mod(element/scrollable): ensure minSize returns correct dimensions

Enforce that `minSize` returns a `Point` with corresponding minimal
dimensions with respect to the provided available size. This means that
an `Element` implementation that provides a `minSize` function may even
return a too small dimension, which would automatically be resized to be
at least as big as the provided size.

src/element.zig

@@ -23,15 +23,26 @@ pub fn Element(Model: type, Event: type) type {
         };
 
         /// Request the minimal size required for this `Element` the provided
-        /// available *size* can be used as a fallback. This is currently only
-        /// used for `Scrollable` elements, such that the nested element in
-        /// the `Scrollable`'s `Container` can request a minimal size for its
-        /// contents.
+        /// available *size* can be used as a fallback. This function ensures
+        /// that the minimal size returned has at least the dimensions of the
+        /// available *size*.
+        ///
+        /// If the associated `Container`'s size is known at compile time (and
+        /// does not change) the size can be directly provided through the
+        /// `.size` Property for the `Container` instead. In this case you
+        /// should not implement / use this function.
+        ///
+        /// Currently only used for `Scrollable` elements, such that the
+        /// directly nested element in the `Scrollable`'s `Container` can
+        /// request a minimal size for its contents.
         pub inline fn minSize(this: @This(), size: Point) Point {
-            return if (this.vtable.minSize) |minSize_fn|
-                minSize_fn(this.ptr, size)
-            else
-                size;
+            if (this.vtable.minSize) |minSize_fn| {
+                const min_size = minSize_fn(this.ptr, size);
+                return .{
+                    .x = @max(size.x, min_size.x),
+                    .y = @max(size.y, min_size.y),
+                };
+            } else return size;
         }
 
         /// Resize the corresponding `Element` with the given *size*.