Applications

What you'll learn

• How the primitives compose into syntax highlighting, navigation, indexing, and editor updates.

Syntax highlighting

Walk with a cursor, classify named nodes by type, and emit spans:

var cursor = tree.cursor();
defer cursor.deinit();
// gotoFirstChild / gotoNextSibling over the tree;
// switch on node.nodeType(): "identifier" → variable color,
// "number" → constant color, operators → punctuation color.

Changed ranges limit repainting to dirty spans after each keystroke.

Code navigation

gotoDescendant(offset) jumps to the node under a click; parent() climbs to the enclosing construct; childByFieldName("left") pulls out operands. Queries like (identifier) @id build document-symbol lists in one pass.

Source indexing and structural search

Compile project-wide queries once ((identifier) @name), execute per file with a reused QueryCursor, and record (file, node.range(), text) triples. Because matching is structural, renames and reformatting do not break the index the way regex would.

Editor integration

The incremental loop from Incremental is the whole protocol: keystroke → InputEdit → parse(old, edit, text) → getChangedRanges → repaint/retokenize only those spans. Parser and cursor reuse keep per-keystroke work proportional to the edit, not the file.

Related guides

• Use Cases for full problem → architecture → example walkthroughs.
• Performance for budgets.