Add UI to modify `FontTweak` live (#5125)

This will make it easier to get nice sizing and vertical alignments of
fonts

crates/egui/src/context.rs

@@ -4,9 +4,15 @@ use std::{borrow::Cow, cell::RefCell, panic::Location, sync::Arc, time::Duration
 
 use containers::area::AreaState;
 use epaint::{
-    emath, emath::TSTransform, mutex::RwLock, pos2, stats::PaintStats, tessellator, text::Fonts,
-    util::OrderedFloat, vec2, ClippedPrimitive, ClippedShape, Color32, ImageData, ImageDelta, Pos2,
-    Rect, TessellationOptions, TextureAtlas, TextureId, Vec2,
+    emath::{self, TSTransform},
+    mutex::RwLock,
+    pos2,
+    stats::PaintStats,
+    tessellator,
+    text::Fonts,
+    util::OrderedFloat,
+    vec2, ClippedPrimitive, ClippedShape, Color32, ImageData, ImageDelta, Pos2, Rect,
+    TessellationOptions, TextureAtlas, TextureId, Vec2,
 };
 
 use crate::{
@@ -2817,6 +2823,10 @@ impl Context {
         let prev_options = self.options(|o| o.clone());
         let mut options = prev_options.clone();
 
+        ui.collapsing("🔠 Font tweak", |ui| {
+            self.fonts_tweak_ui(ui);
+        });
+
         options.ui(ui);
 
         if options != prev_options {
@@ -2824,6 +2834,23 @@ impl Context {
         }
     }
 
+    fn fonts_tweak_ui(&self, ui: &mut Ui) {
+        let mut font_definitions = self.write(|ctx| ctx.font_definitions.clone());
+        let mut changed = false;
+
+        for (name, data) in &mut font_definitions.font_data {
+            ui.collapsing(name, |ui| {
+                if data.tweak.ui(ui).changed() {
+                    changed = true;
+                }
+            });
+        }
+
+        if changed {
+            self.set_fonts(font_definitions);
+        }
+    }
+
     /// Show the state of egui, including its input and output.
     pub fn inspection_ui(&self, ui: &mut Ui) {
         use crate::containers::CollapsingHeader;

crates/egui/src/style.rs

@@ -4,7 +4,7 @@
 
 use std::{collections::BTreeMap, ops::RangeInclusive, sync::Arc};
 
-use epaint::{Rounding, Shadow, Stroke};
+use epaint::{text::FontTweak, Rounding, Shadow, Stroke};
 
 use crate::{
     ecolor::Color32,
@@ -2498,3 +2498,48 @@ impl Widget for &mut crate::Frame {
             .response
     }
 }
+
+impl Widget for &mut FontTweak {
+    fn ui(self, ui: &mut Ui) -> Response {
+        let original: FontTweak = *self;
+
+        let mut response = Grid::new("font_tweak")
+            .num_columns(2)
+            .show(ui, |ui| {
+                let FontTweak {
+                    scale,
+                    y_offset_factor,
+                    y_offset,
+                    baseline_offset_factor,
+                } = self;
+
+                ui.label("Scale");
+                let speed = *scale * 0.01;
+                ui.add(DragValue::new(scale).range(0.01..=10.0).speed(speed));
+                ui.end_row();
+
+                ui.label("y_offset_factor");
+                ui.add(DragValue::new(y_offset_factor).speed(-0.0025));
+                ui.end_row();
+
+                ui.label("y_offset");
+                ui.add(DragValue::new(y_offset).speed(-0.02));
+                ui.end_row();
+
+                ui.label("baseline_offset_factor");
+                ui.add(DragValue::new(baseline_offset_factor).speed(-0.0025));
+                ui.end_row();
+
+                if ui.button("Reset").clicked() {
+                    *self = Default::default();
+                }
+            })
+            .response;
+
+        if *self != original {
+            response.mark_changed();
+        }
+
+        response
+    }
+}

crates/egui/src/ui.rs

@@ -1404,7 +1404,7 @@ impl Ui {
     ///
     /// If this is called multiple times per frame for the same [`crate::ScrollArea`], the deltas will be summed.
     ///
-    /// /// See also: [`Response::scroll_to_me`], [`Ui::scroll_to_rect`], [`Ui::scroll_to_cursor`]
+    /// See also: [`Response::scroll_to_me`], [`Ui::scroll_to_rect`], [`Ui::scroll_to_cursor`]
     ///
     /// ```
     /// # use egui::{Align, Vec2};

crates/egui_demo_lib/src/demo/font_book.rs

@@ -1,9 +1,16 @@
 use std::collections::BTreeMap;
 
+struct GlyphInfo {
+    name: String,
+
+    // What fonts it is available in
+    fonts: Vec<String>,
+}
+
 pub struct FontBook {
     filter: String,
     font_id: egui::FontId,
-    named_chars: BTreeMap<egui::FontFamily, BTreeMap<char, String>>,
+    available_glyphs: BTreeMap<egui::FontFamily, BTreeMap<char, GlyphInfo>>,
 }
 
 impl Default for FontBook {
@@ -11,7 +18,7 @@ impl Default for FontBook {
         Self {
             filter: Default::default(),
             font_id: egui::FontId::proportional(18.0),
-            named_chars: Default::default(),
+            available_glyphs: Default::default(),
         }
     }
 }
@@ -37,7 +44,7 @@ impl crate::View for FontBook {
 
         ui.label(format!(
             "The selected font supports {} characters.",
-            self.named_chars
+            self.available_glyphs
                 .get(&self.font_id.family)
                 .map(|map| map.len())
                 .unwrap_or_default()
@@ -67,8 +74,8 @@ impl crate::View for FontBook {
         });
 
         let filter = &self.filter;
-        let named_chars = self
-            .named_chars
+        let available_glyphs = self
+            .available_glyphs
             .entry(self.font_id.family.clone())
             .or_insert_with(|| available_characters(ui, self.font_id.family.clone()));
 
