svgfe-backdrop-scaled-refframe.yaml

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# An SVGFE *backdrop* filter whose subregions must be MAPPED through the full

# element -> backdrop-root relationship, not merely translated by its offset.

# The filtered element sits in a scale(2) reference frame, so element space and

# backdrop-root space differ by a scale. This is the shape pdf.js produces: it

# scales its text spans, so every find-in-page highlight's backdrop filter has a

# scaling reference frame between it and the backdrop root.

# The subregion is authored away from the transform origin (at 100,100 in element

# space, so 200,200 after the scale) because that is what makes the scale term

# observable: a scale about the origin barely moves a subregion sitting at the

# origin, but moves one at 100,100 by 100px. Applying only the ScaleOffset's

# translation leaves the subregion at 100,100, its coverage no longer overlaps the

# output, the filter is dropped entirely and the red backdrop shows through

# unfiltered. See bug 1975275.

root:

  items:

    - type: rect

      color: red

      bounds: [200, 200, 100, 100]

    - type: reference-frame

      bounds: [0, 0, 50, 50]

      transform: scale(2)

      transform-origin: [0, 0]

      is-2d: true

      items:

        - type: backdrop-filter

          bounds: [100, 100, 50, 50]

          filters:

            - svgfe: SourceGraphic

            - svgfe: flood

              linear: false

              color: green

              subregion: [100, 100, 50, 50]

            - svgfe: compositeover

              linear: false

              subregion: [100, 100, 50, 50]

              in: 1

              in2: 0