Dual Screen GDExtension Plugin

This is a powerful Godot plugin designed to handle multiple screens on Android handhelds like Ayn Thor, Retroid Pocket 5, and RG DS. It provides a low-latency Vulkan-based renderer to project a secondary viewport onto a physical second display.

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Quick Start (Automated Build)

The easiest way to build the plugin is using Docker. You don't need to install Android SDK, NDK, Python, or SCons manually.

Prerequisites

• Docker
• Docker Compose

Building the Plugin

1. Open your terminal in the AynThor/ directory.
2. Run the following command:

   docker-compose up --build

3. Once completed, the ready-to-use plugin will be in AynThor/dist/AynThor.
4. Copy the dist/AynThor folder into your Godot project's addons/ directory.

Note: If you don't want to wait for the build process, you can find the pre-compiled binaries (for both Android and Windows) already available in the AynThor/dist/AynThor folder within this repository.

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How to Use

1. Engine Setup

• Go to Project -> Install Android Build Template.
• In Project Settings, ensure Export -> Android -> Use Gradle Build is ENABLED. The plugin will not work without a Gradle build.
• Enable the AynThor plugin in Project Settings -> Plugins.

2. Scene Setup

1. Create two SubViewportContainer nodes in your scene (one for the main screen, one for the secondary screen).
2. Add a SubViewport as a child to each container.
3. Create an empty Node and attach the AynThorManager.gd script to it.
4. In the Inspector for the Manager node, assign the references to your ViewportContainers and SubViewports.

Pro Tip: Single-Screen Mode

If you don't want to wrap your entire game into SubViewportContainers, you can use the plugin only for the secondary screen. Just create a viewport for the second display and leave the main game as is.

• Limitation: In this mode, you cannot use the swapping feature, as the plugin will not have control over the main window's rendering.

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How it Works

Plugin uses a hybrid architecture to bridge Godot's Rendering Device with Android's Presentation API:

1. Android Layer (Kotlin): Detects secondary displays and creates a Presentation window with a SurfaceView.
2. JNI Bridge (C++): Passes the native ANativeWindow handle from the Android Surface to the GDExtension.
3. Vulkan Renderer (C++/GDExtension):
   • Creates a separate Vulkan Swapchain for the secondary display.
   • Uses vkCmdBlitImage to copy the frame from a Godot SubViewport texture directly to the second screen's swapchain.
   • Supports hardware-level rotation and scaling.

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Technical Details

Compatibility

• Godot Engine: 4.5+ (including 4.6.x)
• Architecture: arm64-v8a (Android), x86_64 (Windows Editor support)
• Minimum Android API: 24 (Nougat)

Project Structure

• CPP/: Native Vulkan implementation and JNI hooks.
• Kotlin/: Android Presentation and Activity lifecycle management.
• GDScript/: Godot-side manager (AynThorManager.gd) and editor export scripts.

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