Ensure that there's always a setFont (Tf) operator before text rendering operators (issue 11651)

The PDF document in question is *corrupt*, since it contains multiple instances of incorrect operators.
We obviously don't want to slow down parsing of *all* documents (since most are valid), just to accommodate a particular bad PDF generator, hence the reason for the inline check before calling the `ensureStateFont` method.

src/core/evaluator.js

@@ -795,6 +795,26 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       return glyphs;
     },
 
+    ensureStateFont(state) {
+      if (state.font) {
+        return;
+      }
+      const reason = new FormatError(
+        "Missing setFont (Tf) operator before text rendering operator."
+      );
+
+      if (this.options.ignoreErrors) {
+        // Missing setFont operator before text rendering operator -- sending
+        // unsupported feature notification and allow rendering to continue.
+        this.handler.send("UnsupportedFeature", {
+          featureId: UNSUPPORTED_FEATURES.font,
+        });
+        warn(`ensureStateFont: "${reason}".`);
+        return;
+      }
+      throw reason;
+    },
+
     setGState: function PartialEvaluator_setGState(
       resources,
       gState,
@@ -1364,9 +1384,17 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
               );
               return;
             case OPS.showText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               args[0] = self.handleText(args[0], stateManager.state);
               break;
             case OPS.showSpacedText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               var arr = args[0];
               var combinedGlyphs = [];
               var arrLength = arr.length;
@@ -1386,11 +1414,19 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
               fn = OPS.showText;
               break;
             case OPS.nextLineShowText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               operatorList.addOp(OPS.nextLine);
               args[0] = self.handleText(args[0], stateManager.state);
               fn = OPS.showText;
               break;
             case OPS.nextLineSetSpacingShowText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               operatorList.addOp(OPS.nextLine);
               operatorList.addOp(OPS.setWordSpacing, [args.shift()]);
               operatorList.addOp(OPS.setCharSpacing, [args.shift()]);
@@ -2056,6 +2092,10 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
               textState.textLineMatrix = IDENTITY_MATRIX.slice();
               break;
             case OPS.showSpacedText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               var items = args[0];
               var offset;
               for (var j = 0, jj = items.length; j < jj; j++) {
@@ -2105,14 +2145,26 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
               }
               break;
             case OPS.showText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               buildTextContentItem(args[0]);
               break;
             case OPS.nextLineShowText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               flushTextContentItem();
               textState.carriageReturn();
               buildTextContentItem(args[0]);
               break;
             case OPS.nextLineSetSpacingShowText:
+              if (!stateManager.state.font) {
+                self.ensureStateFont(stateManager.state);
+                continue;
+              }
               flushTextContentItem();
               textState.wordSpacing = args[0];
               textState.charSpacing = args[1];

test/pdfs/.gitignore

@@ -89,6 +89,7 @@
 !issue11279.pdf
 !issue11362.pdf
 !issue11578_reduced.pdf
+!issue11651.pdf
 !bad-PageLabels.pdf
 !decodeACSuccessive.pdf
 !filled-background.pdf

test/test_manifest.json

@@ -67,6 +67,20 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue11651-eq",
+       "file": "pdfs/issue11651.pdf",
+       "md5": "375233ad8dc4181a06148f8412f35b91",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
+    {  "id": "issue11651-text",
+       "file": "pdfs/issue11651.pdf",
+       "md5": "375233ad8dc4181a06148f8412f35b91",
+       "rounds": 1,
+       "link": false,
+       "type": "text"
+    },
     {  "id": "issue1293",
        "file": "pdfs/issue1293r.pdf",
        "md5": "4a098f5051f34fab036f5bbe88f8deef",