Added text overflow to label.

Generalised text fitting (to width) and implemented binary search.

ui/label.go

@@ -6,10 +6,18 @@ import (
 	"opslag.de/schobers/geom"
 )
 
+type TextOverflow int
+
+const (
+	TextOverflowClip TextOverflow = iota
+	TextOverflowEllipsis
+)
+
 type Label struct {
 	ControlBase
 
 	Text         string
+	TextOverflow TextOverflow
 	DropShadow   color.Color
 
 	desired CachedValue
@@ -55,10 +63,15 @@ func (l *Label) getLabelTopLeft(ctx Context) geom.PointF32 {
 func (l *Label) Render(ctx Context) {
 	l.RenderBackground(ctx)
 	fontColor := l.TextColor(ctx)
-	fontName := l.FontName(ctx)
+	font := l.ActualFont(ctx)
 	topLeft := l.getLabelTopLeft(ctx)
-	if l.DropShadow != nil {
-		ctx.Fonts().TextAlign(fontName, topLeft.Add2D(1, 1), l.DropShadow, l.Text, l.TextAlignment)
+	text := l.Text
+	availableWidth := l.bounds.Dx()
+	if l.TextOverflow == TextOverflowEllipsis {
+		text = fitTextEllipsis(font, text, availableWidth)
 	}
-	ctx.Fonts().TextAlign(fontName, topLeft, fontColor, l.Text, l.TextAlignment)
+	if l.DropShadow != nil {
+		ctx.Renderer().TextAlign(font, topLeft.Add2D(1, 1), l.DropShadow, text, l.TextAlignment)
+	}
+	ctx.Renderer().TextAlign(font, topLeft, fontColor, text, l.TextAlignment)
 }

ui/paragraph.go

@@ -43,37 +43,6 @@ func (p *Paragraph) hashTextDesired(ctx Context) string {
 
 func (p *Paragraph) splitInLines(ctx Context, width float32) []string {
 	font := p.ActualFont(ctx)
-
-	spaces := func(s string) []int { // creates a slice with indices where spaces can be found in string s
-		var spaces []int
-		offset := 0
-		for {
-			space := strings.Index(s[offset:], " ")
-			if space == -1 {
-				return spaces
-			}
-			offset += space
-			spaces = append(spaces, offset)
-			offset++
-		}
-	}
-
-	fit := func(s string) string { // tries to fit as much of string s in width space.
-		if font.WidthOf(s) < width {
-			return s
-		}
-		spaces := spaces(s)
-		// removes one word (delimited by spaces) at a time and tries until the result fits.
-		for split := len(spaces) - 1; split >= 0; split-- {
-			clipped := s[:spaces[split]]
-			if font.WidthOf(clipped) < width {
-				return clipped
-			}
-		}
-		// nothing fits (returns the whole string)...
-		return s
-	}
-
 	var lines []string
 	for _, line := range strings.Split(p.Text, "\n") {
 		if len(line) == 0 {
@@ -82,7 +51,7 @@ func (p *Paragraph) splitInLines(ctx Context, width float32) []string {
 		}
 
 		for len(line) > 0 {
-			clipped := fit(line)
+			clipped := fitTextWord(font, line, width)
 			lines = append(lines, clipped)
 			line = strings.TrimLeft(line[len(clipped):], " ")
 		}

ui/text.go

@@ -0,0 +1,68 @@
+package ui
+
+import "strings"
+
+// findOptimalFit tries to find the optimal (largest) fit for the interval [0..n] by doing a binary search.
+func findOptimalFit(n int, fits func(i int) bool) int {
+	if n < 0 || fits(n) {
+		return n
+	}
+	min, max := 0, n
+	for {
+		if min == max {
+			if min == 0 && !fits(min) {
+				return -1
+			}
+			return min
+		}
+		middle := (max + min + 1) / 2
+		if fits(middle) {
+			min = middle
+		} else {
+			max = middle - 1
+		}
+	}
+}
+
+// findSpaces creates a slice with indices where spaces can be found in string s
+func findSpaces(s string) []int {
+	var spaces []int
+	offset := 0
+	for {
+		space := strings.Index(s[offset:], " ")
+		if space == -1 {
+			return spaces
+		}
+		offset += space
+		spaces = append(spaces, offset)
+		offset++
+	}
+}
+
+func fitTextEllipsis(font Font, text string, availableWidth float32) string {
+	if font.WidthOf(text) <= availableWidth {
+		return text
+	}
+	ellipsis := "..."
+	availableWidth -= font.WidthOf(ellipsis)
+	cut := findOptimalFit(len(text), func(i int) bool { return font.WidthOf(text[:i]) <= availableWidth })
+	if cut == -1 {
+		return ""
+	}
+	return text[:cut] + ellipsis
+}
+
+// fitTextWord tries to fit as much of string s in width space.
+func fitTextWord(font Font, s string, availableWidth float32) string {
+	if font.WidthOf(s) < availableWidth {
+		return s
+	}
+	spaces := findSpaces(s)
+	split := findOptimalFit(len(spaces)-1, func(i int) bool {
+		return font.WidthOf(s[:spaces[i]]) <= availableWidth
+	})
+	if split == -1 {
+		return s
+	}
+	return s[:spaces[split]]
+}