Make the width of the thin space configurable (#8070)

Adds `FontTweak::thin_space_width` and `FontTweak::tab_size`

crates/egui/src/lib.rs

@@ -458,8 +458,8 @@ pub use epaint::{
 pub mod text {
     pub use crate::text_selection::CCursorRange;
     pub use epaint::text::{
-        FontData, FontDefinitions, FontFamily, Fonts, Galley, LayoutJob, LayoutSection, TAB_SIZE,
+        FontData, FontDefinitions, FontFamily, Fonts, Galley, LayoutJob, LayoutSection, TextFormat,
-        TextFormat, TextWrapping, cursor::CCursor,
+        TextWrapping, cursor::CCursor,
     };
 }
 

crates/egui/src/style.rs

@@ -2915,6 +2915,8 @@ impl Widget for &mut FontTweak {
                     y_offset,
                     hinting_override,
                     coords,
+                    thin_space_width,
+                    tab_size,
                 } = self;
 
                 ui.label("Scale");
@@ -2987,6 +2989,21 @@ impl Widget for &mut FontTweak {
                 }
                 ui.end_row();
 
+                ui.label("thin_space_width");
+                ui.horizontal(|ui| {
+                    ui.add(
+                        DragValue::new(thin_space_width)
+                            .range(0.0..=1.0)
+                            .speed(0.01),
+                    );
+                    ui.label("1\u{2009}234\u{2009}567\u{2009}890");
+                });
+                ui.end_row();
+
+                ui.label("tab_size");
+                ui.add(DragValue::new(tab_size).range(0.0..=16.0).speed(0.1));
+                ui.end_row();
+
                 if ui.button("Reset").clicked() {
                     *self = Default::default();
                 }

crates/egui/src/widgets/text_edit/text_buffer.rs

@@ -1,9 +1,9 @@
 use std::{borrow::Cow, ops::Range};
 
-use epaint::{
+use epaint::{Galley, text::cursor::CCursor};
-    Galley,
+
-    text::{TAB_SIZE, cursor::CCursor},
+/// One `\t` character is this many spaces wide (for indentation purposes).
-};
+const TAB_SIZE: usize = 4;
 
 use crate::{
     text::CCursorRange,

crates/egui_demo_lib/tests/snapshots/image_kerning/image_dark_x1.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:2ef07080ca2aa10e128c646479b8b322a092d63f15b35c52ed59015e7c2a0f60
+oid sha256:6d64cc7d014cf063689a4dd8a6cdd87eb944f9637890baf32f59a258342400bf
-size 15434
+size 15400

crates/egui_demo_lib/tests/snapshots/image_kerning/image_dark_x2.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:4edb61c6619d5e44892fa29da0aa0a624306ae637dbbaa057e3fa47c14dc06bd
+oid sha256:9e9f800546cc98bbd92f31072aceef10b5b8b9bbef0db4c8f4dbae652aefec61
-size 35988
+size 35918

crates/egui_demo_lib/tests/snapshots/image_kerning/image_light_x1.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:f8da0c2e37497968864a91fa6bef7c545c37791f4f9b788ea9a2f43dd4ac16b1
+oid sha256:e3f6e1cc6a069ac96ff9e039ce85462453ee943b4cb46080550bc1c0749ad658
-size 16116
+size 16085

crates/egui_demo_lib/tests/snapshots/image_kerning/image_light_x2.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:2a603fcb2eb97943d6be3239b91cacee093adcb55a6dd14af93a72fc8b3a61fa
+oid sha256:5901b5a8201b85b51118193eef300749a4569eedc62043cd4e03f76e73a12f51
-size 39270
+size 39222

crates/epaint/src/text/font.rs

@@ -432,8 +432,7 @@ impl FontFace {
             && let Some(space) = self.glyph_info(' ')
         {
             let glyph_info = GlyphInfo {
-                advance_width_unscaled: (crate::text::TAB_SIZE as f32
+                advance_width_unscaled: (self.tweak.tab_size * space.advance_width_unscaled.0)
-                    * space.advance_width_unscaled.0)
                     .into(),
                 ..space
             };
@@ -441,21 +440,18 @@ impl FontFace {
             return Some(glyph_info);
         }
 
