From 80735cfc0c18fecba50f58c936e9b0094bac31ca Mon Sep 17 00:00:00 2001
From: faiface <faiface@ksp.sk>
Date: Tue, 9 May 2017 15:25:08 +0200
Subject: [PATCH] add Atlas doc
---
text/atlas.go | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/text/atlas.go b/text/atlas.go
index ef0974e..8f19dcf 100644
--- a/text/atlas.go
+++ b/text/atlas.go
@@ -11,12 +11,14 @@ import (
"golang.org/x/image/math/fixed"
)
+// Glyph describes one glyph in an Atlas.
type Glyph struct {
Dot pixel.Vec
Frame pixel.Rect
Advance float64
}
+// Atlas is a set of pre-drawn glyphs of a fixed set of runes. This allows for efficient text drawing.
type Atlas struct {
face font.Face
pic pixel.Picture
@@ -26,6 +28,8 @@ type Atlas struct {
lineHeight float64
}
+// NewAtlas creates a new Atlas containing glyphs of the given set of runes from the given font
+// face.
func NewAtlas(face font.Face, runes []rune) *Atlas {
fixedMapping, fixedBounds := makeSquareMapping(face, runes, fixed.I(2))
@@ -75,35 +79,48 @@ func NewAtlas(face font.Face, runes []rune) *Atlas {
}
}
+// Picture returns the underlying Picture containing an arrangement of all the glyphs contained
+// within the Atlas.
func (a *Atlas) Picture() pixel.Picture {
return a.pic
}
+// Contains reports wheter r in contained within the Atlas.
func (a *Atlas) Contains(r rune) bool {
_, ok := a.mapping[r]
return ok
}
+// Glyph returns the description of r within the Atlas.
func (a *Atlas) Glyph(r rune) Glyph {
return a.mapping[r]
}
+// Kern returns the kerning distance between runes r0 and r1. Positive distance means, that the
+// glyphs should be further apart.
func (a *Atlas) Kern(r0, r1 rune) float64 {
return i2f(a.face.Kern(r0, r1))
}
+// Ascent returns the distance from the top of the line to the baseline.
func (a *Atlas) Ascent() float64 {
return a.ascent
}
+// Descent returns the distance from the baseline to the bottom of the line.
func (a *Atlas) Descent() float64 {
return a.descent
}
+// LineHeight returns the recommended vertical distance between two lines of text.
func (a *Atlas) LineHeight() float64 {
return a.lineHeight
}
+// DrawRune returns parameters necessary for drawing a rune glyph.
+//
+// Rect is a rectangle where the glyph should be positioned. Frame is the glyph frame inside the
+// Atlas's Picture. NewDot is the new position of the dot.
func (a *Atlas) DrawRune(prevR, r rune, dot pixel.Vec) (rect, frame, bounds pixel.Rect, newDot pixel.Vec) {
if !a.Contains(r) {
r = unicode.ReplacementChar
@@ -144,6 +161,8 @@ type fixedGlyph struct {
advance fixed.Int26_6
}
+// makeSquareMapping finds an optimal glyph arrangement of the given runes, so that their common
+// bounding box is as square as possible.
func makeSquareMapping(face font.Face, runes []rune, padding fixed.Int26_6) (map[rune]fixedGlyph, fixed.Rectangle26_6) {
width := sort.Search(int(fixed.I(1024*1024)), func(i int) bool {
width := fixed.Int26_6(i)
@@ -153,6 +172,9 @@ func makeSquareMapping(face font.Face, runes []rune, padding fixed.Int26_6) (map
return makeMapping(face, runes, padding, fixed.Int26_6(width))
}
+// makeMapping arranges glyphs of the given runes into rows in such a way, that no glyph is located
+// fully to the right of the specified width. Specifically, it places glyphs in a row one by one and
+// once it reaches the specified width, it starts a new row.
func makeMapping(face font.Face, runes []rune, padding, width fixed.Int26_6) (map[rune]fixedGlyph, fixed.Rectangle26_6) {
mapping := make(map[rune]fixedGlyph)
bounds := fixed.Rectangle26_6{}
--
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