font: fix rectangle-union for empty rectangles.
The bounding box of a string does not necessarily contain the origin.
Prior to this commit, BoundString(etc, "x") would call grow exactly
once, with the first argument being the (empty) zero rectangle.
Change-Id: Id7d4f6c250ac0749f6dae19d11f4e97f9c6f45bc
Reviewed-on: https://go-review.googlesource.com/34674
Reviewed-by: Dave Day <djd@golang.org>
diff --git a/font/font.go b/font/font.go
index d523baf..2556ebb 100644
--- a/font/font.go
+++ b/font/font.go
@@ -220,7 +220,9 @@
// TODO: set prevC = '\ufffd'?
continue
}
- bounds = grow(bounds, b, advance)
+ b.Min.X += advance
+ b.Max.X += advance
+ bounds = grow(bounds, b)
advance += a
prevC = c
}
@@ -242,25 +244,36 @@
// TODO: set prevC = '\ufffd'?
continue
}
- bounds = grow(bounds, b, advance)
+ b.Min.X += advance
+ b.Max.X += advance
+ bounds = grow(bounds, b)
advance += a
prevC = c
}
return
}
-// grow returns the smallest rectangle containing both b and b2+shift.
-func grow(b, b2 fixed.Rectangle26_6, shift fixed.Int26_6) fixed.Rectangle26_6 {
- x := b2.Min.X + shift
- if b.Min.X > x {
- b.Min.X = x
+func empty(r fixed.Rectangle26_6) bool {
+ return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
+}
+
+// grow returns the smallest rectangle containing both b and b2.
+func grow(b, b2 fixed.Rectangle26_6) fixed.Rectangle26_6 {
+ if empty(b) {
+ return b2
+ }
+ if empty(b2) {
+ return b
+ }
+
+ if b.Min.X > b2.Min.X {
+ b.Min.X = b2.Min.X
}
if b.Min.Y > b2.Min.Y {
b.Min.Y = b2.Min.Y
}
- x = b2.Max.X + shift
- if b.Max.X < x {
- b.Max.X = x
+ if b.Max.X < b2.Max.X {
+ b.Max.X = b2.Max.X
}
if b.Max.Y < b2.Max.Y {
b.Max.Y = b2.Max.Y
diff --git a/font/font_test.go b/font/font_test.go
new file mode 100644
index 0000000..1f05524
--- /dev/null
+++ b/font/font_test.go
@@ -0,0 +1,65 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package font
+
+import (
+ "image"
+ "strings"
+ "testing"
+
+ "golang.org/x/image/math/fixed"
+)
+
+const toyAdvance = fixed.Int26_6(10 << 6)
+
+type toyFace struct{}
+
+func (toyFace) Close() error {
+ return nil
+}
+
+func (toyFace) Glyph(dot fixed.Point26_6, r rune) (image.Rectangle, image.Image, image.Point, fixed.Int26_6, bool) {
+ panic("unimplemented")
+}
+
+func (toyFace) GlyphBounds(r rune) (fixed.Rectangle26_6, fixed.Int26_6, bool) {
+ return fixed.Rectangle26_6{
+ Min: fixed.P(2, 0),
+ Max: fixed.P(6, 1),
+ }, toyAdvance, true
+}
+
+func (toyFace) GlyphAdvance(r rune) (fixed.Int26_6, bool) {
+ return toyAdvance, true
+}
+
+func (toyFace) Kern(r0, r1 rune) fixed.Int26_6 {
+ return 0
+}
+
+func (toyFace) Metrics() Metrics {
+ return Metrics{}
+}
+
+func TestBound(t *testing.T) {
+ wantBounds := []fixed.Rectangle26_6{
+ {Min: fixed.P(0, 0), Max: fixed.P(0, 0)},
+ {Min: fixed.P(2, 0), Max: fixed.P(6, 1)},
+ {Min: fixed.P(2, 0), Max: fixed.P(16, 1)},
+ {Min: fixed.P(2, 0), Max: fixed.P(26, 1)},
+ }
+
+ for i, wantBound := range wantBounds {
+ s := strings.Repeat("x", i)
+ gotBound, gotAdvance := BoundString(toyFace{}, s)
+ if gotBound != wantBound {
+ t.Errorf("i=%d: bound: got %v, want %v", i, gotBound, wantBound)
+ }
+ wantAdvance := toyAdvance * fixed.Int26_6(i)
+ if gotAdvance != wantAdvance {
+ t.Errorf("i=%d: advance: got %v, want %v", i, gotAdvance, wantAdvance)
+ }
+ }
+}
