Add _qutebrowser_ prefix for custom JS functions

With QtWebKit or QtWebEngine with Qt < 5.7, the functions end up in the
page's namespace. We can't easily avoid this, but at least we can name
them in a way which reduces conflicts.

qutebrowser/javascript/scroll.js

@@ -17,7 +17,7 @@
  * along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-function scroll_to_perc(x, y) {
+function _qutebrowser_scroll_to_perc(x, y) {
     var elem = document.documentElement;
     var x_px = window.scrollX;
     var y_px = window.scrollY;
@@ -33,13 +33,13 @@ function scroll_to_perc(x, y) {
     window.scroll(x_px, y_px);
 }
 
-function scroll_delta_page(x, y) {
+function _qutebrowser_scroll_delta_page(x, y) {
     var dx = document.documentElement.clientWidth * x;
     var dy = document.documentElement.clientHeight * y;
     window.scrollBy(dx, dy);
 }
 
-function scroll_pos() {
+function _qutebrowser_scroll_pos() {
     var elem = document.documentElement;
     var dx = (elem.scrollWidth - elem.clientWidth);
     var dy = (elem.scrollHeight - elem.clientHeight);

qutebrowser/utils/javascript.py

@@ -64,7 +64,7 @@ def _convert_js_arg(arg):
 
 def assemble(name, function, *args):
     """Assemble a javascript file and a function call."""
-    code = "{code}\n{function}({args});".format(
+    code = "{code}\n_qutebrowser_{function}({args});".format(
         code=utils.read_file('javascript/{}.js'.format(name)),
         function=function,
         args=', '.join(_convert_js_arg(arg) for arg in args),

tests/unit/utils/test_javascript.py

@@ -140,5 +140,5 @@ def test_convert_js_arg(arg, expected):
 def test_assemble(monkeypatch):
     monkeypatch.setattr(javascript.utils, 'read_file',
                         '<code from {}>'.format)
-    expected = '<code from javascript/foo.js>\nfunc(23);'
+    expected = '<code from javascript/foo.js>\n_qutebrowser_func(23);'
     assert javascript.assemble('foo', 'func', 23) == expected