Code example demo (#823)

egui_demo_lib/src/apps/demo/code_example.rs

@@ -0,0 +1,159 @@
+#[derive(Debug)]
+pub struct CodeExample {
+    name: String,
+    age: u32,
+}
+
+impl Default for CodeExample {
+    fn default() -> Self {
+        Self {
+            name: "Arthur".to_owned(),
+            age: 42,
+        }
+    }
+}
+
+impl CodeExample {
+    fn samples_in_grid(&mut self, ui: &mut egui::Ui) {
+        show_code(ui, r#"ui.heading("Code samples");"#);
+        ui.heading("Code samples");
+        ui.end_row();
+
+        show_code(
+            ui,
+            r#"
+            // Putting things on the same line using ui.horizontal:
+            ui.horizontal(|ui| {
+                ui.label("Your name: ");
+                ui.text_edit_singleline(&mut self.name);
+            });"#,
+        );
+        // Putting things on the same line using ui.horizontal:
+        ui.horizontal(|ui| {
+            ui.label("Your name: ");
+            ui.text_edit_singleline(&mut self.name);
+        });
+        ui.end_row();
+
+        show_code(
+            ui,
+            r#"egui::Slider::new(&mut self.age, 0..=120).text("age")"#,
+        );
+        ui.add(egui::Slider::new(&mut self.age, 0..=120).text("age"));
+        ui.end_row();
+
+        show_code(
+            ui,
+            r#"
+            if ui.button("Click each year").clicked() {
+                self.age += 1;
+            }"#,
+        );
+        if ui.button("Click each year").clicked() {
+            self.age += 1;
+        }
+        ui.end_row();
+
+        show_code(
+            ui,
+            r#"ui.label(format!("Hello '{}', age {}", self.name, self.age));"#,
+        );
+        ui.label(format!("Hello '{}', age {}", self.name, self.age));
+        ui.end_row();
+    }
+}
+
+impl super::Demo for CodeExample {
+    fn name(&self) -> &'static str {
+        "🖮 Code Example"
+    }
+
+    fn show(&mut self, ctx: &egui::CtxRef, open: &mut bool) {
+        use super::View;
+        egui::Window::new(self.name())
+            .open(open)
+            .default_size([800.0, 400.0])
+            .vscroll(false)
+            .hscroll(true)
+            .show(ctx, |ui| self.ui(ui));
+    }
+}
+
+impl super::View for CodeExample {
+    fn ui(&mut self, ui: &mut egui::Ui) {
+        use crate::syntax_highlighting::code_view_ui;
+
+        code_view_ui(
+            ui,
+            r"
+pub struct CodeExample {
+    name: String,
+    age: u32,
+}
+
+impl CodeExample {
+    fn ui(&mut self, ui: &mut egui::Ui) {
+"
+            .trim(),
+        );
+
+        egui::ScrollArea::vertical().show(ui, |ui| {
+            ui.horizontal(|ui| {
+                let indentation = 8.0 * ui.fonts()[egui::TextStyle::Monospace].glyph_width(' ');
+                let item_spacing = ui.spacing_mut().item_spacing;
+                ui.add_space(indentation - item_spacing.x);
+
+                egui::Grid::new("code_samples")
+                    .striped(true)
+                    .num_columns(2)
+                    .min_col_width(16.0)
+                    .spacing([16.0, 8.0])
+                    .show(ui, |ui| {
+                        self.samples_in_grid(ui);
+                    });
+            });
+        });
+
+        code_view_ui(ui, "    }\n}");
+
+        ui.separator();
+
+        code_view_ui(ui, &format!("{:#?}", self));
+
+        ui.separator();
+
+        let mut theme = crate::syntax_highlighting::CodeTheme::from_memory(ui.ctx());
+        ui.collapsing("Theme", |ui| {
+            theme.ui(ui);
+            theme.store_in_memory(ui.ctx());
+        });
+    }
+}
+
+fn show_code(ui: &mut egui::Ui, code: &str) {
+    let code = remove_leading_indentation(code.trim_start_matches('\n'));
+    crate::syntax_highlighting::code_view_ui(ui, &code);
+}
+
+fn remove_leading_indentation(code: &str) -> String {
+    fn is_indent(c: &u8) -> bool {
+        matches!(*c, b' ' | b'\t')
+    }
+
+    let first_line_indent = code.bytes().take_while(is_indent).count();
+
+    let mut out = String::new();
+
+    let mut code = code;
+    while !code.is_empty() {
+        let indent = code.bytes().take_while(is_indent).count();
+        let start = first_line_indent.min(indent);
+        let end = code
+            .find('\n')
+            .map(|endline| endline + 1)
+            .unwrap_or_else(|| code.len());
+        out += &code[start..end];
+        code = &code[end..];
+    }
+    out
+}

egui_demo_lib/src/apps/demo/demo_app_windows.rs

@@ -17,6 +17,7 @@ impl Default for Demos {
     fn default() -> Self {
         Self::from_demos(vec![
             Box::new(super::code_editor::CodeEditor::default()),
+            Box::new(super::code_example::CodeExample::default()),
             Box::new(super::dancing_strings::DancingStrings::default()),
             Box::new(super::drag_and_drop::DragAndDropDemo::default()),
             Box::new(super::font_book::FontBook::default()),

egui_demo_lib/src/apps/demo/mod.rs

@@ -6,6 +6,7 @@
 
 mod app;
 pub mod code_editor;
+pub mod code_example;
 pub mod dancing_strings;
 pub mod demo_app_windows;
 pub mod drag_and_drop;