feat: implement drag and drop (fluxxcode#192)

* implement drag and drop

src/file_dialog.rs

@@ -1,9 +1,8 @@
+use egui::text::{CCursor, CCursorRange};
 use std::fmt::Debug;
 use std::io;
 use std::path::{Path, PathBuf};
 
-use egui::text::{CCursor, CCursorRange};
-
 use crate::config::{
     FileDialogConfig, FileDialogKeyBindings, FileDialogLabels, FileDialogStorage, FileFilter,
     Filter, QuickAccess,
@@ -1136,6 +1135,31 @@ impl FileDialog {
         if !is_open {
             self.cancel();
         }
+
+        let mut new_file_dropped = false;
+
+        // Collect dropped files:
+        ctx.input(|i| {
+            // check if files were dropped
+            if let Some(dropped_file) = i.raw.dropped_files.last() {
+                if let Some(path) = &dropped_file.path {
+                    if path.is_dir() {
+                        // if we dropped a directory, go there
+                        self.load_directory(path.as_path());
+                        new_file_dropped = true;
+                    } else if let Some(parent) = path.parent() {
+                        // else, go to the parent directory
+                        self.load_directory(parent);
+                        new_file_dropped = true;
+                    }
+                }
+            }
+        });
+
+        // update GUI if we dropped a file
+        if new_file_dropped {
+            ctx.request_repaint();
+        }
     }
 
     /// Updates the main modal background of the file dialog window.