Bug 695021: Fix pdf_insert_page operation with empty page tree.

Patch from Thomas Fach-Pedersen to fix the operation of pdf_insert_page
when called with an empty page tree. Many thanks! As noted in the code
with a FIXME this currently throws an error.

Also, cope with being told to add a page "at" INT_MAX as meaning to
add it at the end of the document.

Possibly this code should cope with a Root without a Pages entry, or
a Pages without a Kids too, but we can fix this in future if it ever
becomes a problem.

1 files changed, 13 insertions, 2 deletions

diff --git a/source/pdf/pdf-page.c b/source/pdf/pdf-page.c
index f3c929d2..fd6f71bc 100644
--- a/source/pdf/pdf-page.c
+++ b/source/pdf/pdf-page.c
@@ -590,11 +590,22 @@ pdf_insert_page(pdf_document *doc, pdf_page *page, int at)
 	{
 		if (count == 0)
 		{
-			/* TODO: create new page tree? */
-			fz_throw(ctx, FZ_ERROR_GENERIC, "empty page tree, cannot insert page");
+			pdf_obj *root = pdf_dict_gets(pdf_trailer(doc), "Root");
+			parent = pdf_dict_gets(root, "Pages");
+			if (!parent)
+				fz_throw(doc->ctx, FZ_ERROR_GENERIC, "cannot find page tree");
+
+			kids = pdf_dict_gets(parent, "Kids");
+			if (!kids)
+				fz_throw(doc->ctx, FZ_ERROR_GENERIC, "malformed page tree");
+
+			pdf_array_insert(kids, page_ref, 0);
 		}
 		else if (at >= count)
 		{
+			if (at == INT_MAX)
+				at = count;
+
 			if (at > count)
 				fz_throw(ctx, FZ_ERROR_GENERIC, "cannot insert page beyond end of page tree");