[PATCH] window: add url_filter field

This allows a frontend to filter the URLs which the browser will
navigate to.
---
desktop/browser_window.c | 3 +++
include/netsurf/window.h | 12 ++++++++++++
2 files changed, 15 insertions(+)

diff --git a/desktop/browser_window.c b/desktop/browser_window.c
index 7b553f4e0..522772bbc 100644
--- a/desktop/browser_window.c
+++ b/desktop/browser_window.c
@@ -3313,6 +3313,9 @@ browser_window_navigate(struct browser_window *bw,
assert(bw);
assert(url);

+ if (guit->window->url_filter) {
+ url = guit->window->url_filter(bw->window, url);
+ }
NSLOG(netsurf, INFO, "bw %p, url %s", bw, nsurl_access(url));

/*
diff --git a/include/netsurf/window.h b/include/netsurf/window.h
index 16fd95e30..8ebbfee92 100644
--- a/include/netsurf/window.h
+++ b/include/netsurf/window.h
@@ -376,6 +376,18 @@ struct gui_window_table {
const char *msg,
size_t msglen,
browser_window_console_flags flags);
+
+ /**
+ * Filter URLs for navigation. Return the same nsurl if no filtering is
+ * desired, or leave this table field NULL. The browser will reference
+ * the returned URL.
+ *
+ * \param gw The gui window which is navigating to a URL
+ * \param url The URL being navigated to
+ * \return The same URL, or another URL to load instead.
+ */
+ struct nsurl *(*url_filter)(struct gui_window *gw,
+ struct nsurl *url);
};