Auto merge of #12388 - kilobtye:textarea2, r=pcwalton

Let textarea wrap lines

<!-- Please describe your changes on the following line: -->
1. Change textarea's style from white-space: pre to white-space: pre-wrap.
2. Display insertion point when a line is wrapped.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #10053 (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/12388)
<!-- Reviewable:end -->

3 files changed, 14 insertions, 11 deletions

diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index 5eb20156295..8d036dfc90e 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -29,7 +29,6 @@ use gfx::display_list::{LayeredItem, LayerInfo, LineDisplayItem, OpaqueNode};
 use gfx::display_list::{SolidColorDisplayItem, StackingContext, StackingContextType};
 use gfx::display_list::{TextDisplayItem, TextOrientation, WebRenderImageInfo};
 use gfx::paint_thread::THREAD_TINT_COLORS;
-use gfx::text::glyph::ByteIndex;
 use gfx_traits::{color, ScrollPolicy, StackingContextId};
 use inline::{FIRST_FRAGMENT_OF_ELEMENT, InlineFlow, LAST_FRAGMENT_OF_ELEMENT};
 use ipc_channel::ipc;
@@ -970,7 +969,8 @@ impl FragmentDisplayListBuilding for Fragment {
             Some(insertion_point_index) => insertion_point_index,
             None => return,
         };
-        let range = Range::new(ByteIndex(0), insertion_point_index);
+        let range = Range::new(scanned_text_fragment_info.range.begin(),
+                               insertion_point_index - scanned_text_fragment_info.range.begin());
         let advance = scanned_text_fragment_info.run.advance_for_range(&range);
 
         let insertion_point_bounds;
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index f235bd64331..48499d7e36e 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -882,16 +882,23 @@ impl Fragment {
         let size = LogicalSize::new(self.style.writing_mode,
                                     split.inline_size,
                                     self.border_box.size.block);
-        let flags = match self.specific {
-            SpecificFragmentInfo::ScannedText(ref info) => info.flags,
-            _ => ScannedTextFlags::empty()
+        // Preserve the insertion point if it is in this fragment's range or it is at line end.
+        let (flags, insertion_point) = match self.specific {
+            SpecificFragmentInfo::ScannedText(ref info) => {
+                match info.insertion_point {
+                    Some(index) if split.range.contains(index) => (info.flags, info.insertion_point),
+                    Some(index) if index == ByteIndex(text_run.text.chars().count() as isize - 1) &&
+                        index == split.range.end() => (info.flags, info.insertion_point),
+                    _ => (info.flags, None)
+                }
+            },
+            _ => (ScannedTextFlags::empty(), None)
         };
-        // FIXME(pcwalton): This should modify the insertion point as necessary.
         let info = box ScannedTextFragmentInfo::new(
             text_run,
             split.range,
             size,
-            None,
+            insertion_point,
             flags);
         self.transform(size, SpecificFragmentInfo::ScannedText(info))
     }
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index cb9ef5152df..83ad6b73d82 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -2146,10 +2146,6 @@ pub fn modify_style_for_input_text(style: &mut Arc<ComputedValues>) {
     margin_style.margin_right = computed::LengthOrPercentageOrAuto::Length(Au(0));
     margin_style.margin_bottom = computed::LengthOrPercentageOrAuto::Length(Au(0));
     margin_style.margin_left = computed::LengthOrPercentageOrAuto::Length(Au(0));
-
-    // whitespace inside text input should not be collapsed
-    let inherited_text = Arc::make_mut(&mut style.inheritedtext);
-    inherited_text.white_space = longhands::white_space::computed_value::T::pre;
 }
 
 /// Adjusts the `clip` property so that an inline absolute hypothetical fragment doesn't clip its