Implement changes suggested by Zarko and our subsequent conversations:

 - Add a way to set the minimum PDF version
 - Add a way to force the PDF version
 - Have isEncrypted return true if an /Encrypt dictionary exists even
   when we can't read the file
 - Allow qpdf_init_write to be called multiple times
 - Update some comments in headers


git-svn-id: svn+q:///qpdf/trunk@748 71b93d88-0707-0410-a8cf-f5a4172ac649

2 files changed, 44 insertions, 2 deletions

diff --git a/include/qpdf/QPDFWriter.hh b/include/qpdf/QPDFWriter.hh
index 7d62e476..b5f23457 100644
--- a/include/qpdf/QPDFWriter.hh
+++ b/include/qpdf/QPDFWriter.hh
@@ -34,7 +34,13 @@ class Pl_Count;
 class QPDFWriter
 {
   public:
-    // Passing null as filename means write to stdout
+    // Passing null as filename means write to stdout.  QPDFWriter
+    // will create a zero-length output file upon construction.  If
+    // write fails, the empty or partially written file will not be
+    // deleted.  This is by design: sometimes the partial file may be
+    // useful for tracking down problems.  If your application doesn't
+    // want the partially written file to be left behind, you should
+    // delete it the eventual call to write fails.
     DLL_EXPORT
     QPDFWriter(QPDF& pdf, char const* filename);
     DLL_EXPORT
@@ -78,6 +84,30 @@ class QPDFWriter
     DLL_EXPORT
     void setQDFMode(bool);
 
+    // Set the minimum PDF version.  If the PDF version of the input
+    // file (or previously set minimum version) is less than the
+    // version passed to this method, the PDF version of the output
+    // file will be set to this value.  If the original PDF file's
+    // version or previously set minimum version is already this
+    // version or later, the original file's version will be used.
+    // QPDFWriter automatically sets the minimum version to 1.4 when
+    // R3 encryption parameters are used, and to 1.5 when object
+    // streams are used.
+    DLL_EXPORT
+    void setMinimumPDFVersion(std::string const&);
+
+    // Force the PDF version of the output file to be a given version.
+    // Use of this function may create PDF files that will not work
+    // properly with older PDF viewers.  When a PDF version is set
+    // using this function, qpdf will use this version even if the
+    // file contains features that are not supported in that version
+    // of PDF.  In other words, you should only use this function if
+    // you are sure the PDF file in question has no features of newer
+    // versions of PDF or if you are willing to create files that old
+    // viewers may try to open but not be able to properly interpret.
+    DLL_EXPORT
+    void forcePDFVersion(std::string const&);
+
     // Cause a static /ID value to be generated.  Use only in test
     // suites.
     DLL_EXPORT
@@ -241,6 +271,7 @@ class QPDFWriter
     std::string id1;		// for /ID key of
     std::string id2;		// trailer dictionary
     std::string min_pdf_version;
+    std::string forced_pdf_version;
     int encryption_dict_objid;
     std::string cur_data_key;
     std::list<PointerHolder<Pipeline> > to_delete;
diff --git a/include/qpdf/qpdf-c.h b/include/qpdf/qpdf-c.h
index 11dae4f1..fab8112b 100644
--- a/include/qpdf/qpdf-c.h
+++ b/include/qpdf/qpdf-c.h
@@ -189,7 +189,12 @@ extern "C" {
     /* Supply the name of the file to be written and initialize the
      * qpdf_data object to handle writing operations.  This function
      * also attempts to create the file.  The PDF data is not written
-     * until the call to qpdf_write.
+     * until the call to qpdf_write.  qpdf_init_write may be called
+     * multiple times for the same qpdf_data object.  When
+     * qpdf_init_write is called, all information from previous calls
+     * to functions that set write parameters (qpdf_set_linearization,
+     * etc.) is lost, so any write parameter functions must be called
+     * again.
      */
     DLL_EXPORT
     QPDF_ERROR_CODE qpdf_init_write(qpdf_data qpdf, char const* filename);
@@ -256,6 +261,12 @@ extern "C" {
     DLL_EXPORT
     void qpdf_set_linearization(qpdf_data qpdf, QPDF_BOOL value);
 
+    DLL_EXPORT
+    void qpdf_set_minimum_pdf_version(qpdf_data qpdf, char const* version);
+
+    DLL_EXPORT
+    void qpdf_force_pdf_version(qpdf_data qpdf, char const* version);
+
     /* Do actual write operation. */
     DLL_EXPORT
     QPDF_ERROR_CODE qpdf_write(qpdf_data qpdf);