Package limn.graphics

Interface BackdropEffect

All Known Implementing Classes:
BackdropEffect.Blur, BackdropEffect.Clear, BackdropEffect.Crt, BackdropEffect.Pixelate, BackdropEffect.Wash
public sealed interface BackdropEffect permits BackdropEffect.Clear, BackdropEffect.Wash, BackdropEffect.Pixelate, BackdropEffect.Blur, BackdropEffect.Crt
What a shape does to the pixels already behind it: a material, not a paint. Passed to Canvas.fillBackdropRoundRect(limn.graphics.RoundRect, limn.graphics.BackdropEffect), which re-samples what the frame has drawn so far under the shape, transforms it, and lays the tint() over the result.

A closed set, unlike ImageFormat, and the asymmetry is the point: a format is contributed by whichever encoder is installed, whereas an effect exists only if the renderer has a branch for it. An open type would let a caller name an effect that nothing can draw, and the failure would be a blank rectangle rather than a message.

Every variant carries a tint, because glass is never purely the thing behind it, and because the tint is the documented fallback: a renderer with no backdrop support fills the shape with it and the layout is still right, which is what Canvas.fillBackdropRoundRect(limn.graphics.RoundRect, limn.graphics.BackdropEffect) does by default.

Sizes here are in logical points, like every other dimension a widget passes to a canvas; the renderer converts them using the transform in force.

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Interface
    Description
    static final record 
    BackdropEffect.Blur
    The backdrop blurred along one axis.
    static final record 
    BackdropEffect.Clear
    A transparent pane: the backdrop is not blurred, it is refracted at the rim, the way light bends through the bevelled edge of real glass.
    static final record 
    BackdropEffect.Crt
    The backdrop as a cathode-ray tube shows it: bent onto a curved face and striped by the scan.
    static final record 
    BackdropEffect.Pixelate
    The backdrop reduced to squares: redaction, not decoration.
    static final record 
    BackdropEffect.Wash
    The backdrop, undisplaced, with its saturation moved.

  • Method Summary

    Modifier and Type
    Method
    Description
    float
    reach()
    How far outside its shape this effect reads what is behind it, in points: the blur's radius, the pane's thickness, the cell of a pixelation, and nothing for a wash or a tube, which sample only inside the shape.
    Color
    tint()
    The colour laid over the transformed backdrop, straight (not premultiplied) alpha.

  • Method Details

    • tint

      Color tint()
      The colour laid over the transformed backdrop, straight (not premultiplied) alpha. An alpha of 0 shows the backdrop alone; 1 hides it entirely, which is a plain fill drawn the expensive way.

    • reach

      float reach()
      How far outside its shape this effect reads what is behind it, in points: the blur's radius, the pane's thickness, the cell of a pixelation, and nothing for a wash or a tube, which sample only inside the shape.

      A shape wearing the effect depends on those pixels as much as on the ones under it, so a repaint has to treat a change there as a change behind the shape, and has to repaint that margin with the shape so the effect reads it as the whole frame would have: under what the frame paints later, never over it. A renderer copies at least this much around the shape.

      Returns:
      the reach, 0 or more