Added a horizontal layout

elements/layouts/horizontal.go

@@ -0,0 +1,93 @@
+package layouts
+
+import "image"
+import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/theme"
+
+// Horizontal arranges elements horizontally. Elements at the start of the entry
+// list will be positioned on the left, and elements at the end of the entry
+// list will positioned on the right. All elements have the same height.
+type Horizontal struct {
+	// If Gap is true, a gap will be placed between each element.
+	Gap bool
+
+	// If Pad is true, there will be padding running along the inside of the
+	// layout's border.
+	Pad bool
+}
+
+// Arrange arranges a list of entries horizontally.
+func (layout Horizontal) Arrange (entries []tomo.LayoutEntry, width, height int) {
+	if layout.Pad {
+		width  -= theme.Padding() * 2
+		height -= 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()
+	}
+
+	// set the size and position of each element
+	for index, entry := range entries {
+		if index > 0 && layout.Gap { x += theme.Padding() }
+		
+		entries[index].Position = image.Pt(x, y)
+		entryWidth := 0
+		if entry.Expand {
+			entryWidth = expandingElementWidth
+		} else {
+			entryWidth, _ = entry.MinimumSize()
+		}
+		x += entryWidth
+		entryBounds := entry.Bounds()
+		if entryBounds.Dy() != height || entryBounds.Dx() != entryWidth {
+			entry.Handle (tomo.EventResize {
+				Width:  entryWidth,
+				Height: height,
+			})
+		}
+	}
+}
+
+// MinimumSize returns the minimum width and height that will be needed to
+// arrange the given list of entries.
+func (layout Horizontal) MinimumSize (entries []tomo.LayoutEntry) (width, height int) {
+	for index, entry := range entries {
+		entryWidth, entryHeight := entry.MinimumSize()
+		if entryHeight > height {
+			height = entryHeight
+		}
+		width += entryWidth
+		if layout.Gap && index > 0 {
+			width += theme.Padding()
+		}
+	}
+
+	if layout.Pad {
+		width  += theme.Padding() * 2
+		height += theme.Padding() * 2
+	}
+	return
+}

elements/layouts/vertical.go

@@ -34,7 +34,7 @@ func (layout Vertical) Arrange (entries []tomo.LayoutEntry, width, height int) {
 			_, entryMinHeight := entry.MinimumSize()
 			freeSpace -= entryMinHeight
 		}
-		if index > 0 {
+		if index > 0 && layout.Gap {
 			freeSpace -= theme.Padding()
 		}
 	}
@@ -71,8 +71,8 @@ func (layout Vertical) Arrange (entries []tomo.LayoutEntry, width, height int) {
 	}
 }
 
-// MinimumSize returns the minimum width and height will be needed to arrange
-// the given list of entries.
+// MinimumSize returns the minimum width and height that will be needed to
+// arrange the given list of entries.
 func (layout Vertical) MinimumSize (entries []tomo.LayoutEntry) (width, height int) {
 	for index, entry := range entries {
 		entryWidth, entryHeight := entry.MinimumSize()

examples/horizontalLayout/main.go

@@ -0,0 +1,25 @@
+package main
+
+import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
+import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
+import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
+
+func main () {
+	tomo.Run(run)
+}
+
+func run () {
+	window, _ := tomo.NewWindow(2, 2)
+	window.SetTitle("vertical stack")
+
+	container := basic.NewContainer(layouts.Horizontal { true, true })
+	window.Adopt(container)
+
+	container.Adopt(basic.NewTest(), true)
+	container.Adopt(basic.NewLabel("<- left\nright ->", false), false)
+	container.Adopt(basic.NewTest(), true)
+	
+	window.OnClose(tomo.Stop)
+	window.Show()
+}