Tabs are typically rendered as multiple spaces, but it looks like this skparagraph impl always replaces with a single space. This would result in changed layouts and potentially unexpected tab behavior (one space, expecting 2 spaces), no?

During text shaping, Skia’s SkPagraph converts characters into font glyphs. Most fonts don't have a glyph for \t, so the "unknown" glyph should be selected and a tofu should be drawn. However, some platforms will override this using their own platform-specific logic and select some other glyph instead. This results in differences across platforms:

• Windows, Web - a tofu is rendered
• iOS, Android, macOS, Linux - whitespace is rendered. I believe this is a single space, but I'll double-check this. EDIT: This is a single space on iOS and macOS.

In other words, this change makes Windows consistent with iOS, Android, macOS, and Linux. See this Google internal doc on Flutter control characters for more information.

I agree that drawing a \t as a single space is not ideal behavior. However, proper support for tabs is non-trivial and is out-of-scope for this fix.

The test is failing on CI

FYI I changed the test as the original one failed due to differences in rendering across platforms.

The new test creates 3 images: a baseline image of text containing a space, a baseline image of text containing a tofu, and a test image of text containing a tab. If then compares these three images to verify that a tab is rendered identically to a space on that platform.