LibHTML: Run second layout pass if first layout adds/removes scrollbars

If you do a layout and it turns out that the page contents don't fit in
the viewport vertically, we add a vertical scrollbar. Since the
scrollbar takes up some horizontal space, this reduces the amount of
space available to the page. So we have to do a second layout pass. :^)

Fixes #650.

1 files changed, 11 insertions, 0 deletions

diff --git a/Libraries/LibHTML/HtmlView.cpp b/Libraries/LibHTML/HtmlView.cpp
index 98197b03b4..7dc89defa8 100644
--- a/Libraries/LibHTML/HtmlView.cpp
+++ b/Libraries/LibHTML/HtmlView.cpp
@@ -71,10 +71,21 @@ void HtmlView::layout_and_sync_size()
     if (!document())
         return;
 
+    bool had_vertical_scrollbar = vertical_scrollbar().is_visible();
+    bool had_horizontal_scrollbar = horizontal_scrollbar().is_visible();
+
     main_frame().set_size(available_size());
     document()->layout();
     set_content_size(layout_root()->rect().size());
 
+    // NOTE: If layout caused us to gain or lose scrollbars, we have to lay out again
+    //       since the scrollbars now take up some of the available space.
+    if (had_vertical_scrollbar != vertical_scrollbar().is_visible() || had_horizontal_scrollbar != horizontal_scrollbar().is_visible()) {
+        main_frame().set_size(available_size());
+        document()->layout();
+        set_content_size(layout_root()->rect().size());
+    }
+
 #ifdef HTML_DEBUG
     dbgprintf("\033[33;1mLayout tree after layout:\033[0m\n");
     ::dump_tree(*layout_root());