Clean up shared UI runtime state

src/desktop/input.rs

@@ -0,0 +1,94 @@
+// `CursorState::time` is the sample's own time on every backend. winit
+// carries no timestamp on a pointer event, so the moment it is handed to
+// us is the closest measurement available here -- which is also what the
+// drag code used to do for itself with `Instant::now()`, before Android's
+// batched samples made the difference matter (see `sense::CursorState`).
+use crate::prelude::*;
+use std::time::Instant;
+use winit::{
+    event::{MouseButton, MouseScrollDelta, WindowEvent},
+    keyboard::{Key, NamedKey},
+};
+
+#[derive(Default)]
+pub struct Input {
+    cursor: CursorState,
+    pub modifiers: Modifiers,
+}
+
+impl Input {
+    /// winit's pointer coordinates are physical pixels, which is the
+    /// space the whole tree is laid out and hit-tested in -- see
+    /// `desktop::content_scale`. Nothing is converted here; `dp(...)`
+    /// resolves against the density at layout time instead.
+    pub fn event(&mut self, event: &WindowEvent) -> bool {
+        match event {
+            WindowEvent::CursorMoved { position, .. } => {
+                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32);
+                self.cursor.exists = true;
+                self.cursor.time = Instant::now();
+            }
+            WindowEvent::MouseInput { state, button, .. } => {
+                self.cursor.time = Instant::now();
+                let buttons = &mut self.cursor.buttons;
+                let pressed = state.is_pressed();
+                match button {
+                    MouseButton::Left => buttons.left.update(pressed),
+                    MouseButton::Right => buttons.right.update(pressed),
+                    MouseButton::Middle => buttons.middle.update(pressed),
+                    _ => (),
+                }
+            }
+            WindowEvent::MouseWheel { delta, .. } => {
+                let mut delta = match *delta {
+                    MouseScrollDelta::LineDelta(x, y) => Vec2::new(x, y),
+                    MouseScrollDelta::PixelDelta(pos) => Vec2::new(pos.x as f32, pos.y as f32),
+                };
+                if delta.x == 0.0 && self.modifiers.shift {
+                    delta.x = delta.y;
+                    delta.y = 0.0;
+                }
+                self.cursor.scroll_delta = delta;
+                self.cursor.time = Instant::now();
+            }
+            WindowEvent::CursorLeft { .. } => {
+                self.cursor.exists = false;
+                self.modifiers.clear();
+            }
+            WindowEvent::KeyboardInput { event, .. } => {
+                if let Key::Named(named) = event.logical_key {
+                    let pressed = event.state.is_pressed();
+                    match named {
+                        NamedKey::Control => {
+                            self.modifiers.control = pressed;
+                        }
+                        NamedKey::Shift => {
+                            self.modifiers.shift = pressed;
+                        }
+                        _ => (),
+                    }
+                }
+            }
+            _ => return false,
+        }
+        true
+    }
+
+    pub fn end_frame(&mut self) {
+        self.cursor.end_frame();
+    }
+}
+
+impl DesktopUiState {
+    /// Physical pixels, matching `WindowEvent::Resized` (what
+    /// `UiRenderState::resize` is given) and the swapchain -- see
+    /// `desktop::content_scale`.
+    pub fn window_size(&self) -> Vec2 {
+        let size = self.renderer.window().inner_size();
+        Vec2::new(size.width as f32, size.height as f32)
+    }
+
+    pub fn cursor_state(&self) -> &CursorState {
+        &self.input.cursor
+    }
+}