Make fz_page objects singleton.

Keep a list of currently open pages for each document. Attempting to
load a page that is already loaded will return the same instance again.

1 files changed, 25 insertions, 1 deletions

diff --git a/source/fitz/document.c b/source/fitz/document.c
index 013badb0..26ae93ea 100644
--- a/source/fitz/document.c
+++ b/source/fitz/document.c
@@ -319,9 +319,27 @@ fz_document_output_intent(fz_context *ctx, fz_document *doc)
 fz_page *
 fz_load_page(fz_context *ctx, fz_document *doc, int number)
 {
+	fz_page *page;
+
 	fz_ensure_layout(ctx, doc);
+
+	for (page = doc->open; page; page = page->next)
+		if (page->number == number)
+			return fz_keep_page(ctx, page);
+
 	if (doc && doc->load_page)
-		return doc->load_page(ctx, doc, number);
+	{
+		page = doc->load_page(ctx, doc, number);
+		page->number = number;
+
+		/* Insert new page at the head of the list of open pages. */
+		if ((page->next = doc->open) != NULL)
+			doc->open->prev = &page->next;
+		doc->open = page;
+		page->prev = &doc->open;
+		return page;
+	}
+
 	return NULL;
 }
 
@@ -472,8 +490,14 @@ fz_drop_page(fz_context *ctx, fz_page *page)
 {
 	if (fz_drop_imp(ctx, page, &page->refs))
 	{
+		/* Remove page from the list of open pages */
+		if (page->next != NULL)
+			page->next->prev = page->prev;
+		*page->prev = page->next;
+
 		if (page->drop_page)
 			page->drop_page(ctx, page);
+
 		fz_free(ctx, page);
 	}
 }