Rename the MinMaxConstraint to SizeConstraint and enhancement

Renamed to `SizeConstraint`, add an optional `border` parameter to
deal with `box-sizing: border-box`, and fix its bug when involving
with `calc`.

components/layout/flex.rs

@@ -19,7 +19,7 @@ use fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
 use gfx::display_list::StackingContext;
 use gfx_traits::ScrollRootId;
 use layout_debug;
-use model::{IntrinsicISizes, MaybeAuto, MinMaxConstraint};
+use model::{IntrinsicISizes, MaybeAuto, SizeConstraint};
 use model::{specified, specified_or_none};
 use std::cmp::{max, min};
 use std::ops::Range;
@@ -38,7 +38,7 @@ use style::values::computed::{LengthOrPercentageOrAutoOrContent, LengthOrPercent
 #[derive(Debug)]
 enum AxisSize {
     Definite(Au),
-    MinMax(MinMaxConstraint),
+    MinMax(SizeConstraint),
     Infinite,
 }
 
@@ -62,7 +62,7 @@ impl AxisSize {
                 }
             }
             LengthOrPercentageOrAuto::Auto => {
-                AxisSize::MinMax(MinMaxConstraint::new(content_size, min, max))
+                AxisSize::MinMax(SizeConstraint::new(content_size, min, max, None))
             }
         }
     }

components/layout/fragment.rs

@@ -23,7 +23,7 @@ use inline::{InlineMetrics, LAST_FRAGMENT_OF_ELEMENT, LineMetrics};
 use ipc_channel::ipc::IpcSender;
 #[cfg(debug_assertions)]
 use layout_debug;
-use model::{self, IntrinsicISizes, IntrinsicISizesContribution, MaybeAuto};
+use model::{self, IntrinsicISizes, IntrinsicISizesContribution, MaybeAuto, SizeConstraint};
 use msg::constellation_msg::PipelineId;
 use net_traits::image::base::{Image, ImageMetadata};
 use net_traits::image_cache_thread::{ImageOrMetadataAvailable, UsePlaceholder};
@@ -1202,6 +1202,27 @@ impl Fragment {
         }
     }
 
+
+    /// Return a size constraint that can be used the clamp size in given direction.
+    /// To take `box-sizing: border-box` into account, the `border_padding` field
+    /// must be initialized first.
+    ///
+    /// TODO(stshine): Maybe there is a more convenient way.
+    pub fn size_constraint(&self, containing_size: Option<Au>, direction: Direction) -> SizeConstraint {
+        let (style_min_size, style_max_size) = match direction {
+            Direction::Inline => (self.style.min_inline_size(), self.style.max_inline_size()),
+            Direction::Block => (self.style.min_block_size(), self.style.max_block_size())
+        };
+
+        let border = if self.style().get_position().box_sizing == box_sizing::T::border_box {
+            Some(self.border_padding.start_end(direction))
+        } else {
+            None
+        };
+
+        SizeConstraint::new(containing_size, style_min_size, style_max_size, border)
+    }
+
     /// Returns a guess as to the distances from the margin edge of this fragment to its content
     /// in the inline direction. This will generally be correct unless percentages are involved.
     ///

components/layout/model.rs

@@ -504,64 +504,60 @@ impl ToGfxMatrix for ComputedMatrix {
     }
 }
 
-// https://drafts.csswg.org/css2/visudet.html#min-max-widths
-// https://drafts.csswg.org/css2/visudet.html#min-max-heights
-/// A min or max constraint
-///
-/// A `max` of `None` is equivalent to no limmit for the size in the given
-/// dimension. The `min` is >= 0, as negative values are illegal and by
-/// default `min` is 0.
-#[derive(Debug)]
-pub struct MinMaxConstraint {
-    min: Au,
-    max: Option<Au>
+/// A min-size and max-size constraint. The constructor has a optional `border`
+/// parameter, and when it is present the constraint will be subtracted. This is
+/// used to adjust the constraint for `box-sizing: border-box`, and when you do so
+/// make sure the size you want to clamp is intended to be used for content box.
+#[derive(Clone, Copy, Debug)]
+pub struct SizeConstraint {
+    min_size: Au,
+    max_size: Option<Au>,
 }
 
-impl MinMaxConstraint {
-    /// Create a `MinMaxConstraint` for a dimension given the min, max, and content box size for
-    /// an axis
-    pub fn new(content_size: Option<Au>, min: LengthOrPercentage,
-               max: LengthOrPercentageOrNone) -> MinMaxConstraint {
-        let min = match min {
-            LengthOrPercentage::Length(length) => length,
-            LengthOrPercentage::Percentage(percent) => {
-                match content_size {
-                    Some(size) => size.scale_by(percent),
-                    None => Au(0),
-                }
-            },
-            LengthOrPercentage::Calc(calc) => {
-                match content_size {
-                    Some(size) => size.scale_by(calc.percentage()),
-                    None => Au(0),
-                }
-            }
-        };
-
-        let max = match max {
-            LengthOrPercentageOrNone::Length(length) => Some(length),
-            LengthOrPercentageOrNone::Percentage(percent) => {
-                content_size.map(|size| size.scale_by(percent))
-            },
-            LengthOrPercentageOrNone::Calc(calc) => {
-                content_size.map(|size| size.scale_by(calc.percentage()))
-            }
-            LengthOrPercentageOrNone::None => None,
-        };
-
-        MinMaxConstraint {
-            min: min,
-            max: max
-        }
-    }
-
-    /// Clamp the given size by the given `min` and `max` constraints.
-    pub fn clamp(&self, other: Au) -> Au {
-        if other < self.min {
-            self.min
+impl SizeConstraint {
+    /// Create a `SizeConstraint` for an axis.
+    pub fn new(container_size: Option<Au>,
+               min_size: LengthOrPercentage,
+               max_size: LengthOrPercentageOrNone,
+               border: Option<Au>) -> SizeConstraint {
+        let mut min_size = match container_size {
+            Some(container_size) => specified(min_size, container_size),
+            None => if let LengthOrPercentage::Length(length) = min_size {
+                length
             } else {
-            match self.max {
-                Some(max) if max < other => max,
+                Au(0)
+            }
+        };
+
+        let mut max_size = match container_size {
+            Some(container_size) => specified_or_none(max_size, container_size),
+            None => if let LengthOrPercentageOrNone::Length(length) = max_size {
+                Some(length)
+            } else {
+                None
+            }
+        };
+        // Make sure max size is not smaller than min size.
+        max_size = max_size.map(|x| max(x, min_size));
+
+        if let Some(border) = border {
+            min_size = max((min_size - border), Au(0));
+            max_size = max_size.map(|x| max(x - border, Au(0)));
+        }
+
+        SizeConstraint {
+            min_size: min_size,
+            max_size: max_size
+        }
+    }
+
+    /// Clamp the given size by the given min size and max size constraint.
+    pub fn clamp(&self, other: Au) -> Au {
+        if other < self.min_size {
+            self.min_size
+        } else {
+            match self.max_size {
+                Some(max_size) if max_size < other => max_size,
                 _ => other
             }
         }