OfficeIMO.Chm 3.4.5

OfficeIMO.Chm

Read compiled HTML Help (.chm) in process on Windows, macOS, and Linux. ChmDocument exposes HTML topics, exact entry bytes, embedded resources, hierarchical contents, and the keyword index. Loading does not launch the Windows help viewer, execute scripts, or fetch external resources.

Read a book

using OfficeIMO.Chm;

ChmDocument book = ChmDocument.Load("manual.chm", new ChmReadOptions {
    MaxInputBytes = 64L * 1024 * 1024,
    MaxExpandedBytes = 128L * 1024 * 1024
});
Console.WriteLine(book.Title);
foreach (ChmTopic topic in book.Topics) {
    Console.WriteLine($"{topic.Title}: {topic.Path}");
    string html = topic.ReadHtml();
}
foreach (ChmNavigationItem item in book.TableOfContents) {
    Console.WriteLine($"{item.Name}: {item.Children.Count} children");
}
byte[] image = book.FindEntry("/images/logo.png")!.GetBytes();

Load accepts paths, bytes, and streams; LoadAsync accepts paths and streams. Seekable streams are read from the beginning, restored to their original position, and left open. Forward-only streams are consumed from their current position and left open. The result owns an independent snapshot. GetBytes() returns a copy; OpenRead() exposes a read-only stream.

Topics follow contents order, then unlisted HTML topics in ordinal path order. Contents and index items retain children, multiple links, and See Also labels. FindEntry(reference, sourcePath) resolves relative paths, case differences, URI escapes, queries, and fragments inside the archive. It returns null for missing, unsafe, external, and merged-book references. Raw directory identity remains available as ChmEntry.Name.

Convert through existing engines

ChmConversionResult<OfficeIMO.Html.HtmlConversionDocument> htmlBook =
    book.ToHtmlDocumentResult(new ChmConversionOptions {
        TopicPaths = new[] { "/introduction.html", "/installation.html" },
        MaxOutputBytes = 32L * 1024 * 1024
    });
foreach (var finding in htmlBook.Report.FidelityDiagnostics)
    Console.WriteLine($"{finding.Code}: {finding.Message}");

Topic selection retains book order and rejects unknown or non-topic paths. RequireValue() rejects conversion failure; Report.RequireNoLoss() additionally rejects reported approximations and omissions. Raw archive extraction and converted-document fidelity are separate contracts.

Bounds and ownership

Default read limits are 128 MiB input, 256 MiB expanded LZX data, 32 MiB per entry, 100,000 entries/navigation items, 100,000 combined navigation references, 16 Mi characters of navigation text, and bounded HTML/tree depth. Repeated targets and compiled-table strings count against the aggregate budgets. Limits reject the operation rather than returning a truncated book. ChmReadException.Code identifies malformed or unsupported archives and exhausted limits. Cancellation is cooperative during reads, directory/navigation parsing, decompression, and conversion.

Linked books retain each topic's language, reading direction, and inert container attributes. The first selected topic supplies the book's primary language; the help-book locale supplies a language when the topic has no declaration. EPUB callers can override the publication language with EpubManuscriptOptions.Language.

ChmTopic.ToHtmlDocument() exposes the existing inert HTML model. ConfigureRenderOptions(options, topic.Path) supplies a virtual chm://archive/ base and an archive-only resource resolver. It replaces an existing resolver; remote images, fonts, stylesheets, and files are never loaded by CHM conversion.

The package references OfficeIMO.Core and OfficeIMO.Html. LZX decoding is shared with OneNote in Core; HTML parsing and charset services retain their existing provider boundary. There is no CHMLib, Windows API, external executable, or new third-party codec dependency in the product.

See supported profiles and qualification for exact format and export boundaries.

Generated capability summary

This table is generated from the package-neutral OfficeIMO operation catalog. The detailed source contracts remain authoritative for feature-level behavior and limitations.

The complete rows for OfficeIMO.Chm are published in the generated operation contract.