XFA - Improve text layout

- support paragraph margins, line height, letter spacing, ...
  - compute missing dimensions from fields based almost on the dimensions of caption contents.

src/core/xfa/text.js

@@ -15,17 +15,30 @@
 
 import { selectFont } from "./fonts.js";
 
-const WIDTH_FACTOR = 1.2;
-const HEIGHT_FACTOR = 1.2;
+const WIDTH_FACTOR = 1.05;
 
 class FontInfo {
-  constructor(xfaFont, fontFinder) {
+  constructor(xfaFont, margin, lineHeight, fontFinder) {
+    this.lineHeight = lineHeight;
+    this.paraMargin = margin || {
+      top: 0,
+      bottom: 0,
+      left: 0,
+      right: 0,
+    };
+
     if (!xfaFont) {
       [this.pdfFont, this.xfaFont] = this.defaultFont(fontFinder);
       return;
     }
 
-    this.xfaFont = xfaFont;
+    this.xfaFont = {
+      typeface: xfaFont.typeface,
+      posture: xfaFont.posture,
+      weight: xfaFont.weight,
+      size: xfaFont.size,
+      letterSpacing: xfaFont.letterSpacing,
+    };
     const typeface = fontFinder.find(xfaFont.typeface);
     if (!typeface) {
       [this.pdfFont, this.xfaFont] = this.defaultFont(fontFinder);
@@ -54,6 +67,7 @@ class FontInfo {
         posture: "normal",
         weight: "normal",
         size: 10,
+        letterSpacing: 0,
       };
       return [pdfFont, xfaFont];
     }
@@ -63,29 +77,60 @@ class FontInfo {
       posture: "normal",
       weight: "normal",
       size: 10,
+      letterSpacing: 0,
     };
     return [null, xfaFont];
   }
 }
 
 class FontSelector {
-  constructor(defaultXfaFont, fontFinder) {
+  constructor(
+    defaultXfaFont,
+    defaultParaMargin,
+    defaultLineHeight,
+    fontFinder
+  ) {
     this.fontFinder = fontFinder;
-    this.stack = [new FontInfo(defaultXfaFont, fontFinder)];
+    this.stack = [
+      new FontInfo(
+        defaultXfaFont,
+        defaultParaMargin,
+        defaultLineHeight,
+        fontFinder
+      ),
+    ];
   }
 
-  pushFont(xfaFont) {
+  pushData(xfaFont, margin, lineHeight) {
     const lastFont = this.stack[this.stack.length - 1];
-    for (const name of ["typeface", "posture", "weight", "size"]) {
+    for (const name of [
+      "typeface",
+      "posture",
+      "weight",
+      "size",
+      "letterSpacing",
+    ]) {
       if (!xfaFont[name]) {
         xfaFont[name] = lastFont.xfaFont[name];
       }
     }
 
-    const fontInfo = new FontInfo(xfaFont, this.fontFinder);
+    for (const name of ["top", "bottom", "left", "right"]) {
+      if (isNaN(margin[name])) {
+        margin[name] = lastFont.paraMargin[name];
+      }
+    }
+
+    const fontInfo = new FontInfo(
+      xfaFont,
+      margin,
+      lineHeight || lastFont.lineHeight,
+      this.fontFinder
+    );
     if (!fontInfo.pdfFont) {
       fontInfo.pdfFont = lastFont.pdfFont;
     }
+
     this.stack.push(fontInfo);
   }
 
@@ -102,19 +147,30 @@ class FontSelector {
  * Compute a text area dimensions based on font metrics.
  */
 class TextMeasure {
-  constructor(defaultXfaFont, fonts) {
+  constructor(defaultXfaFont, defaultParaMargin, defaultLineHeight, fonts) {
     this.glyphs = [];
-    this.fontSelector = new FontSelector(defaultXfaFont, fonts);
+    this.fontSelector = new FontSelector(
+      defaultXfaFont,
+      defaultParaMargin,
+      defaultLineHeight,
+      fonts
+    );
+    this.extraHeight = 0;
   }
 
-  pushFont(xfaFont) {
-    return this.fontSelector.pushFont(xfaFont);
+  pushData(xfaFont, margin, lineHeight) {
+    this.fontSelector.pushData(xfaFont, margin, lineHeight);
   }
 
   popFont(xfaFont) {
     return this.fontSelector.popFont();
   }
 
+  addPara() {
+    const lastFont = this.fontSelector.topFont();
+    this.extraHeight += lastFont.paraMargin.top + lastFont.paraMargin.bottom;
+  }
+
   addString(str) {
     if (!str) {
       return;
@@ -123,8 +179,11 @@ class TextMeasure {
     const lastFont = this.fontSelector.topFont();
     const fontSize = lastFont.xfaFont.size;
     if (lastFont.pdfFont) {
+      const letterSpacing = lastFont.xfaFont.letterSpacing;
       const pdfFont = lastFont.pdfFont;
-      const lineHeight = Math.round(Math.max(1, pdfFont.lineHeight) * fontSize);
+      const lineHeight =
+        lastFont.lineHeight ||
+        Math.round(Math.max(1, pdfFont.lineHeight) * fontSize);
       const scale = fontSize / 1000;
 
       for (const line of str.split(/[\u2029\n]/)) {
@@ -133,7 +192,7 @@ class TextMeasure {
 
         for (const glyph of glyphs) {
           this.glyphs.push([
-            glyph.width * scale,
+            glyph.width * scale + letterSpacing,
             lineHeight,
             glyph.unicode === " ",
             false,
@@ -218,9 +277,9 @@ class TextMeasure {
     }
 
     width = Math.max(width, currentLineWidth);
-    height += currentLineHeight;
+    height += currentLineHeight + this.extraHeight;
 
-    return { width: WIDTH_FACTOR * width, height: HEIGHT_FACTOR * height };
+    return { width: WIDTH_FACTOR * width, height };
   }
 }