Horizontal layouts work nearly perfectly

elements/basic/container.go

@@ -301,9 +301,9 @@ func (element *Container) HandleSelection (direction tomo.SelectionDirection) (o
 }
 
 // FIXME: fix this!
-// func (element *Container) MinimumHeightFor (width int) (height int) {
-	// return element.layout.MinimumHeightFor(element.children, width)
-// }
+func (element *Container) MinimumHeightFor (width int) (height int) {
+	return element.layout.MinimumHeightFor(element.children, width)
+}
 
 func (element *Container) HandleDeselection () {
 	element.selected = false

layouts/horizontal.go

@@ -99,20 +99,51 @@ func (layout Horizontal) MinimumHeightFor (
 ) (
 	height int,
 ) {
+	// TODO: maybe put calculating the expanding element width in a separate
+	// method
 	if layout.Pad {
-		width -= theme.Padding() * 2
+		width  -= theme.Padding() * 2
+	}
+	freeSpace := width
+	expandingElements := 0
+
+	// count the number of expanding elements and the amount of free space
+	// for them to collectively occupy
+	for index, entry := range entries {
+		if entry.Expand {
+			expandingElements ++
+		} else {
+			entryMinWidth, _ := entry.MinimumSize()
+			freeSpace -= entryMinWidth
+		}
+		if index > 0 && layout.Gap {
+			freeSpace -= theme.Padding()
+		}
+	}
+	expandingElementWidth := 0
+	if expandingElements > 0 {
+		expandingElementWidth = freeSpace / expandingElements
+	}
+	
+	x, y := 0, 0
+	if layout.Pad {
+		x += theme.Padding()
+		y += theme.Padding()
 	}
 
-	for _, entry := range entries {
-		var entryHeight int
+	// set the size and position of each element
+	for index, entry := range entries {
+		entryWidth, entryHeight := entry.MinimumSize()
+		if entry.Expand {
+			entryWidth = expandingElementWidth
+		}
 		if child, flexible := entry.Element.(tomo.Flexible); flexible {
-			entryHeight = child.MinimumHeightFor(width)
-		} else {
-			_, entryHeight = entry.MinimumSize()
-		}
-		if entryHeight > height {
-			height = entryHeight
+			entryHeight = child.MinimumHeightFor(entryWidth)
 		}
+		if entryHeight > height { height = entryHeight }
+		
+		x += entryWidth
+		if index > 0 && layout.Gap { x += theme.Padding() }
 	}
 
 	if layout.Pad {