Move focus between text fields with tab and shift-tab

TODO.md

@@ -4,7 +4,8 @@ TODO-list for the Egui project. If you looking for something to do, look here.
 
 ## Top priority
 
-* Refactor graphics layers and areas so one don't have to register LayerId:s.
+* Egui-web copy-paste
+* Egui-web fetch
 
 ## Other
 
@@ -13,14 +14,6 @@ TODO-list for the Egui project. If you looking for something to do, look here.
     * [ ] Tooltip widget: Something that looks like this:  (?)  :that shows text on hover.
       * [ ] ui.info_button().on_hover_text("More info here");
     * [ ] Allow adding multiple tooltips to the same widget, showing them all one after the other.
-  * [ ] Text input
-    * [x] Input
-    * [x] Text focus
-    * [x] Cursor movement
-    * [x] Text selection
-    * [x] Clipboard copy/paste
-    * [ ] Text edit undo
-    * [ ] Move focus with tab
   * [ ] Vertical slider
   * [/] Color picker
     * [x] linear rgb <-> sRGB
@@ -32,21 +25,13 @@ TODO-list for the Egui project. If you looking for something to do, look here.
     * [ ] Additive blending aware color picker
     * [ ] Premultiplied alpha is a bit of a pain in the ass. Maybe rethink this a bit.
     * [ ] Hue wheel
-* Containers
-  * [ ] Scroll areas
-    * [x] Vertical scrolling
-    * [x] Scroll-wheel input
-    * [x] Drag background to scroll
-    * [x] Kinetic scrolling
-    * [ ] Horizontal scrolling
 * Input
   * [x] Distinguish between clicks and drags
   * [x] Double-click
   * [x] Text
-  * [x] Get modifier keys
+  * [x] Modifier keys
   * [ ] Support all mouse buttons
   * [ ] Distinguish between touch input and mouse input
-  * [ ] Keyboard shortcuts (copy, paste, undo, select-all, ...?)
 * Text
   * [/] Unicode
     * [x] Shared mutable expanding texture map
@@ -91,26 +76,14 @@ TODO-list for the Egui project. If you looking for something to do, look here.
   * [ ] Ask Egui if an event requires repainting
   * [ ] Only repaint when mouse is over a Egui window (or is pressed and there is an active widget)
 
-## Backends
-
-* [ ] Extract egui_app as egui_backend
-
-* egui_glium
-* egui_web
-  * [ ] async HTTP requests
-* [ ] egui_bitmap: slow reference rasterizer for tests
-  * Port https://github.com/emilk/imgui_software_renderer
-  * Less important: fast rasterizer for embedded 🤷‍♀️
-* [ ] egui_terminal (think ncurses)
-  * [ ] replace `round_to_pixel` with `round_to_X` where user can select X to be e.g. width of a letter
-* [ ] egui_svg: No idea what this would be for :)
+## Integrations
 
 ### egui_web
-
 * [x] Scroll input
 * [x] Change to resize cursor on hover
 * [x] Port most code to Rust
 * [x] Read url fragment and redirect to a subpage (e.g. different examples apps)]
+* [ ] Copy/paste support
 * [ ] Async HTTP requests
 * [ ] Fix WebGL colors/blending (try EXT_sRGB)
 * [ ] Embeddability
@@ -121,6 +94,17 @@ TODO-list for the Egui project. If you looking for something to do, look here.
     * Different Egui instances, same app
     * Allows very nice web integration
 
+### Other
+
+* [ ] Extract egui::app as own library (egui_framework ?)
+* [ ] egui_bitmap: slow reference rasterizer for tests
+  * Port https://github.com/emilk/imgui_software_renderer
+  * Less important: fast rasterizer for embedded 🤷‍♀️
+* [ ] egui_terminal (think ncurses)
+  * [ ] replace `round_to_pixel` with `round_to_X` where user can select X to be e.g. width of a letter
+* [ ] egui_svg: No idea what this would be for :)
+
+
 ## Modularity
 
