Add Getters to grid

grid.go

@@ -1,6 +1,7 @@
 package tui
 
 import (
+	"errors"
 	"image"
 )
 
@@ -98,6 +99,20 @@ func (g *Grid) Draw(p *Painter) {
 	}
 }
 
+// GetCells returns all cells in the grid.
+func (g *Grid) GetCells() map[image.Point]Widget {
+	return g.cells
+}
+
+// GetCell returns the cell at the specified location in the grid.s
+func (g *Grid) GetCell(location image.Point) (Widget, error) {
+	value, ok := g.cells[location]
+	if !ok {
+		return nil, errors.New("Location does not exist")
+	}
+	return value, nil
+}
+
 // MinSizeHint returns the minimum size hint for the grid.
 func (g *Grid) MinSizeHint() image.Point {
 	if g.cols == 0 || g.rows == 0 {

grid_test.go

@@ -238,3 +238,37 @@ func TestGrid_Draw(t *testing.T) {
 		})
 	}
 }
+
+func TestGrid_GetCells(t *testing.T) {
+	grid := NewGrid(0, 0)
+	foo := NewLabel("foo")
+	bar := NewLabel("bar")
+	grid.AppendRow(
+		foo,
+		bar,
+	)
+
+	cells := grid.GetCells()
+	if cells[image.Point{0, 0}] != foo {
+		t.Error("Foo not at expected position")
+	}
+	if cells[image.Point{1, 0}] != bar {
+		t.Error("Bar not at expected position")
+	}
+}
+
+func TestGrid_GetCell(t *testing.T) {
+	grid := NewGrid(0, 0)
+	foo := NewLabel("foo")
+	grid.AppendRow(foo)
+
+	fooCell, err := grid.GetCell(image.Point{0, 0})
+	if err != nil || fooCell != foo {
+		t.Error("Could not retreive Foo cell")
+	}
+
+	nonExistentCell, err := grid.GetCell(image.Point{1, 0})
+	if err == nil || nonExistentCell != nil {
+		t.Error("Nonexistent cell exists")
+	}
+}