Add FileDragAndDropPlugin and FileDragAndDrop resource

crates/bevy_internal/src/default_plugins.rs

@@ -41,6 +41,9 @@ impl PluginGroup for DefaultPlugins {
         #[cfg(feature = "bevy_winit")]
         group.add(bevy_winit::WinitPlugin::default());
 
+        #[cfg(feature = "bevy_winit")]
+        group.add(bevy_winit::FileDragAndDropPlugin::default());
+
         #[cfg(feature = "bevy_wgpu")]
         group.add(bevy_wgpu::WgpuPlugin::default());
     }

crates/bevy_winit/src/drag_and_drop.rs

@@ -0,0 +1,71 @@
+use std::path::PathBuf;
+
+use bevy_app::prelude::*;
+
+use bevy_app::EventReader;
+use bevy_ecs::{IntoSystem, Local, Res, ResMut};
+use bevy_window::{DroppedFile, HoveredFile, HoveredFileCancelled, WindowId};
+
+type FilePath = (PathBuf, WindowId);
+#[derive(Debug, Default)]
+pub struct FileDragAndDrop {
+    hovered_files: Vec<FilePath>,
+    dropped_files: Vec<FilePath>,
+}
+
+impl FileDragAndDrop {
+    pub fn drain(&mut self) -> std::vec::Drain<'_, FilePath> {
+        self.dropped_files.drain(0..)
+    }
+
+    pub fn is_hovered(&self) -> bool {
+        !self.hovered_files.is_empty()
+    }
+}
+
+#[derive(Default)]
+struct DroppedFileSystemState {
+    dropped_filed_event_reader: EventReader<DroppedFile>,
+    hovered_file_event_reader: EventReader<HoveredFile>,
+    // hovered_file_canceled_event_reader: EventReader<HoveredFileCancelled>,
+}
+
+// NOTE: in winit, each Dropped, Hovered, and Canceled are raised once for EACH file
+fn drag_and_drop_system(
+    mut state: Local<DroppedFileSystemState>,
+    mut drag_and_drop: ResMut<FileDragAndDrop>,
+    dropped_file_events: Res<Events<DroppedFile>>,
+    hovered_file_events: Res<Events<HoveredFile>>,
+    mut hovered_file_canceled_events: ResMut<Events<HoveredFileCancelled>>,
+) {
+    for dropped_file in state.dropped_filed_event_reader.iter(&dropped_file_events) {
+        let DroppedFile { id, path_buf } = dropped_file;
+        drag_and_drop.dropped_files.push((path_buf.clone(), *id))
+    }
+
+    for hovered_file in state.hovered_file_event_reader.iter(&hovered_file_events) {
+        let HoveredFile { id, path_buf } = hovered_file;
+        drag_and_drop.hovered_files.push((path_buf.clone(), *id));
+    }
+
+    // Since we only deal with one mouse, we can assume that a cancelled event
+    // means all hovered files are gone.
+    if hovered_file_canceled_events.drain().next().is_some() {
+        hovered_file_canceled_events.clear();
+        drag_and_drop.hovered_files.clear();
+    }
+}
+
+#[derive(Default)]
+pub struct FileDragAndDropPlugin {}
+
+impl Plugin for FileDragAndDropPlugin {
+    fn build(&self, app: &mut AppBuilder) {
+        app.init_resource::<FileDragAndDrop>()
+            .add_system_to_stage(bevy_app::stage::EVENT, drag_and_drop_system.system());
+    }
+
+    fn name(&self) -> &str {
+        std::any::type_name::<Self>()
+    }
+}

crates/bevy_winit/src/lib.rs

@@ -1,6 +1,11 @@
 mod converters;
 mod winit_config;
 mod winit_windows;
+mod drag_and_drop;
+
+pub use drag_and_drop::FileDragAndDrop;
+pub use drag_and_drop::FileDragAndDropPlugin;
+
 use bevy_input::{
     keyboard::KeyboardInput,
     mouse::{MouseButtonInput, MouseMotion, MouseScrollUnit, MouseWheel},

examples/app/drag_and_drop.rs

@@ -1,11 +1,4 @@
-use bevy::prelude::*;
-
-#[derive(Default)]
-struct DroppedFileSystemState {
-    dropped_filed_event_reader: EventReader<DroppedFile>,
-    hovered_file_event_reader: EventReader<HoveredFile>,
-    hovered_file_canceled_event_reader: EventReader<HoveredFileCancelled>,
-}
+use bevy::{prelude::*, winit::FileDragAndDrop};
 
 fn main() {
     App::build()
@@ -14,24 +7,8 @@ fn main() {
         .run();
 }
 
-fn dropped_file_system(
-    mut state: Local<DroppedFileSystemState>,
-    dropped_file_events: Res<Events<DroppedFile>>,
-    hovered_file_events: Res<Events<HoveredFile>>,
-    hovered_file_canceled_events: Res<Events<HoveredFileCancelled>>,
-) {
-    for event in state.dropped_filed_event_reader.iter(&dropped_file_events) {
-        println!("Dropped file{:?}", event);
-    }
-
-    for event in state.hovered_file_event_reader.iter(&hovered_file_events) {
-        println!("Hovered file{:?}", event);
-    }
-
-    for event in state
-        .hovered_file_canceled_event_reader
-        .iter(&hovered_file_canceled_events)
-    {
-        println!("Dropped file{:?}", event);
+fn dropped_file_system(mut drag_and_drop: ResMut<FileDragAndDrop>) {
+    for file in drag_and_drop.drain() {
+        println!("Dropped path {:?}", file);
     }
 }