Document Creation API and Test for Go

PDFTronGo/CMakeLists.txt

@@ -65,6 +65,70 @@ execute_process(
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
 )
 
+# ------------------------------------------------------------------------------
+# HACK: Post-processing of SWIG-generated Go bindings
+#
+# The C++ API uses ElementRef<T> as a value-type wrapper representing an optional
+# reference (IsValid() + GetElement()).
+#
+# Attempts to erase or re-map ElementRef<T> using SWIG Go typemaps (gotype,
+# ctype, imtype, etc.) lead to unstable or invalid generated code, including:
+#   - incorrect C wrapper signatures (value return vs pointer return)
+#   - broken Go code (C++ typedefs emitted into .go files)
+#   - ABI mismatches and compilation errors
+#
+# To produce a stable and idiomatic Go API, we intentionally:
+#   1) Let SWIG generate bindings using ElementRef<T> internally
+#   2) Use Go-side typemaps only for final semantic conversion (Ref -> T | nil)
+#   3) Post-process the generated *.go files to erase the use of artificial '*Ref'
+#      types from the public Go API
+#
+# This post-processing step rewrites:
+#   - function return types (e.g. FooRef -> Foo)
+#   - local variables using Ref types
+# ------------------------------------------------------------------------------
+file(GLOB_RECURSE GO_FILES "${BUILD_DIR}/*.go")
+
+set(ELEMENT_REF_TYPES
+    ContentNode
+    Paragraph
+    TextRun
+    Table
+    TableRow
+    TableCell
+    List
+    ListItem
+)
+
+file(GLOB_RECURSE GO_FILES "${BUILD_DIR}/*.go")
+
+foreach(GO_FILE ${GO_FILES})
+    file(READ "${GO_FILE}" GO_FILE_CONTENT)
+
+    foreach(TYPE ${ELEMENT_REF_TYPES})
+        # Fix function return types:
+        #   (_swig_ret ContentNodeRef) -> (_swig_ret ContentNode)
+        string(REPLACE
+            "As${TYPE}() (_swig_ret ${TYPE}Ref)"
+            "As${TYPE}() (_swig_ret ${TYPE})"
+            GO_FILE_CONTENT
+            "${GO_FILE_CONTENT}"
+        )
+
+        # Fix local variable declarations:
+        #   var swig_r_1 ContentNodeRef -> var swig_r_1 ContentNode
+        string(REPLACE
+            "var swig_r_1 ${TYPE}Ref"
+            "var swig_r_1 ${TYPE}"
+            GO_FILE_CONTENT
+            "${GO_FILE_CONTENT}"
+        )
+    endforeach()
+
+    file(WRITE "${GO_FILE}" "${GO_FILE_CONTENT}")
+endforeach()
+
+
 if ("${SOURCE_GEN_RESULT}" STREQUAL "0")
     message(STATUS "Generating sources for Go bindings using swig... OK")
 else ()

PDFTronGo/pdftron.i

@@ -206,6 +206,10 @@
     #include "SDF/ResultSnapshot.h"
     #include "SDF/DocSnapshot.h"
 
+    // header files in /PDFNetC/Headers/Layout
+    #include "Layout/FlowDocument.h"
+    #include "Layout/ContentTree.h"
+
     using namespace pdftron;
     using namespace FDF;
     using namespace Filters;
@@ -378,6 +382,7 @@ namespace pdftron {
 %template (FieldIterator) pdftron::Common::Iterator<pdftron::PDF::Field>;
 %template (CharIterator) pdftron::Common::Iterator<TRN_CharData>;
 %template (DigitalSignatureFieldIterator) pdftron::Common::Iterator<pdftron::PDF::DigitalSignatureField>;
+%template (ContentNodeIterator) pdftron::Common::Iterator<pdftron::Layout::ContentElement>;
 
 //----------------------------------------------------------------------------------------------
 
@@ -548,6 +553,53 @@ namespace pdftron {
 %include "PDF/WebFontDownloader.h"
 %include "PDF/PDFNetInternalTools.h"
 
+/*
+ * Attempting to handle ElementRef<T> via SWIG typemaps (gotype/ctype/imtype)
+ * causes the SWIG Go backend to generate invalid or unstable code:
+ *   - incorrect C wrapper signatures (value vs pointer returns)
+ *   - broken Go code (C++ typedefs leaked into .go files)
+ *   - ABI mismatches and undefined behavior
+ *
+ * This typemap exists only to perform the last-step conversion from
+ * ElementRef<T> semantics to idiomatic Go semantics:
+ *
+ *     ElementRef<T>   ->   T | nil
+ *
+ * The remaining cleanup (removing Ref suffixes, fixing return types, etc.)
+ * is handled by a controlled post-processing step on the generated Go code
+ * in CMakeLists.txt.
+ */
+%define ELEMENT_REF_GOOUT(T)
+%typemap(goout) pdftron::Layout::ElementRef<T> {
+    if (!($1).IsValid()) {
+        $result = nil
+    } else {
+        $result = ($1).GetElement()
+    }
+}
+%enddef
+
+ELEMENT_REF_GOOUT(pdftron::Layout::ContentNode)
+ELEMENT_REF_GOOUT(pdftron::Layout::Paragraph)
+ELEMENT_REF_GOOUT(pdftron::Layout::TextRun)
+ELEMENT_REF_GOOUT(pdftron::Layout::Table)
+ELEMENT_REF_GOOUT(pdftron::Layout::TableRow)
+ELEMENT_REF_GOOUT(pdftron::Layout::TableCell)
+ELEMENT_REF_GOOUT(pdftron::Layout::List)
+ELEMENT_REF_GOOUT(pdftron::Layout::ListItem)
+
+%include "Layout/ContentTree.h"
+%include "Layout/FlowDocument.h"
+
+%template(ContentNodeRef) pdftron::Layout::ElementRef<pdftron::Layout::ContentNode>;
+%template(ParagraphRef)    pdftron::Layout::ElementRef<pdftron::Layout::Paragraph>;
+%template(TextRunRef)      pdftron::Layout::ElementRef<pdftron::Layout::TextRun>;
+%template(TableRef)        pdftron::Layout::ElementRef<pdftron::Layout::Table>;
+%template(TableRowRef)     pdftron::Layout::ElementRef<pdftron::Layout::TableRow>;
+%template(TableCellRef)    pdftron::Layout::ElementRef<pdftron::Layout::TableCell>;
+%template(ListRef)         pdftron::Layout::ElementRef<pdftron::Layout::List>;
+%template(ListItemRef)     pdftron::Layout::ElementRef<pdftron::Layout::ListItem>;
+
 //Extend Initialize method to call overloaded one internally
 %extend pdftron::PDFNet{
         public: