orisys-app/apps/studio/docs/ui-layout.md

Studio UI layout contract

Rules for the Studio window's layout, and for the tests that prove it. The colour equivalent is ui-palette.md; this file is the layout half.

Scope: apps/studio. The same rules apply to apps/autocal where it has panes of its own.

1. Ownership

Concern	Owner
Top-level panel arrangement, presets, splitter sizes, which panes are visible	view_layout.py (ViewLayoutController)
A panel's internal layout, its own minimums, how it degrades when narrow	that panel's module
Colour and appearance	theme tokens + build_qss (see ui-palette.md)
Shared spacing and minimum sizes	the token module named in §4

A panel MUST NOT set the size of another panel, and MUST NOT reach into the splitter. If a panel needs more room, it raises its own minimum and lets the controller allocate.

One owner per region. A region's geometry is decided in exactly one place. The app_window.py extractions (ViewLayoutController, DisplayPrefsController) are how this is achieved; new layout behaviour belongs in a controller, not in app_window.py.

2. View transitions

The three top-level views are arrangements of the same window. Switching between them is a single operation with a fixed set of effects.

Every path that changes the view MUST go through apply_preset(). It is the only place that applies the complete set, and apply_preset deliberately performs all of:

1. sets view_preset and the persisted preference;
2. sets show_cal from the preset;
3. sets the rail's source view (replay vs live);
4. sets the run-button role (playback vs acquire);
5. applies panel visibility;
6. applies the preset's splitter sizes;
7. switches the chart/replay source and clears replay-only state when leaving replay;
8. updates the brand bar, view checks and replay actions.

MUST NOT write _view_preset, the view_preset preference, or the splitter sizes directly. Doing so produces a state that looks correct in the nav and wrong everywhere else — stale chart source, wrong run role, sizes from the previous view.

The transition that broke

ViewLayoutController.on_cal_panel_toggled(False) set _view_preset = "live" and persisted it without calling apply_preset("live"). The sequence replay → calibration → calibration off therefore ended with view_preset == "live" while the rail still reported the replay source and no live splitter sizes had been requested. The live branch (on_cal_panel_toggled(True)) did call apply_preset, which is what made the asymmetry easy to miss.

This transition MUST be covered by a regression test that asserts the whole effect set of §2, in the controller and again through a real StudioMainWindow. Asserting only view_preset, show_cal and the brand bar — as the existing toggle test does — is what let it through.

3. Per-view arrangement

Each view is described by what it is for, so priority disputes have a reference.

View	Primary pane (gets width first)	Companion panes	Degradation as width shrinks, in order
live	measurement panes (2D/3D)	charts, settings rail	charts narrow to their minimum, then settings rail collapses, then charts scroll
replay	charts (history browsing is the point)	2D pane, rail	2D pane narrows, then hides where the layout allows
calibration	cal_panel — its six-column table and action row need width	rest	the table scrolls horizontally rather than compressing columns below readability

The 3D pane is a peer of the 2D pane, never a replacement for it. Where both are visible they share the measurement region; where only one is, it takes the region.

Squeeze is a designed state, not an accident. For each pane, name what happens at minimum width. "Everything gets smaller" is not a degradation order.

4. Numeric geometry

Not every numeric argument is a defect; blanket replacement of numbers with names is churn. The rule distinguishes by reason:

Kind	Rule
Structural constants — 1 px separator, 1 px rule, a colour-bar's height, a native handle that must stay at zero size	Keep, with a named constant and a comment stating why the number is the value
Shared spacing — margins, gaps, padding shared by more than one panel	MUST come from the shared token module
Content-driven width — a field, a spin box, a label that holds text	MUST derive from sizeHint(), fontMetrics(), or a token for its role. A literal that must hold the longest locale string MUST be justified in a comment
A flexible panel's own minimum	MUST be a named constant with the reason recorded

The token module (shared spacing and minimum sizes) does not exist yet; creating it is a follow-up. Until it does, new shared spacing MUST NOT be introduced as a literal in more than one place.

Text must fit. Any control whose text can change with locale MUST hold the longest supported string without clipping.

5. Enforcement gaps to close

These are stated because the contract is not currently enforced where it claims to be.

1. The palette prohibition is not mechanically enforced. ui-palette.md states that hex literals are not allowed in widget code, but ui_check.audit_palette() reads the theme JSON and checks values and contrast only — it never scans source. Hex literals exist in widget modules today. Either add the source scan or correct the claim in ui-palette.md.
2. The containment check is position-blind. test_ui_smoke.test_children_stay_inside_their_parent compares child.width()/height() against the parent's, and never looks at x/y. Since QWidget.geometry() is parent-relative, a child shifted outside its parent — or overlapping a sibling — passes as long as it is no larger. It MUST compare the full rectangle.
3. Rendered 3D pixels are tested but conditionally. test_scene3d_gl_smoke.py asserts on pixels through grabFramebuffer, and skips without a real GL context. That is the right design; the gap is that the skip is invisible in an ordinary run. Where the GL gate is required, a skip MUST be reported as a failure of the run, not counted as a pass.

6. Tests

The existing suites stay: state assertions are cheap and catch real regressions. What is added is assertions about the visible result.

Tier	What it asserts	Where
Transition	the full effect set of §2, for every path that changes the view, including the breaking sequence	test_view_layout.py (controller) and a window-level test through StudioMainWindow
Geometry	full child rectangles inside parents, no sibling overlap among laid-out peers, required text fits	extend test_ui_smoke.py
Matrix	the above under combinations that historically broke: minimum window size, longest locale, both themes, sensor type, pane state	parametrised in test_ui_smoke.py
Rendered	a few pinned 2D and toolbar snapshots for human review	ui_snapshot.py output, reviewed not asserted
GL pixels	rendered 3D, in the real-context suite only	test_scene3d_gl_smoke.py

On waiting: processEvents() dispatches pending paint events, so it is sufficient to let a layout settle. It does not assert what was painted, and it does not guarantee that later asynchronous work has finished. Tests that depend on completion MUST wait for the signal or condition, not for a fixed number of processEvents() calls. pytest-qt makes that easier and is not a prerequisite.

Golden images, if adopted: pin the window size, scale factor, font and theme, or they will flake and be disabled. A flaky render gate is worse than none.