 * [x] `trait Widget` (`Label`, `Slider`, `Checkbox`, ...)
@@ -163,13 +147,24 @@ Ability to do a search for any widget. The search works even for collapsed regio
   * [x] Collapsing header region
   * [x] Tooltip
   * [x] Movable/resizable windows
-    * [x] Kinetic windows
   * [x] Add support for clicking hyperlinks
+* [x] Text input
+  * [x] Input
+  * [x] Text focus
+  * [x] Cursor movement
+  * [x] Text selection
+  * [x] Clipboard copy/paste
+  * [x] Move focus with tab
+  * [x] Text edit undo
 * Containers
   * [x] Vertical slider
     * [x] Resize any side and corner on windows
     * [x] Fix autoshrink
     * [x] Automatic positioning of new windows
+  * [x] Vertical scroll areas
+    * [x] Scroll-wheel input
+    * [x] Drag background to scroll
+    * [x] Kinetic scrolling
 * Simple animations
 * Clip rects
   * [x] Separate Ui::clip_rect from Ui::rect

egui/src/context.rs

@@ -205,7 +205,7 @@ impl Context {
     }
 
     fn begin_frame_mut(&mut self, new_raw_input: RawInput) {
-        self.memory().begin_frame(&self.input);
+        self.memory().begin_frame(&self.input, &new_raw_input);
 
         self.input = std::mem::take(&mut self.input).begin_frame(new_raw_input);
         *self.available_rect.lock() = Some(self.input.screen_rect());

egui/src/memory.rs

@@ -83,6 +83,18 @@ pub(crate) struct Interaction {
     /// What had keyboard focus previous frame?
     pub kb_focus_id_previous_frame: Option<Id>,
 
+    /// If set, the next widget that is interested in kb_focus will automatically get it.
+    /// Probably because the user pressed Tab.
+    pub kb_focus_give_to_next: bool,
+
+    /// The last widget interested in kb focus.
+    pub kb_focus_last_interested: Option<Id>,
+
+    /// 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,
+
     /// HACK: windows have low priority on dragging.
     /// This is so that if you drag a slider in a window,
     /// the slider will steal the drag away from the window.
@@ -104,7 +116,11 @@ impl Interaction {
         self.click_id.is_some() || self.drag_id.is_some()
     }
 
-    fn begin_frame(&mut self, prev_input: &crate::input::InputState) {
+    fn begin_frame(
+        &mut self,
+        prev_input: &crate::input::InputState,
+        new_input: &crate::input::RawInput,
+    ) {
         self.kb_focus_id_previous_frame = self.kb_focus_id;
         self.click_interest = false;
         self.drag_interest = false;
@@ -118,13 +134,34 @@ impl Interaction {
             self.click_id = None;
             self.drag_id = None;
         }
+
+        self.pressed_tab = false;
+        self.pressed_shift_tab = false;
+        for event in &new_input.events {
+            if let crate::input::Event::Key {
+                key: crate::input::Key::Tab,
+                pressed: true,
+                modifiers,
+            } = event
+            {
+                if modifiers.shift {
+                    self.pressed_shift_tab = true;
+                } else {
+                    self.pressed_tab = true;
+                }
+            }
+        }
     }
 }
 
 impl Memory {
-    pub(crate) fn begin_frame(&mut self, prev_input: &crate::input::InputState) {
+    pub(crate) fn begin_frame(
+        &mut self,
+        prev_input: &crate::input::InputState,
+        new_input: &crate::input::RawInput,
+    ) {
         self.used_ids.clear();
-        self.interaction.begin_frame(prev_input);
+        self.interaction.begin_frame(prev_input, new_input);
 
         if !prev_input.mouse.down {
             self.window_interaction = None;
@@ -169,6 +206,26 @@ impl Memory {
         }
     }
 
+    /// Register this widget as being interested in getting keyboard focus.
+    /// This will allow the user to select it with tab and shift-tab.
+    pub fn interested_in_kb_focus(&mut self, id: Id) {
+        if self.interaction.kb_focus_give_to_next {
+            self.interaction.kb_focus_id = Some(id);
+            self.interaction.kb_focus_give_to_next = false;
+        } else if self.has_kb_focus(id) {
+            if self.interaction.pressed_tab {
+                self.interaction.kb_focus_id = None;
+                self.interaction.kb_focus_give_to_next = true;
+                self.interaction.pressed_tab = false;
+            } else if self.interaction.pressed_shift_tab {
+                self.interaction.kb_focus_id = self.interaction.kb_focus_last_interested;
+                self.interaction.pressed_shift_tab = false;
+            }
+        }
+
+        self.interaction.kb_focus_last_interested = Some(id);
+    }
+
     /// Stop editing of active `TextEdit` (if any).
     pub fn stop_text_input(&mut self) {
         self.interaction.kb_focus_id = None;

egui/src/widgets/text_edit.rs

@@ -252,6 +252,10 @@ impl<'t> Widget for TextEdit<'t> {
         };
         let response = ui.interact(rect, id, sense);
 
+        if enabled {
+            ui.memory().interested_in_kb_focus(id);
+        }
+
         if enabled {
             if let Some(mouse_pos) = ui.input().mouse.pos {
                 // TODO: triple-click to select whole paragraph