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Classic EMF extended pens

This partial rendering family follows EMR_EXTCREATEPEN and its connected classic path/shape operations. It uses the existing pinned renderer and native stroke, brush, clipping and Boolean-composition adapters. Dated checkpoint evidence records actual painting/consumer coverage, failed attempts and focused repairs. Parsing a record alone does not establish painting or complete TortoiseGit image parity.

Record and API contract

The EMR_EXTCREATEPEN record contains an object handle, optional bitmap ranges and a variable LogPenEx object. Bitmap offsets are relative to the whole record; the bitmap need not immediately follow the style array. Bounds, style lengths and optional DIB data must be validated before publishing a reusable pen object.

LogPenEx separates pen type, line style, cap and join. Cosmetic width is one device pixel; geometric width and user-style lengths are logical units. The native outline must therefore retain the full affine mapping instead of reducing a sheared or nonuniformly scaled geometric pen to a single device width.

The ExtCreatePen API limits custom style arrays to sixteen entries. Odd-length arrays reverse the dash/gap roles on their next cycle. Alternate is cosmetic-only. InsideFrame shrinks geometric figures drawn by bounding-rectangle operations; ordinary open paths retain centered strokes. Geometric caps and joins remain independent attributes rather than being discarded with the style bits. Zero-length entries in a nonzero custom cycle remain real dash/gap transitions: round/square caps can paint zero-length dashes, while flat zero-length dashes have no area. Geometric width zero follows a device-hairline policy, including under scaling. These compatibility cases are compared with the Wine pen implementation and its device-width consumer.

Brush attributes define solid, hatch and bitmap-backed paint. Hatch foreground/background and brush origin remain drawing-context state. A pen's brush must paint the stroked outline; it must not be replaced by the currently selected fill brush. Optional DIB headers/bits need their own bounded decoder and palette policy. Styled gaps from extended pens do not receive opaque background fill, following the SetBkMode distinction from CreatePen. Hollow/null pen brushes retain no-ink behavior.

Related state records

EMR_SETMITERLIMIT has a normative unsigned field but Windows product behavior, note 90 uses FLOAT. The adapter accepts both encodings within its existing finite 1…1,000,000 native limit, retaining miter state through Save/Restore. This dual interpretation is a compatibility policy, distinct from either wire description alone. NaN, infinity and out-of-budget values refuse conversion. ArcTo also retains its current-position connector and final position through bounded-shape InsideFrame handling.

Connected scope and limits

The batch covers object selection and saved-state restoration, custom and alternate dashes, geometric caps/joins, hatch/DIB stroke paint, bounded-shape InsideFrame, device/world transforms, clipping and existing ROP2 composition. Malformed or unrepresentable operands must refuse the whole conversion, retaining input bytes and avoiding a successful partial or silently solid fallback.

The existing input, geometry, bitmap, markup, raster-work and helper-deadline budgets remain consumers. This family does not implement framed regions or flood fills, certify Windows-exact cosmetic pixel stepping, every pathological curve, all legacy palette modes, unavailable Windows fonts, signed execution, physical Finder acceptance or the complete WMF/EMF/EMF+ format families.

The macOS adapter chooses one device pixel per cosmetic style unit and aligns integer device centerlines to native pixel centers. ALTERNATE instead walks flattened device paths into alternating complete pixel cells, preserving phase across joined segments and excluding the terminal endpoint. Microsoft defines cosmetic style units by device; Wine's DIB implementation uses a different unit scale. Predefined dash patterns and edge antialiasing therefore have platform adaptation limits. They are not evidence of Windows-exact pixel stepping. DDB patterns without representable serialized bitmap data and dithering hatch aliases remain explicit refusals. Existing native geometry, record, bitmap and aggregate work budgets bound accepted input rather than certifying all numeric extremes.