Add origin calculations to widget rendering

exhibit/block.go

@@ -24,4 +24,6 @@ func (b *Block) SetSize(p image.Point) {
 }
 
 func (b *Block) SetOrigin(p image.Point) {
+	d := p.Sub(b.Rect.Min)
+	b.Rect = b.Rect.Add(d)
 }

exhibit/list_widget.go

@@ -57,14 +57,29 @@ func (l *ListWidget) SetSize(p image.Point) {
 	l.block.SetSize(p)
 }
 
-func (l *ListWidget) Render() Block {
+func (l *ListWidget) Origin() image.Point {
+	l.blockLock.Lock()
+	defer l.blockLock.Unlock()
+
+	return l.block.Rect.Min
+}
+
+func (l *ListWidget) SetOrigin(p image.Point) {
+	l.blockLock.Lock()
+	defer l.blockLock.Unlock()
+
+	l.block.SetOrigin(p)
+}
+
+func (l *ListWidget) Render(origin image.Point) Block {
 	l.blockLock.Lock()
 	defer l.blockLock.Unlock()
 
 	b := NewBlock(0, 0, 0, 0)
-	b.Rect = l.block.Rect
+	b.Rect = l.block.Rect.Add(origin)
 
 	for k, v := range l.block.Cells {
+		k = k.Add(origin)
 		b.Cells[k] = v
 	}
 
@@ -125,6 +140,7 @@ func (l *ListWidget) recalculateCells() {
 	defer l.listLock.Unlock()
 
 	l.blockLock.Lock()
+	origin := l.block.Rect.Min
 	size := l.block.Rect.Size()
 	l.blockLock.Unlock()
 
@@ -140,11 +156,12 @@ func (l *ListWidget) recalculateCells() {
 	for x := 0; x < size.X; x++ {
 		for y := 0; y < size.Y; y++ {
 			c := Cell{Value: ' '}
+			point := image.Pt(x, y).Add(origin)
 
 			if l.border {
-				cell, ok := l.borderCell(image.Point{x, y}, size)
+				cell, ok := l.borderCell(image.Pt(x, y), size)
 				if ok {
-					cells[image.Point{x, y}] = cell
+					cells[point] = cell
 					continue
 				}
 			}
@@ -162,7 +179,7 @@ func (l *ListWidget) recalculateCells() {
 					c = l.list[y-by][i]
 				}
 
-				cells[image.Point{x, y}] = c
+				cells[point] = c
 			}
 		}
 	}

exhibit/scene.go

@@ -1,16 +1,20 @@
 package exhibit
 
+import (
+	"image"
+)
+
 type Scene struct {
 	Terminal *Terminal
 	Window   Widget
 }
 
 func (s *Scene) Render() {
-	//         s.Window.SetSize(s.Terminal.Size())
+	s.Window.SetSize(s.Terminal.Size())
 
 	c := make([]Cell, 0)
 
-	for k, v := range s.Window.Render().Cells {
+	for k, v := range s.Window.Render(image.Point{}).Cells {
 		v.Point = k
 		c = append(c, v)
 	}

exhibit/terminal.go

@@ -217,6 +217,10 @@ func (t *Terminal) reconcileCells() {
 			continue
 		}
 
+		if c.Point.X < 0 || c.Point.Y < 0 {
+			continue
+		}
+
 		current := t.display.Cells[c.Point]
 
 		if current.Value == c.Value {

exhibit/widget.go

@@ -12,7 +12,7 @@ type Border struct {
 }
 
 type Widget interface {
-	Render() Block
+	Render(image.Point) Block
 	Size() image.Point
 	SetSize(image.Point)
 	Attributes() Attributes