archived-wry-cef/src/webview/wkwebview/file_drop.rs

// Copyright 2020-2023 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use std::{
  ffi::{c_void, CStr},
  path::PathBuf,
  rc::Rc,
};

use cocoa::base::{id, BOOL, YES};
use objc::{
  declare::ClassDecl,
  runtime::{class_getInstanceMethod, method_getImplementation, Object, Sel},
};
use once_cell::sync::Lazy;

use crate::{application::window::Window, webview::FileDropEvent};

pub(crate) type NSDragOperation = cocoa::foundation::NSUInteger;
#[allow(non_upper_case_globals)]
const NSDragOperationCopy: NSDragOperation = 1;

static OBJC_DRAGGING_ENTERED: Lazy<extern "C" fn(*const Object, Sel, id) -> NSDragOperation> =
  Lazy::new(|| unsafe {
    std::mem::transmute(method_getImplementation(class_getInstanceMethod(
      class!(WKWebView),
      sel!(draggingEntered:),
    )))
  });

static OBJC_DRAGGING_EXITED: Lazy<extern "C" fn(*const Object, Sel, id)> = Lazy::new(|| unsafe {
  std::mem::transmute(method_getImplementation(class_getInstanceMethod(
    class!(WKWebView),
    sel!(draggingExited:),
  )))
});

static OBJC_PERFORM_DRAG_OPERATION: Lazy<extern "C" fn(*const Object, Sel, id) -> BOOL> =
  Lazy::new(|| unsafe {
    std::mem::transmute(method_getImplementation(class_getInstanceMethod(
      class!(WKWebView),
      sel!(performDragOperation:),
    )))
  });

static OBJC_DRAGGING_UPDATED: Lazy<extern "C" fn(*const Object, Sel, id) -> NSDragOperation> =
  Lazy::new(|| unsafe {
    std::mem::transmute(method_getImplementation(class_getInstanceMethod(
      class!(WKWebView),
      sel!(draggingUpdated:),
    )))
  });

// Safety: objc runtime calls are unsafe
pub(crate) unsafe fn set_file_drop_handler(
  webview: *mut Object,
  window: Rc<Window>,
  handler: Box<dyn Fn(&Window, FileDropEvent) -> bool>,
) -> *mut (Box<dyn Fn(&Window, FileDropEvent) -> bool>, Rc<Window>) {
  let listener = Box::into_raw(Box::new((handler, window)));
  (*webview).set_ivar("FileDropHandler", listener as *mut _ as *mut c_void);
  listener
}

#[allow(clippy::mut_from_ref)]
unsafe fn get_handler(
  this: &Object,
) -> &mut (Box<dyn Fn(&Window, FileDropEvent) -> bool>, Rc<Window>) {
  let delegate: *mut c_void = *this.get_ivar("FileDropHandler");
  &mut *(delegate as *mut (Box<dyn Fn(&Window, FileDropEvent) -> bool>, Rc<Window>))
}

unsafe fn collect_paths(drag_info: id) -> Vec<PathBuf> {
  use cocoa::{
    appkit::{NSFilenamesPboardType, NSPasteboard},
    foundation::{NSFastEnumeration, NSString},
  };

  let pb: id = msg_send![drag_info, draggingPasteboard];
  let mut file_drop_paths = Vec::new();
  let types: id = msg_send![class!(NSArray), arrayWithObject: NSFilenamesPboardType];
  if !NSPasteboard::availableTypeFromArray(pb, types).is_null() {
    for path in NSPasteboard::propertyListForType(pb, NSFilenamesPboardType).iter() {
      file_drop_paths.push(PathBuf::from(
        CStr::from_ptr(NSString::UTF8String(path))
          .to_string_lossy()
          .into_owned(),
      ));
    }
  }
  file_drop_paths
}

extern "C" fn dragging_updated(this: &mut Object, sel: Sel, drag_info: id) -> NSDragOperation {
  let os_operation = OBJC_DRAGGING_UPDATED(this, sel, drag_info);
  if os_operation == 0 {
    // 0 will be returned for a file drop on any arbitrary location on the webview.
    // We'll override that with NSDragOperationCopy.
    NSDragOperationCopy
  } else {
    // A different NSDragOperation is returned when a file is hovered over something like
    // a <input type="file">, so we'll make sure to preserve that behaviour.
    os_operation
  }
}

extern "C" fn dragging_entered(this: &mut Object, sel: Sel, drag_info: id) -> NSDragOperation {
  let listener = unsafe { get_handler(this) };
  let paths = unsafe { collect_paths(drag_info) };

  if !listener.0(&listener.1, FileDropEvent::Hovered(paths)) {
    // Reject the Wry file drop (invoke the OS default behaviour)
    OBJC_DRAGGING_ENTERED(this, sel, drag_info)
  } else {
    NSDragOperationCopy
  }
}

extern "C" fn perform_drag_operation(this: &mut Object, sel: Sel, drag_info: id) -> BOOL {
  let listener = unsafe { get_handler(this) };
  let paths = unsafe { collect_paths(drag_info) };

  if !listener.0(&listener.1, FileDropEvent::Dropped(paths)) {
    // Reject the Wry file drop (invoke the OS default behaviour)
    OBJC_PERFORM_DRAG_OPERATION(this, sel, drag_info)
  } else {
    YES
  }
}

extern "C" fn dragging_exited(this: &mut Object, sel: Sel, drag_info: id) {
  let listener = unsafe { get_handler(this) };
  if !listener.0(&listener.1, FileDropEvent::Cancelled) {
    // Reject the Wry file drop (invoke the OS default behaviour)
    OBJC_DRAGGING_EXITED(this, sel, drag_info);
  }
}

pub(crate) unsafe fn add_file_drop_methods(decl: &mut ClassDecl) {
  decl.add_ivar::<*mut c_void>("FileDropHandler");

  decl.add_method(
    sel!(draggingUpdated:),
    dragging_updated as extern "C" fn(&mut Object, Sel, id) -> NSDragOperation,
  );

  decl.add_method(
    sel!(draggingEntered:),
    dragging_entered as extern "C" fn(&mut Object, Sel, id) -> NSDragOperation,
  );

  decl.add_method(
    sel!(performDragOperation:),
    perform_drag_operation as extern "C" fn(&mut Object, Sel, id) -> BOOL,
  );

  decl.add_method(
    sel!(draggingExited:),
    dragging_exited as extern "C" fn(&mut Object, Sel, id),
  );
}