Architectural Update: Hardware Window, Wayland, and WebGPU

✨ New Wayland Support

Native Wayland Interactor (vtkWaylandRenderWindowInteractor):

A new, dedicated interactor has been implemented for robust event handling on Wayland compositors. It processes pointer (mouse motion, buttons, scrolling) and keyboard inputs directly, using xkbcommon for precise keymap and modifier state management.

Native Wayland Display Protocol Support

This version introduces comprehensive, native support for the Wayland display protocol, providing a modern alternative to X11 on Linux systems. Windows can request standard decorations (title bars, borders) from the Wayland compositor by leveraging the xdg-decoration-unstable-v1 protocol. This ensures applications integrate visually with the user’s desktop environment.

WebGPU on Wayland:

The WebGPU rendering backend is now fully integrated with Wayland surfaces, allowing high-performance graphics in modern Linux environments.

🚀 Platform-Specific Enhancements & WebGPU Integration

Significant advancements have been made to standardize and enhance the rendering experience across diverse operating systems, including Windows, macOS, and Linux. Historically, VTK’s rendering architecture has been characterized by a tightly coupled integration between the windowing system and the graphics stack. However, with the advent of modern graphics APIs, such as WebGPU, which offer more sophisticated and explicit surface descriptors, VTK now implements a clear logical separation between its graphics system and the underlying windowing system.

This architectural shift is embodied by the introduction of the new vtkHardwareWindow class and its specialized sub-classes. These components are meticulously designed to manage platform-specific window system integrations, critically, without incorporating any direct calls to the rendering layer. This distinct separation not only facilitates superior management and independent evolution of these two crucial codebases but also significantly streamlines the integration of future graphics and windowing APIs, thereby enhancing flexibility and long-term maintainability.

Windows: Improved Interactor and Hardware Window Support

The vtkWin32RenderWindowInteractor has been updated to seamlessly support both the legacy OpenGL render window and the new vtkHardwareWindow abstraction.

The vtkWin32HardwareWindow also supports native Windows cursor shapes and visibility controls.

Apple (macOS/Cocoa) WebGPU Rendering via Metal

The vtkCocoaHardwareWindow now utilizes the WebGPU API with the Metal backend, bringing modern, high-performance rendering to macOS applications.

The vtkCocoaHardwareView is set as the “first responder,” allowing it to properly intercept and process system keyboard and mouse events for reliable interaction.

Linux (X11)

Unified Hardware Window: The specialized vtkXWebGPURenderWindow has been removed in favor of the more generic vtkXlibHardwareWindow. This simplifies the architecture by using a single, unified component for X11-based windowing.

🔧 Refactoring & Build System Improvements

Consolidated Win32 Build Logic

A new VTK_USE_WIN32 CMake option has been introduced to replace disparate WIN32 checks as well as the opengl dependent variable VTK_USE_WIN32_OPENGL. This unifies conditional compilation and linking for all Win32 components, simplifying the build configuration for Windows.

CMake Support for Wayland

With the introduction of FindWAYLAND.cmake CMake script, the build system finds and links against required Wayland libraries and generates necessary protocol files, making it straightforward to build with Wayland support enabled. To enable Wayland support, set VTK_USE_Wayland:BOOL=ON.

🐛 Bug Fixes

Fixed Xlib Macro Collision

Resolved a critical compilation error on Linux systems where the Xlib Success macro conflicted with the wgpu::MapAsyncStatus::Success enum, allowing WebGPU code to build correctly with X11 headers. (Commit d8a4c55)