1 files changed, 74 insertions, 0 deletions
diff --git a/ui/grid.go b/ui/grid.go
new file mode 100644
index 0000000..fd0cab7
--- /dev/null
+++ b/ui/grid.go
@@ -0,0 +1,74 @@
+package ui
+
+import "fmt"
+
+type Grid struct {
+	Rows         []DimSpec
+	Columns      []DimSpec
+	Cells        []*GridCell
+	onInvalidate func(d Drawable)
+}
+
+const (
+	SIZE_EXACT  = iota
+	SIZE_WEIGHT = iota
+)
+
+// Specifies the layout of a single row or column
+type DimSpec struct {
+	// One of SIZE_EXACT or SIZE_WEIGHT
+	Strategy uint
+	// If Strategy = SIZE_EXACT, this is the number of cells this dim shall
+	// occupy. If SIZE_WEIGHT, the space left after all exact dims are measured
+	// is distributed amonst the remaining dims weighted by this value.
+	Size *uint
+}
+
+type GridCell struct {
+	Row     uint
+	Column  uint
+	RowSpan uint
+	ColSpan uint
+	Content Drawable
+	invalid bool
+}
+
+func (grid *Grid) Draw(ctx Context) {
+	// TODO
+}
+
+func (grid *Grid) OnInvalidate(onInvalidate func(d Drawable)) {
+	grid.onInvalidate = onInvalidate
+}
+
+func (grid *Grid) AddChild(cell *GridCell) {
+	grid.Cells = append(grid.Cells, cell)
+	cell.Content.OnInvalidate(grid.cellInvalidated)
+	cell.invalid = true
+}
+
+func (grid *Grid) RemoveChild(cell *GridCell) {
+	for i, _cell := range grid.Cells {
+		if _cell == cell {
+			grid.Cells = append(grid.Cells[:i], grid.Cells[i+1:]...)
+			break
+		}
+	}
+}
+
+func (grid *Grid) cellInvalidated(drawable Drawable) {
+	var cell *GridCell
+	for _, cell = range grid.Cells {
+		if cell.Content == drawable {
+			break
+		}
+		cell = nil
+	}
+	if cell == nil {
+		panic(fmt.Errorf("Attempted to invalidate unknown cell"))
+	}
+	cell.invalid = true
+	if grid.onInvalidate != nil {
+		grid.onInvalidate(grid)
+	}
+}