Add pageBreak features: css and avoidAll

Author: eKoopmans

src/plugin/pagebreaks.js

@@ -1,4 +1,5 @@
 import Worker from '../worker.js';
+import { objType, createElement } from './utils.js';
 
 // Add page-break functionality.
 
@@ -7,17 +8,107 @@ var orig = {
   toContainer: Worker.prototype.toContainer
 };
 
+// Add pageBreak default options to the Worker template.
+Worker.template.opt.pageBreak = {
+  mode: ['css', 'legacy'],  // 'avoid-all', 'css', 'legacy', 'whiteline'
+  before: [],
+  after: [],
+  avoid: []
+};
+
 Worker.prototype.toContainer = function toContainer() {
   return orig.toContainer.call(this).then(function toContainer_pagebreak() {
-    // Find all page-break elements and setup page height.
-    var pageBreaks = this.prop.container.querySelectorAll('.html2pdf__page-break');
+    // Setup root element and inner page height.
+    var root = this.prop.container;
     var pxPageHeight = this.prop.pageSize.inner.px.height;
 
-    // Set each page-break element to a block with the appropriate height.
-    Array.prototype.forEach.call(pageBreaks, function pageBreak_loop(el) {
-      el.style.display = 'block';
+    // Check all requested modes.
+    var modeSrc = [].concat(this.opt.pageBreak.mode);
+    var mode = {
+      avoidAll:   modeSrc.indexOf('avoid-all') !== -1,
+      css:        modeSrc.indexOf('css') !== -1,
+      legacy:     modeSrc.indexOf('legacy') !== -1,
+      whiteline:  modeSrc.indexOf('whiteline') !== -1
+    };
+
+    // Get arrays of all explicitly requested elements.
+    var select = {};
+    ['before', 'after', 'avoid'].forEach(function(key) {
+      var all = mode.avoidAll && key === 'avoid';
+      select[key] = all ? [] : [].concat(this.opt.pageBreak[key]);
+      if (select[key].length > 0) {
+        select[key] = Array.prototype.slice.call(
+          root.querySelectorAll(select[key].join(', ')));
+      }
+    });
+
+    // Get all legacy page-break elements.
+    var legacyEls = root.querySelectorAll('.html2pdf__page-break');
+    legacyEls = Array.prototype.slice.call(legacyEls);
+
+    // Loop through all elements.
+    // TODO: Only loop through all if css option is chosen?
+    var els = root.querySelectorAll('*');
+    Array.prototype.forEach.call(els, function pageBreak_loop(el) {
+      // Setup pagebreak rules based on legacy and avoidAll modes.
+      var rules = {
+        before: false,
+        after:  mode.legacy && legacyEls.indexOf(el) !== -1,
+        avoid:  mode.avoidAll
+      };
+
+      // Add rules for css mode.
+      if (mode.css) {
+        // TODO: Check if this is valid with iFrames.
+        var style = window.getComputedStyle(el);
+        // TODO: Handle 'left' and 'right' correctly.
+        // TODO: Add support for 'avoid' on breakBefore/After.
+        var cssOpt = ['always', 'left', 'right'];
+        rules = {
+          before: rules.before || cssOpt.indexOf(style.breakBefore || style.pageBreakBefore) !== -1,
+          after:  rules.after || cssOpt.indexOf(style.breakAfter || style.pageBreakAfter) !== -1,
+          avoid:  rules.avoid || (style.breakInside || style.pageBreakInside) === 'avoid'
+        };
+      }
+
+      // Add rules for explicit requests.
+      Object.keys(rules).forEach(function(key) {
+        rules[key] = rules[key] || select[key].indexOf(el) !== -1;
+      });
+
+      // Get element position on the screen.
+      // TODO: Subtract the top of the container from clientRect.top/bottom?
       var clientRect = el.getBoundingClientRect();
-      el.style.height = pxPageHeight - (clientRect.top % pxPageHeight) + 'px';
-    }, this);
+
+      // Avoid: Check if a break happens mid-element.
+      if (rules.avoid && !rules.before) {
+        var startPage = Math.floor(clientRect.top / pxPageHeight);
+        var endPage = Math.floor(clientRect.bottom / pxPageHeight);
+        var nPages = Math.abs(clientRect.bottom - clientRect.top) / pxPageHeight;
+
+        // Turn on rules.before if the el is broken and is less than a page long.
+        if (endPage !== startPage && nPages < 1) {
+          rules.before = true;
+        }
+      }
+
+      // Before: Create a padding div to push the element to the next page.
+      if (rules.before) {
+        var pad = createElement('div', {style: {
+          display: 'block',
+          height: pxPageHeight - (clientRect.top % pxPageHeight) + 'px'
+        }});
+        el.parentNode.insertBefore(pad, el);
+      }
+
+      // After: Create a padding div to fill the remaining page.
+      if (rules.after) {
+        var pad = createElement('div', {style: {
+          display: 'block',
+          height: pxPageHeight - (clientRect.bottom % pxPageHeight) + 'px'
+        }});
+        el.parentNode.insertAfter(pad, el);
+      }
+    });
   });
 };