fix(mix): avoid NaN channels when alpha delta cancels the weight#689
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fix(mix): avoid NaN channels when alpha delta cancels the weight#689chatman-media wants to merge 1 commit into
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When `x * alphaDelta === -1`, `z` (`1 + x * alphaDelta`) is `0`, but the result was still computed as `(x / z + 1) / 2`, dividing by zero and producing `rgba(NaN,NaN,NaN,0)`. Restructure to match the reference Sass implementation: compute `z` first and skip the division in that case (`combinedWeight1 = x`). The normal path is algebraically unchanged. e.g. `mix(1, 'rgba(255, 0, 0, 0)', 'rgba(0, 0, 255, 1)')` now returns `rgba(255,0,0,0)` instead of `rgba(NaN,NaN,NaN,0)`.
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When `x * alphaDelta === -1`, `z` (`1 + x * alphaDelta`) is `0`, but
weight1was still computed as `(x / z + 1) / 2`, dividing by zero. The result wasrgba(NaN,NaN,NaN,0).Fix mirrors the reference Sass implementation: compute
zfirst and skip the division in that special case (combinedWeight1 = x). The normal path is algebraically identical, so existing outputs are unchanged.Part of #654. Added a regression test (fails without the fix with the exact
rgba(NaN,NaN,NaN,0)); all 252 color tests pass.