From 9be55374185d7352b0c0b61d66c1eb6ed479e207 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emilernerfeldt@gmail.com>
Date: Tue, 21 Apr 2020 14:47:17 +0200
Subject: [PATCH] Animate foldable regions

---
 emigui/src/memory.rs | 20 +++++++++++++++--
 emigui/src/region.rs | 51 +++++++++++++++++++++++++++++++++++---------
 2 files changed, 59 insertions(+), 12 deletions(-)

diff --git a/emigui/src/memory.rs b/emigui/src/memory.rs
index 62e8ebe6..b83be15b 100644
--- a/emigui/src/memory.rs
+++ b/emigui/src/memory.rs
@@ -1,14 +1,30 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 
 use crate::{window::WindowState, *};
 
+// TODO: move together with foldable code into own file
+#[derive(Clone, Copy, Debug)]
+pub struct FoldableState {
+    pub open: bool,
+    pub toggle_time: f64,
+}
+
+impl Default for FoldableState {
+    fn default() -> Self {
+        Self {
+            open: false,
+            toggle_time: -std::f64::INFINITY,
+        }
+    }
+}
+
 #[derive(Clone, Debug, Default)]
 pub struct Memory {
     /// The widget being interacted with (e.g. dragged, in case of a slider).
     pub(crate) active_id: Option<Id>,
 
     /// Which foldable regions are open.
-    pub(crate) open_foldables: HashSet<Id>,
+    pub(crate) foldables: HashMap<Id, FoldableState>,
 
     windows: HashMap<Id, WindowState>,
 
diff --git a/emigui/src/region.rs b/emigui/src/region.rs
index 2bc8e9ef..f0e9d1a9 100644
--- a/emigui/src/region.rs
+++ b/emigui/src/region.rs
@@ -166,23 +166,21 @@ impl Region {
             Some(id),
         );
 
-        let open = {
+        let state = {
             let mut memory = self.ctx.memory.lock();
+            let mut state = memory.foldables.entry(id).or_default();
             if interact.clicked {
-                if memory.open_foldables.contains(&id) {
-                    memory.open_foldables.remove(&id);
-                } else {
-                    memory.open_foldables.insert(id);
-                }
+                state.open = !state.open;
+                state.toggle_time = self.ctx.input.time;
             }
-            memory.open_foldables.contains(&id)
+            *state
         };
 
         let fill_color = self.style.interact_fill_color(&interact);
         let stroke_color = self.style.interact_stroke_color(&interact);
 
         self.add_paint_cmd(PaintCmd::Rect {
-            corner_radius: 5.0,
+            corner_radius: self.style.interaction_corner_radius,
             fill_color,
             outline: Some(Outline::new(1.0, color::WHITE)),
             rect: interact.rect,
@@ -198,7 +196,8 @@ impl Region {
             color: stroke_color,
             width: self.style.line_width,
         });
-        if !open {
+
+        if !state.open {
             // Draw it as a plus:
             self.add_paint_cmd(PaintCmd::Line {
                 points: vec![
@@ -217,7 +216,39 @@ impl Region {
             None,
         );
 
-        if open {
+        let animation_time = self.style().animation_time;
+        let time_since_toggle = (self.ctx.input.time - state.toggle_time) as f32;
+        if time_since_toggle < animation_time {
+            self.indent(id, |region| {
+                // animation time
+
+                let max_height = if state.open {
+                    remap(
+                        time_since_toggle,
+                        0.0,
+                        animation_time,
+                        50.0,   // Get instant feedback
+                        1500.0, // We don't expect to get bigger than this
+                    )
+                } else {
+                    remap_clamp(
+                        time_since_toggle,
+                        0.0,
+                        animation_time,
+                        50.0, // TODO: state.open_height
+                        0.0,
+                    )
+                };
+
+                region
+                    .clip_rect
+                    .set_height(region.clip_rect.height().min(max_height));
+
+                add_contents(region);
+
+                region.bounding_size.y = region.bounding_size.y.min(max_height);
+            });
+        } else if state.open {
             self.indent(id, add_contents);
         }