macOS ImGui External Overlay

A hardware-accelerated, borderless, and transparent external Imgui overlay for macOS (Apple Silicon & Intel). Built with C++ and Objective-C, GLFW, OpenGL, and ImGui.

Note: For the native Apple Metal version, switch to the metal-glfw branch.

Features

• Dual Tracking Modes:
  • Target Window Mode: Attaches the overlay to a specific application, perfectly matching its size and position.
  • Global Mode: Automatically scales to cover the entire primary monitor.
• Global Hotkey: Uses CGEventTap to intercept keystrokes (default: ~), allowing menu toggling from any application.
• Mouse Passthrough: Clicks pass through the transparent overlay to applications below when the menu is closed.

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macOS Security Permissions (Required)

macOS blocks applications from globally reading keystrokes. The hotkey will not work until you grant permission.

1. Open System Settings > Privacy & Security > Accessibility.
2. Add and enable the terminal application you are using to run the project (e.g., Terminal, iTerm2, or VS Code).

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Prerequisites

• Xcode Command Line Tools: xcode-select --install
• CMake (3.14+): brew install cmake

(GLFW and ImGui are downloaded automatically via CMake FetchContent during the build process).

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Building and Running

mkdir build
cd build
cmake ..
make
./GlfwOverlayApp

**Known Issue:** Occasionally, hotkey stops working.