Add basic file drag and drop support (#1096)

Add basic file drag and drop support

Cargo.toml

@@ -142,6 +142,10 @@ path = "examples/3d/z_sort_debug.rs"
 name = "custom_loop"
 path = "examples/app/custom_loop.rs"
 
+[[example]]
+name = "drag_and_drop"
+path = "examples/app/drag_and_drop.rs"
+
 [[example]]
 name = "empty_defaults"
 path = "examples/app/empty_defaults.rs"

crates/bevy_window/src/event.rs

@@ -1,3 +1,5 @@
+use std::path::PathBuf;
+
 use super::{WindowDescriptor, WindowId};
 use bevy_math::Vec2;
 
@@ -77,3 +79,13 @@ pub struct WindowBackendScaleFactorChanged {
     pub id: WindowId,
     pub scale_factor: f64,
 }
+
+/// Events related to files being dragged and dropped on a window.
+#[derive(Debug, Clone)]
+pub enum FileDragAndDrop {
+    DroppedFile { id: WindowId, path_buf: PathBuf },
+
+    HoveredFile { id: WindowId, path_buf: PathBuf },
+
+    HoveredFileCancelled { id: WindowId },
+}

crates/bevy_window/src/lib.rs

@@ -11,8 +11,8 @@ pub use windows::*;
 
 pub mod prelude {
     pub use crate::{
-        CursorEntered, CursorLeft, CursorMoved, ReceivedCharacter, Window, WindowDescriptor,
+        CursorEntered, CursorLeft, CursorMoved, FileDragAndDrop, ReceivedCharacter, Window,
-        Windows,
+        WindowDescriptor, Windows,
     };
 }
 
@@ -46,6 +46,7 @@ impl Plugin for WindowPlugin {
             .add_event::<WindowFocused>()
             .add_event::<WindowScaleFactorChanged>()
             .add_event::<WindowBackendScaleFactorChanged>()
+            .add_event::<FileDragAndDrop>()
             .init_resource::<Windows>();
 
         if self.add_primary_window {

crates/bevy_winit/src/lib.rs

@@ -1,6 +1,7 @@
 mod converters;
 mod winit_config;
 mod winit_windows;
+
 use bevy_input::{
     keyboard::KeyboardInput,
     mouse::{MouseButtonInput, MouseMotion, MouseScrollUnit, MouseWheel},
@@ -14,7 +15,7 @@ use bevy_ecs::{IntoSystem, Resources, World};
 use bevy_math::Vec2;
 use bevy_utils::tracing::{error, trace, warn};
 use bevy_window::{
-    CreateWindow, CursorEntered, CursorLeft, CursorMoved, ReceivedCharacter,
+    CreateWindow, CursorEntered, CursorLeft, CursorMoved, FileDragAndDrop, ReceivedCharacter,
     WindowBackendScaleFactorChanged, WindowCloseRequested, WindowCreated, WindowFocused,
     WindowResized, WindowScaleFactorChanged, Windows,
 };
@@ -397,6 +398,27 @@ pub fn winit_runner_with(mut app: App, mut event_loop: EventLoop<()>) {
                             focused,
                         });
                     }
+                    WindowEvent::DroppedFile(path_buf) => {
+                        let mut events =
+                            app.resources.get_mut::<Events<FileDragAndDrop>>().unwrap();
+                        events.send(FileDragAndDrop::DroppedFile {
+                            id: window_id,
+                            path_buf,
+                        });
+                    }
+                    WindowEvent::HoveredFile(path_buf) => {
+                        let mut events =
+                            app.resources.get_mut::<Events<FileDragAndDrop>>().unwrap();
+                        events.send(FileDragAndDrop::HoveredFile {
+                            id: window_id,
+                            path_buf,
+                        });
+                    }
+                    WindowEvent::HoveredFileCancelled => {
+                        let mut events =
+                            app.resources.get_mut::<Events<FileDragAndDrop>>().unwrap();
+                        events.send(FileDragAndDrop::HoveredFileCancelled { id: window_id });
+                    }
                     _ => {}
                 }
             }

examples/README.md

@@ -81,6 +81,7 @@ Example | File | Description
 Example | File | Description
 --- | --- | ---
 `custom_loop` | [`app/custom_loop.rs`](./app/custom_loop.rs) | Demonstrates how to create a custom runner (to update an app manually).
+`drag_and_drop` | [`app/drag_and_drop.rs`](./app/drag_and_drop.rs) | An example that shows how to handle drag and drop in an app.
 `empty_defaults` | [`app/empty_defaults.rs`](./app/empty_defaults.rs) | An empty application with default plugins
 `empty` | [`app/empty.rs`](./app/empty.rs) | An empty application (does nothing)
 `headless` | [`app/headless.rs`](./app/headless.rs) | An application that runs without default plugins

examples/app/drag_and_drop.rs

@@ -0,0 +1,17 @@
+use bevy::prelude::*;
+
+fn main() {
+    App::build()
+        .add_plugins(DefaultPlugins)
+        .add_system(file_drag_and_drop_system.system())
+        .run();
+}
+
+fn file_drag_and_drop_system(
+    mut reader: Local<EventReader<FileDragAndDrop>>,
+    events: Res<Events<FileDragAndDrop>>,
+) {
+    for event in reader.iter(&events) {
+        println!("{:?}", event);
+    }
+}