[KnifeLemon]

What users notice

• A Windows program or library (.exe, .dll) dropped on Filee opens the images donut and converts to its icon: the one Explorer shows for the file.
  • ICO gives that icon exactly as the program stores it, with every size it has (no size is redrawn from another). A preset that changes the picture or asks for other icon sizes rebuilds the icon from the largest size, as for any picture.
  • PNG (and every other picture target, PDF, SVG tracing, …) uses the largest size.
• A file without an icon of its own (most DLLs, console tools) says so: "This file has no icon of its own (Windows shows a standard one for it)". A 16-bit, damaged or renamed file says it isn't a Windows program Filee can read. Both are translated into all 22 languages.
• Programs are never run or loaded, only read: Filee reads the headers and the icon, nothing else, so a 2 GB installer is as quick as a small tool.
• Programs are converted only when dropped or named. Watch folders skip them (a watched Downloads folder would otherwise turn every installer into a picture, and "Move to originals" would move the installer away), so does a folder given to the command line, and Recent conversions never opens one. Browser drags of .exe stay refused as before.

What changed

• src/Filee.Engines/Magick/ProgramIcon.cs (new): PE32/PE32+ reader that finds the first RT_GROUP_ICON (the icon Explorer shows) and rebuilds an .ico from its RT_ICON entries, with random-access reads and caps (16 MB per size, 64 MB per icon, 16,384 directory entries).
• ImageReader / ImageEncoder: exe is a package like LIVP and KRA (read as the ICO inside it, largest size converted). MagickImageConverter: program → ICO copies the icon as it is when the preset leaves the picture alone (ProgramIcon.KeptAsItIs).
• FormatRegistry: new format exe ("Windows program icon (EXE, DLL)", Image, read only) plus FormatRegistry.Program / IsProgram. FormatFields: graded general, image field.
• Settings schema 78 (after feat(geo): read OpenStreetMap XML (.osm) into the geospatial formats #1355's 77 for .osm): the images donut learns exe and dll; custom claims stay put.
• FolderWatcher.ShouldIgnore, Cli.ExpandInputs, HistoryItemViewModel.CanOpen (HomePageViewModel.cs): leave programs out as described above.
• i18n: error.exe_unreadable, error.exe_no_icon in all 22 files.
• docs/ENGINES.md: ImageMagick row and an EXE / DLL paragraph.

Tests

• tests/Filee.Engines.Tests/ProgramIconTests.cs (new): builds 32 and 64-bit programs and a DLL in the test (MZ/PE headers, one .rsrc section, the resource tree), with icons made by ImageMagick (BMP sizes plus a PNG 256 px size). Covers: PNG of the largest size, ICO byte-identical to the embedded icon, other icon sizes rebuilt from the largest, first group taken, a missing size left out, no icon, cut-short / not-a-program / 16-bit / too-short files.
• tests/Filee.Core.Tests/ProgramFormatTests.cs (new): detection, images donut, schema 77 → 78 migration without taking custom claims. FolderWatcherTests and CliTests gained a program case; FormatFieldsTests count updated.
• Ran: Filee.Core.Tests (all pass), Filee.Cli.Tests (all pass except Zip_to_iso_converts_archive_contents_without_manual_extraction, which fails the same way on main here: no 7-Zip in a fresh worktree), the Magick/route/tracing/3D/Krita/ICNS slice of Filee.Engines.Tests (only FolderIso632Tests.Archive_to_iso_uses_a_direct_archive_route_without_enabling_unrelated_inputs fails, also on main), and App localization/recent-conversion/toolbar tests.
• Checked by hand against real files (not committed): explorer.exe, regedit.exe, dotnet.exe, 32-bit notepad.exe give their full icon (8 to 13 sizes) and a 256 px PNG; kernel32.dll and System32\imageres.dll (icons moved to the .mun file on Windows 11) say they have no icon.

Not covered / for the maintainer

• New installs: the images donut has no ICO slot (front PNG/JPG/WEBP/GIF/PDF/SVG), so there ICO is reached through "Edit pictures" or by adding the ICO preset. Existing libraries (schema 58 layout) have ICO on the front. A small "Programs" donut (ICO, PNG) would put both on the front, at the cost of a new profile and migration; left out for now.
• .mun, .scr, .cpl, .ocx and 16-bit (NE) programs aren't recognised.
• Only the first icon group is taken, not every icon a library holds (e.g. all of imageres.dll).
• macOS and Linux untested by hand; the reader is plain managed code, and the tests run anywhere.

Closes #1188

Also answers #1314 (the same request, filed later); it is left open for the maintainer to close.

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