Mega UI

Lifecycle

When your recipe runs, when your functions are read, and the window rules you inherit for free.

The order of things

When	What happens
Your `Awake`	You `Register` and `Build`. Nothing is drawn — there is no computer in the scene yet.
Player reaches a store	The desktop is built. Your icon appears and your window is drawn, hidden.
Player clicks your icon	Your `Func`s are read, then `OnOpened` fires.
Player opens something else	Your window hides and `OnClosed` fires.
Player walks away	Same as above — minimized, not closed.

Your recipe is kept, not run

Build takes a delegate because your Awake happens long before there is anywhere to draw. Mega UI stores it and runs it when a window exists — and again whenever the desktop is rebuilt, which happens more than once per session.

This is why you never hold a reference

Any GameObject you kept a field for would be destroyed and recreated behind your back. Describing the screen instead of building it is what makes that a non-issue.

Numbers refresh themselves

Everything you passed as a Func is called again every time the window opens. For the common case — a screen showing live values — you write nothing else.

csharp

// Read on every open. No timer, no event, no Refresh call.
r.Value(() => Warehouse.Count.ToString());

Refresh is for shape, not for numbers

Call Refresh when the structure changed — a row that should not be there any more, a section that only exists once something is unlocked.

csharp

private AppHandle _app;

private void OnFeatureUnlocked()
{
    // The screen has a new section now, so it has to be rebuilt.
    _app.Refresh();
}

It is cheap and safe to call when the window is closed. It is not what you use to make a number update — that is already handled.

One window at a time

The game's computer does not stack windows: opening one closes the last. Your app is part of that rule, in all three directions:

Player opens	What happens
Your app, with another mod's open	The other mod's window minimizes
Your app, with Shopping open	Shopping minimizes
Shopping, with your app open	Your app minimizes

Why this is not optional

Before the rule existed, clicking Shopping with a mod window open opened Shopping behind it. The player clicked an icon and the screen did not change — which reads as a broken game, not a broken mod.

Walking away minimizes, it does not close

Leaving the computer hides every window and fires OnClosed. Coming back leaves the desktop as it was. That is the game's own behaviour — ComputerUI calls MinimizeAllTabs, not CloseTab — and your app inherits it rather than inventing something different.

Exceptions cannot escape

Every callback you hand over — a Func, a click handler, OnOpened — is wrapped. A throw is logged with your guid and swallowed.

This is load-bearing rather than polite: an exception reaching the game's EventSystem stops click processing for the entire scene. One mod's null reference would cost the player the mouse in the whole game.