Drag and drop files into egui_glium and egui_web (#637)

* Implement file drag-and-drop for egui_glium

* Implement file drag-and-drop into egui_web

* Cleanup

CHANGELOG.md

@@ -10,9 +10,10 @@ NOTE: [`eframe`](eframe/CHANGELOG.md), [`egui_web`](egui_web/CHANGELOG.md) and [
 ### Added ⭐
 * Plot:
   * [Line styles](https://github.com/emilk/egui/pull/482)
+  * Add `show_background` and `show_axes` methods to `Plot`.
 * [Progress bar](https://github.com/emilk/egui/pull/519)
 * `Grid::num_columns`: allow the last column to take up the rest of the space of the parent `Ui`.
-* Add `show_background` and `show_axes` methods to `Plot`.
+* Add an API for dropping files into egui (see `RawInput`).
 
 ### Changed 🔧
 * Return closure return value from `Area::show`, `ComboBox::show_ui`, `ComboBox::combo_box_with_label`, `Window::show`, `popup::*`, `menu::menu`.

eframe/CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to the `eframe` crate.
 
 
 ## Unreleased
+* Add dragging and dropping files into egui.
 * Improve http fetch API.
 * `run_native` now returns when the app is closed.
 

egui/src/data/input.rs

@@ -57,6 +57,12 @@ pub struct RawInput {
     /// but you can check if egui is using the keyboard with [`crate::Context::wants_keyboard_input`]
     /// and/or the pointer (mouse/touch) with [`crate::Context::is_using_pointer`].
     pub events: Vec<Event>,
+
+    /// Dragged files hovering over egui.
+    pub hovered_files: Vec<HoveredFile>,
+
+    /// Dragged files dropped into egui.
+    pub dropped_files: Vec<DroppedFile>,
 }
 
 impl Default for RawInput {
@@ -72,12 +78,17 @@ impl Default for RawInput {
             predicted_dt: 1.0 / 60.0,
             modifiers: Modifiers::default(),
             events: vec![],
+            hovered_files: Default::default(),
+            dropped_files: Default::default(),
         }
     }
 }
 
 impl RawInput {
-    /// Helper: move volatile (deltas and events), clone the rest
+    /// Helper: move volatile (deltas and events), clone the rest.
+    ///
+    /// * [`Self::hovered_files`] is cloned.
+    /// * [`Self::dropped_files`] is moved.
     pub fn take(&mut self) -> RawInput {
         #![allow(deprecated)] // for screen_size
         let zoom = self.zoom_delta;
@@ -92,10 +103,34 @@ impl RawInput {
             predicted_dt: self.predicted_dt,
             modifiers: self.modifiers,
             events: std::mem::take(&mut self.events),
+            hovered_files: self.hovered_files.clone(),
+            dropped_files: std::mem::take(&mut self.dropped_files),
         }
     }
 }
 
+/// A file about to be dropped into egui.
+#[derive(Clone, Debug, Default)]
+pub struct HoveredFile {
+    /// Set by the `egui_glium` backend.
+    pub path: Option<std::path::PathBuf>,
+    /// With the `egui_web` backend, this is set to the mime-type of the file (if available).
+    pub mime: String,
+}
+
+/// A file dropped into egui.
+#[derive(Clone, Debug, Default)]
+pub struct DroppedFile {
+    /// Set by the `egui_glium` backend.
+    pub path: Option<std::path::PathBuf>,
+    /// Name of the file. Set by the `egui_web` backend.
+    pub name: String,
+    /// Set by the `egui_web` backend.
+    pub last_modified: Option<std::time::SystemTime>,
+    /// Set by the `egui_web` backend.
+    pub bytes: Option<std::sync::Arc<[u8]>>,
+}
+
 /// An input event generated by the integration.
 ///
 /// This only covers events that egui cares about.
@@ -295,6 +330,8 @@ impl RawInput {
             predicted_dt,
             modifiers,
             events,
+            hovered_files,
+            dropped_files,
         } = self;
 
         ui.label(format!("scroll_delta: {:?} points", scroll_delta));
@@ -313,6 +350,8 @@ impl RawInput {
         ui.label(format!("modifiers: {:#?}", modifiers));
         ui.label(format!("events: {:?}", events))
             .on_hover_text("key presses etc");
+        ui.label(format!("hovered_files: {}", hovered_files.len()));
+        ui.label(format!("dropped_files: {}", dropped_files.len()));
     }
 }
 

egui_demo_lib/src/wrap_app.rs

@@ -33,6 +33,8 @@ pub struct WrapApp {
     selected_anchor: String,
     apps: Apps,
     backend_panel: super::backend_panel::BackendPanel,
+    #[cfg_attr(feature = "persistence", serde(skip))]
+    dropped_files: Vec<egui::DroppedFile>,
 }
 
 impl epi::App for WrapApp {
@@ -102,6 +104,8 @@ impl epi::App for WrapApp {
         }
 
         self.backend_panel.end_of_frame(ctx);
+
+        self.ui_file_drag_and_drop(ctx);
     }
 }
 
