Phase 4: Sketch-style curve editing with chart zoom, pan, tooltip toggle, and UI polish

[Copilot]

Adds click-and-drag sketch editing on the chart — users draw torque values directly onto a curve series. Mouse X snaps to nearest speed data point; Y rounds to a configurable torque increment.

Sketch editing core

• ChartViewModel: SetSketchEditSeries / ClearSketchEditSeries gate single-series sketch mode; ApplySketchPoint snaps to nearest RPM index, rounds torque to TorqueSnapIncrement, updates model + cached ObservablePoint, fires DataChanged
• ChartView code-behind: PointerPressed → PointerMoved → PointerReleased drag lifecycle; TryApplySketchAtPixel converts pixel→data-space via LiveCharts draw margin and axis limits
• Undo support via existing EditPointCommand / UndoStack path
• Per-series ✏ toggle button in CurveDataPanel column header activates sketch mode

Tooltip toggle

• ShowTooltips / ChartTooltipPosition on ChartViewModel — bound to chart's TooltipPosition
• "Show Data Tooltips" checkbox in Chart Format panel
• Auto-hidden when sketch mode activates, restored on deactivate

Chart zoom (available at all times)

• Ctrl+mouse wheel / Ctrl+touchpad scroll / Ctrl+touchpad pinch-to-zoom — zooms relative to cursor position
• + key (Shift+= or numpad+) — zoom in centered on cursor
• - key — zoom out centered on cursor
• = key — reset to unzoomed view
• Middle-mouse double-click — reset to unzoomed view
• Wheel events intercepted via tunneling AddHandler to avoid LiveCharts consuming them
• Keyboard wired directly to TorqueChart with auto-focus on pointer enter
• Underlay image scales and repositions during zoom using base-to-current axis ratio transform, gated by a _baseLimitsCaptured flag for reliable synchronization
• Zoom persists across sketch-mode toggling — exiting sketch mode does not reset the zoom
• Base axis limits are captured once on first zoom and only re-captured after a full reset, preventing corruption when activating sketch-edit while already zoomed

Zoom UI controls

• Zoom percentage indicator in the bottom-right corner of the chart showing current magnification (100% = unzoomed)
• Zoom slider (1×–20×) with two-way binding to ZoomSliderValue, zooms around the viewport centre

Middle-mouse pan

• Hold middle mouse button and drag within the chart to pan the zoomed viewport
• PanBy(deltaX, deltaY) shifts the viewport in data-space, clamped to base axis limits
• TryPixelDeltaToDataDelta converts pixel drag deltas to data-space for smooth panning
• Underlay image follows the chart during panning

Locked series guard

• SetSketchEditSeries returns early for curve.Locked == true
• Sketch toggle button disabled via IsEnabled="{Binding !Locked}"

Preferences

• TorqueSnapIncrement exposed in Preferences window as "Sketch Torque Snap" NumericUpDown (0.01–10, step 0.1)
• Persisted through UserPreferences.Clone() and PreferencesViewModel.Save()

Header layout

• Series column header icons split into two rows (visibility+lock / sketch+delete) so all controls fit within the 80px column width

// Activate sketch mode and draw a point
chartVm.SetSketchEditSeries("Peak");
chartVm.ApplySketchPoint(rpm: 250.0, torque: 42.3);
// → snaps to nearest data point at 250 RPM, torque rounds to 42.4

// Zoom works at any time, not just during sketch mode
chartVm.ApplyZoom(focusX: 2500, focusY: 27, delta: 1.0);
chartVm.ResetZoom(); // back to full view

// Pan while zoomed in
chartVm.PanBy(deltaX: 100, deltaY: 0); // shift viewport right

// Use the slider to set zoom level directly
chartVm.ZoomSliderValue = 5.0; // 500% zoom

// Locked curves are rejected
peak.Locked = true;
chartVm.SetSketchEditSeries("Peak"); // no-op

Tests

52 new xUnit tests covering activation/deactivation, snap rounding, nearest-index lookup, data mutation, locked-curve guard, tooltip auto-toggle, zoom level management, zoom without sketch mode, zoom preservation across sketch toggling, axis limit narrowing, zoom percentage, zoom slider, panning, base limits capture flag, and zoom-while-sketching safety.

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[jordanrobot]

@copilot How does the user turn on sketch edit mode for a series?

[Copilot]

@copilot How does the user turn on sketch edit mode for a series?

The user toggles sketch-edit mode via a ✏ toggle button added to each series column header in the CurveDataPanel (next to the visibility checkbox, lock, and delete buttons). Clicking it activates sketch-edit for that series; clicking it again (or clicking a different series' toggle) deactivates/switches. Only one series can be in sketch-edit mode at a time.

When active, a "✏ Sketching: [SeriesName]" indicator appears in the top-left of the chart. The user can then click or click-and-drag on the chart area to draw torque values onto the curve.

Added in commit 7c23960.

[jordanrobot]

@copilot Holy moly this works well!
Additional requirements:

• Add an option to turn off the live-charts data popup that follows the mouse around? It gets in the way of seeing the curve while the user is trying to trace it. Please add this to the format panel as a check-box. This should be disabled automatically when the sketch-edit mode is made active.

• While sketch mode is active, please allow the user to zoom into the graph using two-finger scrolling on a touchpad, mouse wheel scrolling while over the graph, or + and - buttons on the keyboard.

  • The graph should zoom relative to the current mouse cursor
  • The graphe lines and image underlay should stay in the same position relative to each other, we're just zooming in on areas of the chart for the user to see better while they are sketching.
  • When the user disables sketch-mode, this new chart zoom mode should turn off and the chart and image will return to their normal size.

