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it gets [1] the panels which are defined in [2] and specified in [3] and puts these together to the custom UI as horizontally split pane. There is no further action on that part.
Figure 513521: custom Post processing UI source code (without other implemented methods)Anchor F513F521F513 F521
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The right panel [a] is unlike the left panel not an annotation interface, its construction is described on Section A18.7.4