f/dynamic-page-margin: add fix when applied to snaking columns

Author: Ihsan Nurul Iman

src/LayoutBuilder.js

@@ -1364,6 +1364,17 @@ class LayoutBuilder {
 			}
 
 			let positions = this.writer.addLine(line);
+			if (!positions && this.writer.context().inSnakingColumns() && !this.writer.context().isInNestedNonSnakingGroup()) {
+				this.snakingAwarePageBreak(node.pageOrientation);
+
+				if (line.inlines && line.inlines.length > 0) {
+					node._inlines.unshift(...line.inlines);
+				}
+
+				line = this.buildNextLine(node);
+				continue;
+			}
+
 			node.positions.push(positions);
 			line = this.buildNextLine(node);
 			if (line) {

src/PageElementWriter.js

@@ -22,6 +22,12 @@ class PageElementWriter extends ElementWriter {
 	}
 
 	addLine(line, dontUpdateContextPosition, index) {
+		// Outer snaking text needs LayoutBuilder to rebuild the line after a column/page
+		// break so the first carried line wraps to the new column width correctly.
+		if (this.context().inSnakingColumns() && !this.context().isInNestedNonSnakingGroup()) {
+			return super.addLine(line, dontUpdateContextPosition, index);
+		}
+
 		return this._fitOnPage(() => super.addLine(line, dontUpdateContextPosition, index));
 	}
 

tests/integration/snaking_columns.spec.js

@@ -1032,6 +1032,42 @@ describe('Integration test: snaking columns', function () {
 		assert.ok(lineWidth > 150, 'Page 2 separate column should have reset to wide width (>150), found: ' + lineWidth);
 	});
 
+	it('should reflow the first carried line when dynamic margins snake into a narrower column', function () {
+		var dd = {
+			pageMargins: function (currentPage) {
+				return {
+					left: currentPage % 2 === 0 ? 100 : 20,
+					top: 20,
+					right: currentPage % 2 === 0 ? 20 : 100,
+					bottom: 20
+				};
+			},
+			content: [
+				{
+					columns: [
+						{ text: 'Wide content ' + 'text '.repeat(2000), width: 300, fontSize: 10 },
+						{ text: '', width: '*' }
+					],
+					columnGap: 10,
+					snakingColumns: true
+				}
+			]
+		};
+
+		var pages = testHelper.renderPages('A4', dd);
+		var page1 = pages[0];
+		var lines = page1.items.filter(function (item) { return item.type === 'line'; }).map(function (item) { return item.item; });
+		var secondColumnLines = lines.filter(function (line) { return line.x > 320; });
+		var firstSecondColumnLine = secondColumnLines[0];
+		var rightLimit = page1.pageSize.width - page1.pageMargins.right;
+
+		assert.ok(firstSecondColumnLine, 'Page 1 should continue into the second snaking column');
+		assert.ok(
+			firstSecondColumnLine.x + firstSecondColumnLine.getWidth() <= rightLimit + 0.5,
+			'The first carried line in the second column should respect the page right margin'
+		);
+	});
+
 	describe('snaking columns nested checks', function () {
 
 		it('should respect left margin when snaking columns break to next page', function () {