init layout, notifications, tabs & more

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

notification/position.go

@@ -0,0 +1,58 @@
+package notification
+
+// Position anchors the toast stack to one of six spots on the rendered
+// background. There's no center/middle variant: toasts always hug an edge or
+// a corner, never the middle of the screen.
+type Position int
+
+const (
+	Top Position = iota
+	TopLeft
+	TopRight
+	Bottom
+	BottomLeft
+	BottomRight
+)
+
+// margin is the fixed gap, in cells, kept between the toast stack and the
+// edge(s) of the background it's anchored to.
+const margin = 1
+
+// placement resolves the top-left (x, y) coordinate to draw a stack of size
+// (sw, sh) at, given a background of size (w, h) and the anchor position.
+func placement(pos Position, w, h, sw, sh int) (x, y int) {
+	switch pos {
+	case Top:
+		x = (w - sw) / 2
+		y = margin
+	case TopLeft:
+		x = margin
+		y = margin
+	case TopRight:
+		x = w - sw - margin
+		y = margin
+	case Bottom:
+		x = (w - sw) / 2
+		y = h - sh - margin
+	case BottomLeft:
+		x = margin
+		y = h - sh - margin
+	case BottomRight:
+		x = w - sw - margin
+		y = h - sh - margin
+	}
+	if x < 0 {
+		x = 0
+	}
+	if y < 0 {
+		y = 0
+	}
+	return x, y
+}
+
+// anchoredTop reports whether pos hugs the top edge, which decides both the
+// stacking order (see Model.orderedToasts) and which side of an overflowing
+// stack gets clipped (see clipToHeight).
+func (pos Position) anchoredTop() bool {
+	return pos == Top || pos == TopLeft || pos == TopRight
+}