Tinta Core

Tinta Core is a C11 Win32 Markdown and Mermaid viewing control. It exposes the window class Tinta.MarkdownView, supports normal CreateWindowExW hosting, and uses window messages and WM_NOTIFY for integration.

Tinta Core is sdcb's reusable-control rewrite of Tinta C. Tinta C is itself sdcb's pure C rewrite of the original Tinta project.

The original tintac.exe application is not part of this repository. This repository contains the reusable read-only control, a minimal host, and a larger demonstration host.

Build

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build --output-on-failure

Set BUILD_SHARED_LIBS=ON to build tinta_core.dll; the default is a static library. md4c is vendored, so configuring the project requires no downloads.

Optional viewer features can be removed at compile time. All six options are enabled by default:

cmake -S . -B build-mini -G Ninja -DCMAKE_BUILD_TYPE=Release ^
  -DTINTA_ENABLE_UIA=OFF ^
  -DTINTA_ENABLE_MERMAID=OFF ^
  -DTINTA_ENABLE_SYNTAX=OFF ^
  -DTINTA_ENABLE_REMOTE_IMAGES=OFF ^
  -DTINTA_ENABLE_LOCAL_IMAGES=OFF ^
  -DTINTA_ENABLE_SVG=OFF
cmake --build build-mini --target tinta_minimal

The trimmed control still supports Markdown parsing, Direct2D/DirectWrite layout and drawing, selection, scrolling, autosizing and streaming updates. Mermaid source falls back to a normal code block, code blocks use plain monospace text without syntax coloring, and unavailable images fall back to a clickable link. The link uses the alt text when present and the source URI otherwise. TMM_GETOPTIONS does not report image capabilities that were compiled out.

The examples include tinta_minimal, the feature-oriented tinta_demo, and tinta_chat_demo. The chat demo hosts one Markdown control per message, provides a scrolling left/right conversation layout, and sends 128 simulated SSE deltas through the streaming API. Its first response also demonstrates a cached local image and an optional remote image.

For parser hardening and performance work, configure TINTA_BUILD_FUZZERS=ON and/or TINTA_BUILD_BENCHMARKS=ON. These targets are off by default and do not add C++ to a normal library build.

Minimal use

TintaCoreInitialize();
HWND view = CreateWindowExW(0, TINTA_MARKDOWN_VIEW_CLASSW, L"# Hello",
    WS_CHILD | WS_VISIBLE | WS_TABSTOP, x, y, width, height,
    parent, (HMENU)100, instance, NULL);

For UTF-8 input, document origins, Mermaid documents, themes, search, TOC and notifications, include tinta_core.h and use the TMM_* message API.