@@ -144,6 +148,67 @@ impl WrapApp {
             });
         });
     }
+
+    fn ui_file_drag_and_drop(&mut self, ctx: &egui::CtxRef) {
+        use egui::*;
+
+        // Preview hovering files:
+        if !ctx.input().raw.hovered_files.is_empty() {
+            let mut text = "Dropping files:\n".to_owned();
+            for file in &ctx.input().raw.hovered_files {
+                if let Some(path) = &file.path {
+                    text += &format!("\n{}", path.display());
+                } else if !file.mime.is_empty() {
+                    text += &format!("\n{}", file.mime);
+                } else {
+                    text += "\n???";
+                }
+            }
+
+            let painter =
+                ctx.layer_painter(LayerId::new(Order::Foreground, Id::new("file_drop_target")));
+
+            let screen_rect = ctx.input().screen_rect();
+            painter.rect_filled(screen_rect, 0.0, Color32::from_black_alpha(192));
+            painter.text(
+                screen_rect.center(),
+                Align2::CENTER_CENTER,
+                text,
+                TextStyle::Heading,
+                Color32::WHITE,
+            );
+        }
+
+        // Collect dropped files:
+        if !ctx.input().raw.dropped_files.is_empty() {
+            self.dropped_files = ctx.input().raw.dropped_files.clone();
+        }
+
+        // Show dropped files (if any):
+        if !self.dropped_files.is_empty() {
+            let mut open = true;
+            egui::Window::new("Dropped files")
+                .open(&mut open)
+                .show(ctx, |ui| {
+                    for file in &self.dropped_files {
+                        let mut info = if let Some(path) = &file.path {
+                            path.display().to_string()
+                        } else if !file.name.is_empty() {
+                            file.name.clone()
+                        } else {
+                            "???".to_owned()
+                        };
+                        if let Some(bytes) = &file.bytes {
+                            info += &format!(" ({} bytes)", bytes.len());
+                        }
+                        ui.label(info);
+                    }
+                });
+            if !open {
+                self.dropped_files.clear();
+            }
+        }
+    }
 }
 
 fn clock_button(ui: &mut egui::Ui, seconds_since_midnight: f64) -> egui::Response {

egui_glium/CHANGELOG.md

@@ -4,8 +4,9 @@ All notable changes to the `egui_glium` integration will be noted in this file.
 
 
 ## Unreleased
-* Fix native file dialogs hanging (eg. when using [`nfd2`](https://github.com/EmbarkStudios/nfd2)
+* Fix native file dialogs hanging (eg. when using [`rfd`](https://github.com/PolyMeilex/rfd)).
-* [Fix minimize on Windows](https://github.com/emilk/egui/issues/518)
+* Implement drag-and-dropping files into the application.
+* [Fix minimize on Windows](https://github.com/emilk/egui/issues/518).
 * Change `drag_and_drop_support` to `false` by default (Windows only). See <https://github.com/emilk/egui/issues/598>.
 * Don't restore window position on Windows, because the position would sometimes be invalid.
 

egui_glium/src/backend.rs

@@ -266,10 +266,10 @@ pub fn run(mut app: Box<dyn epi::App>, native_options: epi::NativeOptions) {
                     } else {
                         // Winit uses up all the CPU of one core when returning ControlFlow::Wait.
                         // Sleeping here helps, but still uses 1-3% of CPU :(
-                        if is_focused {
+                        if is_focused || !egui.input_state.raw.hovered_files.is_empty() {
                             std::thread::sleep(std::time::Duration::from_millis(10));
                         } else {
-                            std::thread::sleep(std::time::Duration::from_millis(100));
+                            std::thread::sleep(std::time::Duration::from_millis(50));
                         }
                     }
                 }
@@ -287,6 +287,7 @@ pub fn run(mut app: Box<dyn epi::App>, native_options: epi::NativeOptions) {
 
                     // TODO: ask egui if the events warrants a repaint instead of repainting on each event.
                     display.gl_window().window().request_redraw();
+                    repaint_asap = true;
                 }
                 glutin::event::Event::UserEvent(RequestRepaintEvent) => {
                     display.gl_window().window().request_redraw();

egui_glium/src/lib.rs

@@ -255,6 +255,22 @@ pub fn input_to_egui(
                 },
             });
         }
+        WindowEvent::HoveredFile(path) => {
+            input_state.raw.hovered_files.push(egui::HoveredFile {
+                path: Some(path.clone()),
+                ..Default::default()
+            });
+        }
+        WindowEvent::HoveredFileCancelled => {
+            input_state.raw.hovered_files.clear();
+        }
+        WindowEvent::DroppedFile(path) => {
+            input_state.raw.hovered_files.clear();
+            input_state.raw.dropped_files.push(egui::DroppedFile {
+                path: Some(path.clone()),
+                ..Default::default()
+            });
+        }
         _ => {
             // dbg!(event);
         }

egui_web/CHANGELOG.md

@@ -5,6 +5,9 @@ All notable changes to the `egui_web` integration will be noted in this file.
 
