Function buildDecorations

src/cm/indentGuides.ts:160–274

* Build decorations for indent guides

(
	view: EditorView,
	config: Required<IndentGuidesConfig>,
	lineCache: IndentLineCache,
	styleCache: GuideStyleCache,
)

 * Build decorations for indent guides
 */
function buildDecorations(
	view: EditorView,
	config: Required<IndentGuidesConfig>,
	lineCache: IndentLineCache,
	styleCache: GuideStyleCache,
): DecorationSet {
	const builder = new RangeSetBuilder<Decoration>();
	const { state } = view;
	const tabSize = getTabSize(state);
	const indentUnit = getIndentUnitColumns(state);
	const guideStepPx = Math.max(view.defaultCharacterWidth * indentUnit, 1);
	let processedLines = 0;

	for (const { from: blockFrom, to: blockTo } of view.visibleRanges) {
		const startLine = state.doc.lineAt(blockFrom);
		const endLine = state.doc.lineAt(blockTo);
		const firstLineNumber = startLine.number;
		const lastLineNumber = endLine.number;
		const scanStartLine = Math.max(1, firstLineNumber - BLANK_LINE_SCAN_LIMIT);
		const scanEndLine = Math.min(
			state.doc.lines,
			lastLineNumber + BLANK_LINE_SCAN_LIMIT,
		);
		const prevIndentByLine = new Map<number, number>();
		const nextIndentByLine = new Map<number, number>();
		let prevIndent = -1;
		let prevIndentLine = -1;

		for (let lineNum = scanStartLine; lineNum <= scanEndLine; lineNum++) {
			const line = state.doc.line(lineNum);
			const info = getCachedLineInfo(lineNum, line.text, tabSize, lineCache);
			prevIndentByLine.set(
				lineNum,
				lineNum - prevIndentLine <= BLANK_LINE_SCAN_LIMIT ? prevIndent : -1,
			);
			if (!info.blank) {
				prevIndent = info.indentColumns;
				prevIndentLine = lineNum;
			}
		}

		let nextIndent = -1;
		let nextIndentLine = state.doc.lines + 1;
		for (let lineNum = scanEndLine; lineNum >= scanStartLine; lineNum--) {
			const line = state.doc.line(lineNum);
			const info = getCachedLineInfo(lineNum, line.text, tabSize, lineCache);
			nextIndentByLine.set(
				lineNum,
				nextIndentLine - lineNum <= BLANK_LINE_SCAN_LIMIT ? nextIndent : -1,
			);
			if (!info.blank) {
				nextIndent = info.indentColumns;
				nextIndentLine = lineNum;
			}
		}

		for (let lineNum = firstLineNumber; lineNum <= lastLineNumber; lineNum++) {
			if (processedLines >= MAX_VISIBLE_GUIDE_LINES) return builder.finish();