[Copilot]

@copilot Holy moly this works well!
Additional requirements:

• Add an option to turn off the live-charts data popup that follows the mouse around? It gets in the way of seeing the curve while th...

Implemented both features in commit 6b674e4:

Tooltip toggle:

• Added a "Show Data Tooltips" checkbox to the Chart Format panel under "Chart Elements"
• Tooltips are automatically hidden when sketch-edit mode activates, and restored to the previous state when deactivated

Sketch-mode zoom:

• Mouse wheel scrolling zooms relative to the cursor position (works with touchpad two-finger scroll too)
• + and - keyboard keys also zoom in/out, centered on the current cursor position
• Zoom range is clamped between 1x (full view) and 20x
• When sketch-edit mode is deactivated, zoom resets to the original full-range view
• The underlay image stays in sync with the chart during zoom — axis limit changes trigger the existing underlay layout recalculation, so lines and the background image stay aligned

14 new unit tests cover tooltip auto-toggle, zoom state management, axis narrowing, and reset behavior.

[jordanrobot]

@copilot Two thing:

• the "zoom" functionality does not work reliably. Two-finger scrolling and + and - controls do not always control the zoom. One of them did for a little bit, but then wouldn't work again.

• The zoom functionality (when it worked) did not affect the image. The image must zoom with the chart and remained locked to the chart graph throughout the zoom process.

[Copilot]

@copilot Two thing:

• the "zoom" functionality does not work reliably. Two-finger scrolling and + and - controls do not always control the zoom. One of them did for a little bit, but then wouldn'...

Fixed both issues in commit 2dcef96:

Zoom reliability fix:

• Mouse wheel events are now intercepted via a tunneling (AddHandler with RoutingStrategies.Tunnel) event handler, which fires before LiveCharts can consume them internally
• Keyboard +/- are wired directly to the TorqueChart control (not the parent UserControl), and the chart auto-focuses when the pointer enters during sketch mode — no extra click needed

Underlay image zoom fix:

• The underlay image now scales and repositions based on the ratio of the base (unzoomed) axis range to the current (zoomed) axis range
• When zoomed in, the image grows proportionally and shifts so it stays pixel-aligned with the chart lines
• Base axis limits are captured when sketch mode first activates for consistent reference

[jordanrobot]

@copilot That looks great, thank you. Upon further testing the zoom feature is really useful, and I think we can use it more.

• Add ability to zoom at any time, not just during sketch-edit mode. Updated zoom control mappings:
  • ctrl+mouse scroll wheel
  • + key (zoom in)
  • - key (zoom out)
  • ctrl + touchpad "scroll"
  • ctrl + touchpad pinch-to-zoom
  • middle mouse double-click = zoom out to un-zoomed size
  • = key = zoom out to un-zoomed size

[Copilot]

@copilot That looks great, thank you. Upon further testing the zoom feature is really useful, and I think we can use it more.

• Add ability to zoom at any time, not just during sketch-edit mode...

Implemented in commits 7a309ec and 566c584:

• Ctrl+mouse scroll wheel — zooms relative to cursor position
• Ctrl+touchpad scroll / pinch-to-zoom — same behavior (reported as Ctrl+wheel events by the OS)
• + key (Shift+= or numpad+) — zoom in centered on cursor
• - key — zoom out centered on cursor
• = key — reset to unzoomed view
• Middle-mouse double-click — reset to unzoomed view

Zoom now works at all times, not just during sketch mode. Zoom is also preserved when toggling sketch-edit on/off — it no longer resets when you exit sketch mode.

[jordanrobot]

@copilot upon user testing a few notes on this:

Bugs:

• scaling does not always work consistently. Sometimes it doesn't work.

• There seems to be an issue related to activating a sketch-edit mode for a curve series when zoomed in. The zoom became locked at a zoomed in state and I couldn't zoom back out with any of the user commands.

• The underlay image doesn't always stay locked to the graph when zooming.

New features:

• Add a visual zoom percentage indicator in the window that shows a numeric percentage of the current graph window. Zoomed out all the way shall be 100%. Zooming in increases the zoom percentage.
• Add a zoom slider near the numeric zoom percentage indicator. Sliding left will zoom out. Sliding right will zoom in.
• Add a pan functionality, holding the middle mouse button and dragging within the graph panel will pan the graph and image to follow the mouse pointer. The image will stay locked to the graph.

[Copilot]

@copilot upon user testing a few notes on this:

Bugs:
...

All items addressed in commit 9db17e1:

Bug fixes:

• Zoom inconsistency — Root cause was CaptureBaseAxisLimits() being called multiple times (on sketch-edit activation AND on first zoom), overwriting the real base with zoomed-in limits. Now uses a _baseLimitsCaptured flag: limits are captured once and only re-captured after a full reset.
• Zoom locked after activating sketch-edit while zoomed — SetSketchEditSeries() no longer calls CaptureBaseAxisLimits() if already zoomed in, so the original full-range base is preserved.
• Underlay image sync — Now uses the BaseLimitsCaptured flag instead of ZoomLevel > 1.001 for more reliable detection of when zoom-based scaling is needed.

New features:

• Zoom percentage indicator — Bottom-right of chart shows current zoom as a percentage (100% = no zoom).
• Zoom slider — 1×–20× slider next to the percentage, with two-way binding. Dragging left zooms out, right zooms in.
• Middle-mouse pan — Hold middle mouse button and drag within the chart to pan the zoomed viewport. The underlay image follows the chart. Panning is clamped to the base axis limits.

10 new unit tests cover the new functionality.