Windows metafile image comparison

Pinned TortoiseGit: 7338078f8ddd924b8cddee35f512f2286072136d. TortoiseIDiff/MainWindow.cpp:1255 offers WMF/EMF; shared Utils/MiscUI/Picture.cpp::Load uses Windows GDI+ Bitmap decoding. This family adds a bundled macOS decoder for captured WMF, EMF and EMF+ image bytes. Original repository bytes remain the comparison/conflict/save inputs; rasterization creates only a private display representation.

Renderer and source changes

The renderer is MIT-licensed WmfEmfViewer, pinned to 4e0d6d6807349ebfc8f8c681009c14f9e57621ff. Its source and license accompany the packaged runtime. patches/metafile-renderer.patch applies to that exact source; no network or Node/npm runtime is used during conversion. A separate helper uses system JavaScriptCore and receives only captured bytes over stdin. Native adapters provide CoreText font measurement, code-page decoding and bounded ImageIO bitmap conversion. It has no document-derived filesystem or network APIs.

The adaptation implements EMF+ world/page transforms, prepend/append matrices, indexed graphics Save/Restore, containers, clipping rectangle/path/reset/offset and all six clip-combine operations. Clips are captured in device coordinates; a later matrix change cannot move them. SVG groups retain affine geometry for paths, ellipses, text and bitmap parallelograms. Multi-subpath fills retain every subpath. Bounded continued objects assemble before decoding.

Font objects retain original family names instead of replacing them with generic serif/sans/monospace. Native CoreText measurement replaces the upstream fixed 0.6-em estimate. Formatted StringFormat layouts use native shaped outlines for alignment, wrapping, direction, tabs, spacing, trimming and decorations; exact scope and remaining text refusals are listed in formatted text parity. Solid pen caps, joins, units and dash patterns retain their source data. Raw 24-bit BGR, 32-bit BGRX, BGRA and premultiplied BGRA bitmap objects use bounded native conversion. Compressed image signatures determine PNG/JPEG decoding, and actual decoded metadata determines dimensions. Source rectangles and three-point destinations retain cropping and affine mapping. Ordinary WMF clip rectangles and EMF two-color rectangle gradients are implemented. Nested clipping intersects existing clips. EMF+ Header selects EMF+ playback and suppresses classic fallback drawing; only an explicit GetDC interval enables classic records until the next EMF+ record. The dual fixture deliberately gives the fallback a different color to detect the wrong representation or double paint. Matrix Append/Prepend follows GDI+ row-vector order, separately checked with noncommuting scale/translation records against Microsoft's documented order.

The painting interoperability extension tracks ImageAttributes, destination point encodings and gradient-brush support against Microsoft specifications and the independent layout2vector writer. Its current batch validation is separate from the earlier grouped evidence. Native CoreSVG painting limitations require intrinsic-resolution gradient PNGs clipped by the original vector geometry, explicit visible bitmap tiles and separate color opacity. Semantic gradient definitions alone are not the display paint; this subset does not provide unlimited-resolution gradient zoom. Tile markup reserves a bounded aggregate serialized size before expansion, and poorly conditioned large-offset radial boundaries are refused rather than approximated.

Known unsupported painting returns an error instead of guessed coordinate geometry, a grey bitmap placeholder or a successful blank image. Record-chain preflight requires bounded, aligned outer records, complete declared lengths/counts and EOF; EMF+ comments receive their own framing checks. Decoder failures, malformed output, external image references, scripts and DTDs are refused. Parent-owned helper timeout, output limits and cancellation retire the process group before returning.

The classic drawing-state family connects stock DC brush/pen selection, recorded ordinary colored-object replacement and saved drawing-context state to those same painting consumers. A documented common twenty-entry Windows display palette is a macOS compatibility profile; unknown logical colors and explicit hardware indices remain refusals. Live Win32 color APIs do not imply invented serialized setter records.

Intrinsic size and metadata

EMF follows GDI+ physical frame/device metadata, rather than treating its ink bounds as the image's pixel dimensions. Device pixels/millimetres establish DPI; frame extents in 0.01 mm establish rounded raster dimensions at that DPI. The frame origin is mapped to the display origin without rewriting captured records. The separate physical-frame.emf fixture deliberately distinguishes ink bounds from physical dimensions. This follows GDI+ behavior, also visible in Wine's GdipGetMetafileHeaderFromEmf implementation.

Placeable WMF retains logical raster extent and the header's Inch resolution, as GDI+ GdipCreateMetafileFromWmf does. Standard WMF lacks physical dimensions; the native renderer uses an explicit window extent and 96 dpi fallback. It refuses inputs without a usable extent instead of inventing a default 800×600 viewport.

The region and pattern extension adds bounded region trees, region fill/clip records, all 53 hatch styles and bitmap texture brushes. Its own evidence separates newly accepted behavior from this older checkpoint. The compressed-path extension adds relative/RLE region paths and shares validation with drawing, clipping, custom caps and accepted gradient boundaries. Negative region rectangle extents, singular region fill transforms remain explicit refusals. The embedded-metafile family supersedes the former nested-image/texture refusal with bounded child playback and isolated texture surfaces.

