fixed a bug with anticlockwise arcs and ellipses

updated to new sdl library version
tfriedel6 · Oct 1, 2019 · 71741d4 · 71741d4
1 parent 239ab21
commit 71741d4
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Showing 3 changed files with 13 additions and 7 deletions.
diff --git a/go.mod b/go.mod
@@ -6,7 +6,7 @@ require (
 	github.com/go-gl/glfw v0.0.0-20181014061658-691ee1b84c51
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/samuel/go-pcx v0.0.0-20180426214139-d9c017170db4
-	github.com/veandco/go-sdl2 v0.3.0
+	github.com/veandco/go-sdl2 v0.3.3
 	golang.org/x/exp v0.0.0-20181106170214-d68db9428509
 	golang.org/x/image v0.0.0-20181109002202-aa35264064ba
 	golang.org/x/mobile v0.0.0-20181026062114-a27dd33d354d

diff --git a/go.sum b/go.sum
@@ -10,6 +10,8 @@ github.com/samuel/go-pcx v0.0.0-20180426214139-d9c017170db4 h1:Y/KOCu+ZLB730Pude
 github.com/samuel/go-pcx v0.0.0-20180426214139-d9c017170db4/go.mod h1:qxuIawynlRhuaHowuXvd1xjyFWx87Ro4gkZlKRXtHnQ=
 github.com/veandco/go-sdl2 v0.3.0 h1:IWYkHMp8V3v37NsKjszln8FFnX2+ab0538J371t+rss=
 github.com/veandco/go-sdl2 v0.3.0/go.mod h1:FB+kTpX9YTE+urhYiClnRzpOXbiWgaU3+5F2AB78DPg=
+github.com/veandco/go-sdl2 v0.3.3 h1:4/TirgB2MQ7oww3pM3Yfgf1YbChMlAQAmiCPe5koK0I=
+github.com/veandco/go-sdl2 v0.3.3/go.mod h1:FB+kTpX9YTE+urhYiClnRzpOXbiWgaU3+5F2AB78DPg=
 golang.org/x/exp v0.0.0-20181106170214-d68db9428509 h1:k21GX33vzpH/syMF7TgrLxe8ILtvwbyuHtEO3ebR82E=
 golang.org/x/exp v0.0.0-20181106170214-d68db9428509/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/image v0.0.0-20181109002202-aa35264064ba h1:tKfAeDKyjJZwxAJ8TPBZaf6LpvauubUHT8wwpdz+OMM=

diff --git a/path2d.go b/path2d.go
@@ -129,8 +129,10 @@ func (p *Path2D) Arc(x, y, radius, startAngle, endAngle float64, anticlockwise b
 		return
 	}
 
-	if (!anticlockwise && endAngle < startAngle) || (anticlockwise && endAngle > startAngle) {
-		endAngle, startAngle = startAngle, endAngle
+	if !anticlockwise && endAngle < startAngle {
+		endAngle = startAngle + (2*math.Pi - math.Mod(startAngle-endAngle, math.Pi*2))
+	} else if anticlockwise && endAngle > startAngle {
+		endAngle = startAngle - (2*math.Pi - math.Mod(endAngle-startAngle, math.Pi*2))
 	}
 
 	if !anticlockwise {
@@ -142,7 +144,7 @@ func (p *Path2D) Arc(x, y, radius, startAngle, endAngle float64, anticlockwise b
 	} else {
 		diff := startAngle - endAngle
 		if diff >= math.Pi*4 {
-			diff = math.Mod(diff, math.Pi*2)
+			diff = math.Mod(diff, math.Pi*2) + math.Pi*2
 			endAngle = startAngle - diff
 		}
 	}
@@ -274,8 +276,10 @@ func (p *Path2D) Ellipse(x, y, radiusX, radiusY, rotation, startAngle, endAngle
 		return
 	}
 
-	if (!anticlockwise && endAngle < startAngle) || (anticlockwise && endAngle > startAngle) {
-		startAngle, endAngle = endAngle, startAngle
+	if !anticlockwise && endAngle < startAngle {
+		endAngle = startAngle + (2*math.Pi - math.Mod(startAngle-endAngle, math.Pi*2))
+	} else if anticlockwise && endAngle > startAngle {
+		endAngle = startAngle - (2*math.Pi - math.Mod(endAngle-startAngle, math.Pi*2))
 	}
 
 	if !anticlockwise {
@@ -287,7 +291,7 @@ func (p *Path2D) Ellipse(x, y, radiusX, radiusY, rotation, startAngle, endAngle
 	} else {
 		diff := startAngle - endAngle
 		if diff >= math.Pi*4 {
-			diff = math.Mod(diff, math.Pi*2)
+			diff = math.Mod(diff, math.Pi*2) + math.Pi*2
 			endAngle = startAngle - diff
 		}
 	}