Fix bug where vertically aligned text would creep downward

README.md

@@ -1,5 +1,7 @@
 # typeset
 
+[![Go Reference](https://pkg.go.dev/badge/git.tebibyte.media/tomo/typeset.svg)](https://pkg.go.dev/git.tebibyte.media/tomo/typeset)
+
 Typeset provides utilities for text layout, wrapping, and rendering.
 
 The state of a text layout is stored in a TypeSetter, and it can be drawn to any

setter.go

@@ -100,6 +100,7 @@ func (setter *TypeSetter) needAlignedLayout () {
 	setter.alignVertically()
 }
 
+// should only be called from within setter.needAlignedLayout
 func (setter *TypeSetter) alignHorizontally () {
 	if len(setter.lines) == 0 { return }
 	
@@ -120,6 +121,7 @@ func (setter *TypeSetter) alignHorizontally () {
 	}
 }
 
+// should only be called from within setter.needAlignedLayout
 func (setter *TypeSetter) alignVertically () {
 	if setter.height     == 0 { return }
 	if len(setter.lines) == 0 { return }
@@ -129,20 +131,27 @@ func (setter *TypeSetter) alignVertically () {
 	}
 
 	// determine how much to shift lines
-	topOffset     := 0
+	topOffset     := fixed.I(0)
 	contentHeight := setter.layoutBoundsSpace.Dy()
 	if setter.vAlign == AlignMiddle {
-		topOffset += (setter.height - contentHeight) / 2
+		topOffset += fixed.I((setter.height - contentHeight) / 2)
 	} else if setter.vAlign == AlignEnd {
-		topOffset += setter.height - contentHeight
+		topOffset += fixed.I(setter.height - contentHeight)
+	}
+
+	// we may be re-aligning already aligned text. if the text is shifted
+	// away from the origin, account for that.
+	if len(setter.lines) > 0 {
+		topOffset -= setter.lines[0].Y
 	}
 
 	// shift lines
 	for index := range setter.lines {
-		setter.lines[index].Y += fixed.I(topOffset)
+		setter.lines[index].Y += topOffset
 	}
 }
 
+// should only be called from within setter.alignVertically
 func (setter *TypeSetter) justifyVertically () {
 	spaceCount    := len(setter.lines) - 1
 	contentHeight := setter.layoutBoundsSpace.Dy()