Castle Game Engine: User interface features: render with mask (new TCastleMask component), better slider default look, new option ProtectedSidesScaling

New component allows to define a mask (using an arbitrary UI control) and use this mask to limit rendering the children. The mask may be any UI control (or a composition of it). The colors do not matter, only which pixels are drawn by the mask. E.g. you can define a mask using An image …