Struct Typesetter 

pub struct Typesetter { /* private fields */ }

The main entry point for text typesetting.

Owns the font registry, glyph atlas, layout cache, and render state. The typical usage pattern is:

1. Create with Typesetter::new
2. Register fonts with register_font
3. Set default font with set_default_font
4. Set viewport with set_viewport
5. Lay out content with layout_full or layout_blocks
6. Set cursor state with set_cursor
7. Render with render to get a RenderFrame
8. On edits, use relayout_block for incremental updates

Thread safety

Typesetter is !Send + !Sync because its internal fontdb, atlas allocator, and swash scale context are not thread-safe. It lives on the adapter’s render thread alongside the framework’s drawing calls.

Implementations

impl Typesetter

pub fn new() -> Self

Create a new typesetter with no fonts loaded.

Call register_font and set_default_font before laying out any content.

pub fn register_font(&mut self, data: &[u8]) -> FontFaceId

Register a font face from raw TTF/OTF/WOFF bytes.

Parses the font’s name table to extract family, weight, and style, then indexes it for CSS-spec font matching via fontdb. Returns the first face ID (font collections like .ttc may contain multiple faces).

Panics

Panics if the font data contains no parseable faces.

pub fn register_font_as( &mut self, data: &[u8], family: &str, weight: u16, italic: bool, ) -> FontFaceId

Register a font with explicit metadata, overriding the font’s name table.

Use when the font’s internal metadata is unreliable or when aliasing a font to a different family name.

Panics

Panics if the font data contains no parseable faces.

pub fn set_default_font(&mut self, face: FontFaceId, size_px: f32)

Set which font face to use as the document default.

This is the fallback font when a fragment’s TextFormat doesn’t specify a family or the specified family isn’t found.

pub fn set_generic_family(&mut self, generic: &str, family: &str)

Map a generic family name to a registered font family.

Common mappings: "serif" → "Noto Serif", "monospace" → "Fira Code". When text-document specifies font_family: "monospace", the typesetter resolves it through this mapping before querying fontdb.

pub fn font_registry(&self) -> &FontRegistry

Access the font registry for advanced queries (glyph coverage, fallback, etc.).

pub fn set_viewport(&mut self, width: f32, height: f32)

Set the viewport dimensions (visible area in pixels).

The viewport controls:

• Culling: only blocks within the viewport are rendered.
• Selection highlight: multi-line selections extend to viewport width.
• Layout width (in ContentWidthMode::Auto): text wraps at viewport width.

Call this when the window or container resizes.

pub fn set_content_width(&mut self, width: f32)

Set a fixed content width, independent of viewport.

Text wraps at this width regardless of how wide the viewport is. Use for page-like (WYSIWYG) layout or documents with explicit width. Pass f32::INFINITY for no-wrap mode.

pub fn set_content_width_auto(&mut self)

Set content width to follow viewport width (default).

Text reflows when the viewport is resized. This is the standard behavior for editors and web-style layout.

pub fn layout_width(&self) -> f32

The effective width used for text layout (line wrapping, table columns, etc.).

In ContentWidthMode::Auto, equals viewport width. In ContentWidthMode::Fixed, equals the set value.

pub fn set_scroll_offset(&mut self, offset: f32)

Set the vertical scroll offset in pixels from the top of the document.

Affects which blocks are visible (culling) and the screen-space y coordinates in the rendered RenderFrame.

pub fn content_height(&self) -> f32

Total content height after layout, in pixels.

Use for scrollbar range: scrollbar.max = content_height - viewport_height.

pub fn layout_full(&mut self, flow: &FlowSnapshot)

Full layout from a text-document FlowSnapshot.

Converts all snapshot elements (blocks, tables, frames) to internal layout params and lays out the entire document flow. Call this on DocumentReset events or initial document load.

For incremental updates after small edits, prefer relayout_block.

pub fn layout_blocks(&mut self, block_params: Vec<BlockLayoutParams>)

Lay out a list of blocks from scratch (framework-agnostic API).

Replaces all existing layout state with the given blocks. This is the non-text-document equivalent of layout_full. the caller converts snapshot types to BlockLayoutParams.

pub fn add_frame(&mut self, params: &FrameLayoutParams)

Add a frame to the current flow layout.

The frame is placed after all previously laid-out content. Frame position (inline, float, absolute) is determined by FrameLayoutParams::position.

pub fn add_table(&mut self, params: &TableLayoutParams)

Add a table to the current flow layout.

The table is placed after all previously laid-out content.

pub fn relayout_block(&mut self, params: &BlockLayoutParams)

Relayout a single block after its content or formatting changed.

Re-shapes and re-wraps the block, then shifts subsequent blocks if the height changed. Much cheaper than layout_full for single-block edits (typing, formatting changes).

If the block is inside a table cell (BlockSnapshot::table_cell is Some), the table row height is re-measured and content below the table shifts.

pub fn render(&mut self) -> &RenderFrame

Render the visible viewport and return everything needed to draw.

Performs viewport culling (only processes blocks within the scroll window), rasterizes any new glyphs into the atlas, and produces glyph quads, image placeholders, and decoration rectangles.

The returned reference borrows the Typesetter. The adapter should iterate the frame for drawing, then drop the reference before calling any layout/scroll methods on the next frame.

On each call, stale glyphs (unused for ~120 frames) are evicted from the atlas to reclaim space.

pub fn hit_test(&self, x: f32, y: f32) -> Option<HitTestResult>

Map a screen-space point to a document position.

Coordinates are relative to the widget’s top-left corner. The scroll offset is accounted for internally. Returns None if the flow has no content.

pub fn caret_rect(&self, position: usize) -> [f32; 4]

Get the screen-space caret rectangle at a document position.

Returns [x, y, width, height] in screen pixels. Use this to report the caret position to the platform IME system for composition window placement. For drawing the caret, use the [DecorationKind::Cursor] entry in RenderFrame::decorations instead.

pub fn set_cursor(&mut self, cursor: &CursorDisplay)

Update the cursor display state for a single cursor.

The adapter reads position and anchor from text-document’s TextCursor, toggles visible on a blink timer, and passes the result here. The typesetter includes cursor and selection decorations in the next render call.

pub fn set_cursors(&mut self, cursors: &[CursorDisplay])

Update multiple cursors (multi-cursor editing support).

Each cursor independently generates a caret and optional selection highlight.

pub fn set_selection_color(&mut self, color: [f32; 4])

Set the selection highlight color ([r, g, b, a], 0.0-1.0).

Default: [0.26, 0.52, 0.96, 0.3] (translucent blue).

pub fn set_cursor_color(&mut self, color: [f32; 4])

Set the cursor caret color ([r, g, b, a], 0.0-1.0).

Default: [0.0, 0.0, 0.0, 1.0] (black).

pub fn block_visual_info(&self, block_id: usize) -> Option<BlockVisualInfo>

Get the visual position and height of a laid-out block.

Returns None if the block ID is not in the current layout.

pub fn scroll_to_position(&mut self, position: usize) -> f32

Scroll so that the given document position is visible, placing it roughly 1/3 from the top of the viewport.

Returns the new scroll offset.

pub fn ensure_caret_visible(&mut self) -> Option<f32>

Scroll the minimum amount needed to make the current caret visible.

Call after cursor movement (arrow keys, click, typing) to keep the caret in view. Returns Some(new_offset) if scrolling occurred, or None if the caret was already visible.

Trait Implementations

impl Default for Typesetter

fn default() -> Self

Returns the “default value” for a type.