fix(element/scrollable): support deriving Container size of scrollable

src/container.zig

@@ -633,14 +633,13 @@ pub fn Container(comptime Event: type) type {
             }
         }
 
-        fn fit_resize(this: *@This()) Point {
+        pub fn fit_resize(this: *@This()) Point {
             // NOTE this is supposed to be a simple and easy to understand alogrithm, there are currently no optimizations done
             const layout = this.properties.layout;
             var size: Point = switch (layout.direction) {
                 .horizontal => .{ .x = layout.gap * @as(u16, @truncate(this.elements.items.len -| 1)) },
                 .vertical => .{ .y = layout.gap * @as(u16, @truncate(this.elements.items.len -| 1)) },
             };
-            size = Point.add(size, this.properties.size);
 
             if (this.elements.items.len > 0) switch (layout.direction) {
                 .horizontal => size.x += layout.padding.left + layout.padding.right,
@@ -671,8 +670,8 @@ pub fn Container(comptime Event: type) type {
             }
 
             // assign currently calculated size
-            this.size = size;
-            return size;
+            this.size = Point.max(size, this.properties.size);
+            return this.size;
         }
 
         // growable implicitly requires the root `Container` to have a set a size property to the size of the available terminal screen
@@ -818,6 +817,7 @@ pub fn Container(comptime Event: type) type {
         }
 
         pub fn contents(this: *const @This()) ![]const Cell {
+            if (this.size.x == 0 or this.size.y == 0) return Error.TooSmall;
             const cells = try this.allocator.alloc(Cell, @as(usize, this.size.x) * @as(usize, this.size.y));
             @memset(cells, .{});
             errdefer this.allocator.free(cells);