CurveAppearance and CurveAppearanceWidget

CurveAppearanceWidget is a reusable Qt widget that presents a full set of curve-appearance controls to the user. It edits a CurveAppearance struct — a plain-data aggregate that bundles every visual property a plot curve carries. The same struct is the currency exchanged between the widget, BlackchirpPlotCurveBase (which stores and applies the values at draw time), and OverlayBase (which serializes a copy in its metadata blob so overlay curves restore their appearance across sessions).

The widget is used in the plot context-menu’s per-curve configuration panel. The user-guide description of the resulting controls is in Plot Controls.

Appearance fields

CurveAppearance collects the following properties:

color — pen color (QColor).
curveStyle — rendering mode: QwtPlotCurve::Lines, Sticks, Steps, Dots, or NoCurve.
lineThickness — pen width in pixels (double).
lineStyle — dash pattern: Qt::SolidLine, Qt::DashLine, etc. Pass Qt::NoPen to suppress the line completely.
markerStyle — symbol drawn at each data point (QwtSymbol::Style); QwtSymbol::NoSymbol suppresses markers.
markerSize — symbol size in pixels (int).
visible — whether the curve is drawn at all (bool).
autoscale — whether the curve is included when axis limits are computed during an autoscale operation (bool).
yAxis — which Y axis the curve is plotted against (QwtAxisId; maps to the left or right axis).

CurveAppearance is registered with Q_DECLARE_METATYPE so it can be carried in QVariant containers and emitted through queued signals.

Init/apply paths

The widget provides two parallel init/apply paths depending on whether the caller owns a curve object or an overlay object:

Curve path — used by the main plot context menu:

initializeFromCurve(BlackchirpPlotCurveBase*) — reads the current appearance settings from the curve’s storage and populates the controls.
applyToCurve(BlackchirpPlotCurveBase*) — writes the current control state back to the curve, triggering an immediate visual update.

Overlay path — used when editing an overlay curve:

initializeFromOverlay(std::shared_ptr<OverlayBase>) — reads the serialized appearance from the overlay’s metadata blob.
applyToOverlay(std::shared_ptr<OverlayBase>) — writes the current control state into the overlay’s metadata.

Both paths ultimately operate on the same CurveAppearance struct, which is also accessible directly via getCurrentAppearance() and setCurrentAppearance(). Whenever any control changes, the widget emits curveAppearanceChanged(CurveAppearance) so callers can react immediately without polling.

Preset management

When a CurveAppearancePresetManager is attached via setPresetManager(), a preset combo box and Save/Delete buttons become active. The CurveAppearancePresetManager singleton (stored in QSettings) ships with nine default presets — three curve, three stem, and three scatter variants — and persists any user-defined presets across sessions. The widget provides the following preset surface:

applyPreset(name) — loads the named preset and emits curveAppearanceChanged().
saveCurrentAsPreset(name) — saves the current control state as a preset; overwrites an existing entry if the name matches.
deletePreset(name) — removes a user-defined preset (default presets cannot be deleted).
refreshPresetList() — repopulates the combo box from the manager, e.g., after an external preset change.

The widget does not open dialogs itself; it delegates user-input steps (name entry, delete confirmation) to callers via the signals presetSaveRequested(suggestedName) and presetDeleteRequested(presetName).

The user-facing description of the preset workflow — including the nine default presets and the Save Curve Appearance Preset dialog — is in Plot Controls.

API Reference

class CurveAppearanceWidget : public QWidget

Widget that edits the visual appearance of a single plot curve.