[input] keep track of mouse press origin

emigui/src/containers/window.rs

@@ -267,7 +267,6 @@ struct PossibleInteractions {
 pub(crate) struct WindowInteraction {
     pub(crate) area_layer: Layer,
     pub(crate) start_rect: Rect,
-    pub(crate) start_mouse_pos: Pos2,
     pub(crate) left: bool,
     pub(crate) right: bool,
     pub(crate) top: bool,
@@ -345,7 +344,7 @@ fn resize_window(ctx: &Context, window_interaction: &WindowInteraction) -> Optio
         }
     } else {
         // movevement
-        rect = rect.translate(mouse_pos - window_interaction.start_mouse_pos);
+        rect = rect.translate(mouse_pos - ctx.input().mouse.press_origin?);
     }
 
     return Some(rect);
@@ -444,7 +443,6 @@ fn resize_hover(
                 Some(WindowInteraction {
                     area_layer,
                     start_rect: rect,
-                    start_mouse_pos: mouse_pos,
                     left,
                     right,
                     top,

emigui/src/input.rs

@@ -81,6 +81,9 @@ pub struct MouseInput {
     /// None for touch screens when finger is not down.
     pub pos: Option<Pos2>,
 
+    /// Where did the current click/drag originate?
+    pub press_origin: Option<Pos2>,
+
     /// How much the mouse moved compared to last frame, in points.
     pub delta: Vec2,
 
@@ -99,6 +102,7 @@ impl Default for MouseInput {
             pressed: false,
             released: false,
             pos: None,
+            press_origin: None,
             delta: Vec2::zero(),
             velocity: Vec2::zero(),
             pos_tracker: MovementTracker::new(1000, 0.1),
@@ -172,6 +176,13 @@ impl MouseInput {
             .unwrap_or_default();
         let pressed = !self.down && new.mouse_down;
 
+        let mut press_origin = self.press_origin;
+        if pressed {
+            press_origin = new.mouse_pos;
+        } else if !self.down || self.pos.is_none() {
+            press_origin = None;
+        }
+
         if let Some(mouse_pos) = new.mouse_pos {
             self.pos_tracker.add(new.time, mouse_pos);
         } else {
@@ -187,6 +198,7 @@ impl MouseInput {
             pressed,
             released: self.down && !new.mouse_down,
             pos: new.mouse_pos,
+            press_origin,
             delta,
             velocity,
             pos_tracker: self.pos_tracker,
@@ -253,6 +265,7 @@ impl MouseInput {
         ui.add(label!("pressed: {}", self.pressed));
         ui.add(label!("released: {}", self.released));
         ui.add(label!("pos: {:?}", self.pos));
+        ui.add(label!("press_origin: {:?}", self.press_origin));
         ui.add(label!("delta: {:?}", self.delta));
         ui.add(label!(
             "velocity: [{:3.0} {:3.0}] points/sec",