Add grid layout

layouts/grid.go

@@ -0,0 +1,108 @@
+package layouts
+
+import "math"
+import "image"
+import "git.tebibyte.media/tomo/tomo"
+
+// Grid is a layout that arranges boxes in a grid formation with distinct rows
+// and columns. It is great for creating forms.
+type Grid struct {
+	xExpand []bool
+	yExpand []bool
+}
+
+// NewGrid creates a new grid layout. Rows and columns are specified as slices
+// of booleans, where true means a row or column will expand and false means it
+// will contract. Boxes are laid out left to right, then top to bottom. Boxes
+// that go beyond the lengh of rows will be laid out according to columns, but
+// they will not expand vertically.
+func NewGrid (columns, rows []bool) *Grid {
+	this := &Grid {
+		xExpand: columns,
+		yExpand: rows,
+	}
+	return this
+}
+
+func (this *Grid) MinimumSize (hints tomo.LayoutHints, boxes []tomo.Box) image.Point {
+	cols, rows := this.minimums(boxes)
+	size := image.Pt (
+		(len(cols) - 1) * hints.Gap.X,
+		(len(rows) - 1) * hints.Gap.Y)
+	for _, width  := range cols { size.X += width  }
+	for _, height := range rows { size.Y += height }
+	return size
+}
+
+func (this *Grid) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
+	xExpand := func (index int) bool {
+		return this.xExpand[index]
+	}
+	yExpand := func (index int) bool {
+		if index < len(this.yExpand) { return this.yExpand[index] }
+		return false
+	}
+
+	cols, rows := this.minimums(boxes)
+	expand(hints, cols, hints.Bounds.Dx(), xExpand)
+	expand(hints, rows, hints.Bounds.Dy(), yExpand)
+
+	position := hints.Bounds.Min
+	for index, box := range boxes {
+		col, row := index % len(cols), index / len(cols)
+		box.SetBounds(image.Rectangle {
+			Min: position,
+			Max: position.Add(image.Pt(cols[col], rows[row])),
+		})
+		if col == len(cols) - 1 {
+			position.X = hints.Bounds.Min.X
+			position.Y += rows[row] + hints.Gap.Y
+		} else {
+			position.X += cols[col] + hints.Gap.X
+		}
+	}
+}
+
+func (this *Grid) minimums (boxes []tomo.Box) ([]int, []int) {
+	nCols, nRows := this.dimensions(boxes)
+	cols,  rows  := make([]int, nCols), make([]int, nRows)
+
+	for index, box := range boxes {
+		col, row := index % len(cols), index / len(cols)
+		minimum := box.MinimumSize()
+		if cols[col] < minimum.X {
+			cols[col] = minimum.X
+		}
+		if rows[row] < minimum.Y {
+			rows[row] = minimum.Y
+		}
+	}
+	
+	return cols, rows
+}
+
+func (this *Grid) dimensions (boxes []tomo.Box) (int, int) {
+	return len(this.xExpand), ceilDiv(len(boxes), len(this.xExpand)) 
+}
+
+func expand (hints tomo.LayoutHints, sizes []int, space int, expands func (int) bool) {
+	gaps       := len(sizes) - 1
+	freeSpace  := float64(space - hints.Gap.Y * gaps)
+	nExpanding := 0; for index, minimum := range sizes {
+		if expands(index) {
+			nExpanding ++
+		} else {
+			freeSpace -= float64(minimum)
+		}
+	}
+	expandingSize := freeSpace / float64(nExpanding)
+	for index := range sizes {
+		if expands(index) {
+			sizes[index] = int(expandingSize)
+		}
+	}
+}
+
+func ceilDiv (x, y int) int {
+	return int(math.Ceil(float64(x) / float64(y)))
+}

slider.go

@@ -189,7 +189,7 @@ func (this sliderLayout) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
 	if this.vertical {
 		height := gutter.Dy() - handle.Dy()
 		offset := int(float64(height) * this.value)
-		gutter.Max.X = handle.Max.X
+		handle.Max.X = gutter.Dx()
 		boxes[0].SetBounds (
 			handle.
 			Add(image.Pt(0, offset)).
@@ -197,7 +197,7 @@ func (this sliderLayout) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
 	} else {
 		width  := gutter.Dx() - handle.Dx()
 		offset := int(float64(width) * this.value)
-		gutter.Max.Y = handle.Max.Y
+		handle.Max.Y = gutter.Dy()
 		boxes[0].SetBounds (
 			handle.
 			Add(image.Pt(offset, 0)).