Improve the positioning of tooltips

CHANGELOG.md

@@ -14,6 +14,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Add `egui::plot::Plot` to plot some 2D data
 * Add `Ui::hyperlink_to(label, url)`.
 
+### Changed 🔧
+
+* Improve the positioning of tooltips.
+
+
 ## 0.9.0 - 2021-02-07 - Light Mode and much more
 
 <img src="media/0.9.0-disabled.gif" width="50%">

egui/src/containers/popup.rs

@@ -11,21 +11,47 @@ use crate::*;
 /// ```
 /// # let mut ui = egui::Ui::__test();
 /// if ui.ui_contains_pointer() {
-///     egui::show_tooltip(ui.ctx(), |ui| {
+///     egui::show_tooltip(ui.ctx(), egui::Id::new("my_tooltip"), |ui| {
 ///         ui.label("Helpful text");
 ///     });
 /// }
 /// ```
-pub fn show_tooltip(ctx: &CtxRef, add_contents: impl FnOnce(&mut Ui)) {
-    let tooltip_rect = ctx.frame_state().tooltip_rect;
+pub fn show_tooltip(ctx: &CtxRef, id: Id, add_contents: impl FnOnce(&mut Ui)) {
+    show_tooltip_at_pointer(ctx, id, add_contents)
+}
 
-    let window_pos = if let Some(tooltip_rect) = tooltip_rect {
+pub fn show_tooltip_at_pointer(ctx: &CtxRef, id: Id, add_contents: impl FnOnce(&mut Ui)) {
+    let suggested_pos = ctx
+        .input()
+        .pointer
+        .tooltip_pos()
+        .map(|pointer_pos| pointer_pos + vec2(16.0, 16.0));
+    show_tooltip_at(ctx, id, suggested_pos, add_contents)
+}
+
+pub fn show_tooltip_under(ctx: &CtxRef, id: Id, rect: &Rect, add_contents: impl FnOnce(&mut Ui)) {
+    show_tooltip_at(
+        ctx,
+        id,
+        Some(rect.left_bottom() + vec2(-2.0, 4.0)),
+        add_contents,
+    )
+}
+
+pub fn show_tooltip_at(
+    ctx: &CtxRef,
+    mut id: Id,
+    suggested_position: Option<Pos2>,
+    add_contents: impl FnOnce(&mut Ui),
+) {
+    let mut tooltip_rect = Rect::NOTHING;
+
+    let position = if let Some((stored_id, stored_tooltip_rect)) = 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;
         tooltip_rect.left_bottom()
-    } else if let Some(pointer_pos) = ctx.input().pointer.tooltip_pos() {
-        let expected_size = vec2(ctx.style().spacing.tooltip_width, 32.0);
-        let position = pointer_pos + vec2(16.0, 16.0);
-        let position = position.min(ctx.input().screen_rect().right_bottom() - expected_size);
-        let position = position.max(ctx.input().screen_rect().left_top());
+    } else if let Some(position) = suggested_position {
         position
     } else if ctx.memory().everything_is_visible() {
         Pos2::default()
@@ -33,12 +59,15 @@ pub fn show_tooltip(ctx: &CtxRef, add_contents: impl FnOnce(&mut Ui)) {
         return; // No good place for a tooltip :(
     };
 
-    //  TODO: default size
-    let id = Id::tooltip();
-    let response = show_tooltip_area(ctx, id, window_pos, add_contents);
+    let expected_size = ctx.memory().tooltip_size(id);
+    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);
+    let position = position.max(ctx.input().screen_rect().left_top());
 
-    let tooltip_rect = tooltip_rect.unwrap_or(Rect::NOTHING);
-    ctx.frame_state().tooltip_rect = Some(tooltip_rect.union(response.rect));
+    let response = show_tooltip_area(ctx, id, position, add_contents);
+    ctx.memory().set_tooltip_size(id, response.rect.size());
+
+    ctx.frame_state().tooltip_rect = Some((id, tooltip_rect.union(response.rect)));
 }
 
 /// Show some text at the current pointer position (if any).
@@ -50,11 +79,11 @@ pub fn show_tooltip(ctx: &CtxRef, add_contents: impl FnOnce(&mut Ui)) {
 /// ```
 /// # let mut ui = egui::Ui::__test();
 /// if ui.ui_contains_pointer() {
-///     egui::show_tooltip_text(ui.ctx(), "Helpful text");
+///     egui::show_tooltip_text(ui.ctx(), egui::Id::new("my_tooltip"), "Helpful text");
 /// }
 /// ```
-pub fn show_tooltip_text(ctx: &CtxRef, text: impl Into<String>) {
-    show_tooltip(ctx, |ui| {
+pub fn show_tooltip_text(ctx: &CtxRef, id: Id, text: impl Into<String>) {
+    show_tooltip(ctx, id, |ui| {
         ui.add(crate::widgets::Label::new(text));
     })
 }

