top overlay is usually unfocused (and some backends report it as not visible), so the normal focus/idle/visibility throttling would make it sluggish despite showing live data. While overlay mode is active, the frame limiter usesOverlayFpsand bypasses those reductions.Docs / demo / tests
ImGuiAppDemo: a View → Overlay mode toggle with opacity, click-through, and corner controls.OverlayFps-driven frame limiting, idle-bypass, and safe no-op calls.Compatibility
Purely additive — no existing API changed. Tagged
[minor](2.5.1 → 2.6.0).Testing
The .NET 10 SDK could not be installed in this environment (all SDK download hosts return HTTP 403 under the network policy; only NuGet is reachable), so the build/tests were not run locally and rely on CI. The changes were written to compile cleanly: platform-guarded native calls (
OperatingSystem.IsWindows()),OverlayWindow.csexcluded from the iOS target alongsideNativeMethods.cs, and no crefs to iOS-excluded types from files compiled on iOS.https://claude.ai/code/session_01Ngds45GjiRS3syR4uTrrvE
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