allow pageMargins to be defined with a function

This function will receive the pageNumber as argument.

This commit is a port of original work of @seahorsepip in pull request bpampuch#1746

This rework is rebuild on 0.3 version, it adds some unit tests for
new helpers and it has integration tests following comments in original
pull request bpampuch#1746.

src/DocumentContext.js

@@ -1,4 +1,5 @@
 import { isString } from './helpers/variableType';
+import { functionalizePageMargin } from './PageSize';
 import { EventEmitter } from 'events';
 
 /**
@@ -10,10 +11,10 @@ class DocumentContext extends EventEmitter {
 		super();
 		this.pages = [];
 
-		this.pageMargins = pageMargins;
+		this.pageMargins = functionalizePageMargin(pageMargins);
 
-		this.x = pageMargins.left;
-		this.availableWidth = pageSize.width - pageMargins.left - pageMargins.right;
+		this.x = this.pageMargins(1).left;
+		this.availableWidth = pageSize.width - this.pageMargins(1).left - this.pageMargins(1).right;
 		this.availableHeight = 0;
 		this.page = -1;
 
@@ -131,9 +132,13 @@ class DocumentContext extends EventEmitter {
 	}
 
 	initializePage() {
-		this.y = this.pageMargins.top;
-		this.availableHeight = this.getCurrentPage().pageSize.height - this.pageMargins.top - this.pageMargins.bottom;
-		this.pageSnapshot().availableWidth = this.getCurrentPage().pageSize.width - this.pageMargins.left - this.pageMargins.right;
+		this.y = this.getCurrentPage().pageMargins.top;
+		this.availableHeight = this.getCurrentPage().pageSize.height
+			- this.getCurrentPage().pageMargins.top
+			- this.getCurrentPage().pageMargins.bottom;
+		this.pageSnapshot().availableWidth = this.getCurrentPage().pageSize.width
+			- this.getCurrentPage().pageMargins.left
+			- this.getCurrentPage().pageMargins.right;
 	}
 
 	pageSnapshot() {
@@ -147,11 +152,11 @@ class DocumentContext extends EventEmitter {
 	moveTo(x, y) {
 		if (x !== undefined && x !== null) {
 			this.x = x;
-			this.availableWidth = this.getCurrentPage().pageSize.width - this.x - this.pageMargins.right;
+			this.availableWidth = this.getCurrentPage().pageSize.width - this.x - this.getCurrentPage().pageMargins.right;
 		}
 		if (y !== undefined && y !== null) {
 			this.y = y;
-			this.availableHeight = this.getCurrentPage().pageSize.height - this.y - this.pageMargins.bottom;
+			this.availableHeight = this.getCurrentPage().pageSize.height - this.y - this.getCurrentPage().pageMargins.bottom;
 		}
 	}
 
@@ -218,7 +223,11 @@ class DocumentContext extends EventEmitter {
 	}
 
 	addPage(pageSize) {
-		let page = { items: [], pageSize: pageSize };
+		let page = {
+			items: [],
+			pageSize: pageSize,
+			pageMargins: this.pageMargins(this.pages.length + 1),
+		};
 		this.pages.push(page);
 		this.backgroundLength.push(0);
 		this.page = this.pages.length - 1;
@@ -239,8 +248,12 @@ class DocumentContext extends EventEmitter {
 
 	getCurrentPosition() {
 		let pageSize = this.getCurrentPage().pageSize;
-		let innerHeight = pageSize.height - this.pageMargins.top - this.pageMargins.bottom;
-		let innerWidth = pageSize.width - this.pageMargins.left - this.pageMargins.right;
+		let innerHeight = pageSize.height
+			- this.getCurrentPage().pageMargins.top
+			- this.getCurrentPage().pageMargins.bottom;
+		let innerWidth = pageSize.width
+			- this.getCurrentPage().pageMargins.left
+			- this.getCurrentPage().pageMargins.right;
 