Control contract

• Call TintaCoreInitialize before creating the first control and TintaCoreUninitialize after destroying the last one.
• WM_SETTEXT and WM_GETTEXT use UTF-16 Markdown. TMM_SETDOCUMENT accepts UTF-8, a Markdown/Mermaid format, and an optional local or HTTP base URI.
• TMM_STREAM_BEGIN, TMM_STREAM_APPEND, TMM_STREAM_END and TMM_STREAM_CANCEL accept arbitrary UTF-8 delta boundaries. The control copies each delta, coalesces revisions at 20 Hz by default, parses the latest snapshot on a worker thread, commits it transactionally on the HWND thread, and reports displayed revisions with TMN_STREAMUPDATED.
• TMM_SETAUTOSIZE can fit the control height to its content and optionally cap it at a maximum height. Overflow continues to use the control's internal scroll bar, while TMN_AUTOSIZED lets an outer container reflow its layout.
• TMM_SETPAGEMARGINS and TMM_GETPAGEMARGINS configure independent left, top, right, and bottom page margins in 96-DPI device-independent pixels. The defaults are 40, 20, 40, and 40 respectively.
• Input pointers are copied before SendMessage returns. Output messages use caller-owned buffers, so no allocator crosses a static-library or DLL ABI.
• The control owns parsing, Direct2D drawing, scrolling, selection, zoom, search highlights, TOC data, image decoding and UI Automation. File dialogs, persistence, search UI and context menus belong to the host.
• Double-click selects a word. Triple-click selects the complete logical text line, including its trailing newline, and dragging the third click extends the selection by whole logical lines rather than visual wraps.
• With keyboard navigation enabled, Ctrl+0 resets zoom to 100% and Ctrl++/Ctrl+- adjust it by 10%. Ctrl+mouse wheel uses the same steps when mouse zoom is enabled.
• Code blocks show their Markdown language info verbatim in a non-selectable header. Blocks without a language are labeled Plain text; the Copy button shares the header and briefly changes to Copied after a successful copy.
• Code and successfully rendered Mermaid blocks always provide a source Copy/Copied button in their persistent headers. Mermaid headers are labeled Mermaid; parsed failures fall back to the normal code-block header.
• Code and Mermaid headers also include a chevron and toggle an animated collapse when clicked outside Copy. Collapsed blocks retain their source, selection text, search matches, and block-local horizontal position; search or UIA scrolling immediately expands hidden matches.
• Nested inline styles are merged instead of replacing one another. Inline code inside bold, italic, bold-italic, or links keeps the corresponding face and interaction, and punctuation after a code pill has no synthetic space.
• Inline and block HTML <sub>/<sup> map to native script text while preserving nested emphasis, links, code, selection, search, and copy.
• GitHub-style <details>/<summary> can wrap Markdown blocks, including nested Details, Code, Mermaid, images, and SVG. Summary rows toggle with an animated chevron; open controls the initial state, and search or UIA access reveals hidden ancestor Details.
• Mermaid node labels are centered with shape-aware padding. Diamonds, hexagons, circles, and rectangles reserve dimensions appropriate to their outlines while retaining block-local horizontal scrolling.
• Mermaid flowcharts support nested Subgraphs, explicit IDs and titles, group endpoints, per-group directions, and style/classDef styling. A group keeps its local direction until one of its member nodes connects outside; in that case it inherits the parent direction, matching Mermaid. Compound layout keeps nested members inside their containers and emits shape-clipped Direct2D spline routes instead of multi-bend exterior lanes.
• Wide code and Mermaid blocks scroll horizontally inside the block instead of widening the document. Blocks keep a 240-DIP minimum width in extremely narrow hosts; their internal bars support dragging, horizontal wheel input, and Shift+wheel.
• TINTA_OPTION_DOCUMENT_COPY_BUTTON adds an opt-in Copy button at the document's top-right. It is always visible at the top, scrolls away with the document, copies the exact source for the displayed revision, and briefly changes to Copied.
• External links send TMN_LINKACTIVATE; returning zero permits the default ShellExecuteW behavior. Images send TMN_RESOURCEOPENING; the host can return default, block, or replace the resource URI.
• Local and remote image resolution, download failures, decoded WIC sources, and device-specific Direct2D bitmaps are cached per control for the lifetime of a streamed document. Successfully decoded remote pixel data also uses a bounded process cache so later controls do not download/decode it again. Image failures send TMN_RESOURCEERROR; image reflow sends TMN_CONTENTUPDATED.
• SVG images support local files, HTTP(S) resources, and Base64 or percent-encoded data:image/svg+xml URIs. Standalone SVG paragraphs use a persistent SVG header with source Copy and animated collapse; inline SVG follows ordinary image behavior. Rendering uses the Direct2D SVG subset when ID2D1DeviceContext5 is available and otherwise reports one resource error and falls back to a clickable alt-text or URI link. Intrinsic width/height and viewBox determine the natural size (default 300×150 DIP); DTD and entity declarations are rejected.
• The default limits are 64 MiB of Markdown, one million AST nodes, an AST depth of 256, 10,000 Mermaid nodes, 20,000 Mermaid edges, 64 MiB per remote image, 64 million decoded pixels per image, 512 image resources and four concurrent downloads.
• TMM_GETVERSION, TMM_GETCAPABILITIES, and TMM_GETSTATS let hosts inspect the loaded build and current document without relying on compile-time assumptions. TINTA_CAPABILITY_SVG reports that SVG support was compiled in; rendering can still fall back when the current Windows version does not expose ID2D1DeviceContext5.

Tinta.MarkdownView exposes the UI Automation Document, Text and Scroll patterns. Headings and links appear as semantic children, and links implement the Invoke pattern. Text ranges carry their source revision and become unavailable after the document is replaced instead of reading unrelated text.