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.

1 files changed, 14 insertions, 9 deletions

diff --git a/src/exec/state.rs b/src/exec/state.rs
index 65f26439..aa2dde1c 100644
--- a/src/exec/state.rs
+++ b/src/exec/state.rs
@@ -2,10 +2,9 @@ use std::rc::Rc;
 
 use fontdock::{fallback, FallbackTree, FontStretch, FontStyle, FontVariant, FontWeight};
 
-use crate::geom::{
-    Align, Dir, LayoutAligns, LayoutDirs, Length, Linear, Relative, Sides, Size,
-};
+use crate::geom::*;
 use crate::paper::{Paper, PaperClass, PAPER_A4};
+use crate::shaping::VerticalFontMetric;
 
 /// The evaluation state.
 #[derive(Debug, Clone, PartialEq)]
@@ -77,20 +76,20 @@ impl Default for PageState {
 /// Defines paragraph properties.
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct ParState {
+    /// The spacing between paragraphs (dependent on scaled font size).
+    pub spacing: Linear,
+    /// The spacing between lines (dependent on scaled font size).
+    pub leading: Linear,
     /// The spacing between words (dependent on scaled font size).
     pub word_spacing: Linear,
-    /// The spacing between lines (dependent on scaled font size).
-    pub line_spacing: Linear,
-    /// The spacing between paragraphs (dependent on scaled font size).
-    pub par_spacing: Linear,
 }
 
 impl Default for ParState {
     fn default() -> Self {
         Self {
+            spacing: Relative::new(1.0).into(),
+            leading: Relative::new(0.5).into(),
             word_spacing: Relative::new(0.25).into(),
-            line_spacing: Linear::ZERO,
-            par_spacing: Relative::new(0.5).into(),
         }
     }
 }
@@ -106,6 +105,10 @@ pub struct FontState {
     pub size: Length,
     /// The linear to apply on the base font size.
     pub scale: Linear,
+    /// The top end of the text bounding box.
+    pub top_edge: VerticalFontMetric,
+    /// The bottom end of the text bounding box.
+    pub bottom_edge: VerticalFontMetric,
     /// Whether the strong toggle is active or inactive. This determines
     /// whether the next `*` adds or removes font weight.
     pub strong: bool,
@@ -141,6 +144,8 @@ impl Default for FontState {
                 stretch: FontStretch::Normal,
             },
             size: Length::pt(11.0),
+            top_edge: VerticalFontMetric::CapHeight,
+            bottom_edge: VerticalFontMetric::Baseline,
             scale: Linear::ONE,
             strong: false,
             emph: false,