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};