Generate default AP stream for underline annotation.

core/fpdfdoc/cpvt_generateap.cpp

Index: core/fpdfdoc/cpvt_generateap.cpp
diff --git a/core/fpdfdoc/cpvt_generateap.cpp b/core/fpdfdoc/cpvt_generateap.cpp
index 56b661271702cb5e3f6ad2c75f6ccad1b58d056a..6d43b03ae935288b04fa2f5da8967d7b29193ffe 100644
--- a/core/fpdfdoc/cpvt_generateap.cpp
+++ b/core/fpdfdoc/cpvt_generateap.cpp
@@ -443,6 +443,23 @@ bool GenerateWidgetAP(CPDF_Document* pDoc,
   return true;
 }
 
+CPDF_Dictionary* GenerateExtGStateDict(CFX_ByteString sName,
+                                       FX_FLOAT fCAForStroke,
+                                       FX_FLOAT fCAForNonStroke,
+                                       CFX_ByteString sBlendMode) {
+  CPDF_Dictionary* pGSDict = new CPDF_Dictionary;
+  pGSDict->SetAtString("Type", "ExtGState");
+  pGSDict->SetAtNumber("CA", fCAForStroke);
+  pGSDict->SetAtNumber("ca", fCAForNonStroke);
+  pGSDict->SetAtBoolean("AIS", false);
+  pGSDict->SetAtString("BM", sBlendMode);
+
+  CPDF_Dictionary* pExtGStateDict = new CPDF_Dictionary;
+  pExtGStateDict->SetAt(sName, pGSDict);
+
+  return pExtGStateDict;
+}
+
 }  // namespace
 
 bool FPDF_GenerateAP(CPDF_Document* pDoc, CPDF_Dictionary* pAnnotDict) {
@@ -501,7 +518,8 @@ bool CPVT_GenerateAP::GenerateHighlightAP(CPDF_Document* pDoc,
     return false;
 
   CFX_ByteTextBuf sAppStream;
-  sAppStream << "/GS gs ";
+  CFX_ByteString sExtGSDictName = "GS";
+  sAppStream << "/" << sExtGSDictName << " gs ";
 
   if (pAnnotDict->KeyExist("C")) {
     CPDF_Array* pColor = pAnnotDict->GetArrayBy("C");
@@ -536,18 +554,71 @@ bool CPVT_GenerateAP::GenerateHighlightAP(CPDF_Document* pDoc,
   pStreamDict->SetAtMatrix("Matrix", CFX_Matrix());
   pStreamDict->SetAtRect("BBox", rect);
 
-  CPDF_Dictionary* pGSDict = new CPDF_Dictionary;
-  pGSDict->SetAtString("Type", "ExtGState");
-  pGSDict->SetAtNumber("ca", 1);
-  pGSDict->SetAtNumber("CA", 1);
-  pGSDict->SetAtBoolean("AIS", false);
-  pGSDict->SetAtString("BM", "Multiply");
+  CPDF_Dictionary* pResourceDict = new CPDF_Dictionary;
+  FX_FLOAT fCAForStroke =
+      pAnnotDict->KeyExist("CA") ? pAnnotDict->GetNumberBy("CA") : 1.0;
+  FX_FLOAT fCAForNonStroke =
+      pAnnotDict->KeyExist("ca") ? pAnnotDict->GetNumberBy("ca") : 1.0;

[jaepark, 2016/08/01 23:10:52]

Although I think this is correct implementation, other PDF viewers (including
Adobe Acrobat Reader), are only depending on the value of "CA" to determine the
opacity of the annotation. 

For example, for highlight annotation, if CA is 1.0 and ca is 0.5, I think the
opacity should be 0.5 since Highlight is fill (non stroke) operation. However,
Acrobat Reader shows 1.0 opacity.

Also, Okular does not generate "ca" field when creating Highlight annotation (it
only generates "CA" field).

