SDL: Fixed SDL_strncmp() logic in portal dialog code

From a5b0041b4a1f278eac800b4240bd3b1c5b7d2b99 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Mon, 27 May 2024 07:46:58 -0700
Subject: [PATCH] Fixed SDL_strncmp() logic in portal dialog code

Also removed redundant calls to SDL_strlen()

Fixes https://github.com/libsdl-org/SDL/issues/9899
---
 src/dialog/unix/SDL_portaldialog.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/dialog/unix/SDL_portaldialog.c b/src/dialog/unix/SDL_portaldialog.c
index d0a52d59c82cd..8aa55bfde2053 100644
--- a/src/dialog/unix/SDL_portaldialog.c
+++ b/src/dialog/unix/SDL_portaldialog.c
@@ -226,6 +226,8 @@ static DBusHandlerResult DBus_MessageFilter(DBusConnection *conn, DBusMessage *m
 
         while (dbus->message_iter_get_arg_type(&uri_entry) == DBUS_TYPE_STRING)
         {
+            const char *prefix = "file://";
+            const int prefix_len = 7;
             const char *uri = NULL;
 
             if (current >= length - 1) {
@@ -241,8 +243,8 @@ static DBusHandlerResult DBus_MessageFilter(DBusConnection *conn, DBusMessage *m
 
             /* https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.FileChooser.html */
             /* Returned paths will always start with 'file://'; truncate it */
-            if (SDL_strncmp(uri, "file://", SDL_strlen("file://"))) {
-                path[current] = uri + SDL_strlen("file://");
+            if (SDL_strncmp(uri, prefix, prefix_len) == 0) {
+                path[current] = uri + prefix_len;
             } else if (SDL_strstr(uri, "://")) {
                 SDL_SetError("Portal dialogs: Unsupported protocol: %s", uri);
                 signal_data->callback(signal_data->userdata, NULL, -1);