Fix tooltips overlapping widgets (#566) (#568)

Tooltips are now shown above the widget if they do not fit under it.

egui/src/containers/popup.rs

@@ -8,28 +8,34 @@ use crate::*;
 #[derive(Clone, Debug, Default)]
 pub(crate) struct MonoState {
     last_id: Option<Id>,
-    last_size: Option<Vec2>,
+    last_size: Vec<Vec2>,
 }
 
 impl MonoState {
-    fn tooltip_size(&self, id: Id) -> Option<Vec2> {
+    fn tooltip_size(&self, id: Id, index: usize) -> Option<Vec2> {
         if self.last_id == Some(id) {
-            self.last_size
+            self.last_size.get(index).cloned()
         } else {
             None
         }
     }
 
-    fn set_tooltip_size(&mut self, id: Id, size: Vec2) {
+    fn set_tooltip_size(&mut self, id: Id, index: usize, size: Vec2) {
         if self.last_id == Some(id) {
-            if let Some(stored_size) = &mut self.last_size {
-                *stored_size = stored_size.max(size);
-                return;
+            if let Some(stored_size) = self.last_size.get_mut(index) {
+                *stored_size = size;
+            } else {
+                self.last_size
+                    .extend((0..index - self.last_size.len()).map(|_| Vec2::ZERO));
+                self.last_size.push(size);
             }
+            return;
         }
 
         self.last_id = Some(id);
-        self.last_size = Some(size);
+        self.last_size.clear();
+        self.last_size.extend((0..index).map(|_| Vec2::ZERO));
+        self.last_size.push(size);
     }
 }
 
@@ -84,16 +90,21 @@ pub fn show_tooltip_at_pointer<R>(
     show_tooltip_at(ctx, id, suggested_pos, add_contents)
 }
 
+/// Show a tooltip under the given area.
+///
+/// If the tooltip does not fit under the area, it tries to place it above it instead.
 pub fn show_tooltip_under<R>(
     ctx: &CtxRef,
     id: Id,
     rect: &Rect,
     add_contents: impl FnOnce(&mut Ui) -> R,
 ) -> Option<R> {
-    show_tooltip_at(
+    let expanded_rect = rect.expand2(vec2(2.0, 4.0));
+    show_tooltip_at_avoid(
         ctx,
         id,
-        Some(rect.left_bottom() + vec2(-2.0, 4.0)),
+        Some(expanded_rect.left_bottom()),
+        expanded_rect,
         add_contents,
     )
 }
@@ -103,16 +114,31 @@ pub fn show_tooltip_under<R>(
 /// Returns `None` if the tooltip could not be placed.
 pub fn show_tooltip_at<R>(
     ctx: &CtxRef,
-    mut id: Id,
+    id: Id,
     suggested_position: Option<Pos2>,
     add_contents: impl FnOnce(&mut Ui) -> R,
 ) -> Option<R> {
-    let mut tooltip_rect = Rect::NOTHING;
+    show_tooltip_at_avoid(ctx, id, suggested_position, Rect::NOTHING, add_contents)
+}
 
-    let position = if let Some((stored_id, stored_tooltip_rect)) = ctx.frame_state().tooltip_rect {
+fn show_tooltip_at_avoid<R>(
+    ctx: &CtxRef,
+    mut id: Id,
+    suggested_position: Option<Pos2>,
+    mut avoid_rect: Rect,
+    add_contents: impl FnOnce(&mut Ui) -> R,
+) -> Option<R> {
+    let mut tooltip_rect = Rect::NOTHING;
+    let mut count = 0;
+
+    let position = if let Some((stored_id, stored_tooltip_rect, stored_count)) =
+        ctx.frame_state().tooltip_rect
+    {
         // if there are multiple tooltips open they should use the same id for the `tooltip_size` caching to work.
         id = stored_id;
         tooltip_rect = stored_tooltip_rect;
+        count = stored_count;
+        avoid_rect = avoid_rect.union(tooltip_rect);
         tooltip_rect.left_bottom()
     } else if let Some(position) = suggested_position {
         position
@@ -126,18 +152,31 @@ pub fn show_tooltip_at<R>(
         .memory()
         .data_temp
         .get_or_default::<crate::containers::popup::MonoState>()
-        .tooltip_size(id);
+        .tooltip_size(id, count);
     let expected_size = expected_size.unwrap_or_else(|| vec2(64.0, 32.0));
     let position = position.min(ctx.input().screen_rect().right_bottom() - expected_size);
+    // Place the tooltip above the avoid_rect if necessary.
+    let new_rect = Rect::from_min_size(position, expected_size);
+    // Note: We do not use Rect::intersects() since it returns true even if the rects only touch.
+    let position = if avoid_rect.min.x < new_rect.max.x
+        && new_rect.min.x < avoid_rect.max.x
+        && avoid_rect.min.y < new_rect.max.y
+        && new_rect.min.y < avoid_rect.max.y
+    {
+        Pos2::new(position.x, avoid_rect.min.y - expected_size.y)
+    } else {
+        position
+    };
+
     let position = position.max(ctx.input().screen_rect().left_top());
 
     let InnerResponse { inner, response } = show_tooltip_area(ctx, id, position, add_contents);
     ctx.memory()
         .data_temp
         .get_mut_or_default::<crate::containers::popup::MonoState>()
-        .set_tooltip_size(id, response.rect.size());
+        .set_tooltip_size(id, count, response.rect.size());
 
-    ctx.frame_state().tooltip_rect = Some((id, tooltip_rect.union(response.rect)));
+    ctx.frame_state().tooltip_rect = Some((id, tooltip_rect.union(response.rect), count + 1));
     Some(inner)
 }
 

egui/src/frame_state.rs

@@ -24,7 +24,7 @@ pub(crate) struct FrameState {
     /// If a tooltip has been shown this frame, where was it?
     /// This is used to prevent multiple tooltips to cover each other.
     /// Initialized to `None` at the start of each frame.
-    pub(crate) tooltip_rect: Option<(Id, Rect)>,
+    pub(crate) tooltip_rect: Option<(Id, Rect, usize)>,
 
     /// Cleared by the first `ScrollArea` that makes use of it.
     pub(crate) scroll_delta: Vec2,