 		return {
 			pageNumber: this.page + 1,
@@ -249,8 +262,9 @@ class DocumentContext extends EventEmitter {
 			pageInnerWidth: innerWidth,
 			left: this.x,
 			top: this.y,
-			verticalRatio: ((this.y - this.pageMargins.top) / innerHeight),
-			horizontalRatio: ((this.x - this.pageMargins.left) / innerWidth)
+			verticalRatio: ((this.y - this.getCurrentPage().pageMargins.top) / innerHeight),
+			horizontalRatio: ((this.x - this.getCurrentPage().pageMargins.left) / innerWidth),
+			pageMargins: this.getCurrentPage().pageMargins,
 		};
 	}
 }

src/ElementWriter.js

@@ -362,7 +362,9 @@ class ElementWriter extends EventEmitter {
 	 */
 	pushContext(contextOrWidth, height) {
 		if (contextOrWidth === undefined) {
-			height = this.context().getCurrentPage().height - this.context().pageMargins.top - this.context().pageMargins.bottom;
+			height = this.context().getCurrentPage().height
+				- this.context().getCurrentPage().pageMargins.top
+				- this.context().getCurrentPage().pageMargins.bottom;
 			contextOrWidth = this.context().availableWidth;
 		}
 

src/LayoutBuilder.js

@@ -219,7 +219,7 @@ class LayoutBuilder {
 			let node = nodeGetter(pageIndex + 1, l, this.writer.context().pages[pageIndex].pageSize);
 
 			if (node) {
-				let sizes = sizeFunction(this.writer.context().getCurrentPage().pageSize, this.pageMargins);
+				let sizes = sizeFunction(this.writer.context().getCurrentPage().pageSize, this.writer.context().getCurrentPage().pageMargins);
 				this.writer.beginUnbreakableBlock(sizes.width, sizes.height);
 				node = this.docPreprocessor.preprocessDocument(node);
 				this.processNode(this.docMeasure.measureDocument(node));

src/PageSize.js

@@ -1,5 +1,5 @@
 import sizes from './standardPageSizes';
-import { isString, isNumber } from './helpers/variableType';
+import { isString, isNumber, isFunction, isObject, isValue } from './helpers/variableType';
 
 export function normalizePageSize(pageSize, pageOrientation) {
 	function isNeedSwapPageSizes(pageOrientation) {
@@ -36,6 +36,27 @@ export function normalizePageSize(pageSize, pageOrientation) {
 	return size;
 }
 
+function isPageMarginObject(margin) {
+	if (isObject(margin)) {
+		const { left, top, right, bottom } = margin;
+
+		if (isValue(left) && isValue(top) && isValue(right) && isValue(bottom)) {
+			return true;
+		}
+	}
+	return false;
+}
+
+
+/*
+ * Accepts margin definition as being:
+ *   * a number to set same margin size on all margins
+ *   * a function which will receive pageNumber as argument
+ *   * an array with two numbers to set horizontal and vertical margin respectively
+ *   * an array with four numbers to set left, top, right and bottom margin respectively
+ *
+ * Normalized value is an object with the four margins as property.
+ * */
 export function normalizePageMargin(margin) {
 	if (isNumber(margin)) {
 		margin = { left: margin, right: margin, top: margin, bottom: margin };
@@ -49,5 +70,43 @@ export function normalizePageMargin(margin) {
 		}
 	}
 
+	if (!isFunction(margin) && !isPageMarginObject(margin)) {
+		throw new Error('Invalid pageMargins definition');
+	}
+
 	return margin;
 }
+
+/*
+ * Returns a function accepting pageNumber as argument and returning
+ * a normalized page margin object
+ * */
+export function functionalizePageMargin(margin) {
+	let marginFn;
+	if (isFunction(margin)) {
+		marginFn = function (pageNumber) {
+			return normalizePageMargin(margin(pageNumber));
+		};
+	} else {
+		if (!isPageMarginObject(margin)) {
+			margin = normalizePageMargin(margin);
+		}
+
+		const { left, top, right, bottom } = margin;
+		marginFn = function () {
+			return {
+				left,
+				top,
+				right,
+				bottom,
+			};
+		};
+
+	}
+
+	if (!isFunction(marginFn)) {
+		throw new Error(`Unable to functionalize pageMargin: ${margin}`);
+	}
+
+	return marginFn;
+}

src/helpers/variableType.js

@@ -14,6 +14,14 @@ export function isNumber(variable) {
 	return (typeof variable === 'number') || (variable instanceof Number);
 }
 
