🪟 Overlay-Renderer

Overlay-Renderer is a lightweight, fully-customizable overlay framework for Direct3D 11 + ImGui.NET on Windows.

It’s designed for real-time overlays that render on top of existing applications (like games or productivity tools)
without stealing focus or blocking input — except where you want it to.

---

✨ Features

• 🖼️ True transparent overlay – Renders ImGui windows and content over any window.
• 🧩 Click-through regions – Only interactive where your ImGui windows are.
• 🎨 ImGui styling system – Fully supports custom ImGui themes and style presets.
• 🧠 Automatic window tracking – Follows the target app’s position and size in real time.
• 🖱️ Input passthrough logic – Keyboard and mouse events go to the right target.
• ⚡ Direct3D 11 renderer – Efficient compositing through DirectComposition.
• 💬 Simple integration – Drop it into any .NET app and call a few setup methods.

---

🧱 Architecture Overview

Overlay-Renderer contains the following components:

Component	Purpose
OverlayWindow	Manages the topmost transparent window, input hit-regions, focus behavior.
D3DHost	Handles Direct3D 11 device creation, swap chain, and frame rendering.
ImGuiRendererD3D11	Bridges ImGui.NET with D3D11 — responsible for frame lifecycle and texture uploads.
HitTestRegions	Calculates where the overlay should receive clicks (ImGui window bounds).
ImGuiInput	Feeds global mouse/keyboard state into ImGui.
WindowTracker	Keeps the overlay window aligned with its target application window.
FindProcess	Locates and waits for a process’ main window handle.
Logger	Simple thread-safe logging helper for console and file output.

---

🧰 Technologies

• .NET 8.0
• C# 11
• Direct3D 11 via Win32 interop (CsWin32)
• ImGui.NET for GUI rendering
• DirectComposition for hardware-accelerated transparency
• Windows API (HWND, RECT, SetWindowRgn, WM_NCHITTEST, etc.)
• WebView2

---

🚀 Quick Start

1. Add the project reference

Add Overlay-Renderer to your solution and reference it from your app project:

Right-click your project → Add → Project Reference → check "Overlay-Renderer"

2. Create and attach an overlay

using Overlay_Renderer;
using Overlay_Renderer.Methods;
using Overlay_Renderer.ImGuiRenderer;
using Overlay_Renderer.Helpers;
using ImGuiNET;
using Windows.Win32.Foundation;

IntPtr targetHwnd = FindProcess.WaitForMainWindow("SomeApp");
if (targetHwnd == IntPtr.Zero)
{
    Logger.Error("App not found!");
    return;
}

using var overlay = new OverlayWindow(new HWND(targetHwnd));
using var d3d = new D3DHost(overlay.Hwnd);
using var imgui = new ImGuiRendererD3D11(d3d.Device, d3d.Context);

// Optional: apply built-in style
ImGuiStylePresets.ApplyDark();

// Example render loop
while (true)
{
    d3d.BeginFrame();
    imgui.NewFrame(overlay.ClientWidth, overlay.ClientHeight);

    ImGui.Begin("Overlay Test");
    ImGui.Text("Hello from Overlay-Renderer!");
    HitTestRegions.AddCurrentWindow();
    ImGui.End();

    HitTestRegions.ApplyToOverlay(overlay);

    imgui.Render(d3d.SwapChain);
    d3d.Present();
}

This creates a fully functional overlay window aligned with the target process.

---

🧠 How It Works

Overlay-Renderer uses a layered, transparent, non-activating window (WS_EX_LAYERED | WS_EX_NOACTIVATE) and shapes it each frame using SetWindowRgn() to match your ImGui windows.
That means:

• Areas outside ImGui are not part of the window (click-through).
• Areas under ImGui are fully interactive (for sliders, buttons, etc).
• The app underneath always keeps keyboard focus.

---

🎨 Styling

Custom styles live in ImGuiStylePresets.cs.
You can define your own look easily:

var style = ImGui.GetStyle();
style.WindowRounding = 6f;
style.FrameRounding = 3f;
style.Colors[(int)ImGuiCol.WindowBg] = new Vector4(0.1f, 0.1f, 0.1f, 0.94f);

Then apply it on startup:

ImGuiStylePresets.ApplyDark();

---

🧩 Integrating with Other Projects

If you’re writing your own overlay (like Starboard):

1. Add Overlay-Renderer as a Project Reference.
2. Import the namespaces:

   using Overlay_Renderer;
   using Overlay_Renderer.Methods;
   using Overlay_Renderer.ImGuiRenderer;
   using Overlay_Renderer.Helpers;

3. Use the provided utilities to manage:
   • process detection (FindProcess)
   • overlay lifecycle (OverlayWindow, D3DHost)
   • ImGui integration (ImGuiRendererD3D11)
   • region updates (HitTestRegions)
   • window sync (WindowTracker)

---

🧪 Example Project

See Starboard for a real-world integration example:

• Tracks the Star Citizen client window
• Draws custom ImGui windows
• Demonstrates region shaping, input routing, and DPI handling

---

🧰 Development

Requirements

• Visual Studio 2022 or Rider
• .NET 8 SDK
• Windows 10+ with Direct3D 11

---

⚖️ License

Apache-2.0 License

---

💬 Credits

Built with ❤️ by Rayla
Powered by ImGui.NET, WebView2 and Microsoft CsWin32

---