Snapping: tangent and perpendicular snapping, View > Snapping (#2530)

Squashed from #2537 onto main.

crates/engine/src/cmd/prefscmds.rs

@@ -235,6 +235,8 @@ pub const PREF_SPECS: &[PrefSpec] = &[
     p!("measurementLabels", "Smart Guides", "Display Options", "Measurement Labels", bool),
     p!("spacingGuides", "Smart Guides", "Display Options", "Spacing Guides", bool),
     p!("snappingTolerance", "Smart Guides", "", "Snapping Tolerance", num(0.0, 40.0, "pt")),
+    p!("snapTangent", "Smart Guides", "Geometric Guides", "Snap to Tangent", bool),
+    p!("snapPerpendicular", "Smart Guides", "Geometric Guides", "Snap to Perpendicular", bool),
     // Slices
     p!("showSliceNumbers", "Slices", "", "Show Slice Numbers", bool),
     p!("sliceLineColor", "Slices", "", "Line Color", color),

crates/engine/src/lib.rs

@@ -969,6 +969,8 @@ pub struct Prefs {
     pub measurement_labels: bool,
     pub spacing_guides: bool,
     pub snapping_tolerance: f64,
+    pub snap_tangent: bool,
+    pub snap_perpendicular: bool,
     // Slices
     pub show_slice_numbers: bool,
     pub slice_line_color: String,
@@ -1218,6 +1220,8 @@ impl Default for Prefs {
             measurement_labels: true,
             spacing_guides: true,
             snapping_tolerance: 4.0,
+            snap_tangent: true,
+            snap_perpendicular: true,
             show_slice_numbers: true,
             slice_line_color: s("#ff3f3f"),
             hyphenation_language: s("English: USA"),

crates/engine/src/tooling.rs

@@ -238,6 +238,8 @@ impl Session {
             // wins instead of pixels quietly rounding every drag to whole points (#1816).
             snap_to_pixel: view.snap_to_pixel && !view.snap_to_grid,
             snap_to_point: view.snap_to_point,
+            snap_tangent: self.prefs.snap_tangent,
+            snap_perpendicular: self.prefs.snap_perpendicular,
             snap_to_glyph: view.snap_to_glyph && view.smart_guides && !view.snap_to_grid,
             corner_widgets: view.corner_widgets,
             fill_active: self.fill_active,