Make v-align and scale of user fonts tweakable (#1241)

* Add ability to "tweak" the scale and y-offsets of individual fonts
* Change default font tweak

This help vertically center large text.

CHANGELOG.md

@@ -13,6 +13,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
   * Easily change text styles with `Style::text_styles`.
   * Added `Ui::text_style_height`.
   * Added `TextStyle::resolve`.
+* Made v-align and scale of user fonts tweakable ([#1241](https://github.com/emilk/egui/pull/1027)).
 * `Context::load_texture` to convert an image into a texture which can be displayed using e.g. `ui.image(texture, size)` ([#1110](https://github.com/emilk/egui/pull/1110)).
 * Added `Ui::add_visible` and `Ui::add_visible_ui`.
 * Opt-in dependency on `tracing` crate for logging warnings ([#1192](https://github.com/emilk/egui/pull/1192)).

epaint/CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to the epaint crate will be documented in this file.
 * Much improved font selection ([#1154](https://github.com/emilk/egui/pull/1154)):
   * Replaced `TextStyle` with `FontId` which lets you pick any font size and font family.
   * Replaced `Fonts::font_image` with `font_image_delta` for partial font atlas updates.
+* Made v-align and scale of user fonts tweakable ([#1241](https://github.com/emilk/egui/pull/1027)).
 * Added `ImageData` and `TextureManager` for loading images into textures ([#1110](https://github.com/emilk/egui/pull/1110)).
 * Added `Shape::dashed_line_many` ([#1027](https://github.com/emilk/egui/pull/1027)).
 * Replaced `corner_radius: f32` with `rounding: Rounding`, allowing per-corner rounding settings ([#1206](https://github.com/emilk/egui/pull/1206)).

epaint/src/text/font.rs

@@ -73,20 +73,22 @@ impl FontImpl {
         pixels_per_point: f32,
         ab_glyph_font: ab_glyph::FontArc,
         scale_in_pixels: u32,
-        y_offset: f32,
+        y_offset_points: f32,
     ) -> FontImpl {
         assert!(scale_in_pixels > 0);
         assert!(pixels_per_point > 0.0);
 
         let height_in_points = scale_in_pixels as f32 / pixels_per_point;
 
-        // TODO: use v_metrics for line spacing ?
-        // let v = rusttype_font.v_metrics(Scale::uniform(scale_in_pixels));
-        // let height_in_pixels = v.ascent - v.descent + v.line_gap;
-        // let height_in_points = height_in_pixels / pixels_per_point;
+        // TODO: use these font metrics?
+        // use ab_glyph::ScaleFont as _;
+        // let scaled = ab_glyph_font.as_scaled(scale_in_pixels as f32);
+        // dbg!(scaled.ascent());
+        // dbg!(scaled.descent());
+        // dbg!(scaled.line_gap());
 
         // Round to closest pixel:
-        let y_offset = (y_offset * pixels_per_point).round() / pixels_per_point;
+        let y_offset = (y_offset_points * pixels_per_point).round() / pixels_per_point;
 
         Self {
             ab_glyph_font,

epaint/src/text/fonts.rs

@@ -120,24 +120,70 @@ pub struct FontData {
     /// Which font face in the file to use.
     /// When in doubt, use `0`.
     pub index: u32,
+
+    /// Extra scale and vertical tweak to apply to all text of this font.
+    pub tweak: FontTweak,
 }
 
 impl FontData {
     pub fn from_static(font: &'static [u8]) -> Self {
         Self {
             font: std::borrow::Cow::Borrowed(font),
             index: 0,
+            tweak: Default::default(),
         }
     }
 
     pub fn from_owned(font: Vec<u8>) -> Self {
         Self {
             font: std::borrow::Cow::Owned(font),
             index: 0,
+            tweak: Default::default(),
+        }
+    }
+
+    pub fn tweak(self, tweak: FontTweak) -> Self {
+        Self { tweak, ..self }
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+/// Extra scale and vertical tweak to apply to all text of a certain font.
+#[derive(Copy, Clone, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct FontTweak {
+    /// Scale the font by this much.
+    ///
+    /// Default: `1.0` (no scaling).
+    pub scale: f32,
+
+    /// Shift font downwards by this fraction of the font size (in points).
+    ///
+    /// A positive value shifts the text upwards.
+    /// A negative value shifts it downwards.
+    ///
+    /// Example value: `-0.2`.
+    pub y_offset_factor: f32,
+
+    /// Shift font downwards by this amount of logical points.
+    ///
+    /// Example value: `-1.0`.
+    pub y_offset: f32,
+}
+
+impl Default for FontTweak {
+    fn default() -> Self {
+        Self {
+            scale: 1.0,
+            y_offset_factor: -0.2, // makes the default fonts look more centered in buttons and such
+            y_offset: 0.0,
         }
     }
 }
 