+/**
+ * @param {any} variable
+ * @returns {boolean}
+ */
+export function isFunction(variable) {
+	return (typeof variable === 'function') || (variable instanceof Function);
+}
+
 /**
  * @param {any} variable
  * @returns {boolean}

tests/integration/integrationTestHelper.js

@@ -6,8 +6,8 @@ var LayoutBuilder = require('../../js/LayoutBuilder').default;
 var SVGMeasure = require('../../js/SVGMeasure').default;
 
 class IntegrationTestHelper {
-	constructor() {
-		this.MARGINS = { top: 40, left: 40, right: 40, bottom: 40 };
+	constructor(options = {}) {
+		this.MARGINS = options.margins || { top: 40, left: 40, right: 40, bottom: 40 };
 		this.LINE_HEIGHT = 14.0625;
 		this.DEFAULT_BULLET_SPACER = '9. ';
 	}
@@ -28,7 +28,7 @@ class IntegrationTestHelper {
 		var pageSize = { width: size[0], height: size[1], orientation: 'portrait' };
 
 		this.pdfDocument = new PDFDocument(fontDescriptors, docDefinition.images, docDefinition.attachments, { size: [pageSize.width, pageSize.height], compress: false });
-		var builder = new LayoutBuilder(pageSize, { left: this.MARGINS.left, right: this.MARGINS.right, top: this.MARGINS.top, bottom: this.MARGINS.bottom }, new SVGMeasure());
+		var builder = new LayoutBuilder(pageSize, this.MARGINS, new SVGMeasure());
 
