The developer created OpenRTL, an open-source implementation of the RTL/VCL paradigm using standard C++17. The project aims to replicate the architecture of RAD Studio without relying on proprietary compilers, closed libraries, or specific licenses. The core implementation was achieved in approximately 1,500 lines of code.
The architecture separates the VCL layer from platform-specific details. It uses an abstract interface, IOSDriver, to handle interactions with the operating system. This design ensures that the VCL layer remains platform-agnostic, as it does not contain platform-specific code like Win32 constants or headers.
Events are normalized through the OSEvent structure, which converts system-specific messages into a unified format. This allows the VCL layer to process events such as mouse clicks or key presses without needing to know the underlying platform, whether it is Windows, GTK, or Cocoa.
The project highlights the distinction between ownership and visual hierarchy, a core concept in VCL. By using an opaque pointer, IOSHandle, the VCL layer manages controls without needing to understand the specific window handles used by different operating systems, such as HWND in Win32 or GtkWidget in GTK4.
