Symptom

Opening a Project.Diagram node’s view face (ScreenCore.viewExpanded(), the view:<id> path) rendered the diagram collapsed to a thin strip at the bottom of the screen, with the time-range selector squeezed to roughly one character wide (its “Range”/”Minute”/”Hour” labels wrapped one letter per line). The same SVG rendered correctly in the edit face’s Preview box, so the SVG pipeline itself was fine — this was purely a layout bug in the view face.

Root cause

Two independent defects compounded, and an earlier fix attempt addressed neither fully:

1. ViewScreenToolbar’s internal Spacer(Modifier.weight(1f, true)). A weight child forces its Row to claim the entire incoming max width during Compose’s unweighted-children-first measurement pass — regardless of what modifier the caller applies to the toolbar. DiagramScreen’s header row placed ViewScreenToolbar beside TimeRangeSelector(Modifier.weight(1f)); the toolbar’s internal weight consumed the row before the selector’s own weight had anything left to claim. A first fix attempt added an optional modifier parameter and passed Modifier.wrapContentWidth() from the caller, but wrapContentWidth() only relaxes the minimum width constraint passed to a child — it does not touch the maximum, so the internal weight spacer kept expanding to the unchanged max and the row stayed starved.
2. fillMaxSize() inside an unbounded-height scroll container. DiagramScreen renders inside NodeEditorContainer’s Settings-tab content column, which is Modifier.fillMaxSize().verticalScroll(...). verticalScroll hands its content an unbounded (Constraints.Infinity) max height so it can scroll past the viewport. Modifier.fillMaxSize()/fillMaxHeight() has no effect once the incoming max is Constraints.Infinity (documented Compose behavior) — so the diagram’s image-hosting Box collapsed to whatever minimal height its own children happened to report.

Fix

• ViewScreenToolbar (composeApp/.../ui/ViewScreenToolbar.kt) dropped the internal weighted Spacer entirely and now takes a modifier: Modifier = Modifier.fillMaxWidth() parameter applied directly to its Row, with Arrangement.End doing the right-alignment Arrangement.End was always capable of doing on its own. The default preserves the existing full-width, right-pinned look for standalone callers (CameraScreen); DiagramScreen now passes Modifier.wrapContentWidth(), which works correctly once there is no interior weight forcing the row to the max.
• DiagramScreen (composeApp/.../krillapp/project/diagram/DiagramScreen.kt) no longer sizes its diagram Box with fillMaxSize(). It now derives an exact height from the box’s (always-bounded) width via Modifier.aspectRatio(...), using the loaded SVG’s own viewBox/width/height ratio when available (extracted as the pure, unit-tested diagramBoxAspectRatio(SvgDimensions?)), falling back to a 16:9 placeholder before the SVG loads. This sidesteps the unbounded-max-height problem entirely instead of fighting it — the same pattern CameraView.kt already used successfully for its own full-screen node view.

Prevention

• A composable that needs a weight-based spacer to right-align content should not also be usable beside another weighted sibling — the two interact through the shared parent Row’s measurement pass in a way no modifier applied at the call site can override. Prefer Arrangement.End/Arrangement.SpaceBetween on a row whose width the caller controls via an accepted modifier parameter, so the row’s own sizing is single-owner.
• Modifier.fillMaxSize()/fillMaxHeight() silently becomes a no-op once an ancestor hands down Constraints.Infinity for that axis (any verticalScroll content column, LazyColumn, etc.) — it does not throw or warn. A full-screen “view” composable that will be embedded inside a scrollable container should size its primary content from a bounded axis (aspectRatio, heightIn(min = ...), or an explicit .height(...)) rather than fillMaxSize(), and should be spot-checked by actually opening its view face — not just its edit face’s preview, which may sit in a differently-constrained parent.
• Added DiagramScreenViewLayoutTest (composeApp/src/desktopTest/.../DiagramScreenViewLayoutTest.kt) using runDesktopComposeUiTest to measure real layout output: it calls the actual shipped ViewScreenToolbar + TimeRangeSelector composables in the same side-by-side arrangement DiagramScreen uses and asserts the selector keeps the majority of the header’s width, plus a pure-function test of diagramBoxAspectRatio. Verified red before the fix (fails to even compile without the new modifier parameter; reproduced the narrow-width assertion failure directly by temporarily reintroducing the old weighted-spacer behavior against the new signature).