Draft metrics hinting support

src/buffer.rs

@@ -216,6 +216,7 @@ pub struct Buffer {
     wrap: Wrap,
     monospace_width: Option<f32>,
     tab_width: u16,
+    hint: bool,
 }
 
 impl Clone for Buffer {
@@ -230,6 +231,7 @@ impl Clone for Buffer {
             wrap: self.wrap,
             monospace_width: self.monospace_width,
             tab_width: self.tab_width,
+            hint: self.hint,
         }
     }
 }
@@ -246,7 +248,7 @@ impl Buffer {
     /// # Panics
     ///
     /// Will panic if `metrics.line_height` is zero.
-    pub fn new_empty(metrics: Metrics) -> Self {
+    pub fn new_empty(metrics: Metrics, hint: bool) -> Self {
         assert_ne!(metrics.line_height, 0.0, "line height cannot be 0");
         Self {
             lines: Vec::new(),
@@ -258,6 +260,7 @@ impl Buffer {
             wrap: Wrap::WordOrGlyph,
             monospace_width: None,
             tab_width: 8,
+            hint,
         }
     }
 
@@ -266,8 +269,8 @@ impl Buffer {
     /// # Panics
     ///
     /// Will panic if `metrics.line_height` is zero.
-    pub fn new(font_system: &mut FontSystem, metrics: Metrics) -> Self {
-        let mut buffer = Self::new_empty(metrics);
+    pub fn new(font_system: &mut FontSystem, metrics: Metrics, hint: bool) -> Self {
+        let mut buffer = Self::new_empty(metrics, hint);
         buffer.set_text(font_system, "", &Attrs::new(), Shaping::Advanced, None);
         buffer
     }
@@ -297,6 +300,7 @@ impl Buffer {
                     self.wrap,
                     self.monospace_width,
                     self.tab_width,
+                    self.hint,
                 );
             }
         }
@@ -540,6 +544,7 @@ impl Buffer {
             self.wrap,
             self.monospace_width,
             self.tab_width,
+            self.hint,
         ))
     }
 
@@ -719,7 +724,7 @@ impl Buffer {
     /// ```
     /// # use cosmic_text::{Attrs, Buffer, Family, FontSystem, Metrics, Shaping};
     /// # let mut font_system = FontSystem::new();
-    /// let mut buffer = Buffer::new_empty(Metrics::new(32.0, 44.0));
+    /// let mut buffer = Buffer::new_empty(Metrics::new(32.0, 44.0), false);
     /// let attrs = Attrs::new().family(Family::Serif);
     /// buffer.set_rich_text(
     ///     &mut font_system,
@@ -1448,7 +1453,7 @@ impl BorrowedWithFontSystem<'_, Buffer> {
     /// ```
     /// # use cosmic_text::{Attrs, Buffer, Family, FontSystem, Metrics, Shaping};
     /// # let mut font_system = FontSystem::new();
-    /// let mut buffer = Buffer::new_empty(Metrics::new(32.0, 44.0));
+    /// let mut buffer = Buffer::new_empty(Metrics::new(32.0, 44.0), false);
     /// let attrs = Attrs::new().family(Family::Serif);
     /// buffer.set_rich_text(
     ///     &mut font_system,

src/buffer_line.rs

@@ -243,6 +243,7 @@ impl BufferLine {
         wrap: Wrap,
         match_mono_width: Option<f32>,
         tab_width: u16,
+        hint: bool,
     ) -> &[LayoutLine] {
         if self.layout_opt.is_unused() {
             let align = self.align;
@@ -259,6 +260,7 @@ impl BufferLine {
                 align,
                 &mut layout,
                 match_mono_width,
+                hint,
             );
             self.layout_opt.set_used(layout);
         }

src/lib.rs

@@ -24,7 +24,7 @@
 //! let metrics = Metrics::new(14.0, 20.0);
 //!
 //! // A Buffer provides shaping and layout for a UTF-8 string, create one per text widget
-//! let mut buffer = Buffer::new(&mut font_system, metrics);
+//! let mut buffer = Buffer::new(&mut font_system, metrics, false);
 //!
 //! // Borrow buffer together with the font system for more convenient method calls
 //! let mut buffer = buffer.borrow_with(&mut font_system);

src/shape.rs

@@ -1152,6 +1152,7 @@ impl ShapeLine {
         wrap: Wrap,
         align: Option<Align>,
         match_mono_width: Option<f32>,
+        hint: bool,
     ) -> Vec<LayoutLine> {
         let mut lines = Vec::with_capacity(1);
         self.layout_to_buffer(
@@ -1162,6 +1163,7 @@ impl ShapeLine {
             align,
             &mut lines,
             match_mono_width,
+            hint,
         );
         lines
     }
@@ -1175,6 +1177,7 @@ impl ShapeLine {
         align: Option<Align>,
         layout_lines: &mut Vec<LayoutLine>,
         match_mono_width: Option<f32>,
+        hint: bool,
     ) {
         fn add_to_visual_line(
             vl: &mut VisualLine,
@@ -1550,6 +1553,10 @@ impl ShapeLine {
                 x += alignment_correction;
             }
 
+            if hint {
+                x = x.round();
+            }
+
             // TODO: Only certain `is_whitespace` chars are typically expanded but this is what is
             // currently used to compute `visual_line.spaces`.
             //
@@ -1628,6 +1635,9 @@ impl ShapeLine {
                                 // Round to nearest monospace width
                                 x_advance = ((x_advance / match_em_width).round()) * match_em_width;
                             }
+                            if hint {
+                                x_advance = x_advance.round();
+                            }
                             if self.rtl {
                                 x -= x_advance;
                             }