Add control of line height and letter spacing

crates/egui/src/lib.rs

@@ -92,14 +92,16 @@
 //! # });
 //! ```
 //!
-//! ## Conventions
+//! ## Coordinate system
+//! The left-top corner of the screen is `(0.0, 0.0)`,
+//! with X increasing to the right and Y increasing downwards.
 //!
-//! Conventions unless otherwise specified:
+//! `egui` uses logical _points_ as its coordinate system.
+//! Those related to physical _pixels_ by the `pixels_per_point` scale factor.
+//! For example, a high-dpi screeen can have `pixels_per_point = 2.0`,
+//! meaning there are two physical screen pixels for each logical point.
 //!
-//! * angles are in radians
-//! * `Vec2::X` is right and `Vec2::Y` is down.
-//! * `Pos2::ZERO` is left top.
-//! * Positions and sizes are measured in _points_. Each point may consist of many physical pixels.
+//! Angles are in radians, and are measured clockwise from the X-axis, which has angle=0.
 //!
 //! # Integrating with egui
 //!
@@ -352,7 +354,7 @@ pub mod text {
     pub use crate::text_edit::CCursorRange;
     pub use epaint::text::{
         cursor::CCursor, FontData, FontDefinitions, FontFamily, Fonts, Galley, LayoutJob,
-        LayoutSection, TextFormat, TAB_SIZE,
+        LayoutSection, TextFormat, TextWrapping, TAB_SIZE,
     };
 }
 

crates/egui/src/widget_text.rs

@@ -1,5 +1,4 @@
-use std::borrow::Cow;
-use std::sync::Arc;
+use std::{borrow::Cow, sync::Arc};
 
 use crate::{
     style::WidgetVisuals, text::LayoutJob, Align, Color32, FontFamily, FontSelection, Galley, Pos2,
@@ -25,6 +24,8 @@ use crate::{
 pub struct RichText {
     text: String,
     size: Option<f32>,
+    extra_letter_spacing: f32,
+    line_height: Option<f32>,
     family: Option<FontFamily>,
     text_style: Option<TextStyle>,
     background_color: Color32,
@@ -100,6 +101,32 @@ impl RichText {
         self
     }
 
+    /// Extra spacing between letters, in points.
+    ///
+    /// Default: 0.0.
+    ///
+    /// For even text it is recommended you round this to an even number of _pixels_,
+    /// e.g. using [`crate::Painter::round_to_pixel`].
+    #[inline]
+    pub fn extra_letter_spacing(mut self, extra_letter_spacing: f32) -> Self {
+        self.extra_letter_spacing = extra_letter_spacing;
+        self
+    }
+
+    /// Explicit line height of the text in points.
+    ///
+    /// This is the distance between the bottom row of two subsequent lines of text.
+    ///
+    /// If `None` (the default), the line height is determined by the font.
+    ///
+    /// For even text it is recommended you round this to an even number of _pixels_,
+    /// e.g. using [`crate::Painter::round_to_pixel`].
+    #[inline]
+    pub fn line_height(mut self, line_height: Option<f32>) -> Self {
+        self.line_height = line_height;
+        self
+    }
+
     /// Select the font family.
     ///
     /// This overrides the value from [`Self::text_style`].
@@ -253,6 +280,8 @@ impl RichText {
         let Self {
             text,
             size,
+            extra_letter_spacing,
+            line_height,
             family,
             text_style,
             background_color,
@@ -309,6 +338,8 @@ impl RichText {
 
         let text_format = crate::text::TextFormat {
             font_id,
+            extra_letter_spacing,
+            line_height,
             color: text_color,
             background: background_color,
             italics,

crates/egui_demo_lib/src/demo/demo_app_windows.rs

@@ -35,7 +35,8 @@ impl Default for Demos {
             Box::<super::sliders::Sliders>::default(),
             Box::<super::strip_demo::StripDemo>::default(),
             Box::<super::table_demo::TableDemo>::default(),
-            Box::<super::text_edit::TextEdit>::default(),
+            Box::<super::text_edit::TextEditDemo>::default(),
+            Box::<super::text_layout::TextLayoutDemo>::default(),
             Box::<super::widget_gallery::WidgetGallery>::default(),
             Box::<super::window_options::WindowOptions>::default(),
             Box::<super::tests::WindowResizeTest>::default(),

crates/egui_demo_lib/src/demo/misc_demo_window.rs

@@ -1,14 +1,12 @@
 use super::*;
-use egui::{epaint::text::TextWrapping, *};
+use egui::*;
 