+// ----------------------------------------------------------------------------
+
 fn ab_glyph_font_from_font_data(name: &str, data: &FontData) -> ab_glyph::FontArc {
     match &data.font {
         std::borrow::Cow::Borrowed(bytes) => {
@@ -220,10 +266,17 @@ impl Default for FontDefinitions {
                 "NotoEmoji-Regular".to_owned(),
                 FontData::from_static(include_bytes!("../../fonts/NotoEmoji-Regular.ttf")),
             );
+
             // Bigger emojis, and more. <http://jslegers.github.io/emoji-icon-font/>:
             font_data.insert(
                 "emoji-icon-font".to_owned(),
-                FontData::from_static(include_bytes!("../../fonts/emoji-icon-font.ttf")),
+                FontData::from_static(include_bytes!("../../fonts/emoji-icon-font.ttf")).tweak(
+                    FontTweak {
+                        scale: 0.8,            // make it smaller
+                        y_offset_factor: 0.07, // move it down slightly
+                        y_offset: 0.0,
+                    },
+                ),
             );
 
             families.insert(
@@ -603,7 +656,7 @@ impl GalleyCache {
 struct FontImplCache {
     atlas: Arc<Mutex<TextureAtlas>>,
     pixels_per_point: f32,
-    ab_glyph_fonts: BTreeMap<String, ab_glyph::FontArc>,
+    ab_glyph_fonts: BTreeMap<String, (FontTweak, ab_glyph::FontArc)>,
 
     /// Map font pixel sizes and names to the cached `FontImpl`.
     cache: ahash::AHashMap<(u32, String), Arc<FontImpl>>,
@@ -617,7 +670,11 @@ impl FontImplCache {
     ) -> Self {
         let ab_glyph_fonts = font_data
             .iter()
-            .map(|(name, font_data)| (name.clone(), ab_glyph_font_from_font_data(name, font_data)))
+            .map(|(name, font_data)| {
+                let tweak = font_data.tweak;
+                let ab_glyph = ab_glyph_font_from_font_data(name, font_data);
+                (name.clone(), (tweak, ab_glyph))
+            })
             .collect();
 
         Self {
@@ -638,35 +695,28 @@ impl FontImplCache {
     }
 
     pub fn font_impl(&mut self, scale_in_pixels: u32, font_name: &str) -> Arc<FontImpl> {
-        let scale_in_pixels = if font_name == "emoji-icon-font" {
-            (scale_in_pixels as f32 * 0.8).round() as u32 // TODO: remove font scale HACK!
-        } else {
-            scale_in_pixels
-        };
+        let (tweak, ab_glyph_font) = self
+            .ab_glyph_fonts
+            .get(font_name)
+            .unwrap_or_else(|| panic!("No font data found for {:?}", font_name))
+            .clone();
 
-        let y_offset = if font_name == "emoji-icon-font" {
+        let scale_in_pixels = (scale_in_pixels as f32 * tweak.scale).round() as u32;
+
+        let y_offset_points = {
             let scale_in_points = scale_in_pixels as f32 / self.pixels_per_point;
-            scale_in_points * 0.29375 // TODO: remove font alignment hack
-        } else {
-            0.0
-        };
-        let y_offset = y_offset - 3.0; // Tweaked to make text look centered in buttons and text edit fields
+            scale_in_points * tweak.y_offset_factor
+        } + tweak.y_offset;
 
         self.cache
             .entry((scale_in_pixels, font_name.to_owned()))
             .or_insert_with(|| {
-                let ab_glyph_font = self
-                    .ab_glyph_fonts
-                    .get(font_name)
-                    .unwrap_or_else(|| panic!("No font data found for {:?}", font_name))
-                    .clone();
-
                 Arc::new(FontImpl::new(
                     self.atlas.clone(),
                     self.pixels_per_point,
                     ab_glyph_font,
                     scale_in_pixels,
-                    y_offset,
+                    y_offset_points,
                 ))
             })
             .clone()