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@@ -37,6 +37,10 @@ The @Terminal.Gui.Application MainLoop will iterate over all Views in an applica
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Each of these steps can be overridden by developers using the standard [Terminal.Gui cancellable event pattern](events.md). For example, the base @Terminal.Gui.View always clears the viewport. To override this, a subclass can override @Terminal.Gui.View.OnClearingViewport to simply return `true`. Or, a user of `View` can subscribe to the @Terminal.Gui.View.ClearingViewport event and set the `Cancel` argument to `true`.
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+### Declaring that drawing is needed
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+If a View need to redraw because something changed within it's Content Area it can call @Terminal.Gui.View.SetNeedsDisplay. If a View needs to be redrawn because something has changed the size of the Viewport, it can call @Terminal.Gui.View.SetNeedsLayout.
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## Coordinate System for Drawing
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The @Terminal.Gui.View draw APIs all take coordinates specified in *Viewport-Relative* coordinates. That is, `0, 0` is the top-left cell visible to the user.
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Tig