3 files changed, 129 insertions, 7 deletions
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index bda81450d3d..8cce6576890 100644
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -68,6 +68,14 @@ enum ValueMode {
     Filename,
 }
 
+#[derive(JSTraceable, PartialEq, Copy, Clone)]
+#[derive(HeapSizeOf)]
+enum SelectionDirection {
+    Forward,
+    Backward,
+    None
+}
+
 #[dom_struct]
 pub struct HTMLInputElement {
     htmlelement: HTMLElement,
@@ -83,6 +91,8 @@ pub struct HTMLInputElement {
     // https://html.spec.whatwg.org/multipage/#concept-input-value-dirty-flag
     value_dirty: Cell<bool>,
 
+    selection_direction: Cell<SelectionDirection>,
+
     // TODO: selected files for file input
 }
 
@@ -132,6 +142,7 @@ impl HTMLInputElement {
             textinput: DOMRefCell::new(TextInput::new(Single, DOMString::new(), chan, None)),
             activation_state: DOMRefCell::new(InputActivationState::new()),
             value_dirty: Cell::new(false),
+            selection_direction: Cell::new(SelectionDirection::None)
         }
     }
 
@@ -164,6 +175,31 @@ impl HTMLInputElement {
         }
     }
 
+    // this method exists so that the functions SetSelectionStart() and SetSelectionEnd()
+    // don't needlessly allocate strings
+    fn set_selection_range(&self, start: u32, end: u32, direction: &SelectionDirection) {
+        let mut text_input = self.textinput.borrow_mut();
+
+        let mut start = start as usize;
+        let mut end = end as usize;
+
+        let text_end = text_input.get_content().len();
+        if start > text_end {
+            start = text_end;
+        }
+        if end > text_end {
+            end = text_end;
+        }
+
+        if start >= end {
+            start = end;
+        }
+
+        text_input.selection_begin = Some(text_input.get_text_point_for_absolute_point(start));
+        text_input.edit_point = text_input.get_text_point_for_absolute_point(end);
+        self.selection_direction.set(*direction);
+    }
+
 }
 
 pub trait LayoutHTMLInputElementHelpers {
@@ -444,6 +480,64 @@ impl HTMLInputElementMethods for HTMLInputElement {
             self.upcast::<HTMLElement>().labels()
         }
     }
+
+    // https://html.spec.whatwg.org/multipage/#dom-input-selectionstart
+    fn SelectionStart(&self) -> u32 {
+        let text_input = self.textinput.borrow();
+        let selection_start = match text_input.selection_begin {
+            Some(selection_begin_point) => {
+                text_input.get_absolute_point_for_text_point(&selection_begin_point)
+            },
+            None => text_input.get_absolute_insertion_point()
+        };
+
+        selection_start as u32
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-selectionstart
+    fn SetSelectionStart(&self, start: u32) {
+        self.set_selection_range(start, self.SelectionEnd(), &self.selection_direction.get());
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-selectionend
+    fn SelectionEnd(&self) -> u32 {
+        let text_input = self.textinput.borrow();
+        text_input.get_absolute_insertion_point() as u32
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-selectionend
+    fn SetSelectionEnd(&self, end: u32) {
+        self.set_selection_range(self.SelectionStart(), end, &self.selection_direction.get());
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-selectiondirection
+    fn SelectionDirection(&self) -> DOMString {
+        match self.selection_direction.get() {
+            SelectionDirection::Forward => DOMString::from("forward"),
+            SelectionDirection::Backward => DOMString::from("backward"),
+            SelectionDirection::None => DOMString::from("none"),
+        }
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-selectiondirection
+    fn SetSelectionDirection(&self, direction: DOMString) {
+        self.SetSelectionRange(self.SelectionStart(), self.SelectionEnd(), Some(direction));
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-textarea/input-setselectionrange
+    fn SetSelectionRange(&self, start: u32, end: u32, direction: Option<DOMString>) {
+        let selection_direction = match direction {
+            Some(selection_direction) => {
+                match &*selection_direction {
+                    "forward" => SelectionDirection::Forward,
+                    "backward" => SelectionDirection::Backward,
+                    _ => SelectionDirection::None,
+                }
+            },
+            None => SelectionDirection::None,
+        };
+        self.set_selection_range(start, end, &selection_direction);
+    }
 }
 
 
diff --git a/components/script/dom/webidls/HTMLInputElement.webidl b/components/script/dom/webidls/HTMLInputElement.webidl
index d213334ef83..2e1c6215f2b 100644
--- a/components/script/dom/webidls/HTMLInputElement.webidl
+++ b/components/script/dom/webidls/HTMLInputElement.webidl
@@ -62,13 +62,13 @@ interface HTMLInputElement : HTMLElement {
   readonly attribute NodeList labels;
 
   //void select();
-  //         attribute unsigned long selectionStart;
-  //         attribute unsigned long selectionEnd;
-  //         attribute DOMString selectionDirection;
+           attribute unsigned long selectionStart;
+           attribute unsigned long selectionEnd;
+           attribute DOMString selectionDirection;
   //void setRangeText(DOMString replacement);
   //void setRangeText(DOMString replacement, unsigned long start, unsigned long end,
   //                  optional SelectionMode selectionMode = "preserve");
-  //void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
+  void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
 
   // also has obsolete members
 };
diff --git a/components/script/textinput.rs b/components/script/textinput.rs
index 02fb79e04a8..f407592a0ef 100644
--- a/components/script/textinput.rs
+++ b/components/script/textinput.rs
@@ -36,7 +36,7 @@ pub struct TextInput<T: ClipboardProvider> {
     /// Current cursor input point
     pub edit_point: TextPoint,
     /// Beginning of selection range with edit_point as end that can span multiple lines.
-    selection_begin: Option<TextPoint>,
+    pub selection_begin: Option<TextPoint>,
     /// Is this a multiline input?
     multiline: bool,
     #[ignore_heap_size_of = "Can't easily measure this generic type"]
@@ -500,12 +500,40 @@ impl<T: ClipboardProvider> TextInput<T> {
     }
 
     pub fn get_absolute_insertion_point(&self) -> usize {
+        self.get_absolute_point_for_text_point(&self.edit_point)
+    }
+
+    pub fn get_absolute_point_for_text_point(&self, text_point: &TextPoint) -> usize {
         self.lines.iter().enumerate().fold(0, |acc, (i, val)| {
-            if i < self.edit_point.line {
+            if i < text_point.line {
                 acc + val.len() + 1 // +1 for the \n
             } else {
                 acc
             }
-        }) + self.edit_point.index
+        }) + text_point.index
+    }
+
+    pub fn get_text_point_for_absolute_point(&self, abs_point: usize) -> TextPoint {
+        let mut index = abs_point;
+        let mut line = 0;
+
+        let last_line_idx = self.lines.len() - 1;
+        self.lines.iter().enumerate().fold(0, |acc, (i, val)| {
+            if i != last_line_idx {
+                let line_end = max(val.len(), 1);
+                let new_acc = acc + line_end;
+                if abs_point > new_acc && index > line_end {
+                    index -= line_end + 1;
+                    line += 1;
+                }
+                new_acc
+            } else {
+                acc
+            }
+        });
+
+        TextPoint {
+            line: line, index: index
+        }
     }
 }