Fixed bug in textinput::adjust_vertical concerning selection_origin update

This bug was discovered using the F* formal verification framework.

Style changes (match -> if let)

Replace if let Some(_) by .is_some()

1 files changed, 22 insertions, 1 deletions

diff --git a/components/script/textinput.rs b/components/script/textinput.rs
index 2f36b08dbd9..54bc7131f48 100644
--- a/components/script/textinput.rs
+++ b/components/script/textinput.rs
@@ -442,12 +442,23 @@ impl<T: ClipboardProvider> TextInput<T> {
         let target_line: isize = self.edit_point.line as isize + adjust;
 
         if target_line < 0 {
-            self.edit_point.index = 0;
             self.edit_point.line = 0;
+            self.edit_point.index = 0;
+            if self.selection_origin.is_some() &&
+                (self.selection_direction == SelectionDirection::None ||
+                    self.selection_direction == SelectionDirection::Forward)
+            {
+                self.selection_origin = Some(TextPoint { line: 0, index: 0 });
+            }
             return;
         } else if target_line as usize >= self.lines.len() {
             self.edit_point.line = self.lines.len() - 1;
             self.edit_point.index = self.current_line_length();
+            if self.selection_origin.is_some() &&
+                (self.selection_direction == SelectionDirection::Backward)
+            {
+                self.selection_origin = Some(self.edit_point);
+            }
             return;
         }
 
@@ -456,6 +467,16 @@ impl<T: ClipboardProvider> TextInput<T> {
             .count();
         self.edit_point.line = target_line as usize;
         self.edit_point.index = len_of_first_n_chars(&self.lines[self.edit_point.line], col);
+        if let Some(origin) = self.selection_origin {
+            if ((self.selection_direction == SelectionDirection::None ||
+                self.selection_direction == SelectionDirection::Forward) &&
+                self.edit_point <= origin) ||
+                (self.selection_direction == SelectionDirection::Backward &&
+                    origin <= self.edit_point)
+            {
+                self.selection_origin = Some(self.edit_point);
+            }
+        }
         self.assert_ok_selection();
     }