Vi-style editor and other editor improvements (#40)

* WIP VI wrapper for editor

* WIP: block cursor

* Create Edit trait, run CI on all feature options

* Add prints describing build steps to ci.sh

* Custom rendering for Vi editor

* Clippy fixes

* More clippy fixes

* Show clippy results in CI

* Fix for Redox

* Fix clippy lint

* Add vi feature to enable vi-style editor

* Add escape to libcosmic text box

src/edit/mod.rs

@@ -0,0 +1,93 @@
+#[cfg(not(feature = "std"))]
+use alloc::string::String;
+
+use crate::{Buffer, Cursor};
+#[cfg(feature = "swash")]
+use crate::Color;
+
+pub use self::editor::*;
+mod editor;
+
+#[cfg(feature = "syntect")]
+pub use self::syntect::*;
+#[cfg(feature = "syntect")]
+mod syntect;
+
+#[cfg(feature = "vi")]
+pub use self::vi::*;
+#[cfg(feature = "vi")]
+mod vi;
+
+/// An action to perform on an [`Editor`]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Action {
+    /// Move cursor to previous character ([Self::Left] in LTR, [Self::Right] in RTL)
+    Previous,
+    /// Move cursor to next character ([Self::Right] in LTR, [Self::Left] in RTL)
+    Next,
+    /// Move cursor left
+    Left,
+    /// Move cursor right
+    Right,
+    /// Move cursor up
+    Up,
+    /// Move cursor down
+    Down,
+    /// Move cursor to start of line
+    Home,
+    /// Move cursor to end of line
+    End,
+    /// Scroll up one page
+    PageUp,
+    /// Scroll down one page
+    PageDown,
+    /// Escape, clears selection
+    Escape,
+    /// Insert character at cursor
+    Insert(char),
+    /// Create new line
+    Enter,
+    /// Delete text behind cursor
+    Backspace,
+    /// Delete text in front of cursor
+    Delete,
+    /// Mouse click at specified position
+    Click { x: i32, y: i32 },
+    /// Mouse drag to specified position
+    Drag { x: i32, y: i32 },
+    /// Scroll specified number of lines
+    Scroll { lines: i32 },
+}
+
+/// A trait to allow easy replacements of [`Editor`], like `SyntaxEditor`
+pub trait Edit<'a> {
+    /// Get the internal [`Buffer`]
+    fn buffer(&self) -> &Buffer<'a>;
+
+    /// Get the internal [`Buffer`], mutably
+    fn buffer_mut(&mut self) -> &mut Buffer<'a>;
+
+    /// Get the current cursor position
+    fn cursor(&self) -> Cursor;
+
+    /// Get the current selection position
+    fn select_opt(&self) -> Option<Cursor>;
+
+    /// Shape lines until scroll, after adjusting scroll if the cursor moved
+    fn shape_as_needed(&mut self);
+
+    /// Copy selection
+    fn copy_selection(&mut self) -> Option<String>;
+
+    /// Delete selection, adjusting cursor and returning true if there was a selection
+    // Also used by backspace, delete, insert, and enter when there is a selection
+    fn delete_selection(&mut self) -> bool;
+
+    /// Perform an [Action] on the editor
+    fn action(&mut self, action: Action);
+
+    /// Draw the editor
+    #[cfg(feature = "swash")]
+    fn draw<F>(&self, cache: &mut crate::SwashCache, color: Color, f: F)
+        where F: FnMut(i32, i32, u32, u32, Color);
+}