Use line_gap as top padding

Fixes #143

layout/CHANGELOG.md

@@ -1,3 +1,6 @@
+# Unreleased
+* Use font line_gap as top-padding for layouts to address issues with glyphs taller than the font ascent.
+
 # 0.2.3
 * Default layouts: Keep word trailing space width if ending in a hard break or end of all glyphs _e.g. `"Foo \n"`_ _(This particularly changes the layout of right & centre aligned text ending in spaces)_. 
 

layout/src/builtin.rs

@@ -723,11 +723,12 @@ mod layout_test {
  ],
  );
 
+ let sfont = A_FONT.as_scaled(40.0);
  for g in glyphs {
  println!("{:?}", (g.glyph.scale, g.glyph.position));
  // all glyphs should have the same ascent drawing position
  let y_pos = g.glyph.position.y;
- assert_relative_eq!(y_pos, A_FONT.as_scaled(40.0).ascent());
+ assert_relative_eq!(y_pos, sfont.ascent() + sfont.line_gap());
  }
  }
 

layout/src/lines.rs

@@ -20,17 +20,21 @@ impl Line {
  /// Returns line glyphs positioned on the screen and aligned.
  pub fn aligned_on_screen(
  mut self,
- screen_position: (f32, f32),
+ (screen_x, screen_y): (f32, f32),
  h_align: HorizontalAlign,
  v_align: VerticalAlign,
  ) -> Vec<SectionGlyph> {
  if self.glyphs.is_empty() {
  return Vec::new();
  }
 
+ // use line_gap as top-padding for all lines
+ // fixes issues with glyphs taller than the ascent
+ let screen_y = screen_y + self.max_v_metrics.line_gap;
+
  // implement v-aligns when they're are supported
  let screen_left = match h_align {
- HorizontalAlign::Left => point(screen_position.0, screen_position.1),
+ HorizontalAlign::Left => point(screen_x, screen_y),
  // - Right alignment attained from left by shifting the line
  // leftwards by the rightmost x distance from render position
  // - Central alignment is attained from left by shifting the line
@@ -40,7 +44,7 @@ impl Line {
  if h_align == HorizontalAlign::Center {
  shift_left /= 2.0;
  }
- point(screen_position.0 - shift_left, screen_position.1)
+ point(screen_x - shift_left, screen_y)
  }
  };
 

layout/src/words.rs

@@ -17,7 +17,7 @@ pub(crate) struct VMetrics {
 impl VMetrics {
  #[inline]
  pub fn height(&self) -> f32 {
- self.ascent - self.descent
+ self.ascent - self.descent + self.line_gap
  }
 
  #[inline]