add functions to check which button triggered a drag start & end (#2507)

* add button release events for drags

* add utility functions

* fix CHANGELOG.md

* fix CHANGELOG.md

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

CHANGELOG.md

@@ -6,6 +6,8 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 
 ## Unreleased
 ### Added ⭐
+* Add `Response::drag_started_by` and `Response::drag_released_by` for convenience, similar to `dragged` and `dragged_by` ([#2507](https://github.com/emilk/egui/pull/2507)).
+* Add `PointerState::*_pressed` to check if the given button was pressed in this frame ([#2507](https://github.com/emilk/egui/pull/2507)).
 * `Event::Key` now has a `repeat` field that is set to `true` if the event was the result of a key-repeat ([#2435](https://github.com/emilk/egui/pull/2435)).
 * Add `Slider::drag_value_speed`, which lets you ask for finer precision when dragging the slider value rather than the actual slider.
 * Add `Memory::any_popup_open`, which returns true if any popup is currently open ([#2464](https://github.com/emilk/egui/pull/2464)).
@@ -23,6 +25,7 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 * Default `ComboBox` is now controlled with `Spacing::combo_width` ([#2621](https://github.com/emilk/egui/pull/2621)).
 
 ### Fixed 🐛
+* Trigger `PointerEvent::Released` for drags ([#2507](https://github.com/emilk/egui/pull/2507)).
 * Expose `TextEdit`'s multiline flag to AccessKit ([#2448](https://github.com/emilk/egui/pull/2448)).
 * Don't render `\r` (Carriage Return) ([#2452](https://github.com/emilk/egui/pull/2452)).
 * The `button_padding` style option works closer as expected with image+text buttons now ([#2510](https://github.com/emilk/egui/pull/2510)).

crates/egui/src/context.rs

@@ -564,17 +564,17 @@ impl Context {
                             }
                         }
                     }
-                    PointerEvent::Released(click) => {
+                    PointerEvent::Released { click, button } => {
                         response.drag_released = response.dragged;
                         response.dragged = false;
 
                         if hovered && response.is_pointer_button_down_on {
                             if let Some(click) = click {
                                 let clicked = hovered && response.is_pointer_button_down_on;
-                                response.clicked[click.button as usize] = clicked;
+                                response.clicked[*button as usize] = clicked;
-                                response.double_clicked[click.button as usize] =
+                                response.double_clicked[*button as usize] =
                                     clicked && click.is_double();
-                                response.triple_clicked[click.button as usize] =
+                                response.triple_clicked[*button as usize] =
                                     clicked && click.is_triple();
                             }
                         }

crates/egui/src/input_state.rs

@@ -447,7 +447,6 @@ impl InputState {
 #[derive(Clone, Debug, PartialEq)]
 pub(crate) struct Click {
     pub pos: Pos2,
-    pub button: PointerButton,
     /// 1 or 2 (double-click) or 3 (triple-click)
     pub count: u32,
     /// Allows you to check for e.g. shift-click
@@ -471,7 +470,10 @@ pub(crate) enum PointerEvent {
         position: Pos2,
         button: PointerButton,
     },
-    Released(Option<Click>),
+    Released {
+        click: Option<Click>,
+        button: PointerButton,
+    },
 }
 
 impl PointerEvent {
@@ -480,11 +482,11 @@ impl PointerEvent {
     }
 
     pub fn is_release(&self) -> bool {
-        matches!(self, PointerEvent::Released(_))
+        matches!(self, PointerEvent::Released { .. })
     }
 
     pub fn is_click(&self) -> bool {
-        matches!(self, PointerEvent::Released(Some(_click)))
+        matches!(self, PointerEvent::Released { click: Some(_), .. })
     }
 }
 
@@ -639,7 +641,6 @@ impl PointerState {
 
                             Some(Click {
                                 pos,
-                                button,
                                 count,
                                 modifiers,
                             })
@@ -647,7 +648,8 @@ impl PointerState {
                             None
                         };
 
-                        self.pointer_events.push(PointerEvent::Released(click));
+                        self.pointer_events
+                            .push(PointerEvent::Released { click, button });
 
