GtkBackend,Gtk3Backend: Fix path start point handling

Author: stackotter

Sources/Gtk3Backend/Gtk3Backend.swift

@@ -1296,13 +1296,19 @@ public final class Gtk3Backend: AppBackend {
             }
         }
 
-        for action in actions {
+        for (index, action) in actions.enumerated() {
             switch action {
                 case .moveTo(let point):
                     cairo_move_to(cairo, point.x, point.y)
                 case .lineTo(let point):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     cairo_line_to(cairo, point.x, point.y)
                 case .quadCurve(let control, let end):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     var startX = 0.0
                     var startY = 0.0
                     cairo_get_current_point(cairo, &startX, &startY)
@@ -1316,6 +1322,9 @@ public final class Gtk3Backend: AppBackend {
                         end.x, end.y
                     )
                 case .cubicCurve(let control1, let control2, let end):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     cairo_curve_to(
                         cairo,
                         control1.x, control1.y,

Sources/GtkBackend/GtkBackend.swift

@@ -1341,13 +1341,19 @@ public final class GtkBackend: AppBackend {
             }
         }
 
-        for action in actions {
+        for (index, action) in actions.enumerated() {
             switch action {
                 case .moveTo(let point):
                     cairo_move_to(cairo, point.x, point.y)
                 case .lineTo(let point):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     cairo_line_to(cairo, point.x, point.y)
                 case .quadCurve(let control, let end):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     var startX = 0.0
                     var startY = 0.0
                     cairo_get_current_point(cairo, &startX, &startY)
@@ -1361,6 +1367,9 @@ public final class GtkBackend: AppBackend {
                         end.x, end.y
                     )
                 case .cubicCurve(let control1, let control2, let end):
+                    if index == 0 {
+                        cairo_move_to(cairo, 0, 0)
+                    }
                     cairo_curve_to(
                         cairo,
                         control1.x, control1.y,

Sources/SwiftCrossUI/Values/Path.swift

@@ -201,8 +201,11 @@ public struct Path {
     /// The types of actions that can be performed on a path.
     public enum Action: Equatable {
         case moveTo(SIMD2<Double>)
+        /// If this is the first action in a path then (0, 0) is inferred to be the start point.
         case lineTo(SIMD2<Double>)
+        /// If this is the first action in a path then (0, 0) is inferred to be the start point.
         case quadCurve(control: SIMD2<Double>, end: SIMD2<Double>)
+        /// If this is the first action in a path then (0, 0) is inferred to be the start point.
         case cubicCurve(control1: SIMD2<Double>, control2: SIMD2<Double>, end: SIMD2<Double>)
         case rectangle(Rect)
         case circle(center: SIMD2<Double>, radius: Double)