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>
This commit is contained in:
Nigel Tao 2016-12-21 22:38:45 +11:00
parent f1b1ff53e1
commit 3ba119400e
2 changed files with 88 additions and 10 deletions

View File

@ -220,7 +220,9 @@ func BoundBytes(f Face, s []byte) (bounds fixed.Rectangle26_6, advance fixed.Int
// TODO: set prevC = '\ufffd'? // TODO: set prevC = '\ufffd'?
continue continue
} }
bounds = grow(bounds, b, advance) b.Min.X += advance
b.Max.X += advance
bounds = grow(bounds, b)
advance += a advance += a
prevC = c prevC = c
} }
@ -242,25 +244,36 @@ func BoundString(f Face, s string) (bounds fixed.Rectangle26_6, advance fixed.In
// TODO: set prevC = '\ufffd'? // TODO: set prevC = '\ufffd'?
continue continue
} }
bounds = grow(bounds, b, advance) b.Min.X += advance
b.Max.X += advance
bounds = grow(bounds, b)
advance += a advance += a
prevC = c prevC = c
} }
return return
} }
// grow returns the smallest rectangle containing both b and b2+shift. func empty(r fixed.Rectangle26_6) bool {
func grow(b, b2 fixed.Rectangle26_6, shift fixed.Int26_6) fixed.Rectangle26_6 { return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
x := b2.Min.X + shift }
if b.Min.X > x {
b.Min.X = x // 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 { if b.Min.Y > b2.Min.Y {
b.Min.Y = b2.Min.Y b.Min.Y = b2.Min.Y
} }
x = b2.Max.X + shift if b.Max.X < b2.Max.X {
if b.Max.X < x { b.Max.X = b2.Max.X
b.Max.X = x
} }
if b.Max.Y < b2.Max.Y { if b.Max.Y < b2.Max.Y {
b.Max.Y = b2.Max.Y b.Max.Y = b2.Max.Y

65
font/font_test.go Normal file
View File

@ -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)
}
}
}