Add sk_colorfilter_new_overdraw C API#262
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Wraps SkOverdrawColorFilter::MakeWithSkColors to expose overdraw visualization filter that maps overdraw counts (0-5+) to a 6-color palette. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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) Add SKColorFilter.CreateOverdraw() for overdraw visualization (mono#4227) Context: mono#3941 Changes: mono/skia#262 Implements overdraw visualization support by wrapping Skia's SkOverdrawColorFilter, which maps overdraw counts (0–5+) to a 6-color heat-map palette for rendering performance debugging. ~~ Problem ~~ SkiaSharp wrapped SKOverdrawCanvas (which tracks draw counts by writing to the alpha channel) but did not expose SkOverdrawColorFilter (which converts those alpha values into visible colors). Users could generate overdraw data but not visualize it without dropping into native code. Issue mono#3941 requested the missing API to complete the overdraw debugging workflow. ~~ Solution ~~ Added SKColorFilter.CreateOverdraw() with the standard Span-triple pattern: - CreateOverdraw(ReadOnlySpan<SKColor>) — primary overload - CreateOverdraw(SKColor[]) — convenience overload Input validation ensures exactly 6 colors are provided (throws ArgumentException otherwise, ArgumentNullException for null arrays). ~~ C API ~~ Requires mono/skia#262, which adds sk_colorfilter_new_overdraw() wrapping SkOverdrawColorFilter::MakeWithSkColors(). The C API accepts a 6-element color array and returns an sk_colorfilter_t*. ~~ Gallery Sample and Tests ~~ Added OverdrawVisualizationSample showing side-by-side comparison of normal rendering vs overdraw visualization. The sample demonstrates the full workflow: 1. Create offscreen A8 surface 2. Wrap in SKOverdrawCanvas (writes counts to alpha) 3. Draw overlapping shapes 4. Snapshot to image 5. Apply CreateOverdraw filter when drawing the image Tests cover creation, validation (wrong length, null), Span equivalence, and rendering with SKOverdrawCanvas to verify the filter correctly maps alpha values to colors. ~~ Submodule Update ~~ Updates externals/skia to a10e10524a (dev/issue-3941-colorfilter-overdraw rebased on 214e2d2f38) to include the required C API. The cgmanifest.json is updated accordingly. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Matthew Leibowitz <mattleibow@live.com>
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C API for SKColorFilter.CreateOverdraw() - wraps SkOverdrawColorFilter::MakeWithSkColors.
Maps overdraw counts (0-5+) to a 6-color palette for rendering performance debugging.
Part of mono/SkiaSharp#3941 and mono/SkiaSharp#4227