Represents an adjustment to apply to an image primitive.
This can be used to compensate for a difference between the bounds of
the images expected by the primitive and the bounds that were actually
drawn in the texture cache.
Per-frame scratch data for an Image primitive. Captures the per-frame
outputs of ImageData::update: the source render task (or a Range of
per-tile tasks for tiled images), normalized-uvs flag, image
adjustment from snapshots, and a tight local clip rect derived from
the prim’s clip chain. Pushed during prepare and read by batch.
How to compute the effective stretch size for an image primitive, per
axis. FillsPrim resolves to the (snapped) prim-rect extent at
frame-build so the value sent to the GPU lands on the snapped pixel
grid. Explicit keeps the gecko-specified value verbatim. Per-axis
because gecko can specify a background tile that fills the prim on
one axis but tiles on the other (e.g. background-repeat: repeat-y
with background-size: 116.8px 0.8px).