From 7fc2b1cd877a82b053acb1fb3702a9eb04f0bb64 Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Sat, 9 Sep 2023 20:22:10 -0400
Subject: [PATCH] Text boxes now have properly constrained
 scrolling/autoscrolling

---
 textbox.go | 68 ++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 58 insertions(+), 10 deletions(-)

diff --git a/textbox.go b/textbox.go
index d277467..e54c0e2 100644
--- a/textbox.go
+++ b/textbox.go
@@ -59,7 +59,7 @@ func (this *textBox) ContentBounds () image.Rectangle {
 }
 
 func (this *textBox) ScrollTo (point image.Point) {
-	// TODO: constrain scroll
+	if this.scroll == point { return }
 	this.scroll = point
 	this.invalidateLayout()
 }
@@ -115,6 +115,7 @@ func (this *textBox) Select (dot text.Dot) {
 	if this.dot == dot  { return }
 	this.SetFocused(true)
 	this.dot = dot
+	this.scrollToDot()
 	this.on.dotChange.Broadcast()
 	this.invalidateDraw()
 }
@@ -275,16 +276,13 @@ func (this *textBox) normalizedLayoutBoundsSpace () image.Rectangle {
 }
 
 func (this *textBox) contentMinimum () image.Point {
-	minimum := image.Pt (
-		this.drawer.Em().Round(),
-		this.drawer.LineHeight().Round())
+	minimum := this.drawer.MinimumSize()
 
-	textSize := this.drawer.MinimumSize()
-	if !this.hOverflow && !this.wrap {
-		minimum.X = textSize.X
+	if this.hOverflow || this.wrap {
+		minimum.X = this.drawer.Em().Round()
 	}
-	if !this.vOverflow {
-		 minimum.Y = textSize.Y
+	if this.vOverflow {
+		minimum.Y = this.drawer.LineHeight().Round()
 	}
 
 	return minimum.Add(this.box.contentMinimum())
@@ -298,9 +296,59 @@ func (this *textBox) doLayout () {
 	this.drawer.SetMaxWidth(innerBounds.Dx())
 	this.drawer.SetMaxHeight(innerBounds.Dy())
 
-	this.contentBounds = this.normalizedLayoutBoundsSpace().Add(this.scroll)
+	this.contentBounds = this.normalizedLayoutBoundsSpace()
+	this.constrainScroll()
+	this.contentBounds = this.contentBounds.Add(this.scroll)
 
 	if previousContentBounds != this.contentBounds {
 		this.on.contentBoundsChange.Broadcast()
 	}
 }
+
+func (this *textBox) constrainScroll () {
+	innerBounds := this.InnerBounds()
+	width  := this.contentBounds.Dx()
+	height := this.contentBounds.Dy()
+
+	// X
+	if width <= innerBounds.Dx() {
+		this.scroll.X = 0
+	} else if this.scroll.X < 0 {
+		this.scroll.X = 0
+	} else if this.scroll.X > width - innerBounds.Dx() {
+		this.scroll.X = width - innerBounds.Dx()
+	}
+
+	// Y
+	if height <= innerBounds.Dy() {
+		this.scroll.Y = 0
+	} else if this.scroll.Y < 0 {
+		this.scroll.Y = 0
+	} else if this.scroll.Y > height - innerBounds.Dy() {
+		this.scroll.Y = height - innerBounds.Dy()
+	}
+}
+
+func (this *textBox) scrollToDot () {
+	dot := roundPt(this.drawer.PositionAt(this.dot.End)).Add(this.textOffset())
+	innerBounds := this.InnerBounds()
+	scroll      := this.scroll
+	em          := this.drawer.Em().Round()
+	lineHeight  := this.drawer.LineHeight().Round()
+
+	// X
+	if dot.X < innerBounds.Min.X + em {
+		scroll.X -= innerBounds.Min.X - dot.X + em
+	} else if dot.X > innerBounds.Max.X - em {
+		scroll.X += dot.X - innerBounds.Max.X + em
+	}
+
+	// Y
+	if dot.Y < innerBounds.Min.Y + lineHeight {
+		scroll.Y -= innerBounds.Min.Y - dot.Y + lineHeight
+	} else if dot.Y > innerBounds.Max.Y - lineHeight {
+		scroll.Y += dot.Y - innerBounds.Max.Y + lineHeight
+	}
+	
+	this.ScrollTo(scroll)
+}