Serde feature: Add serde derives to input related structs (#4100)

We plan to store input data for creating automated tests, hence the need
for more serde derives on input related structs.

---------

Co-authored-by: Georg Weisert <georg.weisert@freshx.de>

crates/egui/src/input_state.rs

@@ -22,6 +22,7 @@ const MAX_DOUBLE_CLICK_DELAY: f64 = 0.3; // TODO(emilk): move to settings
 /// You can check if `egui` is using the inputs using
 /// [`crate::Context::wants_pointer_input`] and [`crate::Context::wants_keyboard_input`].
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct InputState {
     /// The raw input we got this frame from the backend.
     pub raw: RawInput,
@@ -546,6 +547,7 @@ impl InputState {
 
 /// A pointer (mouse or touch) click.
 #[derive(Clone, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub(crate) struct Click {
     pub pos: Pos2,
 
@@ -567,6 +569,7 @@ impl Click {
 }
 
 #[derive(Clone, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub(crate) enum PointerEvent {
     Moved(Pos2),
     Pressed {
@@ -595,6 +598,7 @@ impl PointerEvent {
 
 /// Mouse or touch state.
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct PointerState {
     /// Latest known time
     time: f64,

crates/egui/src/input_state/touch_state.rs

@@ -64,6 +64,7 @@ pub struct MultiTouchInfo {
 
 /// The current state (for a specific touch device) of touch events and gestures.
 #[derive(Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub(crate) struct TouchState {
     /// Technical identifier of the touch device. This is used to identify relevant touch events
     /// for this [`TouchState`] instance.
@@ -83,6 +84,7 @@ pub(crate) struct TouchState {
 }
 
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 struct GestureState {
     start_time: f64,
     start_pointer_pos: Pos2,
@@ -93,6 +95,7 @@ struct GestureState {
 
 /// Gesture data that can change over time
 #[derive(Clone, Copy, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 struct DynGestureState {
     /// used for proportional zooming
     avg_distance: f32,
@@ -110,6 +113,7 @@ struct DynGestureState {
 /// Describes an individual touch (finger or digitizer) on the touch surface. Instances exist as
 /// long as the finger/pen touches the surface.
 #[derive(Clone, Copy, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 struct ActiveTouch {
     /// Current position of this touch, in device coordinates (not necessarily screen position)
     pos: Pos2,
@@ -302,6 +306,7 @@ impl Debug for TouchState {
 }
 
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 enum PinchType {
     Horizontal,
     Vertical,

crates/emath/src/history.rs

@@ -16,6 +16,7 @@ use std::collections::VecDeque;
 /// or for smoothed velocity (e.g. mouse pointer speed).
 /// All times are in seconds.
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct History<T> {
     /// In elements, i.e. of `values.len()`.
     /// The length is initially zero, but once past `min_len` will not shrink below it.