vcl pdfium render: handle widget annotations for form fields

Note that we render the bitmaps without FPDF_ANNOT, so comments are not
rendered into the bitmaps, rather we create them on top of the bitmaps
in Draw, explicitly.

FPDF_FFLDraw() draws content which is already an annotation, but not yet
interactive content; so this just fixes "missing text", as far as the
user is concerned.

Verified that e.g. vcl/qa/cppunit/data/PangramAcrobatAnnotations.pdf
indeed still doesn't render comments into bitmaps after this.

(cherry picked from commit 92cba30d5ce45e4f4a9516a80c9fe9915add6905)

Conflicts:
	include/vcl/filter/PDFiumLibrary.hxx
	vcl/qa/cppunit/PDFiumLibraryTest.cxx
	vcl/source/filter/ipdf/pdfread.cxx
	vcl/source/pdf/PDFiumLibrary.cxx

Change-Id: I2b74d585729305cc1d3a9fefa258d4d76d1bd038
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/115167
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

3 files changed, 145 insertions, 0 deletions

diff --git a/vcl/qa/cppunit/PDFiumLibraryTest.cxx b/vcl/qa/cppunit/PDFiumLibraryTest.cxx
index f18681c0adda..54f5e70e00d3 100644
--- a/vcl/qa/cppunit/PDFiumLibraryTest.cxx
+++ b/vcl/qa/cppunit/PDFiumLibraryTest.cxx
@@ -25,6 +25,8 @@
 #include <tools/stream.hxx>
 
 #include <vcl/filter/PDFiumLibrary.hxx>
+#include <vcl/pdfread.hxx>
+#include <vcl/bitmapaccess.hxx>
 
 class PDFiumLibraryTest : public test::BootstrapFixtureBase
 {
@@ -39,6 +41,7 @@ class PDFiumLibraryTest : public test::BootstrapFixtureBase
     void testAnnotationsMadeInEvince();
     void testAnnotationsMadeInAcrobat();
     void testTools();
+    void testFormFields();
 
     CPPUNIT_TEST_SUITE(PDFiumLibraryTest);
     CPPUNIT_TEST(testDocument);
@@ -47,6 +50,7 @@ class PDFiumLibraryTest : public test::BootstrapFixtureBase
     CPPUNIT_TEST(testAnnotationsMadeInEvince);
     CPPUNIT_TEST(testAnnotationsMadeInAcrobat);
     CPPUNIT_TEST(testTools);
+    CPPUNIT_TEST(testFormFields);
     CPPUNIT_TEST_SUITE_END();
 };
 
@@ -287,6 +291,41 @@ void PDFiumLibraryTest::testAnnotationsMadeInAcrobat()
     }
 }
 
