Architecture

The shape

Three rules hold this together, and each is enforced by a test rather than by discipline.

WinMux.Core references no platform assembly. Everything portable lives there. If the layout engine ever needs a window handle, the design has gone wrong.

WinMux.Platform is the shape of an operating system, never an implementation of one. It states intent — place this window here, tell me when focus moves — not steps, because the steps are what differ between systems. WinMux.Shell declares zero DllImport, and exactly one file in it names a concrete operating system.

A hosted application lives in its own process. WinMux.PaneHost owns the window; the shell never calls a foreign application’s handle. A frozen application freezes its own host and WinMux stays alive — which was measured rather than assumed.

Why it is shaped that way

The decisions are written down as they are made, with what failed as well as what worked. They are the most useful thing in the repository if you are changing something and want to know whether the obvious approach has already been tried.

Worth starting with:

• ADR 0001 — why a hosted application gets its own process, and the six-second freeze that proved it.
• ADR 0012 — how panes became extensible, and why a pane kind is a string rather than an enum.
• ADR 0016 — the chrome, and a day mostly spent on a bug that was not in the application.
• ADR 0017 — a constraint the project carried for three phases, finally measured, and describing the wrong symptom the whole time.