simple grid layout

src/theme_definition.rs

@@ -441,6 +441,10 @@ pub enum Layout {
     /// Don't layout children in any order.  Children must specify manual alignments to
     /// avoid overlap.
     Free,
+
+    /// Layout children in grid rows, left to right, starting a new row
+    /// to prevent placing children outside the parent inner bounds.
+    Grid,
 }
 
 /// Widget or text horizontal and vertical alignment.

src/widget.rs

@@ -209,6 +209,7 @@ impl Widget {
             Layout::Horizontal => self.cursor.x += gap,
             Layout::Vertical => self.cursor.y += gap,
             Layout::Free => (),
+            Layout::Grid => self.cursor.x += gap,
         }
     }
 
@@ -1260,6 +1261,13 @@ impl<'a> WidgetBuilder<'a> {
                 Horizontal => parent.cursor.x += x + parent.layout_spacing.x,
                 Vertical => parent.cursor.y += y + parent.layout_spacing.y,
                 Free => (),
+                Grid => {
+                    parent.cursor.x += x + parent.layout_spacing.x;
+                    if parent.cursor.x + size.x > parent.inner_size().x {
+                        parent.cursor.x = 0.0;
+                        parent.cursor.y += y + parent.layout_spacing.y;
+                    }
+                }
             }
         }