Rudimentary text selection with keybaord keys

elements/basic/textbox.go

@@ -97,16 +97,30 @@ func (element *TextBox) HandleKeyDown(key input.Key, modifiers input.Modifiers)
 		textChanged = true
 			
 	case key == input.KeyLeft:
-		element.dot = textmanip.MoveLeft (
-			element.text,
-			element.dot,
-			modifiers.Control)
+		if modifiers.Shift {
+			element.dot = textmanip.SelectLeft (
+				element.text,
+				element.dot,
+				modifiers.Control)
+		} else {
+			element.dot = textmanip.MoveLeft (
+				element.text,
+				element.dot,
+				modifiers.Control)
+		}
 			
 	case key == input.KeyRight:
-		element.dot = textmanip.MoveRight (
-			element.text,
-			element.dot,
-			modifiers.Control)
+		if modifiers.Shift {
+			element.dot = textmanip.SelectRight (
+				element.text,
+				element.dot,
+				modifiers.Control)
+		} else {
+			element.dot = textmanip.MoveRight (
+				element.text,
+				element.dot,
+				modifiers.Control)
+		}
 		
 	case key.Printable():
 		element.text, element.dot = textmanip.Type (
@@ -299,14 +313,28 @@ func (element *TextBox) draw () {
 	}
 	pattern := element.theme.Pattern(theme.PatternSunken, state)
 	artist.FillRectangle(element.core, pattern, bounds)
+	offset := bounds.Min.Add (image.Point {
+		X: element.config.Padding() - element.scroll,
+		Y: element.config.Padding(),
+	})
 
-	if len(element.text) == 0 && !element.Focused() {
+	if element.Focused() && !element.dot.Empty() {
+		// draw selection bounds
+		accent := element.theme.Pattern (
+			theme.PatternAccent,  state)
+		canon := element.dot.Canon()
+		start := element.valueDrawer.PositionOf(canon.Start).Add(offset)
+		end   := element.valueDrawer.PositionOf(canon.End).Add(offset)
+		end.Y += element.valueDrawer.LineHeight().Round()
+		artist.FillRectangle (
+			element.core,
+			accent,
+			image.Rectangle { start, end })
+	}
+
+	if len(element.text) == 0 {
 		// draw placeholder
 		textBounds := element.placeholderDrawer.LayoutBounds()
-		offset := bounds.Min.Add (image.Point {
-			X: element.config.Padding(),
-			Y: element.config.Padding(),
-		})
 		foreground := element.theme.Pattern (
 			theme.PatternForeground,
 			theme.PatternState { Disabled: true })
@@ -317,30 +345,27 @@ func (element *TextBox) draw () {
 	} else {
 		// draw input value
 		textBounds := element.valueDrawer.LayoutBounds()
-		offset := bounds.Min.Add (image.Point {
-			X: element.config.Padding() - element.scroll,
-			Y: element.config.Padding(),
-		})
 		foreground := element.theme.Pattern (
 			theme.PatternForeground,  state)
 		element.valueDrawer.Draw (
 			element.core,
 			foreground,
 			offset.Sub(textBounds.Min))
-
-		if element.Focused() {
-			// cursor
-			// TODO: draw selection if exists
-			cursorPosition := element.valueDrawer.PositionOf (
-				element.dot.End)
-			artist.Line (
-				element.core,
-				foreground, 1,
-				cursorPosition.Add(offset),
-				image.Pt (
-					cursorPosition.X,
-					cursorPosition.Y + element.valueDrawer.
-					LineHeight().Round()).Add(offset))
-		}
+	}
+	
+	if element.Focused() && element.dot.Empty() {
+		// draw cursor
+		foreground := element.theme.Pattern (
+			theme.PatternForeground,  state)
+		cursorPosition := element.valueDrawer.PositionOf (
+			element.dot.End)
+		artist.Line (
+			element.core,
+			foreground, 1,
+			cursorPosition.Add(offset),
+			image.Pt (
+				cursorPosition.X,
+				cursorPosition.Y + element.valueDrawer.
+				LineHeight().Round()).Add(offset))
 	}
 }

textmanip/textmanip.go

@@ -34,12 +34,19 @@ func (dot Dot) Sub (delta int) Dot {
 	}
 }
 
-func WordToLeft (text []rune, dot Dot) (length int) {
-	cursor := dot.End
-	if cursor < 1 { return }
-	if cursor > len(text) { cursor = len(text) }
+func (dot Dot) Constrain (length int) Dot {
+	if dot.Start < 0      { dot.Start = 0 }
+	if dot.Start > length { dot.Start = length}
+	if dot.End < 0        { dot.End = 0 }
+	if dot.End > length   { dot.End = length}
+	return dot
+}
 
-	index := cursor - 1
+func WordToLeft (text []rune, position int) (length int) {
+	if position < 1 { return }
+	if position > len(text) { position = len(text) }
+
+	index := position - 1
 	for index >= 0 && unicode.IsSpace(text[index]) {
 		length ++
 		index --
@@ -51,12 +58,11 @@ func WordToLeft (text []rune, dot Dot) (length int) {
 	return
 }
 