 		return builder.layoutDocument(
 			docDefinition.content,

tests/integration/pageMargins.spec.js

@@ -0,0 +1,125 @@
+'use strict';
+
+var assert = require('assert');
+
+var integrationTestHelper = require('./integrationTestHelper');
+
+describe('Integration test: pageMargins', function () {
+	it('margins values with function using different values for even and odd pages', function () {
+		function marginFn(pageNumber) {
+			if (pageNumber % 2 === 0) {
+				return 10;
+			}
+			return [20, 30];
+		}
+
+		var testHelper = new integrationTestHelper({ margins: marginFn });
+
+		var pages = testHelper.renderPages('A7', {
+			content: [
+				{ text: 'First page', pageBreak: 'after' },
+				{ text: 'Second page', pageBreak: 'after' },
+				{ text: 'Third page', pageBreak: 'after' },
+				{ text: 'Fourth page'},
+			]
+		});
+
+		assert.equal(pages.length, 4);
+		assert.deepEqual(pages[0].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[1].pageMargins, { left: 10, right: 10, top: 10, bottom: 10 });
+		assert.deepEqual(pages[2].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[3].pageMargins, { left: 10, right: 10, top: 10, bottom: 10 });
+	});
+
+	it('margins values when function use dynamic left value', function () {
+		function marginFn(pageNumber) {
+			return [(pageNumber %2 === 0) ? 0 : 20, 30, 30, 30];
+		}
+
+		var testHelper = new integrationTestHelper({ margins: marginFn });
+
+		var pages = testHelper.renderPages('A7', {
+			content: [
+				{ text: 'First page', pageBreak: 'after' },
+				{ text: 'Second page', pageBreak: 'after' },
+				{ text: 'Third page', pageBreak: 'after' },
+				{ text: 'Fourth page'},
+			]
+		});
+
+		assert.equal(pages.length, 4);
+		assert.deepEqual(pages[0].pageMargins, { left: 20, right: 30, top: 30, bottom: 30 });
+		assert.deepEqual(pages[1].pageMargins, { left: 0, right: 30, top: 30, bottom: 30 });
+		assert.deepEqual(pages[2].pageMargins, { left: 20, right: 30, top: 30, bottom: 30 });
+		assert.deepEqual(pages[3].pageMargins, { left: 0, right: 30, top: 30, bottom: 30 });
+	});
+
+	it('margins values when function use dynamic top value', function () {
+		function marginFn(pageNumber) {
+			return [30, (pageNumber % 2 === 0) ? 0 : 20, 30, 30];
+		}
+
+		var testHelper = new integrationTestHelper({ margins: marginFn });
+
+		var pages = testHelper.renderPages('A7', {
+			content: [
+				{ text: 'First page', pageBreak: 'after' },
+				{ text: 'Second page', pageBreak: 'after' },
+				{ text: 'Third page', pageBreak: 'after' },
+				{ text: 'Fourth page'},
+			]
+		});
+
+		assert.equal(pages.length, 4);
+		assert.deepEqual(pages[0].pageMargins, { left: 30, right: 30, top: 20, bottom: 30 });
+		assert.deepEqual(pages[1].pageMargins, { left: 30, right: 30, top: 0, bottom: 30 });
+		assert.deepEqual(pages[2].pageMargins, { left: 30, right: 30, top: 20, bottom: 30 });
+		assert.deepEqual(pages[3].pageMargins, { left: 30, right: 30, top: 0, bottom: 30 });
+	});
+
+	it('margins values when function use dynamic horizontal value', function () {
+		function marginFn(pageNumber) {
+			return [(pageNumber %2 === 0) ? 0 : 20, 30];
+		}
+
+		var testHelper = new integrationTestHelper({ margins: marginFn });
+
+		var pages = testHelper.renderPages('A7', {
+			content: [
+				{ text: 'First page', pageBreak: 'after' },
+				{ text: 'Second page', pageBreak: 'after' },
+				{ text: 'Third page', pageBreak: 'after' },
+				{ text: 'Fourth page'},
+			]
+		});
+
+		assert.equal(pages.length, 4);
+		assert.deepEqual(pages[0].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[1].pageMargins, { left: 0, right: 0, top: 30, bottom: 30 });
+		assert.deepEqual(pages[2].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[3].pageMargins, { left: 0, right: 0, top: 30, bottom: 30 });
+	});
+
+	it('margins values when function use dynamic vertical value', function () {
+		function marginFn(pageNumber) {
+			return [20, (pageNumber %2 === 0) ? 0 : 30];
+		}
+
+		var testHelper = new integrationTestHelper({ margins: marginFn });
+
+		var pages = testHelper.renderPages('A7', {
+			content: [
+				{ text: 'First page', pageBreak: 'after' },
+				{ text: 'Second page', pageBreak: 'after' },
+				{ text: 'Third page', pageBreak: 'after' },
+				{ text: 'Fourth page'},
+			]
+		});
+
+		assert.equal(pages.length, 4);
+		assert.deepEqual(pages[0].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[1].pageMargins, { left: 20, right: 20, top: 0, bottom: 0 });
+		assert.deepEqual(pages[2].pageMargins, { left: 20, right: 20, top: 30, bottom: 30 });
+		assert.deepEqual(pages[3].pageMargins, { left: 20, right: 20, top: 0, bottom: 0 });
+	});
+});

tests/unit/LayoutBuilder.spec.js

@@ -1910,7 +1910,7 @@ describe('LayoutBuilder', function () {
 
 			builder.layoutDocument(docStructure, pdfDocument, styleDictionary, defaultStyle, background, header, footer, watermark, pageBreakBeforeFunction);
 
-			assert.deepEqual(pageBreakBeforeFunction.getCall(0).args[0].startPosition, { pageNumber: 1, left: 40, top: 40, verticalRatio: 0, horizontalRatio: 0, pageOrientation: 'portrait', pageInnerHeight: 720, pageInnerWidth: 320 });
+			assert.deepEqual(pageBreakBeforeFunction.getCall(0).args[0].startPosition, { pageNumber: 1, left: 40, top: 40, verticalRatio: 0, horizontalRatio: 0, pageOrientation: 'portrait', pageInnerHeight: 720, pageInnerWidth: 320, pageMargins: { left: 40, top: 40, right: 40, bottom: 40 } });
 		});
 
 		it('should provide the pageOrientation of the node', function () {