Tab identation for multiline text edit (#246)

Lock focus on multiline text edit, and insert tabs on tab char

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

egui/src/memory.rs

@@ -141,8 +141,12 @@ pub(crate) struct Focus {
     /// The last widget interested in focus.
     last_interested: Option<Id>,
 
+    /// If `true`, pressing tab will NOT move focus away from the current widget.
+    is_focus_locked: bool,
+
     /// Set at the beginning of the frame, set to `false` when "used".
     pressed_tab: bool,
+
     /// Set at the beginning of the frame, set to `false` when "used".
     pressed_shift_tab: bool,
 }
@@ -199,6 +203,7 @@ impl Focus {
                 }
             ) {
                 self.id = None;
+                self.is_focus_locked = false;
                 break;
             }
 
@@ -208,6 +213,7 @@ impl Focus {
                 modifiers,
             } = event
             {
+                if !self.is_focus_locked {
                     if modifiers.shift {
                         self.pressed_shift_tab = true;
                     } else {
@@ -216,6 +222,7 @@ impl Focus {
                 }
             }
         }
+    }
 
     pub(crate) fn end_frame(&mut self, used_ids: &epaint::ahash::AHashMap<Id, Pos2>) {
         if let Some(id) = self.id {
@@ -238,11 +245,11 @@ impl Focus {
             self.id = Some(id);
             self.give_to_next = false;
         } else if self.id == Some(id) {
-            if self.pressed_tab {
+            if self.pressed_tab && !self.is_focus_locked {
                 self.id = None;
                 self.give_to_next = true;
                 self.pressed_tab = false;
-            } else if self.pressed_shift_tab {
+            } else if self.pressed_shift_tab && !self.is_focus_locked {
                 self.id_next_frame = self.last_interested; // frame-delay so gained_focus works
                 self.pressed_shift_tab = false;
             }
@@ -302,11 +309,26 @@ impl Memory {
         self.interaction.focus.id == Some(id)
     }
 
+    pub(crate) fn lock_focus(&mut self, id: Id, b: bool) {
+        if self.had_focus_last_frame(id) && self.has_focus(id) {
+            self.interaction.focus.is_focus_locked = b;
+        }
+    }
+
+    pub(crate) fn has_lock_focus(&mut self, id: Id) -> bool {
+        if self.had_focus_last_frame(id) && self.has_focus(id) {
+            self.interaction.focus.is_focus_locked
+        } else {
+            false
+        }
+    }
+
     /// Give keyboard focus to a specific widget.
     /// See also [`crate::Response::request_focus`].
     #[inline(always)]
     pub fn request_focus(&mut self, id: Id) {
         self.interaction.focus.id = Some(id);
+        self.interaction.focus.is_focus_locked = false;
     }
 
     /// Surrender keyboard focus for a specific widget.
@@ -315,6 +337,7 @@ impl Memory {
     pub fn surrender_focus(&mut self, id: Id) {
         if self.interaction.focus.id == Some(id) {
             self.interaction.focus.id = None;
+            self.interaction.focus.is_focus_locked = false;
         }
     }
 

egui/src/ui.rs

@@ -934,6 +934,22 @@ impl Ui {
         TextEdit::multiline(text).ui(self)
     }
 
+    /// A `TextEdit` for code editing.
+    ///
+    /// This will be multiline, monospace, and will insert tabs instead of moving focus.
+    ///
+    /// See also [`TextEdit::code_editor`].
+    pub fn code_editor(&mut self, text: &mut String) -> Response {
+        self.add(TextEdit::multiline(text).code_editor())
+    }
+
+    /// A `TextEdit` for code editing with configurable `Tab` management.
+    ///
+    /// Se also [`TextEdit::code_editor_with_config`].
+    pub fn code_editor_with_config(&mut self, text: &mut String, config: CodingConfig) -> Response {
+        self.add(TextEdit::multiline(text).code_editor_with_config(config))
+    }
+
     /// Usage: `if ui.button("Click me").clicked() { … }`
     ///
     /// Shortcut for `add(Button::new(text))`

egui/src/widgets/text_edit.rs

@@ -108,6 +108,12 @@ impl CCursorPair {
     }
 }
 
+#[derive(Clone, Copy, Debug, Default)]
+#[cfg_attr(feature = "persistence", derive(serde::Deserialize, serde::Serialize))]
+pub struct CodingConfig {
+    pub tab_moves_focus: bool,
+}
+
 /// A text region that the user can edit the contents of.
 ///
 /// See also [`Ui::text_edit_singleline`] and  [`Ui::text_edit_multiline`].
@@ -140,6 +146,7 @@ pub struct TextEdit<'t> {
     enabled: bool,
     desired_width: Option<f32>,
     desired_height_rows: usize,
+    tab_moves_focus: bool,
 }
 impl<'t> TextEdit<'t> {
     pub fn cursor(ui: &Ui, id: Id) -> Option<CursorPair> {
@@ -171,6 +178,7 @@ impl<'t> TextEdit<'t> {
             enabled: true,
             desired_width: None,
             desired_height_rows: 1,
+            tab_moves_focus: true,
         }
     }
 
@@ -189,9 +197,37 @@ impl<'t> TextEdit<'t> {
             enabled: true,
             desired_width: None,
             desired_height_rows: 4,
+            tab_moves_focus: true,
         }
     }
 
