Plot interaction methods (#766)

* move to a basic plot builder with callback
* add some interaction methods
* move interaction demo to its own panel

CHANGELOG.md

@@ -12,13 +12,15 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * You can now read and write the cursor of a `TextEdit` ([#848](https://github.com/emilk/egui/pull/848)).
 * Most widgets containing text (`Label`, `Button` etc) now supports rich text ([#855](https://github.com/emilk/egui/pull/855)).
 * When using a custom font you can now specify a font index ([#873](https://github.com/emilk/egui/pull/873)).
+* You can now read the plot coordinates of the mouse when building a `Plot` ([#766](https://github.com/emilk/egui/pull/766)).
 
 ### Changed 🔧
 * Unifiy the four `Memory` data buckets (`data`, `data_temp`, `id_data` and `id_data_temp`) into a single `Memory::data`, with a new interface ([#836](https://github.com/emilk/egui/pull/836)).
 * `ui.add(Button::new("…").text_color(…))` is now `ui.button(RichText::new("…").color(…))` (same for `Label` )([#855](https://github.com/emilk/egui/pull/855)).
 * Replace `CtxRef::begin_frame` and `end_frame` with `CtxRef::run` ([#872](https://github.com/emilk/egui/pull/872)).
 * Replace `Ui::__test` with `egui::__run_test_ui` ([#872](https://github.com/emilk/egui/pull/872)).
 * Replace `scroll_delta` and `zoom_delta` in `RawInput` with `Event::Scroll` and `Event::Zoom`.
+* Plots now provide a `show` method that has to be used to add items to and show the plot ([#766](https://github.com/emilk/egui/pull/766)).
 
 ### Fixed 🐛
 * Fix `ComboBox` and other popups getting clipped to parent window ([#885](https://github.com/emilk/egui/pull/885)).
@@ -33,6 +35,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * [sumibi-yakitori](https://github.com/sumibi-yakitori) ([#830](https://github.com/emilk/egui/pull/830))
 * [5225225](https://github.com/5225225): ([#849](https://github.com/emilk/egui/pull/849)).
 * [t18b219k](https://github.com/t18b219k): ([#868](https://github.com/emilk/egui/pull/868)).
+* [EmbersArc](https://github.com/EmbersArc): ([#766](https://github.com/emilk/egui/pull/766)).
 
 
 ## 0.15.0 - 2021-10-24 - Syntax highlighting and hscroll

egui/src/widgets/plot/items.rs

@@ -30,6 +30,16 @@ impl Value {
             y: y.into(),
         }
     }
+
+    #[inline(always)]
+    pub fn to_pos2(self) -> Pos2 {
+        Pos2::new(self.x as f32, self.y as f32)
+    }
+
+    #[inline(always)]
+    pub fn to_vec2(self) -> Vec2 {
+        Vec2::new(self.x as f32, self.y as f32)
+    }
 }
 
 // ----------------------------------------------------------------------------