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Last updated at 2:09 am UTC on 15 September 2016
Morph subclass: #TransformMorph
	instanceVariableNames: 'transform smoothing localBounds'
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Morphic-Basic'

Class comment (5.1)
A TransformMorph introduces a 2-D transformation between its (global) coordinates and the (local) coordinates of its submorphs, while also clipping all display to its bounds. Specifically, with no offset, angle or scaling, a submorph with coordinates (0@0) will appear exactly at the topLeft of the windowMorph (its position). Rotation and scaling are relative to the local origin, (0@0).

instance var type description
transform MorphicTransform The coordinate transform between my coordinates and the local coordinates of my submorphs.
smoothing anInteger in 1..3 Perform smoothing of my contents during drawing
1 No smoothing (#smoothingOff)
2 Smoothing w/ edge adjacent pixels (#smoothingOn)
3 Smoothing w/ edge and corner adj pixels
localBounds Rectangle or nil caches the value of #localSubmorphBounds for performance

TransformMorphs operate with two different display strategies, depending on whether the transformation is a pure translation or not. If so, then they simply use a clipping canvas and display their submorphs with the appropriate offset. If the transformation includes scaling or rotation, then a caching canvas is used, whose active area covers the fullBounds of the submorphs intersected with the source quadrilateral corresponding to the window bounds.

TransfromMorph is used in ScrollPane.