+void PDFiumLibraryTest::testFormFields()
+{
+    // Given a document with a form field that looks like plain text:
+    OUString aURL = getFullUrl(u"form-fields.pdf");
+    SvFileStream aFileStream(aURL, StreamMode::READ);
+    SvMemoryStream aMemory;
+    aMemory.WriteStream(aFileStream);
+    aMemory.Seek(0);
+
+    // When rendering its first (and only) page to a bitmap:
+    std::vector<Bitmap> aBitmaps;
+    int nRet = vcl::RenderPDFBitmaps(aMemory.GetData(), aMemory.GetSize(), aBitmaps);
+    CPPUNIT_ASSERT(nRet);
+    CPPUNIT_ASSERT_EQUAL(static_cast<size_t>(1), aBitmaps.size());
+
+    // Then make sure the bitmap contains that text:
+    Bitmap aBitmap = aBitmaps[0];
+    BitmapReadAccess aAccess(aBitmap);
+    Size aSize = aBitmap.GetSizePixel();
+    std::set<sal_uInt32> aColors;
+    for (long y = 0; y < aSize.Height(); ++y)
+    {
+        for (long x = 0; x < aSize.Width(); ++x)
+        {
+            aColors.insert(static_cast<sal_uInt32>(aAccess.GetPixel(y, x)));
+        }
+    }
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected greater than: 1
+    // - Actual  : 1
+    // i.e. at least black text and white background is expected (possibly more, due to
+    // anti-aliasing), but nothing was rendered.
+    CPPUNIT_ASSERT_GREATER(static_cast<size_t>(1), aColors.size());
+}
+
 void PDFiumLibraryTest::testTools()
 {
     OUString sConverted = vcl::pdf::convertPdfDateToISO8601("D:20200612201322+02'00");
diff --git a/vcl/qa/cppunit/data/form-fields.pdf b/vcl/qa/cppunit/data/form-fields.pdf
new file mode 100644
index 000000000000..a014b36c9821
--- /dev/null
+++ b/vcl/qa/cppunit/data/form-fields.pdf
@@ -0,0 +1,95 @@
+%PDF-1.7
+% ò¤ô
+1 0 obj <<
+  /Type /Catalog
+  /Pages 5 0 R
+>>
+endobj
+
+2 0 obj <<
+  /Length 0
+>>
+stream
+endstream 
+endobj
+
+3 0 obj <<
+  /Font <<
+    /TT1 4 0 R
+  >>
+>>
+endobj
+
+4 0 obj <<
+ /Type /Font
+ /Subtype /Type1
+ /Name /TT1
+ /BaseFont/Helvetica
+>>
+endobj
+
+5 0 obj <<
+  /Type /Pages
+  /Kids [6 0 R]
+  /Count 1
+  /MediaBox [ 0 0 612 446 ]
+>>
+endobj
+
+6 0 obj <<
+  /Type /Page
+  /Parent 5 0 R
+  /Resources 3 0 R
+  /Contents 2 0 R
+  /Annots [7 0 R]
+>>
+endobj
+
+7 0 obj <<
+  /Type /Annot
+  /Subtype /Widget
+  /T (T)
+  /V (V)
+  /DA (/Helv 0 Tf 0 g)
+  /Rect [ 0 0 612 446 ]
+  /FT /Tx
+  /AP <<
+    /N 8 0 R
+  >>
+>>
+endobj
+
+8 0 obj <<
+  /Type /XObject
+  /Subtype /Form
+  /Matrix [1.0 0.0 0.0 1.0 0.0 0.0]
+  /Resources 3 0 R
+  /BBox [ 0 0 612 446 ]
+  /Length 55
+>>
+stream
+  BT
+  /TT1 24 Tf
+  1 0 0 1 260 254 Tm
+  (test)Tj
+  ET
+endstream 
+endobj
+xref
+0 9
+0000000000 65535 f 
+0000000015 00000 n 
+0000000069 00000 n 
+0000000121 00000 n 
+0000000174 00000 n 
+0000000259 00000 n 
+0000000351 00000 n 
+0000000458 00000 n 
+0000000616 00000 n 
+trailer <<
+  /Root 1 0 R
+  /Size 9
+>>
+startxref
+836
+%%EOF
diff --git a/vcl/source/filter/ipdf/pdfread.cxx b/vcl/source/filter/ipdf/pdfread.cxx
index e4af2a0e865b..acc45bc4d9e4 100644
--- a/vcl/source/filter/ipdf/pdfread.cxx
+++ b/vcl/source/filter/ipdf/pdfread.cxx
@@ -15,6 +15,7 @@
 #include <fpdfview.h>
 #include <fpdf_edit.h>
 #include <fpdf_save.h>
+#include <fpdf_formfill.h>
 #endif
 
 #include <vcl/graph.hxx>
@@ -174,6 +175,10 @@ size_t RenderPDFBitmaps(const void* pBuffer, int nSize, std::vector<Bitmap>& rBi
     if (!pPdfDocument)
         return 0;
 
+    FPDF_FORMFILLINFO aFormCallbacks = {};
+    aFormCallbacks.version = 1;
+    FPDF_FORMHANDLE pFormHandle = FPDFDOC_InitFormFillEnvironment(pPdfDocument, &aFormCallbacks);
+
     const int nPageCount = FPDF_GetPageCount(pPdfDocument);
     if (nPages <= 0)
         nPages = nPageCount;
@@ -207,6 +212,10 @@ size_t RenderPDFBitmaps(const void* pBuffer, int nSize, std::vector<Bitmap>& rBi
         FPDF_RenderPageBitmap(pPdfBitmap, pPdfPage, /*start_x=*/0, /*start_y=*/0, nPageWidth,
                               nPageHeight, /*rotate=*/0, /*flags=*/0);
 
+        // Render widget annotations for FormFields.
+        FPDF_FFLDraw(pFormHandle, pPdfBitmap, pPdfPage, /*start_x=*/0, /*start_y=*/0, nPageWidth,
+                     nPageHeight, /*rotate=*/0, /*flags=*/0);
+
         // Save the buffer as a bitmap.
         Bitmap aBitmap(Size(nPageWidth, nPageHeight), 24);
         {
@@ -226,6 +235,8 @@ size_t RenderPDFBitmaps(const void* pBuffer, int nSize, std::vector<Bitmap>& rBi
         FPDF_ClosePage(pPdfPage);
     }
 
+    FPDFDOC_ExitFormFillEnvironment(pFormHandle);
+
     FPDF_CloseDocument(pPdfDocument);
 
     return rBitmaps.size();