@@ -78,8 +85,11 @@ impl crate::View for FontBook {
             ui.horizontal_wrapped(|ui| {
                 ui.spacing_mut().item_spacing = egui::Vec2::splat(2.0);
 
-                for (&chr, name) in named_chars {
-                    if filter.is_empty() || name.contains(filter) || *filter == chr.to_string() {
+                for (&chr, glyph_info) in available_glyphs {
+                    if filter.is_empty()
+                        || glyph_info.name.contains(filter)
+                        || *filter == chr.to_string()
+                    {
                         let button = egui::Button::new(
                             egui::RichText::new(chr.to_string()).font(self.font_id.clone()),
                         )
@@ -89,7 +99,10 @@ impl crate::View for FontBook {
                             ui.label(
                                 egui::RichText::new(chr.to_string()).font(self.font_id.clone()),
                             );
-                            ui.label(format!("{}\nU+{:X}\n\nClick to copy", name, chr as u32));
+                            ui.label(format!(
+                                "{}\nU+{:X}\n\nFound in: {:?}\n\nClick to copy",
+                                glyph_info.name, chr as u32, glyph_info.fonts
+                            ));
                         };
 
                         if ui.add(button).on_hover_ui(tooltip_ui).clicked() {
@@ -102,15 +115,23 @@ impl crate::View for FontBook {
     }
 }
 
-fn available_characters(ui: &egui::Ui, family: egui::FontFamily) -> BTreeMap<char, String> {
+fn available_characters(ui: &egui::Ui, family: egui::FontFamily) -> BTreeMap<char, GlyphInfo> {
     ui.fonts(|f| {
         f.lock()
             .fonts
             .font(&egui::FontId::new(10.0, family)) // size is arbitrary for getting the characters
             .characters()
             .iter()
-            .filter(|chr| !chr.is_whitespace() && !chr.is_ascii_control())
-            .map(|&chr| (chr, char_name(chr)))
+            .filter(|(chr, _fonts)| !chr.is_whitespace() && !chr.is_ascii_control())
+            .map(|(chr, fonts)| {
+                (
+                    *chr,
+                    GlyphInfo {
+                        name: char_name(*chr),
+                        fonts: fonts.clone(),
+                    },
+                )
+            })
             .collect()
     })
 }

crates/epaint/src/text/font.rs

@@ -1,11 +1,13 @@
+use std::collections::BTreeMap;
+use std::sync::Arc;
+
+use emath::{vec2, Vec2};
+
 use crate::{
     mutex::{Mutex, RwLock},
     text::FontTweak,
     TextureAtlas,
 };
-use emath::{vec2, Vec2};
-use std::collections::BTreeSet;
-use std::sync::Arc;
 
 // ----------------------------------------------------------------------------
 
@@ -330,7 +332,7 @@ pub struct Font {
     fonts: Vec<Arc<FontImpl>>,
 
     /// Lazily calculated.
-    characters: Option<BTreeSet<char>>,
+    characters: Option<BTreeMap<char, Vec<String>>>,
 
     replacement_glyph: (FontIndex, GlyphInfo),
     pixels_per_point: f32,
@@ -398,12 +400,14 @@ impl Font {
         self.glyph_info(crate::text::PASSWORD_REPLACEMENT_CHAR);
     }
 
-    /// All supported characters.
-    pub fn characters(&mut self) -> &BTreeSet<char> {
+    /// All supported characters, and in which font they are available in.
+    pub fn characters(&mut self) -> &BTreeMap<char, Vec<String>> {
         self.characters.get_or_insert_with(|| {
-            let mut characters = BTreeSet::new();
+            let mut characters: BTreeMap<char, Vec<String>> = Default::default();
             for font in &self.fonts {
-                characters.extend(font.characters());
+                for chr in font.characters() {
+                    characters.entry(chr).or_default().push(font.name.clone());
+                }
             }
             characters
         })

crates/epaint/src/text/fonts.rs

@@ -159,6 +159,8 @@ pub struct FontTweak {
     /// Shift font's glyphs downwards by this fraction of the font size (in points).
     /// this is only a visual effect and does not affect the text layout.
     ///
+    /// Affects larger font sizes more.
+    ///
     /// A positive value shifts the text downwards.
     /// A negative value shifts it upwards.
     ///
@@ -168,6 +170,8 @@ pub struct FontTweak {
     /// Shift font's glyphs downwards by this amount of logical points.
     /// this is only a visual effect and does not affect the text layout.
     ///
+    /// Affects all font sizes equally.
+    ///
     /// Example value: `2.0`.
     pub y_offset: f32,
 

crates/epaint/src/text/text_layout.rs

@@ -482,7 +482,7 @@ fn replace_last_glyph_with_overflow_character(
 
 /// Horizontally aligned the text on a row.
 ///
-/// /// Ignores the Y coordinate.
+/// Ignores the Y coordinate.
 fn halign_and_justify_row(
     point_scale: PointScale,
     row: &mut Row,