Runs the §85 checks for a readPixels region against the size the target's
attachments actually have. Throws a RangeError on the first violation —
inside a backend's readPixels that surfaces as a rejection, per the
member's contract.
A region must be integer-valued (texels, not fractions of them), non-empty
(an empty read has no defined byte length that is not zero, and a caller
who wants nothing should not call), and lie wholly inside the target — a
read that hangs off the edge would have to invent texels no attachment
holds. Shared by every backend so the refusal is one refusal (§62).
Runs the §85 checks for a
readPixelsregion against the size the target's attachments actually have. Throws aRangeErroron the first violation — inside a backend'sreadPixelsthat surfaces as a rejection, per the member's contract.A region must be integer-valued (texels, not fractions of them), non-empty (an empty read has no defined byte length that is not zero, and a caller who wants nothing should not call), and lie wholly inside the target — a read that hangs off the edge would have to invent texels no attachment holds. Shared by every backend so the refusal is one refusal (§62).