ref(container): split size and position calculations

src/element.zig

@@ -107,8 +107,7 @@ pub fn Scrollable(Event: type) type {
             this.size = size;
             // TODO scrollbar space - depending on configuration and only if necessary?
             this.container_size = Point.max(size, this.min_size);
-            this.container_origin = size; // TODO the size should be a provided origin
-            this.container.resize(this.container_size);
+            this.container.resize(.{}, this.container_size);
         }
 
         fn reposition(ctx: *anyopaque, origin: Point) void {
@@ -247,7 +246,7 @@ test "scrollable vertical" {
     var renderer: testing.Renderer = .init(allocator, size);
     defer renderer.deinit();
 
-    container.resize(size);
+    container.resize(.{}, size);
     try renderer.render(Container(event.SystemEvent), &container);
     try testing.expectEqualCells(.{}, renderer.size, @import("test/element/scrollable.vertical.top.zon"), renderer.screen);
 
@@ -321,7 +320,7 @@ test "scrollable horizontal" {
     var renderer: testing.Renderer = .init(allocator, size);
     defer renderer.deinit();
 
-    container.resize(size);
+    container.resize(.{}, size);
     try renderer.render(Container(event.SystemEvent), &container);
     try testing.expectEqualCells(.{}, renderer.size, @import("test/element/scrollable.horizontal.left.zon"), renderer.screen);