View — State

View.State.cs owns the dirty-flag system that lets the framework skip work it does not need to redo.

ViewFlags

ViewFlags is a bit-field on every view. Flags come in pairs: one for the view itself and one for "any descendant has this flag".

Flag	Meaning
`Animated`	This view has time-dependent state; needs `AnimateCore` next frame
`DescendantAnimated`	A descendant requested an animation frame
`MeasureChanged`	This view's desired size may have changed
`ArrangeChanged`	This view's child layout may have changed
`DescendantArrangeChanged`	A descendant needs re-arranging
`RenderChanged`	This view needs to be redrawn
`DescendantRenderChanged`	A descendant needs to be redrawn
`HitTestChanged`	This view's hit-test result may have changed
`DescendantHitTestChanged`	A descendant's hit-test result may have changed
`Active`	View is live — receives events, animates, renders
`Attached`	View is connected to a platform window

Invalidation

Views signal that something has changed by calling an Invalidate* method. Each one:

Sets the matching flag on this
Calls the corresponding OnChild*Changed on the parent, which propagates the Descendant* flag up the tree

protected void InvalidateMeasure()
protected void InvalidateArrange()
protected void InvalidateRender()
protected void InvalidateHitTest()

Propagation stops as soon as the ancestor already carries the Descendant* flag — no redundant notifications travel further up.

Validation

Layout shells clear flags after processing a view:

public void ValidateMeasure()
public void ValidateArrange()   // also clears DescendantArrangeChanged
public void ValidateRender()    // also clears DescendantRenderChanged
public void ValidateHitTest()   // also clears DescendantHitTestChanged

A parent can call ValidateMeasure() on a child to acknowledge a measure change it has decided to absorb (e.g. a grid that keeps column widths stable regardless of cell content changes).

Animation

protected void RequestAnimationFrame()

Call this inside AnimateCore when the animation should continue on the next frame. Sets ViewFlags.Animated and notifies ancestors via OnChildRequestedAnimationFrame.

Pointer capture

public void CapturePointer(int pointerId)
public void ReleasePointer(int pointerId)