-        if c == '\u{2009}' {
+        if (c == '\u{2009}' || c == '\u{202F}')
-            // Thin space, often used as thousands deliminator: 1 234 567 890
+            && let Some(space) = self.glyph_info(' ')
-            // https://www.compart.com/en/unicode/U+2009
+        {
-            // https://en.wikipedia.org/wiki/Thin_space
+            // Thin space (U+2009) and narrow no-break space (U+202F),
-
+            // often used as thousands separator: 1 234 567 890
-            if let Some(space) = self.glyph_info(' ') {
+            let advance_width = self.tweak.thin_space_width * space.advance_width_unscaled.0;
-                let em = self.font.borrow_dependent().metrics.units_per_em as f32;
+            let glyph_info = GlyphInfo {
-                let advance_width = f32::min(em / 6.0, space.advance_width_unscaled.0 * 0.5); // TODO(emilk): make configurable
+                advance_width_unscaled: advance_width.into(),
-                let glyph_info = GlyphInfo {
+                ..space
-                    advance_width_unscaled: advance_width.into(),
+            };
-                    ..space
+            self.glyph_info_cache.insert(c, glyph_info);
-                };
+            return Some(glyph_info);
-                self.glyph_info_cache.insert(c, glyph_info);
-                return Some(glyph_info);
-            }
         }
 
         if invisible_char(c) {

crates/epaint/src/text/fonts.rs

@@ -193,6 +193,19 @@ pub struct FontTweak {
 
     /// Override the font's default variation coordinates.
     pub coords: VariationCoords,
+
+    /// Width of a thin space (`\u{2009}`) and narrow no-break space (`\u{202F}`),
+    /// as a fraction of the normal space width.
+    ///
+    /// Thin space is often used as a thousands separator: `1 234 567`.
+    ///
+    /// Default: `0.5` (half a normal space).
+    pub thin_space_width: f32,
+
+    /// Width of a tab character (`\t`), measured in number of space widths.
+    ///
+    /// Default: `4.0`.
+    pub tab_size: f32,
 }
 
 impl Default for FontTweak {
@@ -203,6 +216,8 @@ impl Default for FontTweak {
             y_offset: 0.0,
             hinting_override: None,
             coords: VariationCoords::default(),
+            thin_space_width: 0.5,
+            tab_size: 4.0,
         }
     }
 }

crates/epaint/src/text/mod.rs

@@ -6,9 +6,6 @@ mod fonts;
 mod text_layout;
 mod text_layout_types;
 
-/// One `\t` character is this many spaces wide.
-pub const TAB_SIZE: usize = 4;
-
 pub use {
     fonts::{
         FontData, FontDefinitions, FontFamily, FontId, FontInsert, FontPriority, FontTweak, Fonts,

crates/epaint/src/text/text_layout.rs

@@ -8,7 +8,6 @@ use crate::{
     Color32, Mesh, Stroke, Vertex,
     stroke::PathStroke,
     text::{
-        TAB_SIZE,
         font::{StyledMetrics, UvRect, is_cjk, is_cjk_break_allowed},
         fonts::FontFaceKey,
     },
@@ -250,11 +249,23 @@ fn layout_shaped_run(
             .unwrap_or('\u{FFFD}'); // Unicode Replacement Character
 
         // Tab is a layout concept, not a glyph — the shaper doesn't know about tab stops.
-        // Override the advance width to TAB_SIZE × space width.
+        // Override the advance width using the font's configured tab size.
         if chr == '\t' {
+            let tweak = font.fonts_by_id.get(&run.font_key).map(|ff| ff.tweak());
+            let tab_size = tweak.map_or(4.0, |t| t.tab_size);
             let (_, space_info) = font.glyph_info(' ');
             let space_width_px = space_info.advance_width_unscaled.0 * px_scale;
-            advance_width_px = TAB_SIZE as f32 * space_width_px;
+            advance_width_px = tab_size * space_width_px;
+        }
+
+        // Thin space (U+2009) and narrow no-break space (U+202F):
+        // override the shaper's advance width with the configured fraction of a space.
+        if chr == '\u{2009}' || chr == '\u{202F}' {
+            let tweak = font.fonts_by_id.get(&run.font_key).map(|ff| ff.tweak());
+            let thin_space_width = tweak.map_or(0.5, |t| t.thin_space_width);
+            let (_, space_info) = font.glyph_info(' ');
+            let space_width_px = space_info.advance_width_unscaled.0 * px_scale;
+            advance_width_px = thin_space_width * space_width_px;
         }
 
         // Apply extra_letter_spacing only at cluster boundaries,