Add a parser to get font data from the default appearance (#12831)

* Add a parser to get font data from the default appearance
 - pdfium & poppler use a special parser too to get these info.

* Update src/core/default_appearance.js

Co-authored-by: Jonas Jenwald <jonas.jenwald@gmail.com>

Co-authored-by: Jonas Jenwald <jonas.jenwald@gmail.com>

src/core/annotation.js

@@ -35,6 +35,10 @@ import {
 } from "../shared/util.js";
 import { Catalog, FileSpec, ObjectLoader } from "./obj.js";
 import { collectActions, getInheritableProperty } from "./core_utils.js";
+import {
+  createDefaultAppearance,
+  parseDefaultAppearance,
+} from "./default_appearance.js";
 import { Dict, isDict, isName, isRef, isStream, Name } from "./primitives.js";
 import { ColorSpace } from "./colorspace.js";
 import { OperatorList } from "./operator_list.js";
@@ -993,6 +997,10 @@ class WidgetAnnotation extends Annotation {
     data.defaultAppearance = isString(defaultAppearance)
       ? defaultAppearance
       : "";
+    this._defaultAppearanceData = parseDefaultAppearance(
+      data.defaultAppearance
+    );
+
     const fieldType = getInheritableProperty({ dict, key: "FT" });
     data.fieldType = isName(fieldType) ? fieldType.name : null;
 
@@ -1288,12 +1296,14 @@ class WidgetAnnotation extends Annotation {
       // Doing so prevents exceptions and allows saving/printing
       // the file as expected.
       this.data.defaultAppearance = "/Helvetica 0 Tf 0 g";
+      this._defaultAppearanceData = parseDefaultAppearance(
+        this.data.defaultAppearance
+      );
     }
 
-    const fontInfo = await this._getFontData(evaluator, task);
-    const [font, fontName] = fontInfo;
-    const fontSize = this._computeFontSize(...fontInfo, totalHeight);
-    this._fontName = fontName;
+    const font = await this._getFontData(evaluator, task);
+    const fontSize = this._computeFontSize(font, totalHeight);
+    this._fontName = this._defaultAppearanceData.fontName.name;
 
     let descent = font.descent;
     if (isNaN(descent)) {
@@ -1364,27 +1374,30 @@ class WidgetAnnotation extends Annotation {
   async _getFontData(evaluator, task) {
     const operatorList = new OperatorList();
     const initialState = {
-      fontSize: 0,
       font: null,
-      fontName: null,
       clone() {
         return this;
       },
     };
 
-    await evaluator.getOperatorList({
-      stream: new StringStream(this.data.defaultAppearance),
-      task,
-      resources: this._fieldResources.mergedResources,
+    const { fontName, fontSize } = this._defaultAppearanceData;
+    await evaluator.handleSetFont(
+      this._fieldResources.mergedResources,
+      [fontName, fontSize],
+      /* fontRef = */ null,
       operatorList,
+      task,
       initialState,
-    });
+      /* fallbackFontDict = */ null
+    );
 
-    return [initialState.font, initialState.fontName, initialState.fontSize];
+    return initialState.font;
   }
 
-  _computeFontSize(font, fontName, fontSize, height) {
-    if (fontSize === null || fontSize === 0) {
+  _computeFontSize(font, height) {
+    let fontSize = this._defaultAppearanceData.fontSize;
+    if (!fontSize) {
+      const { fontColor, fontName } = this._defaultAppearanceData;
       let capHeight;
       if (font.capHeight) {
         capHeight = font.capHeight;
@@ -1403,15 +1416,11 @@ class WidgetAnnotation extends Annotation {
       // 1.5 * capHeight * fontSize seems to be a good value for lineHeight
       fontSize = Math.max(1, Math.floor(height / (1.5 * capHeight)));
 