I'm not sure if I'm misinterpreting the spec of CA and ca in ExtGState (SECTION
4.3.4 Graphics State Parameter Dictionaries, TABLE 4.8 Entries in a graphics
state parameter dictionary).

[Lei Zhang, 2016/08/01 23:16:24]

Have you considered adding more tests to exercise this code and see what the
correct output should be?

You can write your own PDFs by hand. Take a look at testing/resources/*.in, and
testing/tools/fixup_pdf_template.py.

+  pResourceDict->SetAt("ExtGState",
+                       GenerateExtGStateDict(sExtGSDictName, fCAForStroke,
+                                             fCAForNonStroke, "Multiply"));
 
-  CPDF_Dictionary* pExtGStateDict = new CPDF_Dictionary;
-  pExtGStateDict->SetAt("GS", pGSDict);
+  pStreamDict->SetAt("Resources", pResourceDict);
+  return true;
+}
+
+bool CPVT_GenerateAP::GenerateUnderlineAP(CPDF_Document* pDoc,
+                                          CPDF_Dictionary* pAnnotDict) {
+  // If AP dictionary exists, we use the appearance defined in the
+  // existing AP dictionary.
+  if (pAnnotDict->KeyExist("AP"))
+    return false;
+
+  CFX_ByteTextBuf sAppStream;
+  CFX_ByteString sExtGSDictName = "GS";
+  sAppStream << "/" << sExtGSDictName << " gs ";
+
+  if (pAnnotDict->KeyExist("C")) {
+    CPDF_Array* pColor = pAnnotDict->GetArrayBy("C");
+    CPVT_Color color = CPVT_Color::ParseColor(*pColor);
+    sAppStream << CPVT_GenerateAP::GenerateColorAP(color, FALSE);
+  } else {
+    // Defaults to 0x000000 color for underline.
+    sAppStream << "0 0 0 RG\n";
+  }
+
+  CFX_FloatRect rect = pAnnotDict->GetRectBy("Rect");
+  rect.Normalize();
+
+  FX_FLOAT fLineWidth = 1.0;
+  sAppStream << fLineWidth << " w " << rect.left << " "
+             << rect.bottom + fLineWidth << " m " << rect.right << " "
+             << rect.bottom + fLineWidth << " l S\n";
+
+  CPDF_Dictionary* pAPDict = new CPDF_Dictionary;
+  pAnnotDict->SetAt("AP", pAPDict);
+
+  CPDF_Stream* pNormalStream = new CPDF_Stream(nullptr, 0, nullptr);
+  int32_t objnum = pDoc->AddIndirectObject(pNormalStream);
+  pAnnotDict->GetDictBy("AP")->SetAtReference("N", pDoc, objnum);
+
+  pNormalStream->SetData(reinterpret_cast<uint8_t*>(sAppStream.GetBuffer()),
+                         sAppStream.GetSize(), FALSE, FALSE);
+
+  CPDF_Dictionary* pStreamDict = pNormalStream->GetDict();
+  pStreamDict->SetAtInteger("FormType", 1);
+  pStreamDict->SetAtString("Subtype", "Form");
+  pStreamDict->SetAtMatrix("Matrix", CFX_Matrix());
+  pStreamDict->SetAtRect("BBox", rect);
 
   CPDF_Dictionary* pResourceDict = new CPDF_Dictionary;
-  pResourceDict->SetAt("ExtGState", pExtGStateDict);
+  FX_FLOAT fCAForStroke =
+      pAnnotDict->KeyExist("CA") ? pAnnotDict->GetNumberBy("CA") : 1.0;
+  FX_FLOAT fCAForNonStroke =
+      pAnnotDict->KeyExist("ca") ? pAnnotDict->GetNumberBy("ca") : 1.0;
+  pResourceDict->SetAt("ExtGState",
+                       GenerateExtGStateDict(sExtGSDictName, fCAForStroke,
+                                             fCAForNonStroke, "Normal"));
 
   pStreamDict->SetAt("Resources", pResourceDict);
   return true;