+    /// When this is true, then pass focus to the next
+    /// widget.
+    pub fn tab_moves_focus(mut self, b: bool) -> Self {
+        self.tab_moves_focus = b;
+        self
+    }
+
+    /// Build a `TextEdit` focused on code editing.
+    /// By default it comes with:
+    /// - monospaced font
+    /// - focus lock
+    pub fn code_editor(self) -> Self {
+        self.text_style(TextStyle::Monospace).tab_moves_focus(false)
+    }
+
+    /// Build a `TextEdit` focused on code editing with configurable `Tab` management.
+    ///
+    /// Shortcut for:
+    /// ```rust, ignore
+    /// egui::TextEdit::multiline(code_snippet)
+    ///     .code_editor()
+    ///     .tab_moves_focus(tab_moves_focus);
+    /// ```
+    pub fn code_editor_with_config(self, config: CodingConfig) -> Self {
+        self.code_editor().tab_moves_focus(config.tab_moves_focus)
+    }
+
     pub fn id(mut self, id: Id) -> Self {
         self.id = Some(id);
         self
@@ -312,6 +348,7 @@ impl<'t> TextEdit<'t> {
             enabled,
             desired_width,
             desired_height_rows,
+            tab_moves_focus,
         } = self;
 
         let text_style = text_style.unwrap_or_else(|| ui.style().body_text_style);
@@ -417,6 +454,8 @@ impl<'t> TextEdit<'t> {
 
         let mut text_cursor = None;
         if ui.memory().has_focus(id) && enabled {
+            ui.memory().lock_focus(id, !tab_moves_focus);
+
             let mut cursorp = state
                 .cursorp
                 .map(|cursorp| {
@@ -466,12 +505,27 @@ impl<'t> TextEdit<'t> {
                             && text_to_insert != "\r"
                         {
                             let mut ccursor = delete_selected(text, &cursorp);
+
                             insert_text(&mut ccursor, text, text_to_insert);
                             Some(CCursorPair::one(ccursor))
                         } else {
                             None
                         }
                     }
+                    Event::Key {
+                        key: Key::Tab,
+                        pressed: true,
+                        ..
+                    } => {
+                        if multiline && ui.memory().has_lock_focus(id) {
+                            let mut ccursor = delete_selected(text, &cursorp);
+
+                            insert_text(&mut ccursor, text, "\t");
+                            Some(CCursorPair::one(ccursor))
+                        } else {
+                            None
+                        }
+                    }
                     Event::Key {
                         key: Key::Enter,
                         pressed: true,

egui_demo_lib/src/apps/demo/widgets.rs

@@ -22,8 +22,11 @@ pub struct Widgets {
     radio: Enum,
     angle: f32,
     color: Color32,
+    show_password: bool,
     single_line_text_input: String,
     multiline_text_input: String,
+    tab_moves_focus: bool,
+    code_snippet: String,
 }
 
 impl Default for Widgets {
@@ -35,7 +38,31 @@ impl Default for Widgets {
             angle: std::f32::consts::TAU / 3.0,
             color: (Rgba::from_rgb(0.0, 1.0, 0.5) * 0.75).into(),
             single_line_text_input: "Hello World!".to_owned(),
+            show_password: false,
+            tab_moves_focus: false,
+
             multiline_text_input: "Text can both be so wide that it needs a line break, but you can also add manual line break by pressing enter, creating new paragraphs.\nThis is the start of the next paragraph.\n\nClick me to edit me!".to_owned(),
+            code_snippet: r#"// Full identation blocks
+            // Spaces Spaces Spaces
+			// Tab Tab Tab
+    	    // Spaces Tab Spaces
+	    	// Tab Spaces Tab
+
+// Partial identation blocks
+ 	// Space Tab
+  	// Space Space Tab
+   	// Space Space Space Tab
+ // Space / / Space
+  // Space Space / /
+   // Space Space Space /
+
+// Use the configs above to play with the tab management
+// Also existing	tabs	are	kept				as	tabs.
+
+fn main() {
+    println!("Hello world!");
+}
+"#.to_owned(),
         }
     }
 }
@@ -144,7 +171,26 @@ impl Widgets {
             ui.memory().id_data.insert(show_password_id, show_password);
         });
 
+        ui.separator();
+
         ui.label("Multiline text input:");
         ui.text_edit_multiline(&mut self.multiline_text_input);
+
+        ui.separator();
+
+        ui.horizontal(|ui| {
+            ui.label("Code editor:");
+
+            ui.separator();
+
+            ui.checkbox(&mut self.tab_moves_focus, "Tabs moves focus");
+        });
+
+        ui.code_editor_with_config(
+            &mut self.code_snippet,
+            CodingConfig {
+                tab_moves_focus: self.tab_moves_focus,
+            },
+        );
     }
 }

epaint/src/text/font.rs

@@ -120,7 +120,7 @@ impl FontImpl {
 
             if c == '\t' {
                 if let Some(space) = self.glyph_info(' ') {
-                    glyph_info.advance_width = 4.0 * space.advance_width;
+                    glyph_info.advance_width = crate::text::MAX_TAB_SIZE * space.advance_width;
                 }
             }
 
@@ -285,6 +285,7 @@ impl Font {
         for c in text.chars() {
             if !self.fonts.is_empty() {
                 let (font_index, glyph_info) = self.glyph_info(c);
+
                 let font_impl = &self.fonts[font_index];
 
                 if let Some(last_glyph_id) = last_glyph_id {

epaint/src/text/mod.rs

@@ -5,6 +5,9 @@ mod font;
 mod fonts;
 mod galley;
 
+/// Default size for a `\t` character.
+pub const MAX_TAB_SIZE: f32 = 4.0;
+
 pub use {
     fonts::{FontDefinitions, FontFamily, Fonts, TextStyle},
     galley::{Galley, Row},