Take the zoom from the node editor rather than doing it here

[matt-edmondson]

ktsu.ImGui.NodeEditor 3.20.0 carries NodeEditorRenderer.Zoom and FitToView (ktsu-dev/ImGuiApp#359), so this application's own copy comes out. Net −197 lines.

What goes

EnterViewSpace, LeaveViewSpace, IsUnzoomed, the ViewState record and the dictionary it lived in, the fontScaled flag, the MinZoom/MaxZoom/FitMargin constants, and FittingZoom.

Zoom now forwards to renderer.Zoom rather than holding a second value beside it. FitView calls renderer.FitToView(Graph.Engine, Graph.Engine.WorldOrigin * 2f) and keeps its own return value and status message — the world origin is kept on the middle of the canvas, so twice the origin is the whole of it. The toolbar slider takes its bounds from NodeEditorRenderer.MinZoom/MaxZoom.

Why the library's is better, not just tidier

Three things the version here could not do from outside the renderer:

• Nothing zoomed reaches the engine at all. The transform now sits at the seam between the engine and ImNodes. This application had to wrap it around the whole frame — scale the engine's positions, draw, unscale them — because from outside there was nowhere else to put it.
• The node editor's own lengths scale too: padding, corner rounding, pin sizes, grid spacing. Unreachable from here, and visible — the background grid now shrinks with the graph instead of staying put underneath it.
• A size measured while zoomed is no longer trusted as the node's size. The font size rounds to whole pixels and ImGui's spacing inside a node doesn't scale, so a measurement taken at 0.5× and scaled back is off by the padding. That is the part the copy here got wrong first time round, in the way that compounds: sizes only arrive when they change, so unscaling every frame re-divided the same value and within a second the nodes were thousands of times their real size.

Tests

328 passing (329 before; two zoom tests removed, one rewritten).

FitView_DoesNotMagnifyAGraphThatAlreadyFits only restated library behaviour, so it goes — the library tests it. The two kept are the ones the library cannot cover:

• FitView_ZoomsOutUntilTheGraphFits now stands for the plumbing: that this application hands over the right canvas. Passing the wrong rectangle would fit the graph to the wrong thing and no library test would notice.
• Zoom_IsTheRenderersOwn (was Zoom_IsHeldWithinTheRangeTheSliderOffers) asserts the property forwards, using the renderer's clamping as the evidence: a value it would refuse coming back changed is what says the property didn't just store what it was given.

Verified visually through the harness: the graph at 100%, at 50% with grid and node chrome scaled together, and back to 100% in exactly its original size and place.

🤖 Generated with Claude Code

https://claude.ai/code/session_01QwzCFb8zhd263sZeRbF7ba

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud