[css-will-change-1] proposal: will-change: integer-transform

Proposal: will-change: integer-transform. This allows the browser to use high quality anti-aliasing when initially rasterizing the text, and continue using the same rasterized text as the transform changes. Engines that do not use subpixel anti-aliasing would treat this as an alias for will-change: transform.

In https://crrev.com/645003, chromium/blink stopped using subpixel anti-aliasing when will-change: transform is used, as it avoids needing to re-raster if the pixel alignment of the text changes. This idea is explicitly referenced in the spec:

If any non-initial value of a property would cause rendering differences on the element (such as using a different anti-aliasing strategy for text), the user agent should use that alternate rendering when the property is specified in will-change, to avoid sudden rendering differences when the property is eventually changed.

This change caused the Monaco editor (used by VSCode) to lose high-quality text rendering (see: https://crbug.com/1016062). This proposal is a standard way to maintain high-quality text while hinting that the transform will change.

Start by reading the quoted will-change guidance in the issue and the linked Chromium/Blink change, then review the Monaco/VSCode rendering problem and the referenced CSSWG context. Done means reaching and documenting a standards decision on whether integer-transform should be added and how it should behave for engines with and without subpixel anti-aliasing.