                         self.press_origin = None;
                         self.press_start_time = None;
@@ -775,11 +777,28 @@ impl PointerState {
         self.pointer_events.iter().any(|event| event.is_release())
     }
 
+    /// Was the button given pressed this frame?
+    pub fn button_pressed(&self, button: PointerButton) -> bool {
+        self.pointer_events
+            .iter()
+            .any(|event| matches!(event, &PointerEvent::Pressed{button: b, ..} if button == b))
+    }
+
     /// Was the button given released this frame?
     pub fn button_released(&self, button: PointerButton) -> bool {
         self.pointer_events
             .iter()
-            .any(|event| matches!(event, &PointerEvent::Released(Some(Click{button: b, ..})) if button == b))
+            .any(|event| matches!(event, &PointerEvent::Released{button: b, ..} if button == b))
+    }
+
+    /// Was the primary button pressed this frame?
+    pub fn primary_pressed(&self) -> bool {
+        self.button_pressed(PointerButton::Primary)
+    }
+
+    /// Was the secondary button pressed this frame?
+    pub fn secondary_pressed(&self) -> bool {
+        self.button_pressed(PointerButton::Secondary)
     }
 
     /// Was the primary button released this frame?
@@ -811,16 +830,28 @@ impl PointerState {
 
     /// Was the button given double clicked this frame?
     pub fn button_double_clicked(&self, button: PointerButton) -> bool {
-        self.pointer_events
+        self.pointer_events.iter().any(|event| {
-            .iter()
+            matches!(
-            .any(|event| matches!(&event, PointerEvent::Released(Some(click)) if click.button == button && click.is_double()))
+                &event,
+                PointerEvent::Released {
+                    click: Some(click),
+                    button: b,
+                } if *b == button && click.is_double()
+            )
+        })
     }
 
     /// Was the button given triple clicked this frame?
     pub fn button_triple_clicked(&self, button: PointerButton) -> bool {
-        self.pointer_events
+        self.pointer_events.iter().any(|event| {
-            .iter()
+            matches!(
-            .any(|event| matches!(&event, PointerEvent::Released(Some(click)) if click.button == button && click.is_triple()))
+                &event,
+                PointerEvent::Released {
+                    click: Some(click),
+                    button: b,
+                } if *b == button && click.is_triple()
+            )
+        })
     }
 
     /// Was the primary button clicked this frame?
@@ -833,18 +864,6 @@ impl PointerState {
         self.button_clicked(PointerButton::Secondary)
     }
 
-    // /// Was this button pressed (`!down -> down`) this frame?
-    // /// This can sometimes return `true` even if `any_down() == false`
-    // /// because a press can be shorted than one frame.
-    // pub fn button_pressed(&self, button: PointerButton) -> bool {
-    //     self.pointer_events.iter().any(|event| event.is_press())
-    // }
-
-    // /// Was this button released (`down -> !down`) this frame?
-    // pub fn button_released(&self, button: PointerButton) -> bool {
-    //     self.pointer_events.iter().any(|event| event.is_release())
-    // }
-
     /// Is this button currently down?
     #[inline(always)]
     pub fn button_down(&self, button: PointerButton) -> bool {

crates/egui/src/response.rs

@@ -278,11 +278,21 @@ impl Response {
         self.dragged && self.ctx.input().pointer.any_pressed()
     }
 
+    /// Did a drag on this widgets by the button begin this frame?
+    pub fn drag_started_by(&self, button: PointerButton) -> bool {
+        self.drag_started() && self.ctx.input().pointer.button_pressed(button)
+    }
+
     /// The widget was being dragged, but now it has been released.
     pub fn drag_released(&self) -> bool {
         self.drag_released
     }
 
+    /// The widget was being dragged by the button, but now it has been released.
+    pub fn drag_released_by(&self, button: PointerButton) -> bool {
+        self.drag_released() && self.ctx.input().pointer.button_released(button)
+    }
+
     /// If dragged, how many points were we dragged and in what direction?
     pub fn drag_delta(&self) -> Vec2 {
         if self.dragged() {