app.slint carried show-launch, show-library, show-identity, show-settings,
show-import and show-merge as separate booleans, so the root component chose
what to draw with five- and six-term conjunctions and nothing stopped two of
them being true at once. Replaced with two enums: View { develop, library,
identity, launch } for which top-level screen is showing, and Page { none,
settings, import, merge } for which page, if any, is drawn over it.
Two values rather than one, because the two questions are genuinely
different. Settings, Import and Merge are reachable from more than one View
and are drawn outermost without touching it — closing one has to return to
whichever View was already current, and today that works because the
underlying property is left alone while the page sits over it. A single
View with five or more variants would need a second field remembering what
to return to; Page needs nothing to remember, since View was never
overwritten in the first place. Identity, by contrast, genuinely replaces
the window the way Launch and Library do (see the existing "like the launch
screen" comment on its `if`), so it is a View variant, not a Page.
Every `if` chain in app.slint that used to compare four, five or six
booleans now compares active-view and active-page to at most one variant
each. library-visible collapsed from a six-term conjunction to
`active-page == Page.none && active-view == View.library`.
The Rust side follows: every set_show_*/get_show_* call in library_ui.rs,
identity_ui.rs, settings_ui.rs, merge_ui.rs, import_ui.rs, launch_ui.rs and
lib.rs now reads or writes active-view or active-page instead, including
lib.rs's startup match (View.launch vs View.develop, since a Startup that
skips the launch screen used to leave both old booleans false and fall
through the chain to develop) and identity_ui's close handler, which now
writes View.library or View.develop in one call where it used to write
show-library then show-identity separately.
back_one_step needed one deliberate adjustment beyond the mechanical
rename. Identity was never represented in NavState: back had nothing to do
when Identity was opened from the library (show-library stayed true,
unread by IdentityScreen's own condition) and could only reach ToLibrary
when opened from develop, which likewise wrote a property IdentityScreen
never read — so escaping out of Identity was invisible in both cases before
this change. With a single active-view, falling into the general case
would instead overwrite the value IdentityScreen's `if` does read and close
it as an unintended side effect. back_one_step now swallows the gesture
while View.identity is current, reproducing the same "nothing visible
happens" outcome for both origins without threading identity_ui's private
came-from-library state through lib.rs for one screen.
Verified with tools/manual/drive.py against a private Xvfb and the debug
build: launch screen to library, Settings opened and closed, Identity
opened and closed (including Escape doing nothing while it is open),
develop opened from a cell and closed both by the back button and by
Escape. Screenshots under verify/.