Text input (#143)

* update: iced 0.10.0

* wip: text input

* wip: text inputs with icons and buttons

* wip: improve text input

* refactor: text input styling

* chore: add scale factor

* chore(text_input): add winit example and do some cleanup

src/widget/text_input/cursor.rs

@@ -0,0 +1,173 @@
+//! Track the cursor of a text input.
+use super::value::Value;
+
+/// The cursor of a text input.
+#[derive(Debug, Copy, Clone)]
+pub struct Cursor {
+    state: State,
+}
+
+/// The state of a [`Cursor`].
+#[derive(Debug, Copy, Clone)]
+pub enum State {
+    /// Cursor without a selection
+    Index(usize),
+
+    /// Cursor selecting a range of text
+    Selection {
+        /// The start of the selection
+        start: usize,
+        /// The end of the selection
+        end: usize,
+    },
+}
+
+impl Default for Cursor {
+    fn default() -> Self {
+        Cursor {
+            state: State::Index(0),
+        }
+    }
+}
+
+impl Cursor {
+    /// Returns the [`State`] of the [`Cursor`].
+    #[must_use]
+    pub fn state(&self, value: &Value) -> State {
+        match self.state {
+            State::Index(index) => State::Index(index.min(value.len())),
+            State::Selection { start, end } => {
+                let start = start.min(value.len());
+                let end = end.min(value.len());
+
+                if start == end {
+                    State::Index(start)
+                } else {
+                    State::Selection { start, end }
+                }
+            }
+        }
+    }
+
+    /// Returns the current selection of the [`Cursor`] for the given [`Value`].
+    ///
+    /// `start` is guaranteed to be <= than `end`.
+    #[must_use]
+    pub fn selection(&self, value: &Value) -> Option<(usize, usize)> {
+        match self.state(value) {
+            State::Selection { start, end } => Some((start.min(end), start.max(end))),
+            State::Index(_) => None,
+        }
+    }
+
+    pub(crate) fn move_to(&mut self, position: usize) {
+        self.state = State::Index(position);
+    }
+
+    pub(crate) fn move_right(&mut self, value: &Value) {
+        self.move_right_by_amount(value, 1);
+    }
+
+    pub(crate) fn move_right_by_words(&mut self, value: &Value) {
+        self.move_to(value.next_end_of_word(self.right(value)));
+    }
+
+    pub(crate) fn move_right_by_amount(&mut self, value: &Value, amount: usize) {
+        match self.state(value) {
+            State::Index(index) => self.move_to(index.saturating_add(amount).min(value.len())),
+            State::Selection { start, end } => self.move_to(end.max(start)),
+        }
+    }
+
+    pub(crate) fn move_left(&mut self, value: &Value) {
+        match self.state(value) {
+            State::Index(index) if index > 0 => self.move_to(index - 1),
+            State::Selection { start, end } => self.move_to(start.min(end)),
+            State::Index(_) => self.move_to(0),
+        }
+    }
+
+    pub(crate) fn move_left_by_words(&mut self, value: &Value) {
+        self.move_to(value.previous_start_of_word(self.left(value)));
+    }
+
+    pub(crate) fn select_range(&mut self, start: usize, end: usize) {
+        if start == end {
+            self.state = State::Index(start);
+        } else {
+            self.state = State::Selection { start, end };
+        }
+    }
+
+    pub(crate) fn select_left(&mut self, value: &Value) {
+        match self.state(value) {
+            State::Index(index) if index > 0 => self.select_range(index, index - 1),
+            State::Selection { start, end } if end > 0 => self.select_range(start, end - 1),
+            _ => {}
+        }
+    }
+
+    pub(crate) fn select_right(&mut self, value: &Value) {
+        match self.state(value) {
+            State::Index(index) if index < value.len() => self.select_range(index, index + 1),
+            State::Selection { start, end } if end < value.len() => {
+                self.select_range(start, end + 1);
+            }
+            _ => {}
+        }
+    }
+
+    pub(crate) fn select_left_by_words(&mut self, value: &Value) {
+        match self.state(value) {
+            State::Index(index) => self.select_range(index, value.previous_start_of_word(index)),
+            State::Selection { start, end } => {
+                self.select_range(start, value.previous_start_of_word(end));
+            }
+        }
+    }
+
+    pub(crate) fn select_right_by_words(&mut self, value: &Value) {
+        match self.state(value) {
+            State::Index(index) => self.select_range(index, value.next_end_of_word(index)),
+            State::Selection { start, end } => {
+                self.select_range(start, value.next_end_of_word(end));
+            }
+        }
+    }
+
+    pub(crate) fn select_all(&mut self, value: &Value) {
+        self.select_range(0, value.len());
+    }
+
+    pub(crate) fn start(&self, value: &Value) -> usize {
+        let start = match self.state {
+            State::Index(index) => index,
+            State::Selection { start, .. } => start,
+        };
+
+        start.min(value.len())
+    }
+
+    pub(crate) fn end(&self, value: &Value) -> usize {
+        let end = match self.state {
+            State::Index(index) => index,
+            State::Selection { end, .. } => end,
+        };
+
+        end.min(value.len())
+    }
+
+    fn left(&self, value: &Value) -> usize {
+        match self.state(value) {
+            State::Index(index) => index,
+            State::Selection { start, end } => start.min(end),
+        }
+    }
+
+    fn right(&self, value: &Value) -> usize {
+        match self.state(value) {
+            State::Index(index) => index,
+            State::Selection { start, end } => start.max(end),
+        }
+    }
+}