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<Rect>,
+    pub(crate) tooltip_rect: Option<(Id, Rect)>,
 
     /// Cleared by the first `ScrollArea` that makes use of it.
     pub(crate) scroll_delta: Vec2,

egui/src/id.rs

@@ -32,14 +32,11 @@ use std::hash::Hash;
 pub struct Id(u64);
 
 impl Id {
-    pub fn background() -> Self {
+    pub(crate) fn background() -> Self {
         Self(0)
     }
 
-    pub fn tooltip() -> Self {
-        Self(1)
-    }
-
+    /// Generate a new `Id` by hashing some source (e.g. a string or integer).
     pub fn new(source: impl Hash) -> Id {
         // NOTE: AHasher is NOT suitable for this!
         use std::collections::hash_map::DefaultHasher;
@@ -49,6 +46,7 @@ impl Id {
         Id(hasher.finish())
     }
 
+    /// Generate a new `Id` by hashing the parent `Id` and the given argument.
     pub fn with(self, child: impl Hash) -> Id {
         // NOTE: AHasher is NOT suitable for this!
         use std::collections::hash_map::DefaultHasher;

egui/src/memory.rs

@@ -2,7 +2,7 @@ use std::collections::{HashMap, HashSet};
 
 use crate::{
     area, collapsing_header, menu, resize, scroll_area, util::Cache, widgets::text_edit, window,
-    Id, LayerId, Pos2, Rect, Style,
+    Id, LayerId, Pos2, Rect, Style, Vec2,
 };
 use epaint::color::{Color32, Hsva};
 
@@ -51,6 +51,10 @@ pub struct Memory {
     #[cfg_attr(feature = "persistence", serde(skip))]
     popup: Option<Id>,
 
+    /// Used to clamp the tooltip to the screen.
+    #[cfg_attr(feature = "persistence", serde(skip))]
+    tooltip_size: Option<(Id, Vec2)>,
+
     #[cfg_attr(feature = "persistence", serde(skip))]
     everything_is_visible: bool,
 }
@@ -254,6 +258,29 @@ impl Memory {
     pub fn reset_areas(&mut self) {
         self.areas = Default::default();
     }
+
+    pub(crate) fn tooltip_size(&self, id: Id) -> Option<Vec2> {
+        if let Some((stored_id, stored_size)) = self.tooltip_size {
+            if stored_id == id {
+                Some(stored_size)
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn set_tooltip_size(&mut self, id: Id, size: Vec2) {
+        if let Some((stored_id, stored_size)) = &mut self.tooltip_size {
+            if *stored_id == id {
+                *stored_size = stored_size.max(size);
+                return;
+            }
+        }
+
+        self.tooltip_size = Some((id, size));
+    }
 }
 
 /// ## Popups

egui/src/response.rs

@@ -193,7 +193,12 @@ impl Response {
         if (self.hovered() && self.ctx.input().pointer.tooltip_pos().is_some())
             || self.ctx.memory().everything_is_visible()
         {
-            crate::containers::show_tooltip(&self.ctx, add_contents);
+            crate::containers::show_tooltip_under(
+                &self.ctx,
+                self.id.with("__tooltip"),
+                &self.rect,
+                add_contents,
+            );
         }
         self
     }

egui/src/style.rs

@@ -293,7 +293,7 @@ impl Default for Spacing {
             text_edit_width: 280.0,
             icon_width: 16.0,
             icon_spacing: 0.0,
-            tooltip_width: 400.0,
+            tooltip_width: 600.0,
         }
     }
 }
@@ -505,7 +505,7 @@ impl Spacing {
         ui.add(Slider::f32(text_edit_width, 0.0..=1000.0).text("text_edit_width"));
         ui.add(Slider::f32(icon_width, 0.0..=60.0).text("icon_width"));
         ui.add(Slider::f32(icon_spacing, 0.0..=10.0).text("icon_spacing"));
-        ui.add(Slider::f32(tooltip_width, 0.0..=10.0).text("tooltip_width"));
+        ui.add(Slider::f32(tooltip_width, 0.0..=1000.0).text("tooltip_width"));
 
         ui.vertical_centered(|ui| reset_button(ui, self));
     }