Now Memory::interaction is stored per viewport in Memory::interactions

This will allow in the future drag and drop betwen windows
Fixes if a an other window is rendered will forgot what was draging, this was very annoying

crates/egui/src/context.rs

@@ -240,6 +240,7 @@ impl ContextImpl {
         self.memory.begin_frame(
             self.input.get(&viewport_id).unwrap_or(&Default::default()),
             &new_raw_input,
+            viewport_id,
         );
 
         let input = self
@@ -1299,6 +1300,14 @@ impl Context {
     /// Call at the end of each frame.
     #[must_use]
     pub fn end_frame(&self) -> FullOutput {
+        let mut viewports: Vec<u64> = self.read(|ctx| {
+            ctx.viewports
+                .iter()
+                .map(|(_, (_, id, _, _, _))| *id)
+                .collect()
+        });
+        viewports.push(0);
+
         if self.input(|i| i.wants_repaint()) {
             self.request_repaint();
         }
@@ -1306,6 +1315,7 @@ impl Context {
         let textures_delta = self.write(|ctx| {
             ctx.memory.end_frame(
                 ctx.input.get(&ctx.current_rendering_viewport).unwrap(),
+                &viewports,
                 &ctx.frame_state.used_ids,
             );
 
@@ -1352,14 +1362,6 @@ impl Context {
             }
         }
 
-        let mut viewports: Vec<u64> = self.read(|ctx| {
-            ctx.viewports
-                .iter()
-                .map(|(_, (_, id, _, _, _))| *id)
-                .collect()
-        });
-        viewports.push(0);
-
         self.write(|ctx| ctx.input.retain(|id, _| viewports.contains(&id)));
 
         let repaint_after = self.write(|ctx| {

crates/egui/src/memory.rs

@@ -1,3 +1,5 @@
+use ahash::HashMap;
+
 use crate::{area, window, Id, IdMap, InputState, LayerId, Pos2, Rect, Style};
 
 // ----------------------------------------------------------------------------
@@ -69,9 +71,16 @@ pub struct Memory {
     #[cfg_attr(feature = "persistence", serde(skip))]
     pub(crate) new_font_definitions: Option<epaint::text::FontDefinitions>,
 
+    #[cfg_attr(feature = "persistence", serde(skip))]
+    pub(crate) interactions: HashMap<u64, Interaction>,
+
     #[cfg_attr(feature = "persistence", serde(skip))]
     pub(crate) interaction: Interaction,
 
+    // Current viewport
+    #[cfg_attr(feature = "persistence", serde(skip))]
+    pub(crate) viewport_id: u64,
+
     #[cfg_attr(feature = "persistence", serde(skip))]
     pub(crate) window_interaction: Option<window::WindowInteraction>,
 
@@ -354,19 +363,33 @@ impl Memory {
         &mut self,
         prev_input: &crate::input_state::InputState,
         new_input: &crate::data::input::RawInput,
+        viewport_id: u64,
     ) {
-        self.interaction.begin_frame(prev_input, new_input);
+        self.viewport_id = viewport_id;
+        self.interactions
+            .entry(viewport_id)
+            .or_default()
+            .begin_frame(prev_input, new_input);
+        self.interaction = self.interactions.remove(&viewport_id).unwrap();
 
         if !prev_input.pointer.any_down() {
             self.window_interaction = None;
         }
     }
 
-    pub(crate) fn end_frame(&mut self, input: &InputState, used_ids: &IdMap<Rect>) {
+    pub(crate) fn end_frame(
+        &mut self,
+        input: &InputState,
+        viewports: &[u64],
+        used_ids: &IdMap<Rect>,
+    ) {
         self.caches.update();
         self.areas.end_frame();
         self.interaction.focus.end_frame(used_ids);
+        self.interactions
+            .insert(self.viewport_id, std::mem::take(&mut self.interaction));
         self.drag_value.end_frame(input);
+        self.interactions.retain(|id, _| viewports.contains(id))
     }
 
     /// Top-most layer at the given position.