Explicit remaining format behavior

The formatted text extension adds native shaped glyph outlines for DrawString layouts, including direction, tabs, tracking, wrapping and trimming. The separate positioned text family connects driver strings, font-specific glyph indices and classic W text advances to native outlines, with its own checkpoint and font/record limits. This is useful three-format support, not complete GDI compatibility. Remaining unsupported features include DisplayFormatControl, locale-specific digit substitution and measured-character-range queries, gradients outside the accepted painting subset, file-format-only Left/Outset/Right pen alignment, alternate-format/terminal-server records. The SourceCopy family adds ordered alpha replacement, independent coverage and saved drawing state through native image consumers, with a separate grouped checkpoint. The pen extension adds transformed nibs, compound bands, standard caps, joins, dash styles and Center/Inset positioning across the nine EMF+ stroke record families. The indexed/16-bit bitmap extension covers 1/4/8-bit indexed palettes and RGB555/RGB565/ARGB1555 for images and texture brushes. The high-depth bitmap continuation adds raw 16-bit grayscale, 48-bit RGB and 64-bit ARGB/premultiplied ARGB through a documented eight-bit display profile. Windows internal thirteen-bit/HDR identity, and uncommon embedded compressed formats remain open. Embedded WMF/EMF/EMF+ image objects are now covered by the separate embedded-image family, with explicit Windows-reference and native-profile limits. The direct scanline and gradient family adds WMF/EMF direct bitmap bands and classic rectangle/triangle meshes; partial compressed bands and unsupported compressed alpha packing remain explicit gaps. The classic clipping extension covers all five GDI region combinations, path clips, rectangle clips, offsets and metaregions. The connected classic region/flood family addresses region fill/frame/invert and destination-dependent border/surface fill, with its own implementation and checkpoint boundary. The classic Boolean raster extension covers ROP2 and ROP3 evaluation with bounded destination/source/pattern playback, including its later masked/parallelogram/transparent/alpha transfer family. Its dated evidence records actual local checks; unsupported transfer records and geometry retain explicit refusals. Classic extended pens have a separate stroke/brush/state checkpoint. The classic bitmap-brush family connects serialized WMF pattern brushes and EMF monochrome/DIB brushes to those shared paint consumers. Its independent source contract separates live monochrome colors, supplied RGB tables and late logical-palette binding. The family has its own implementation/checkpoint boundary rather than inheriting an older pass. Windows-only fonts can substitute through CoreText. Exact GDI glyph metrics, text shaping, pen dash/cap combinations, every classic record variant and pixel identity across all Windows metafiles have not been certified.

The original synthetic corpus is in Tests/TurtleGitCoreTests/Fixtures/Metafile; MetafileImageTests covers actual color pixels, transforms/clips, bitmaps, physical metadata, text preservation, malformed/unsupported outcomes, SVG policy and owned helper cancellation/deadline cleanup. The grouped evidence records actual build/Core/native executions, failed attempts and retained limits. No complete Finder/signed deployment, physical image-window acceptance or whole-application parity is implied.

Independent writer reference

The user-provided layout2vector was inspected at 2e0a96b9f87f2a8c0ff649963a67dfccd73bf5bb (MIT). Its src/writers/emf-writer.ts and src/writers/emfplus-writer.ts implement export writers; no WMF writer or metafile import renderer was found in that revision. The synthetic writer tests and paint probes provide an independent reference for font/string-format objects, image source rectangles, clipping and gradients. They are not shipped as TurtleGit's decoder. Default ImageAttributes objects and EMF+ gradient brushes exposed the concrete interoperability cases addressed by the painting extension. That document distinguishes the accepted subset, explicit refusals and pending validation. Existing web-derived output files have not been copied into the application or fixtures.

Selected signed-parent acceptance, October 19

Actual signed runtime evidence now covers the packaged inherited-sandbox helper and native image loader in a disposable Apple Development AppStore parent. Eight WMF/EMF/EMF+ samples check vector, text, bitmap, gradient, region, hatch, indexed4 and RGB565 texture output. Malformed refusal, an actual post-launch deadline, source-byte preservation, private request-directory removal and owned-process drainage pass. No shipping GUI or installed Finder workflow was launched. This selected corpus does not establish all-record graphics fidelity or App Store distribution acceptance.

Independent decoder reference

The user-provided BaseHmiTypes renderer was inspected at f491a9514f935d64b54bc62ec70606db19f9105a (MIT, copyright 2026 JFK Solutions). Its classic clip masks and metaregion/offset lifecycle informed the classic clipping extension; its original license is retained and bundled. It is a self-contained decoder reference, whereas layout2vector supplies independent export writers. TurtleGit retains its own framing checks, explicit unsupported-record errors, budgets, native text/bitmap bridges and affine playback. BaseHmiTypes' EMF+ object reader covers paths and images; TurtleGit retains its own bounded pen and custom-cap implementation.