From 3ba119400e6fd98bf5100d1c17303c377b6521e9 Mon Sep 17 00:00:00 2001 From: Nigel Tao Date: Wed, 21 Dec 2016 22:38:45 +1100 Subject: [PATCH] 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 --- font/font.go | 33 ++++++++++++++++-------- font/font_test.go | 65 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 88 insertions(+), 10 deletions(-) create mode 100644 font/font_test.go 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 @@ func BoundBytes(f Face, s []byte) (bounds fixed.Rectangle26_6, advance fixed.Int // 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 @@ func BoundString(f Face, s string) (bounds fixed.Rectangle26_6, advance fixed.In // 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) + } + } +}