Auto merge of #14000 - Wafflespeanut:grid, r=Manishearth

Stylo: Basic support for grid-{row,column}-{start,end}

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build-geckolib` does not report any errors
- [x] `./mach test-tidy` does not report any errors

<!-- Either: -->
- [ ] There are tests for these changes

<!-- 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/14000)
<!-- Reviewable:end -->

components/style/properties/gecko.mako.rs

@@ -5,7 +5,7 @@
 // `data` comes from components/style/properties.mako.rs; see build.rs for more details.
 
 <%!
-    from data import to_rust_ident
+    from data import to_rust_ident, to_camel_case
     from data import Keyword
 %>
 <%namespace name="helpers" file="/helpers.mako.rs" />
@@ -631,8 +631,15 @@ class Corner(object):
         self.x_index = 2 * index
         self.y_index = 2 * index + 1
 
+class GridLine(object):
+    def __init__(self, name):
+        self.ident = "grid-" + name.lower()
+        self.name = self.ident.replace('-', '_')
+        self.gecko = "m" + to_camel_case(self.ident)
+
 SIDES = [Side("Top", 0), Side("Right", 1), Side("Bottom", 2), Side("Left", 3)]
 CORNERS = [Corner("TOP_LEFT", 0), Corner("TOP_RIGHT", 1), Corner("BOTTOM_RIGHT", 2), Corner("BOTTOM_LEFT", 3)]
+GRID_LINES = map(GridLine, ["row-start", "row-end", "column-start", "column-end"])
 %>
 
 #[allow(dead_code)]
@@ -822,7 +829,7 @@ fn static_assert() {
     % endfor
 </%self:impl_trait>
 
-<% skip_position_longhands = " ".join(x.ident for x in SIDES) %>
+<% skip_position_longhands = " ".join(x.ident for x in SIDES + GRID_LINES) %>
 <%self:impl_trait style_struct_name="Position"
                   skip_longhands="${skip_position_longhands} z-index box-sizing order">
 
@@ -884,6 +891,27 @@ fn static_assert() {
 
     ${impl_simple_copy('order', 'mOrder')}
 
+    % for value in GRID_LINES:
+    pub fn set_${value.name}(&mut self, v: longhands::${value.name}::computed_value::T) {
+        use nsstring::nsCString;
+        use gecko_bindings::structs::{nsStyleGridLine_kMinLine, nsStyleGridLine_kMaxLine};
+
+        let ident = v.ident.unwrap_or(String::new());
+        self.gecko.${value.gecko}.mLineName.assign_utf8(&nsCString::from(&*ident));
+        self.gecko.${value.gecko}.mHasSpan = v.is_span;
+        self.gecko.${value.gecko}.mInteger = v.integer.map(|i| {
+            // clamping the integer between a range
+            cmp::max(nsStyleGridLine_kMinLine, cmp::min(i, nsStyleGridLine_kMaxLine))
+        }).unwrap_or(0);
+    }
+
+    pub fn copy_${value.name}_from(&mut self, other: &Self) {
+        self.gecko.${value.gecko}.mHasSpan = other.gecko.${value.gecko}.mHasSpan;
+        self.gecko.${value.gecko}.mInteger = other.gecko.${value.gecko}.mInteger;
+        self.gecko.${value.gecko}.mLineName.assign(&other.gecko.${value.gecko}.mLineName);
+    }
+    % endfor
+
 </%self:impl_trait>
 
 <% skip_outline_longhands = " ".join("outline-style outline-width".split() +

components/style/properties/longhand/box.mako.rs

@@ -18,8 +18,7 @@
         values = """inline block inline-block
             table inline-table table-row-group table-header-group table-footer-group
             table-row table-column-group table-column table-cell table-caption
-            list-item flex
-            none
+            list-item flex none
         """.split()
         if product == "gecko":
             values += """inline-flex grid inline-grid ruby ruby-base ruby-base-container

components/style/properties/longhand/position.mako.rs

@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+<%! from data import to_rust_ident %>
 <%namespace name="helpers" file="/helpers.mako.rs" />
 <% from data import ALL_SIZES, PHYSICAL_SIDES, LOGICAL_SIDES %>
 
@@ -180,3 +181,14 @@ ${helpers.single_keyword("box-sizing",
 // https://drafts.csswg.org/css-images-3/
 ${helpers.single_keyword("object-fit", "fill contain cover none scale-down",
                          products="gecko", animatable=False)}
+
+// https://drafts.csswg.org/css-grid/#propdef-grid-row-start
+<% grid_longhands = ["grid-row-start", "grid-row-end", "grid-column-start", "grid-column-end"] %>
+
+% for longhand in grid_longhands:
+    ${helpers.predefined_type("%s" % longhand,
+                              "GridLine",
+                              "Default::default()",
+                              animatable=False,
+                              products="gecko")}
+% endfor