Add API for making buffers write-only, and allow reading from them by default#320
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Add API for making buffers write-only, and allow reading from them by default#320
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To allow reading from the buffer by default.
madsmtm
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ids1024
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Jan 27, 2026
| /// Set the buffer as optimized for only being written to. | ||
| /// | ||
| /// Setting this allows the underlying storage to bypass certain caches and reduce cache | ||
| /// pollution. In turn, this may make reading from the buffer data perform very poorly. |
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So it's not really "write only", but more optimized for not reading? Though I guess it should generally be treated the same...
Not sure if any other name would be more appropriate for this method. Maybe not.
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Maybe write_optimized? Or read_penalized?
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In #313, I added a note that reading from the pixel buffer is discouraged, because I wanted to set
kIOSurfaceMapWriteCombineCacheon macOS once I got around to implementing properIOSurfacesupport. See e.g. the following links for a few places where it's used in the wild:I thought this was fine, because I couldn't see a use-case where you'd need to read from the pixel buffer, but that was perhaps a bit hasty, I found at least one use-case: converting the alpha mode (premultiplying components or making the alpha channel opaque) by modifying the buffer in-place in a separate step before presenting it buffer.
This means that the argument for only having the mutable version instead of distinct
pixels/pixels_mut,pixel_rows/pixel_rows_mutandpixels_iter/pixels_iter_mutmethods is a bit weaker.WDYT? Should we provide both immutable and mutable methods on
Buffer<'_>?