improve model formula notations

Author: hexqnt

src/app.rs

@@ -95,8 +95,8 @@ use self::status::StatusMessage;
 #[cfg(not(target_arch = "wasm32"))]
 use self::types::dialog_directory_from_path;
 use self::types::{
-    ExtendedMetrics, FormulaSvgCache, ModelFormulaInfo, ParamInitMethod, PlotTool,
-    SampledCurveCache, SprayBrush, UiLanguage, params_to_input_strings,
+    ExtendedMetrics, FormulaReferenceSection, FormulaSvgCache, ModelFormulaInfo, ParamInitMethod,
+    PlotTool, SampledCurveCache, SprayBrush, UiLanguage, params_to_input_strings,
 };
 use crate::domain::{
     AdamConfig, CurveFamily, CurveParams, FitResult, LbfgsConfig, NelderMeadConfig, NewtonCgConfig,

src/app/bootstrap.rs

@@ -121,7 +121,7 @@ impl Default for CurveFitApp {
             result_metrics: None,
             residual_plot_points: Vec::new(),
             spline_plot_curve: None,
-            formula_svg_cache: None,
+            formula_svg_cache: Vec::new(),
             sampled_curve_cache: None,
             iteration_diagnostics: IterationDiagnostics::default(),
             status: Some(StatusMessage::Ready),