-      let fontRegex = new RegExp(`/${fontName}\\s+[0-9.]+\\s+Tf`);
-      if (this.data.defaultAppearance.search(fontRegex) === -1) {
-        // The font size is missing
-        fontRegex = new RegExp(`/${fontName}\\s+Tf`);
-      }
-      this.data.defaultAppearance = this.data.defaultAppearance.replace(
-        fontRegex,
-        `/${fontName} ${fontSize} Tf`
-      );
+      this.data.defaultAppearance = createDefaultAppearance({
+        fontSize,
+        fontName,
+        fontColor,
+      });
     }
     return fontSize;
   }

src/core/default_appearance.js

@@ -0,0 +1,96 @@
+/* Copyright 2020 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { isName, Name } from "./primitives.js";
+import { OPS, warn } from "../shared/util.js";
+import { ColorSpace } from "./colorspace.js";
+import { escapePDFName } from "./core_utils.js";
+import { EvaluatorPreprocessor } from "./evaluator.js";
+import { StringStream } from "./stream.js";
+
+class DefaultAppearanceEvaluator extends EvaluatorPreprocessor {
+  constructor(str) {
+    super(new StringStream(str));
+  }
+
+  parse() {
+    const operation = {
+      fn: 0,
+      args: [],
+    };
+    const result = {
+      fontSize: 0,
+      fontName: Name.get(""),
+      fontColor: new Uint8ClampedArray([0, 0, 0]) /* black */,
+    };
+
+    try {
+      while (this.read(operation)) {
+        if (this.stateManager.stateStack.length !== 0) {
+          // Don't get info in save/restore sections.
+          args.length = 0;
+          continue;
+        }
+        const { fn, args } = operation;
+        switch (fn | 0) {
+          case OPS.setFont:
+            const [fontName, fontSize] = args;
+            if (isName(fontName)) {
+              result.fontName = fontName;
+            }
+            if (typeof fontSize === "number" && fontSize > 0) {
+              result.fontSize = fontSize;
+            }
+            break;
+          case OPS.setFillRGBColor:
+            ColorSpace.singletons.rgb.getRgbItem(args, 0, result.fontColor, 0);
+            break;
+          case OPS.setFillGray:
+            ColorSpace.singletons.gray.getRgbItem(args, 0, result.fontColor, 0);
+            break;
+          case OPS.setFillColorSpace:
+            ColorSpace.singletons.cmyk.getRgbItem(args, 0, result.fontColor, 0);
+            break;
+        }
+        args.length = 0;
+      }
+    } catch (reason) {
+      warn(`parseDefaultAppearance - ignoring errors: "${reason}".`);
+    }
+
+    return result;
+  }
+}
+
+// Parse DA to extract font and color information.
+function parseDefaultAppearance(str) {
+  return new DefaultAppearanceEvaluator(str).parse();
+}
+
+// Create default appearance string from some information.
+function createDefaultAppearance({ fontSize, fontName, fontColor }) {
+  let colorCmd;
+  if (fontColor.every(c => c === 0)) {
+    colorCmd = "0 g";
+  } else {
+    colorCmd =
+      Array.from(fontColor)
+        .map(c => (c / 255).toFixed(2))
+        .join(" ") + " rg";
+  }
+  return `/${escapePDFName(fontName.name)} ${fontSize} Tf ${colorCmd}`;
+}
+
+export { createDefaultAppearance, parseDefaultAppearance };

src/core/evaluator.js

@@ -797,12 +797,10 @@ class PartialEvaluator {
     fallbackFontDict = null
   ) {
     // TODO(mack): Not needed?
-    var fontName,
-      fontSize = 0;
+    var fontName;
     if (fontArgs) {
       fontArgs = fontArgs.slice();
       fontName = fontArgs[0].name;
-      fontSize = fontArgs[1];
     }
 
     return this.loadFont(fontName, fontRef, resources, fallbackFontDict)
@@ -835,8 +833,6 @@ class PartialEvaluator {
       })
       .then(translated => {
         state.font = translated.font;
-        state.fontSize = fontSize;
-        state.fontName = fontName;
         translated.send(this.handler);
         return translated.loadedName;
       });
@@ -3714,7 +3710,7 @@ class TranslatedFont {
 }
 
 class StateManager {
-  constructor(initialState) {
+  constructor(initialState = new EvalState()) {
     this.state = initialState;
     this.stateStack = [];
   }
@@ -3985,7 +3981,7 @@ class EvaluatorPreprocessor {
     return shadow(this, "MAX_INVALID_PATH_OPS", 20);
   }
 
-  constructor(stream, xref, stateManager) {
+  constructor(stream, xref, stateManager = new StateManager()) {
     // TODO(mduan): pass array of knownCommands rather than this.opMap
     // dictionary
     this.parser = new Parser({
@@ -4126,4 +4122,4 @@ class EvaluatorPreprocessor {
   }
 }
 
-export { PartialEvaluator };
+export { EvaluatorPreprocessor, PartialEvaluator };