 /// Showcase some ui code
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct MiscDemoWindow {
     num_columns: usize,
 
-    text_break: TextBreakDemo,
-
     widgets: Widgets,
     colors: ColorWidgets,
     custom_collapsing_header: CustomCollapsingHeader,
@@ -24,8 +22,6 @@ impl Default for MiscDemoWindow {
         MiscDemoWindow {
             num_columns: 2,
 
-            text_break: Default::default(),
-
             widgets: Default::default(),
             colors: Default::default(),
             custom_collapsing_header: Default::default(),
@@ -72,8 +68,6 @@ impl View for MiscDemoWindow {
             .default_open(false)
             .show(ui, |ui| {
                 text_layout_demo(ui);
-                ui.separator();
-                self.text_break.ui(ui);
                 ui.vertical_centered(|ui| {
                     ui.add(crate::egui_github_link_file_line!());
                 });
@@ -644,63 +638,3 @@ fn text_layout_demo(ui: &mut Ui) {
 
     ui.label(job);
 }
-
-#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-#[cfg_attr(feature = "serde", serde(default))]
-struct TextBreakDemo {
-    break_anywhere: bool,
-    max_rows: usize,
-    overflow_character: Option<char>,
-}
-
-impl Default for TextBreakDemo {
-    fn default() -> Self {
-        Self {
-            max_rows: 1,
-            break_anywhere: true,
-            overflow_character: Some('…'),
-        }
-    }
-}
-
-impl TextBreakDemo {
-    pub fn ui(&mut self, ui: &mut Ui) {
-        let Self {
-            break_anywhere,
-            max_rows,
-            overflow_character,
-        } = self;
-
-        use egui::text::LayoutJob;
-
-        ui.horizontal(|ui| {
-            ui.add(DragValue::new(max_rows));
-            ui.label("Max rows");
-        });
-
-        ui.horizontal(|ui| {
-            ui.label("Line-break:");
-            ui.radio_value(break_anywhere, false, "word boundaries");
-            ui.radio_value(break_anywhere, true, "anywhere");
-        });
-
-        ui.horizontal(|ui| {
-            ui.selectable_value(overflow_character, None, "None");
-            ui.selectable_value(overflow_character, Some('…'), "…");
-            ui.selectable_value(overflow_character, Some('—'), "—");
-            ui.selectable_value(overflow_character, Some('-'), "  -  ");
-            ui.label("Overflow character");
-        });
-
-        let mut job =
-            LayoutJob::single_section(crate::LOREM_IPSUM_LONG.to_owned(), TextFormat::default());
-        job.wrap = TextWrapping {
-            max_rows: *max_rows,
-            break_anywhere: *break_anywhere,
-            overflow_character: *overflow_character,
-            ..Default::default()
-        };
-
-        ui.label(job); // `Label` overrides some of the wrapping settings, e.g. wrap width
-    }
-}

crates/egui_demo_lib/src/demo/mod.rs

@@ -26,6 +26,7 @@ pub mod strip_demo;
 pub mod table_demo;
 pub mod tests;
 pub mod text_edit;
+pub mod text_layout;
 pub mod toggle_switch;
 pub mod widget_gallery;
 pub mod window_options;

crates/egui_demo_lib/src/demo/text_edit.rs

@@ -1,20 +1,20 @@
-/// Showcase [`TextEdit`].
+/// Showcase [`egui::TextEdit`].
 #[derive(PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
-pub struct TextEdit {
+pub struct TextEditDemo {
     pub text: String,
 }
 
-impl Default for TextEdit {
+impl Default for TextEditDemo {
     fn default() -> Self {
         Self {
             text: "Edit this text".to_owned(),
         }
     }
 }
 
-impl super::Demo for TextEdit {
+impl super::Demo for TextEditDemo {
     fn name(&self) -> &'static str {
         "🖹 TextEdit"
     }
@@ -30,7 +30,7 @@ impl super::Demo for TextEdit {
     }
 }
 
