Implement input hints based on the active tool state (#388)

* Hook up user input hints to display in the frontend status bar

Closes #171

* MVP hint system based on tool FSM

* Fix hints for Fill and Eyedropper tools

* Add icons for keyboard shortcuts

* Fix hints for Pen Tool

* Cleanup

editor/src/misc/hints.rs

@@ -0,0 +1,20 @@
+use serde::{Deserialize, Serialize};
+
+use crate::input::keyboard::{Key, MouseMotion};
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct HintData(pub Vec<HintGroup>);
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct HintGroup(pub Vec<HintInfo>);
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct HintInfo {
+	pub key_groups: Vec<KeysGroup>,
+	pub mouse: Option<MouseMotion>,
+	pub label: String,
+	pub plus: bool, // Prepend the "+" symbol indicating that this is a refinement upon a previous entry in the group
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct KeysGroup(pub Vec<Key>); // Only use `Key`s that exist on a physical keyboard

editor/src/misc/mod.rs

@@ -2,7 +2,9 @@
 pub mod macros;
 pub mod derivable_custom_traits;
 mod error;
+pub mod hints;
 pub mod test_utils;
 
 pub use error::EditorError;
+pub use hints::*;
 pub use macros::*;