Configurable font edges ⚙

Adds top-edge and bottom-edge parameters to the font function. These define how
the box around a word is computed. The possible values are:
- ascender
- cap-height (default top edge)
- x-height
- baseline (default bottom edge)
- descender

The defaults are chosen so that it's easy to create good-looking designs with
vertical alignment. Since they are much tighter than what most other software
uses by default, the default leading had to be increased to 50% of the font size
and paragraph spacing to 100% of the font size.

The values cap-height and x-height fall back to ascender in case they are zero
because this value may occur in fonts that don't have glyphs with cap- or
x-height (like Twitter Color Emoji). Since cap-height is the default top edge,
doing no fallback would break things badly.

Removes softness in favor of a simple boolean for pages and a more finegread u8
for spacing. This is needed to make paragraph spacing consume line spacing
created by hard line breaks.

2 files changed, 20 insertions, 20 deletions

diff --git a/src/layout/spacing.rs b/src/layout/spacing.rs
index 4b564a2b..2bcb7ac1 100644
--- a/src/layout/spacing.rs
+++ b/src/layout/spacing.rs
@@ -1,7 +1,6 @@
 use std::fmt::{self, Debug, Formatter};
 
 use super::*;
-use crate::exec::Softness;
 
 /// A spacing node.
 #[derive(Copy, Clone, PartialEq)]
@@ -10,13 +9,11 @@ pub struct NodeSpacing {
     pub amount: Length,
     /// Defines how spacing interacts with surrounding spacing.
     ///
-    /// Hard spacing assures that a fixed amount of spacing will always be
-    /// inserted. Soft spacing will be consumed by previous soft spacing or
-    /// neighbouring hard spacing and can be used to insert overridable spacing,
-    /// e.g. between words or paragraphs.
-    ///
-    /// This field is only used in evaluation, not in layouting.
-    pub softness: Softness,
+    /// Hard spacing (`softness = 0`) assures that a fixed amount of spacing
+    /// will always be inserted. Soft spacing (`softness >= 1`) will be consumed
+    /// by other spacing with lower softness and can be used to insert
+    /// overridable spacing, e.g. between words or paragraphs.
+    pub softness: u8,
 }
 
 impl Layout for NodeSpacing {
@@ -27,10 +24,7 @@ impl Layout for NodeSpacing {
 
 impl Debug for NodeSpacing {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        match self.softness {
-            Softness::Soft => write!(f, "Soft({})", self.amount),
-            Softness::Hard => write!(f, "Hard({})", self.amount),
-        }
+        write!(f, "Spacing({}, {})", self.amount, self.softness)
     }
 }
 
diff --git a/src/layout/text.rs b/src/layout/text.rs
index 256a6e6d..7b4eb08e 100644
--- a/src/layout/text.rs
+++ b/src/layout/text.rs
@@ -4,35 +4,41 @@ use std::rc::Rc;
 use fontdock::{FallbackTree, FontVariant};
 
 use super::*;
-use crate::shaping;
+use crate::shaping::{shape, VerticalFontMetric};
 
 /// A text node.
 #[derive(Clone, PartialEq)]
 pub struct NodeText {
+    /// The text.
+    pub text: String,
     /// The text direction.
     pub dir: Dir,
     /// How to align this text node in its parent.
     pub aligns: LayoutAligns,
-    /// The text.
-    pub text: String,
-    /// The font size.
-    pub font_size: Length,
     /// The families used for font fallback.
     pub families: Rc<FallbackTree>,
     /// The font variant,
     pub variant: FontVariant,
+    /// The font size.
+    pub font_size: Length,
+    /// The top end of the text bounding box.
+    pub top_edge: VerticalFontMetric,
+    /// The bottom end of the text bounding box.
+    pub bottom_edge: VerticalFontMetric,
 }
 
 impl Layout for NodeText {
     fn layout(&self, ctx: &mut LayoutContext, _: &Areas) -> Layouted {
         Layouted::Frame(
-            shaping::shape(
+            shape(
                 &self.text,
                 self.dir,
-                self.font_size,
-                &mut ctx.env.fonts,
                 &self.families,
                 self.variant,
+                self.font_size,
+                self.top_edge,
+                self.bottom_edge,
+                &mut ctx.env.fonts,
             ),
             self.aligns,
         )