-impl super::View for TextEdit {
+impl super::View for TextEditDemo {
     fn ui(&mut self, ui: &mut egui::Ui) {
         let Self { text } = self;
 

crates/egui_demo_lib/src/demo/text_layout.rs

@@ -0,0 +1,135 @@
+/// Showcase text layout
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "serde", serde(default))]
+pub struct TextLayoutDemo {
+    break_anywhere: bool,
+    max_rows: usize,
+    overflow_character: Option<char>,
+    extra_letter_spacing_pixels: i32,
+    line_height_pixels: u32,
+}
+
+impl Default for TextLayoutDemo {
+    fn default() -> Self {
+        Self {
+            max_rows: 3,
+            break_anywhere: true,
+            overflow_character: Some('…'),
+            extra_letter_spacing_pixels: 0,
+            line_height_pixels: 0,
+        }
+    }
+}
+
+impl super::Demo for TextLayoutDemo {
+    fn name(&self) -> &'static str {
+        "🖹 Text Layout"
+    }
+
+    fn show(&mut self, ctx: &egui::Context, open: &mut bool) {
+        egui::Window::new(self.name())
+            .open(open)
+            .resizable(true)
+            .show(ctx, |ui| {
+                use super::View as _;
+                self.ui(ui);
+            });
+    }
+}
+
+impl super::View for TextLayoutDemo {
+    fn ui(&mut self, ui: &mut egui::Ui) {
+        let Self {
+            break_anywhere,
+            max_rows,
+            overflow_character,
+            extra_letter_spacing_pixels,
+            line_height_pixels,
+        } = self;
+
+        use egui::text::LayoutJob;
+
+        let pixels_per_point = ui.ctx().pixels_per_point();
+        let points_per_pixel = 1.0 / pixels_per_point;
+
+        ui.vertical_centered(|ui| {
+            ui.add(crate::egui_github_link_file_line!());
+        });
+
+        ui.add_space(12.0);
+
+        egui::Grid::new("TextLayoutDemo")
+            .num_columns(2)
+            .show(ui, |ui| {
+                ui.label("Max rows:");
+                ui.add(egui::DragValue::new(max_rows));
+                ui.end_row();
+
+                ui.label("Line-break:");
+                ui.horizontal(|ui| {
+                    ui.radio_value(break_anywhere, false, "word boundaries");
+                    ui.radio_value(break_anywhere, true, "anywhere");
+                });
+                ui.end_row();
+
+                ui.label("Overflow character:");
+                ui.horizontal(|ui| {
+                    ui.selectable_value(overflow_character, None, "None");
+                    ui.selectable_value(overflow_character, Some('…'), "…");
+                    ui.selectable_value(overflow_character, Some('—'), "—");
+                    ui.selectable_value(overflow_character, Some('-'), "  -  ");
+                });
+                ui.end_row();
+
+                ui.label("Extra letter spacing:");
+                ui.add(egui::DragValue::new(extra_letter_spacing_pixels).suffix(" pixels"));
+                ui.end_row();
+
+                ui.label("Line height:");
+                ui.horizontal(|ui| {
+                    if ui
+                        .selectable_label(*line_height_pixels == 0, "Default")
+                        .clicked()
+                    {
+                        *line_height_pixels = 0;
+                    }
+                    if ui
+                        .selectable_label(*line_height_pixels != 0, "Custom")
+                        .clicked()
+                    {
+                        *line_height_pixels = (pixels_per_point * 20.0).round() as _;
+                    }
+                    if *line_height_pixels != 0 {
+                        ui.add(egui::DragValue::new(line_height_pixels).suffix(" pixels"));
+                    }
+                });
+                ui.end_row();
+            });
+
+        ui.add_space(12.0);
+
+        egui::ScrollArea::vertical().show(ui, |ui| {
+            let extra_letter_spacing = points_per_pixel * *extra_letter_spacing_pixels as f32;
+            let line_height =
+                (*line_height_pixels != 0).then_some(points_per_pixel * *line_height_pixels as f32);
+
+            let mut job = LayoutJob::single_section(
+                crate::LOREM_IPSUM_LONG.to_owned(),
+                egui::TextFormat {
+                    extra_letter_spacing,
+                    line_height,
+                    ..Default::default()
+                },
+            );
+            job.wrap = egui::text::TextWrapping {
+                max_rows: *max_rows,
+                break_anywhere: *break_anywhere,
+                overflow_character: *overflow_character,
+                ..Default::default()
+            };
+
+            // NOTE: `Label` overrides some of the wrapping settings, e.g. wrap width
+            ui.label(job);
+        });
+    }
+}

crates/egui_demo_lib/src/easy_mark/easy_mark_highlighter.rs

@@ -188,5 +188,6 @@ fn format_from_style(
         underline,
         strikethrough,
         valign,
+        ..Default::default()
     }
 }