 ## Unreleased
 
+### Added ⭐
+* Added support for dragging and dropping files into the browser window.
+
 
 ## 0.13.0 - 2021-06-24
 

egui_web/Cargo.toml

@@ -56,18 +56,25 @@ screen_reader = ["tts"] # experimental
 [dependencies.web-sys]
 version = "0.3.52"
 features = [
+  "BinaryType",
+  "Blob",
   "Clipboard",
   "ClipboardEvent",
   "CompositionEvent",
   "console",
   "CssStyleDeclaration",
   "DataTransfer",
+  "DataTransferItem",
+  "DataTransferItemList",
   "Document",
   "DomRect",
+  "DragEvent",
   "Element",
   "Event",
   "EventListener",
   "EventTarget",
+  "File",
+  "FileList",
   "FocusEvent",
   "HtmlCanvasElement",
   "HtmlElement",

egui_web/src/lib.rs

@@ -1087,6 +1087,105 @@ fn install_canvas_events(runner_ref: &AppRunnerRef) -> Result<(), JsValue> {
         closure.forget();
     }
 
+    {
+        let event_name = "dragover";
+        let runner_ref = runner_ref.clone();
+        let closure = Closure::wrap(Box::new(move |event: web_sys::DragEvent| {
+            if let Some(data_transfer) = event.data_transfer() {
+                let mut runner_lock = runner_ref.0.lock();
+                runner_lock.input.raw.hovered_files.clear();
+                for i in 0..data_transfer.items().length() {
+                    if let Some(item) = data_transfer.items().get(i) {
+                        runner_lock.input.raw.hovered_files.push(egui::HoveredFile {
+                            mime: item.type_(),
+                            ..Default::default()
+                        });
+                    }
+                }
+                runner_lock.needs_repaint.set_true();
+                event.stop_propagation();
+                event.prevent_default();
+            }
+        }) as Box<dyn FnMut(_)>);
+        canvas.add_event_listener_with_callback(event_name, closure.as_ref().unchecked_ref())?;
+        closure.forget();
+    }
+
+    {
+        let event_name = "dragleave";
+        let runner_ref = runner_ref.clone();
+        let closure = Closure::wrap(Box::new(move |event: web_sys::DragEvent| {
+            let mut runner_lock = runner_ref.0.lock();
+            runner_lock.input.raw.hovered_files.clear();
+            runner_lock.needs_repaint.set_true();
+            event.stop_propagation();
+            event.prevent_default();
+        }) as Box<dyn FnMut(_)>);
+        canvas.add_event_listener_with_callback(event_name, closure.as_ref().unchecked_ref())?;
+        closure.forget();
+    }
+
+    {
+        let event_name = "drop";
+        let runner_ref = runner_ref.clone();
+        let closure = Closure::wrap(Box::new(move |event: web_sys::DragEvent| {
+            if let Some(data_transfer) = event.data_transfer() {
+                {
+                    let mut runner_lock = runner_ref.0.lock();
+                    runner_lock.input.raw.hovered_files.clear();
+                    runner_lock.needs_repaint.set_true();
+                }
+
+                if let Some(files) = data_transfer.files() {
+                    for i in 0..files.length() {
+                        if let Some(file) = files.get(i) {
+                            let name = file.name();
+                            let last_modified = std::time::UNIX_EPOCH
+                                + std::time::Duration::from_millis(file.last_modified() as u64);
+
+                            console_log(format!("Loading {:?} ({} bytes)…", name, file.size()));
+
+                            let future = wasm_bindgen_futures::JsFuture::from(file.array_buffer());
+
+                            let runner_ref = runner_ref.clone();
+                            let future = async move {
+                                match future.await {
+                                    Ok(array_buffer) => {
+                                        let bytes = js_sys::Uint8Array::new(&array_buffer).to_vec();
+                                        console_log(format!(
+                                            "Loaded {:?} ({} bytes).",
+                                            name,
+                                            bytes.len()
+                                        ));
+
+                                        let mut runner_lock = runner_ref.0.lock();
+                                        runner_lock.input.raw.dropped_files.push(
+                                            egui::DroppedFile {
+                                                name,
+                                                last_modified: Some(last_modified),
+                                                bytes: Some(bytes.into()),
+                                                ..Default::default()
+                                            },
+                                        );
+                                        runner_lock.needs_repaint.set_true();
+                                    }
+                                    Err(err) => {
+                                        console_error(format!("Failed to read file: {:?}", err));
+                                    }
+                                }
+                            };
+                            wasm_bindgen_futures::spawn_local(future);
+                        }
+                    }
+                }
+                event.stop_propagation();
+                event.prevent_default();
+            }
+        }) as Box<dyn FnMut(_)>);
+        canvas.add_event_listener_with_callback(event_name, closure.as_ref().unchecked_ref())?;
+        closure.forget();
+    }
+
     Ok(())
 }