Canvas

The Canvas panel is the layout option closest to traditional graphical environments. You specify where elements go using coordinate positions. As with the rest of the Windows Presentation Foundation, these coordinates are device-independent units of 1/96 inch relative to the upper-left corner.

You may have noticed that elements themselves have no X or Y or Left or Top property. When using a Canvas panel, you specify the location of child elements with the static methods Canvas.SetLeft and Canvas.SetTop. Like the SetDock method defined by DockPaneland the SetRow, SetColumn, SetRowSpan, and SetColumnSpan methods defined by GridSetLeft and SetTop are associated with attached properties defined by the Canvas class. If you'd like, you can alternatively use Canvas.SetRight or Canvas.SetBottom, to specify the location of the right or bottom of the child element relative to the right or bottom of the Canvas.

Some of the Shapes classesspecifically, Line, Path, Polygon, and Polylinealready contain coordinate data. If you add these elements to the Children collection of a Canvas panel and don't set any coordinates, they will be positioned based on the coordinate data of the element. Any explicit coordinate position that you set with SetLeft or SetTop is added to the coordinate data of the element.

Many elements, such as controls, will properly size themselves on a Canvas. However, some elements will not (for example, the Rectangle and Ellipse classes), and for those you must assign explicit Width and Height values. It is also common to assign the Width and Height properties of the Canvas panel itself.

It's also possibleand often desirableto overlap elements on a Canvas panel. As you've seen, you can put multiple elements into the cells of a Grid, but the effect is often difficult to control. With Canvas, the layering of elements is easy to control and predict. The elements added to the Children collection earlier are covered by those added later.

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