-func WordToRight (text []rune, dot Dot) (length int) {
-	cursor := dot.End
-	if cursor < 0 { return }
-	if cursor > len(text) { cursor = len(text) }
+func WordToRight (text []rune, position int) (length int) {
+	if position < 0 { return }
+	if position > len(text) { position = len(text) }
 
-	index := cursor
+	index := position
 	for index < len(text) && unicode.IsSpace(text[index]) {
 		length ++
 		index ++
@@ -68,41 +74,46 @@ func WordToRight (text []rune, dot Dot) (length int) {
 	return
 }
 
-func Backspace (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
-	if dot.Empty() {
-		cursor := dot.End
-		if cursor < 1         { return text, dot }
-		if cursor > len(text) { cursor = len(text) }
+func WordAround (text []rune, position int) (around Dot) {
+	return Dot {
+		WordToLeft(text, position),
+		WordToRight(text, position),
+	}
+}
 
+func Backspace (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
+	dot = dot.Constrain(len(text))
+	if dot.Empty() {
 		distance := 1
 		if word {
-			distance = WordToLeft(text, dot)
+			distance = WordToLeft(text, dot.End)
 		}
-		result = append(result, text[:cursor - distance]...)
-		result = append(result, text[cursor:]...)
-		moved = EmptyDot(cursor - distance)
+		result = append (
+			result,
+			text[:dot.Sub(distance).Constrain(len(text)).End]...)
+		result = append(result, text[dot.End:]...)
+		moved = EmptyDot(dot.Sub(distance).Start)
+		return
 	} else {
 		return Delete(text, dot, word)
 	}
-
-	return
 }
 
 func Delete (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
+	dot = dot.Constrain(len(text))
 	if dot.Empty() {
-		cursor := dot.End
-		if cursor < 0         { return text, dot }
-		if cursor > len(text) { cursor = len(text) }
-
 		distance := 1
 		if word {
-			distance = WordToRight(text, dot)
+			distance = WordToRight(text, dot.End)
 		}
-		result = append(result, text[:cursor]...)
-		result = append(result, text[cursor + distance:]...)
+		result = append(result, text[:dot.End]...)
+		result = append (
+			result,
+			text[dot.Add(distance).Constrain(len(text)).End:]...)
 		moved = dot
 		return	
 	} else {
+		dot = dot.Canon()
 		result = append(result, text[:dot.Start]...)
 		result = append(result, text[dot.End:]...)
 		moved = EmptyDot(dot.Start)
@@ -111,50 +122,61 @@ func Delete (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
 }
 
 func Type (text []rune, dot Dot, character rune) (result []rune, moved Dot) {
+	dot = dot.Constrain(len(text))
 	if dot.Empty() {
-		cursor := dot.End
-		if cursor < 0         { cursor = 0 }
-		if cursor > len(text) { cursor = len(text) }
-		result = append(result, text[:cursor]...)
+		result = append(result, text[:dot.End]...)
 		result = append(result, character)
-		if cursor < len(text) {
-			result = append(result, text[cursor:]...)
+		if dot.End < len(text) {
+			result = append(result, text[dot.End:]...)
 		}
-		moved = EmptyDot(cursor + 1)
+		moved = EmptyDot(dot.Add(1).End)
 		return
 	} else {
+		dot = dot.Canon()
 		result = append(result, text[:dot.Start]...)
 		result = append(result, character)
 		result = append(result, text[dot.End:]...)
-		moved = EmptyDot(dot.Start)
+		moved = EmptyDot(dot.Add(1).Start)
 		return
 	}
 }
 
 func MoveLeft (text []rune, dot Dot, word bool) (moved Dot) {
-	cursor := dot.Start
-
-	if cursor < 1         { return EmptyDot(cursor) }
-	if cursor > len(text) { cursor = len(text) }
-
+	dot = dot.Constrain(len(text))
 	distance := 1
 	if word {
-		distance = WordToLeft(text, dot)
+		distance = WordToLeft(text, dot.Start)
 	}
-	moved = EmptyDot(cursor - distance)
+	moved = EmptyDot(dot.Sub(distance).Start)
 	return
 }
 
 func MoveRight (text []rune, dot Dot, word bool) (moved Dot) {
-	cursor := dot.End
-	
-	if cursor < 0         { return EmptyDot(cursor) }
-	if cursor > len(text) { cursor = len(text) }
-
+	dot = dot.Constrain(len(text))
 	distance := 1
 	if word {
-		distance = WordToRight(text, dot)
+		distance = WordToRight(text, dot.End)
 	}
-	moved = EmptyDot(cursor + distance)
+	moved = EmptyDot(dot.Add(distance).End)
 	return
 }
+
+func SelectLeft (text []rune, dot Dot, word bool) (moved Dot) {
+	dot = dot.Constrain(len(text))
+	distance := 1
+	if word {
+		distance = WordToLeft(text, dot.Start)
+	}
+	dot.Start -= distance
+	return dot
+}
+
+func SelectRight (text []rune, dot Dot, word bool) (moved Dot) {
+	dot = dot.Constrain(len(text))
+	distance := 1
+	if word {
+		distance = WordToRight(text, dot.End)
+	}
+	dot.Start += distance
+	return dot
+}