Auto merge of #8559 - glennw:transform-layers, r=pcwalton

Include transform changes in list that cause incremental reflows.

Also ensure that 3d translations get layers.

Fixes #8329.

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components/layout/block.rs

@@ -55,7 +55,7 @@ use std::cmp::{max, min};
 use std::fmt;
 use std::sync::Arc;
 use style::computed_values::{border_collapse, box_sizing, display, float, overflow_x, overflow_y};
-use style::computed_values::{position, text_align, transform, transform_style};
+use style::computed_values::{position, text_align, transform_style};
 use style::properties::ComputedValues;
 use style::values::computed::{LengthOrNone, LengthOrPercentageOrNone};
 use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto};
@@ -585,33 +585,6 @@ impl BlockFlow {
         }
     }
 
-    pub fn transform_requires_layer(&self) -> bool {
-        // Check if the transform matrix is 2D or 3D
-        if let Some(ref transform_list) = self.fragment.style().get_effects().transform.0 {
-            for transform in transform_list {
-                match *transform {
-                    transform::ComputedOperation::Perspective(..) => {
-                        return true;
-                    }
-                    transform::ComputedOperation::Matrix(m) => {
-                        // See http://dev.w3.org/csswg/css-transforms/#2d-matrix
-                        if m.m31 != 0.0 || m.m32 != 0.0 ||
-                           m.m13 != 0.0 || m.m23 != 0.0 ||
-                           m.m43 != 0.0 || m.m14 != 0.0 ||
-                           m.m24 != 0.0 || m.m34 != 0.0 ||
-                           m.m33 != 1.0 || m.m44 != 1.0 {
-                            return true;
-                        }
-                    }
-                    _ => {}
-                }
-            }
-        }
-
-        // Neither perspective nor transform present
-        false
-    }
-
     /// Compute the actual inline size and position for this block.
     pub fn compute_used_inline_size(&mut self,
                                     layout_context: &LayoutContext,
@@ -1560,7 +1533,7 @@ impl BlockFlow {
 
         // This flow needs a layer if it has a 3d transform, or provides perspective
         // to child layers. See http://dev.w3.org/csswg/css-transforms/#3d-rendering-contexts.
-        let has_3d_transform = self.transform_requires_layer();
+        let has_3d_transform = self.fragment.style().transform_requires_layer();
         let has_perspective = self.fragment.style().get_effects().perspective !=
             LengthOrNone::None;
 

components/layout/incremental.rs

@@ -191,6 +191,12 @@ pub fn compute_damage(old: &Option<Arc<ComputedValues>>, new: &ComputedValues) -
         get_font.font_size, get_font.font_stretch
     ]);
 
+    // If the layer requirements of this flow have changed due to the value
+    // of the transform, then reflow is required to rebuild the layers.
+    if old.transform_requires_layer() != new.transform_requires_layer() {
+        damage.insert(rebuild_and_reflow());
+    }
+
     // FIXME: test somehow that we checked every CSS property
     damage
 }

components/style/properties.mako.rs

@@ -6227,6 +6227,38 @@ impl ComputedValues {
         effects.transform_style
     }
 
+    pub fn transform_requires_layer(&self) -> bool {
+        // Check if the transform matrix is 2D or 3D
+        if let Some(ref transform_list) = self.get_effects().transform.0 {
+            for transform in transform_list {
+                match *transform {
+                    computed_values::transform::ComputedOperation::Perspective(..) => {
+                        return true;
+                    }
+                    computed_values::transform::ComputedOperation::Matrix(m) => {
+                        // See http://dev.w3.org/csswg/css-transforms/#2d-matrix
+                        if m.m31 != 0.0 || m.m32 != 0.0 ||
+                           m.m13 != 0.0 || m.m23 != 0.0 ||
+                           m.m43 != 0.0 || m.m14 != 0.0 ||
+                           m.m24 != 0.0 || m.m34 != 0.0 ||
+                           m.m33 != 1.0 || m.m44 != 1.0 {
+                            return true;
+                        }
+                    }
+                    computed_values::transform::ComputedOperation::Translate(_, _, z) => {
+                        if z != Au(0) {
+                            return true;
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        // Neither perspective nor transform present
+        false
+    }
+
     % for style_struct in STYLE_STRUCTS:
     #[inline]
     pub fn get_${style_struct.name.lower()}