Some Fixes

* Correctly compute PDF page number from given fz_location
* Add mehod `apply_css` to reflowable documents.

Author: JorjMcKie

src/__init__.py

@@ -5767,6 +5767,24 @@ def layout(self, rect=None, width=0, height=0, fontsize=11):
         self._reset_page_refs()
         self.init_doc()
 
+    def apply_css(self, css: str, append: bool = True):
+        """Apply CSS to a reflowable document.
+
+        If 'append' evaluates to True, the CSS will be appended to
+        the default CSS of this document type.
+        Otherwise the default CSS will be ignored.
+        """
+        if self.is_closed or self.is_encrypted:
+            raise ValueError("document closed or encrypted")
+        doc = self.this
+        if not mupdf.fz_is_document_reflowable(doc):
+            return
+        if not isinstance(css, str) or not css:
+            return
+        append = int(bool(append))  # ensure integer
+        mupdf.fz_style_document(doc, append, css)
+
+
     def load_page(self, page_id):
         """Load a page.
 
@@ -19107,6 +19125,12 @@ def JM_convert_to_pdf(doc, fp, tp, rotate) -> bytes:
     Convert any MuPDF document to a PDF
     Returns bytes object containing the PDF, created via 'write' function.
     '''
+
+    def loc_to_pno(doc, loc):
+        """Convert location to page number."""
+        pno = sum(mupdf.fz_count_chapter_pages(doc, i) for i in range(loc.chapter))
+        return pno + loc.page
+
     pdfout = mupdf.PdfDocument()
     incr = 1
     s = fp
@@ -19117,6 +19141,7 @@ def JM_convert_to_pdf(doc, fp, tp, rotate) -> bytes:
         e = fp      # ... range
     rot = JM_norm_rotation(rotate)
     i = fp
+    pno = -1  # init current PDF page number
     internal_links = []  # collect PDF-wide internal links here
     while 1:  # interpret & write document pages as PDF pages
         if not _INRANGE(i, s, e):
@@ -19129,10 +19154,11 @@ def JM_convert_to_pdf(doc, fp, tp, rotate) -> bytes:
         dev = None
         page_obj = mupdf.pdf_add_page(pdfout, mediabox, rot, resources, contents)
         mupdf.pdf_insert_page(pdfout, -1, page_obj)
+        pno += 1
 
         # also copy links to the output PDF page
         # get the PDF page we've just created
-        pdf_page = mupdf.pdf_load_page(pdfout, i)
+        pdf_page = mupdf.pdf_load_page(pdfout, pno)
 
         # loop through source page links
         link = mupdf.fz_load_links(page)  # load first link
@@ -19146,29 +19172,44 @@ def JM_convert_to_pdf(doc, fp, tp, rotate) -> bytes:
             else:  # internal links done when PDF is complete
                 # find target of internal link
                 ret, xp, yp = mupdf.fz_resolve_link(doc, uri)
-                ilink={"page": i, "ret": ret, "from": rect, "h": rect.y1-rect.y0, "w": rect.x1-rect.x0, "xp": xp, "yp": yp}
+                if (ret.chapter, ret.page) == (-1, -1):
+                    # could not resolve link destination
+                    continue
+                ilink = {"page": pno,
+                    "ret": ret,
+                    "from": rect,
+                    "h": rect.y1 - rect.y0,
+                    "w": rect.x1 - rect.x0,
+                    "xp": xp,
+                    "yp": yp,
+                }
                 internal_links.append(ilink)
             link = link.next()
-        
+
         i += incr
 
-    # PDF created - now write it to Python bytearray
     # insert any internal links collected before:
+    pno = None  # init PDF page number
     for ilink in internal_links:
-        pdf_page = mupdf.pdf_load_page(pdfout, ilink["page"])
+        this_pno = ilink["page"]
+        if pno != this_pno:
+            pdf_page = mupdf.pdf_load_page(pdfout, this_pno)
+            pno = this_pno
         ret = ilink["ret"]
         dest = mupdf.fz_link_dest()
-        dest.type = 7  # XYZ destination format
-        dest.loc.chapter = ret.chapter
-        dest.loc.page = ret.page
+        dest.type = mupdf.FZ_LINK_DEST_XYZ
+        dest.loc.chapter = 0  # PDFs have 1 chapter
+        dest.loc.page = loc_to_pno(doc, ret)
         dest.h = ilink["h"]
         dest.w = ilink["w"]
         dest.x = ilink["xp"]
         dest.y = ilink["yp"]
         dest.zoom = 0
-        rect=ilink["from"]
+        rect = ilink["from"]
         uri = mupdf.pdf_new_uri_from_explicit_dest(mupdf.FzLinkDest(dest))
         mupdf.pdf_create_link(pdf_page, rect, uri)
+
+    # PDF created - now write it out
     # prepare write options structure
     opts = mupdf.PdfWriteOptions()
     opts.do_garbage         = 3