# Bug 2062742: content in a picture cache slice whose raster space is offset from
# the root by a fraction of a device pixel must be rasterized on the slice's own
# grid - the grid its tiles actually composite on.
#
# A slice composites its tiles 1:1 at a *rounded* device offset
# (`CompositeState::get_device_rect`), so raster pixel N lands on a whole device
# pixel. When the frame-time snap pass (`SpaceSnapper`) snapped against the root
# instead, the slice's fractional offset ended up inside the content: the border
# authored at 30 below sat at 30.5 in the slice's space. `create_quad_primitive`
# then rounds the coverage rect of non-anti-aliased edges and quantizes that half
# pixel away again - but the pattern rect is deliberately left exact, so the
# displaced coverage crops the border's cached corner texture by up to half a pixel
# on one side and repeats clamped texels on the other. The corners come out clipped
# and uneven rather than merely shifted.
#
# The fractional slice offset needs a reference frame that is `is-2d` (so
# `find_scroll_root` keeps looking for a scroll root below it, giving the scroll
# frame its own slice) and `should-snap: false` (so its fractional offset survives
# to frame time). In Firefox that is the reference frame Gecko emits for a
# stacking context with a non-zero origin.
#
# The reference builds the same scene with the half pixel moved out of the slice
# offset and into the prim rect, so the border is at the same absolute position
# (root 30.5) reached through a slice that is already on the device grid.
---
root:
  items:
    - type: rect
      bounds: [0, 0, 400, 300]
      color: white
    - type: reference-frame
      bounds: [0, 0, 400, 300]
      transform: translate(0.5, 0)
      is-2d: true
      should-snap: false
      items:
        - type: scroll-frame
          bounds: [0, 0, 300, 260]
          content-size: [300, 600]
          items:
            - type: border
              bounds: [30, 30, 100, 100]
              width: 1
              border-type: normal
              style: solid
              radius: 10
              color: black