Merge e966c8c into d18f93b

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Unreleased
+
+- Adds a new method `MinMaxXYs (XY, XY, bool)` to the `Envelope` type. The
+  first two return values are the minimum and maximum XY values in the
+  envelope, and the third return value indicates whether or not the first two
+  are defined (they are only defined for non-empty envelopes).
+
 ## v0.33.0
 
 2021-10-11

geom/alg_point_on_surface.go

@@ -83,9 +83,8 @@ func pointOnAreaSurface(poly Polygon) (Point, float64) {
 	}
 
 	// Create bisector.
-	envMin, minOK := env.Min().XY()
-	envMax, maxOK := env.Max().XY()
-	if !minOK || !maxOK {
+	envMin, envMax, ok := env.MinMaxXYs()
+	if !ok {
 		return Point{}, 0
 	}
 

geom/type_envelope.go

@@ -150,6 +150,17 @@ func (e Envelope) Max() Point {
 	return e.max().asUncheckedPoint()
 }
 
+// MinMaxXYs returns the two XY values in the envelope that contain the minimum
+// (first return value) and maximum (second return value) X and Y values in the
+// envelope. The third return value is true if and only if the Envelope is
+// non-empty and thus the first two return values are populated.
+func (e Envelope) MinMaxXYs() (XY, XY, bool) {
+	if e.IsEmpty() {
+		return XY{}, XY{}, false
+	}
+	return e.min(), e.max(), true
+}
+
 // ExtendToIncludeXY returns the smallest envelope that contains all of the
 // points in this envelope along with the provided point. It gives an error if
 // the XY contains NaN or +/- Infinite coordinates.

geom/type_envelope_test.go

@@ -186,6 +186,19 @@ func TestEnvelopeAttributes(t *testing.T) {
 			t.Run("Max", func(t *testing.T) {
 				expectGeomEqWKT(t, tc.env.Max().AsGeometry(), tc.max)
 			})
+			t.Run("MinMaxXYs", func(t *testing.T) {
+				gotMin, gotMax, gotOK := tc.env.MinMaxXYs()
+				expectBoolEq(t, gotOK, !tc.isEmpty)
+				if gotOK {
+					wantMin, minOK := geomFromWKT(t, tc.min).AsPoint().XY()
+					expectTrue(t, minOK)
+					expectXYEq(t, gotMin, wantMin)
+
+					wantMax, maxOK := geomFromWKT(t, tc.max).AsPoint().XY()
+					expectTrue(t, maxOK)
+					expectXYEq(t, gotMax, wantMax)
+				}
+			})
 			t.Run("AsGeometry", func(t *testing.T) {
 				expectGeomEqWKT(t, tc.env.AsGeometry(), tc.geom, IgnoreOrder)
 			})