From b14683a5523c4dd25d71ed97ab263799c64114c4 Mon Sep 17 00:00:00 2001
From: Laurent Le Goff <legoff.laurent@gmail.com>
Date: Thu, 30 Apr 2015 18:06:25 +0200
Subject: [PATCH] Start working on text

---
 draw2dimg/ftgc.go | 46 +--------------------------
 draw2dimg/text.go | 80 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 45 deletions(-)
 create mode 100644 draw2dimg/text.go

diff --git a/draw2dimg/ftgc.go b/draw2dimg/ftgc.go
index 2e0da66..d7f668e 100644
--- a/draw2dimg/ftgc.go
+++ b/draw2dimg/ftgc.go
@@ -113,53 +113,9 @@ func (gc *GraphicContext) loadCurrentFont() (*truetype.Font, error) {
 	return font, nil
 }
 
-func fUnitsToFloat64(x int32) float64 {
-	scaled := x << 2
-	return float64(scaled/256) + float64(scaled%256)/256.0
-}
-
 // p is a truetype.Point measured in FUnits and positive Y going upwards.
 // The returned value is the same thing measured in floating point and positive Y
 // going downwards.
-func pointToF64Point(p truetype.Point) (x, y float64) {
-	return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y)
-}
-
-// drawContour draws the given closed contour at the given sub-pixel offset.
-func (gc *GraphicContext) drawContour(ps []truetype.Point, dx, dy float64) {
-	if len(ps) == 0 {
-		return
-	}
-	startX, startY := pointToF64Point(ps[0])
-	gc.MoveTo(startX+dx, startY+dy)
-	q0X, q0Y, on0 := startX, startY, true
-	for _, p := range ps[1:] {
-		qX, qY := pointToF64Point(p)
-		on := p.Flags&0x01 != 0
-		if on {
-			if on0 {
-				gc.LineTo(qX+dx, qY+dy)
-			} else {
-				gc.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
-			}
-		} else {
-			if on0 {
-				// No-op.
-			} else {
-				midX := (q0X + qX) / 2
-				midY := (q0Y + qY) / 2
-				gc.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
-			}
-		}
-		q0X, q0Y, on0 = qX, qY, on
-	}
-	// Close the curve.
-	if on0 {
-		gc.LineTo(startX+dx, startY+dy)
-	} else {
-		gc.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
-	}
-}
 
 func (gc *GraphicContext) drawGlyph(glyph truetype.Index, dx, dy float64) error {
 	if err := gc.glyphBuf.Load(gc.Current.Font, gc.Current.Scale, glyph, truetype.NoHinting); err != nil {
@@ -167,7 +123,7 @@ func (gc *GraphicContext) drawGlyph(glyph truetype.Index, dx, dy float64) error
 	}
 	e0 := 0
 	for _, e1 := range gc.glyphBuf.End {
-		gc.drawContour(gc.glyphBuf.Point[e0:e1], dx, dy)
+		DrawContour(gc, gc.glyphBuf.Point[e0:e1], dx, dy)
 		e0 = e1
 	}
 	return nil
diff --git a/draw2dimg/text.go b/draw2dimg/text.go
new file mode 100644
index 0000000..c858c1d
--- /dev/null
+++ b/draw2dimg/text.go
@@ -0,0 +1,80 @@
+package draw2dimg
+
+import (
+	"code.google.com/p/freetype-go/freetype/truetype"
+	"github.com/llgcode/draw2d"
+)
+
+// drawContour draws the given closed contour at the given sub-pixel offset.
+func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) {
+	if len(ps) == 0 {
+		return
+	}
+	startX, startY := pointToF64Point(ps[0])
+	path.MoveTo(startX+dx, startY+dy)
+	q0X, q0Y, on0 := startX, startY, true
+	for _, p := range ps[1:] {
+		qX, qY := pointToF64Point(p)
+		on := p.Flags&0x01 != 0
+		if on {
+			if on0 {
+				path.LineTo(qX+dx, qY+dy)
+			} else {
+				path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
+			}
+		} else {
+			if on0 {
+				// No-op.
+			} else {
+				midX := (q0X + qX) / 2
+				midY := (q0Y + qY) / 2
+				path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
+			}
+		}
+		q0X, q0Y, on0 = qX, qY, on
+	}
+	// Close the curve.
+	if on0 {
+		path.LineTo(startX+dx, startY+dy)
+	} else {
+		path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
+	}
+}
+
+func pointToF64Point(p truetype.Point) (x, y float64) {
+	return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y)
+}
+
+func fUnitsToFloat64(x int32) float64 {
+	scaled := x << 2
+	return float64(scaled/256) + float64(scaled%256)/256.0
+}
+
+// FontExtents contains font metric information.
+type FontExtents struct {
+	// Ascent is the distance that the text
+	// extends above the baseline.
+	Ascent float64
+
+	// Descent is the distance that the text
+	// extends below the baseline.  The descent
+	// is given as a negative value.
+	Descent float64
+
+	// Height is the distance from the lowest
+	// descending point to the highest ascending
+	// point.
+	Height float64
+}
+
+// TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro
+// Extents returns the FontExtents for a font.
+func Extents(font *truetype.Font, size float64) FontExtents {
+	bounds := font.Bounds(font.FUnitsPerEm())
+	scale := size / float64(font.FUnitsPerEm())
+	return FontExtents{
+		Ascent:  float64(bounds.YMax) * scale,
+		Descent: float64(bounds.YMin) * scale,
+		Height:  float64(bounds.YMax-bounds.YMin) * scale,
+	}
+}