[thisisgm]

Files that carry a picture of themselves now show it as their thumbnail, and a font is drawn in its own letters, one commit each with its own tests. This is stacked on #67, whose branch is its base, and adds two commits; the suite goes from 215 to 220 tests. No library or depends entry is added: the containers are zip files read with the zlib #67 already links, and a font is drawn by Qt from the file's bytes.

What you'd notice

• Books, comics, documents, parts and drawings show their own picture. An EPUB shows its cover, a comic archive (CBZ) its first page, an OpenDocument or Office file the preview it was saved with, a 3MF or FreeCAD part its render, and a Krita or OpenRaster drawing its merged image. Folio reads the zip's directory and that one member by their offsets, never the whole file, on the thumbnail workers like every other thumbnail, with the same cache, the same sizes and the same record of a miss. In the grid, the list, the columns, the details pane and the preview window alike.
• A font shows "Aa" in itself. A TrueType, OpenType, collection, WOFF, WOFF2 or Type 1 font is drawn black on white from its own bytes and is never added to the application's fonts. A font without those letters shows its first two letters, and one without letters its first two characters. A .otf file is drawn whichever type its extension gives it, since the MIME database shares that ending with an OpenDocument template. A Type 1 font, which is PostScript and so text to the MIME database, is no longer previewed as its source.
• An installed thumbnailer still wins. As for camera RAW files in Thumbnails: camera RAW, a checked cache, clearer misses #66, Folio draws these only where no thumbnailer is installed for the type, so nothing changes where one already draws them. For a type Folio now draws, the hint that names a package to install is no longer shown.
• A damaged or hostile file costs nothing. A file is opened without waiting and read only if it is a regular file. At most 8192 entries and 8 MiB of directory are walked, a member over 64 MiB is refused before any memory is taken for it, inflation stops at the size the entry claims, and a picture over the pixel limit RAW files already have is not decoded. Zip64, encrypted and multi-disk archives are refused, and a name inside is only ever compared, never opened as a path.

Screenshots

A folder with two books, a 3MF part, a FreeCAD part, a Krita painting and four fonts, on a machine with no thumbnailer for any of these types. In the grid at its largest tiles: #67 above, this branch below. The symbol font shows what it draws for "A" and "a", an alpha in each case.

The details pane on a book, each part, the painting and a font: #67 above, this branch below.

The same folder as a list: #67 on the left, this branch on the right.

And in columns.

Tests

Five new cases, each failing without its commit: every type shows the member it keeps, picked out by its size, with both EPUB generations, both ways an Office or 3MF file names its thumbnail, and the fallback members; a container without its picture, or a broken one, is remembered as a miss and not read again; each limit above is shown at its edge (8192 entries drawn and 8193 not, 64 MiB drawn and one byte more not, a stream that inflates past its claim, zip64, encryption, a second disk, an absolute path inside, a picture claiming 20000 by 20000 pixels, a pipe named like a document); a container is read on a thumbnail worker and never once its request is cancelled; and a font is drawn in its own letters with each fallback, as a collection, as WOFF and as an .otf, and never joins the application's fonts. The case that names the package for a type now checks that an OpenDocument file names none. Every commit builds and passes the suite on its own, also with TMPDIR set to a folder whose name has a space, where only extractRefusesWhatWouldLandOutside fails, as it does on main.

Limits

• WOFF2 and Type 1 fonts are drawn when the system's FreeType decodes them; no case here builds one.
• A font file over 64 MiB is not drawn.
• An .otf file is still named an OpenDocument formula template in its type line. Naming it a font is part of Previews: archive names, font sheets, media length #63.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge, with the earlier non-blocking font-scan concern still open.

Findings

1.  Symbol fonts waste worker time ▶

Summary

Adds thumbnails from pictures stored inside books, documents, parts, and drawings, plus font samples drawn from each font’s own bytes.

• Files with saved pictures now show them as thumbnails.
• Font files show a sample drawn from their own letters.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Thumbnail request] --> B{Fresh cached picture?}
  B -->|Yes| C[Return picture]
  B -->|No| D{Installed thumbnailer?}
  D -->|Yes| E[Run thumbnailer]
  D -->|No, supported embedded format| F[Read stored picture or draw font]
  E --> G[Save picture or failure]
  F --> G

Loading

_{Reviews (2) · Last reviewed commit: "Thumbnail a font by drawing it" · Reviewed by Greptile}

[greptile-apps]

Symbol fonts waste worker time

sample() scans through 0x10FFFF whenever a font has fewer than two drawable letters. Symbol-only fonts therefore walk the whole Unicode range even after finding both fallback characters, calling glyphFor() for every printable letter. This adds needless work to each uncached thumbnail and holds a thumbnail worker until the scan ends. Walk the font’s mapped characters instead, or bound the search.