Add wrappers for starting and stopping modal windows (#129)

* Add App::run_modal_for_window.

This is a wrapper around https://developer.apple.com/documentation/appkit/nsapplication/1428436-runmodalforwindow.

* Add wrapper for stopModalWithCode, and conversions for ModalResponse.

* Make run_modal_for_window borrow a reference, rather than take the value.

The reference is needed because the caller may still need to use the
window after the dialog is finished.

* Add a note about using the sheets API for modal views.

* Move the ModalResponse enum from the filesystem module to the appkit::app module.

It is now being used outside of filesystem, and this more closely mirrors
the location of this enum with AppKit.

* Make run_modal_for_window have the same semantics as begin_sheet.

Specifically, allow windows with delegates to be used.

src/appkit/app/enums.rs

@@ -1,6 +1,6 @@
 //! Various types used at the AppController level.
 
-use crate::foundation::NSUInteger;
+use crate::foundation::{NSInteger, NSUInteger};
 
 /// Used for determining how an application should handle quitting/terminating.
 /// You return this in your `AppController` `should_terminate` method.
@@ -156,3 +156,68 @@ impl From<&PresentationOption> for NSUInteger {
         }
     }
 }
+
+/// Represents a modal response for macOS modal dialogs.
+#[derive(Copy, Clone, Debug)]
+pub enum ModalResponse {
+    /// The user hit the "Ok" button.
+    Ok,
+
+    /// Continue.
+    Continue,
+
+    /// Canceled.
+    Canceled,
+
+    /// Stopped.
+    Stopped,
+
+    /// Aborted.
+    Aborted,
+
+    /// The first button in the dialog was clicked.
+    FirstButtonReturned,
+
+    /// The second button in the dialog was clicked.
+    SecondButtonReturned,
+
+    /// The third button in the dialog was clicked.
+    ThirdButtonReturned
+}
+
+impl From<NSInteger> for ModalResponse {
+    fn from(i: NSInteger) -> Self {
+        match i {
+            1 => ModalResponse::Ok,
+            0 => ModalResponse::Canceled,
+            1000 => ModalResponse::FirstButtonReturned,
+            1001 => ModalResponse::SecondButtonReturned,
+            1002 => ModalResponse::ThirdButtonReturned,
+            -1000 => ModalResponse::Stopped,
+            -1001 => ModalResponse::Aborted,
+            -1002 => ModalResponse::Continue,
+
+            // @TODO: Definitely don't panic here, wtf was I thinking?
+            // Probably make this a ModalResponse::Unknown or something so a user can
+            // gracefully handle.
+            e => {
+                panic!("Unknown NSModalResponse sent back! {}", e);
+            }
+        }
+    }
+}
+
+impl Into<NSInteger> for ModalResponse {
+    fn into(self) -> NSInteger {
+        match self {
+            ModalResponse::Ok => 1,
+            ModalResponse::Canceled => 0,
+            ModalResponse::FirstButtonReturned => 1000,
+            ModalResponse::SecondButtonReturned => 1001,
+            ModalResponse::ThirdButtonReturned => 1002,
+            ModalResponse::Stopped => -1000,
+            ModalResponse::Aborted => -1001,
+            ModalResponse::Continue => -1002
+        }
+    }
+}

src/appkit/app/mod.rs

@@ -44,7 +44,7 @@ use objc::runtime::Object;
 use objc::{class, msg_send, msg_send_id, sel};
 
 use crate::appkit::menu::Menu;
-use crate::foundation::{id, nil, AutoReleasePool, NSUInteger, NO, YES};
+use crate::foundation::{id, nil, AutoReleasePool, NSInteger, NSUInteger, NO, YES};
 use crate::invoker::TargetActionHandler;
 use crate::notification_center::Dispatcher;
 use crate::utils::activate_cocoa_multithreading;
@@ -63,7 +63,7 @@ pub use enums::*;
 mod traits;
 pub use traits::AppDelegate;
 
-use super::window::Window;
+use super::window::{Window, WindowDelegate};
 
 pub(crate) static APP_PTR: &str = "rstAppPtr";
 
@@ -319,4 +319,31 @@ impl App {
             let _: () = msg_send![app, terminate: nil];
         });
     }
+
+    /// Starts a modal event loop for the given window.
+    ///
+    /// This method runs a modal event loop for the specified window synchronously.
+    /// It displays the specified window, makes it key, starts the run loop, and
+    /// processes events for that window.
+    ///
+    /// Modern MacOS modal views should really be using the sheets API, but this
+    /// is still part of AppKit, so provided for completeness.  As with
+    /// begin_sheet, a WindowDelegate is required.
+    pub fn run_modal_for_window<W>(window: &Window<W>) -> ModalResponse
+    where
+        W: WindowDelegate + 'static
+    {
+        shared_application(|app| unsafe {
+            let modal_response: NSInteger = msg_send![app, runModalForWindow: &*window.objc];
+            modal_response.into()
+        })
+    }
+
+    /// Stop the current modal window, returning the given code.
+    pub fn stop_modal_with_code(modal_response: ModalResponse) {
+        shared_application(|app| unsafe {
+            let response: NSInteger = modal_response.into();
+            let _: () = msg_send![app, stopModalWithCode: response];
+        });
+    }
 }

src/filesystem/enums.rs

@@ -2,56 +2,6 @@
 
 use crate::foundation::{NSInteger, NSUInteger};
 
-/// Represents a modal response for macOS modal dialogs.
-#[derive(Copy, Clone, Debug)]
-pub enum ModalResponse {
-    /// The user hit the "Ok" button.
-    Ok,
-
-    /// Continue.
-    Continue,
-
-    /// Canceled.
-    Canceled,
-
-    /// Stopped.
-    Stopped,
-
-    /// Aborted.
-    Aborted,
-
-    /// The first button in the dialog was clicked.
-    FirstButtonReturned,
-
-    /// The second button in the dialog was clicked.
-    SecondButtonReturned,
-
-    /// The third button in the dialog was clicked.
-    ThirdButtonReturned
-}
-
-impl From<NSInteger> for ModalResponse {
-    fn from(i: NSInteger) -> Self {
-        match i {
-            1 => ModalResponse::Ok,
-            0 => ModalResponse::Canceled,
-            1000 => ModalResponse::FirstButtonReturned,
-            1001 => ModalResponse::SecondButtonReturned,
-            1002 => ModalResponse::ThirdButtonReturned,
-            -1000 => ModalResponse::Stopped,
-            -1001 => ModalResponse::Aborted,
-            -1002 => ModalResponse::Continue,
-
-            // @TODO: Definitely don't panic here, wtf was I thinking?
-            // Probably make this a ModalResponse::Unknown or something so a user can
-            // gracefully handle.
-            e => {
-                panic!("Unknown NSModalResponse sent back! {}", e);
-            }
-        }
-    }
-}
-
 /// Represents a type of search path used in file manager calls.
 #[derive(Copy, Clone, Debug)]
 pub enum SearchPathDomainMask {

src/filesystem/select.rs

@@ -10,7 +10,7 @@ use objc::rc::{Id, Shared};
 use objc::runtime::Object;
 use objc::{class, msg_send, msg_send_id, sel};
 
-use crate::filesystem::enums::ModalResponse;
+use crate::appkit::ModalResponse;
 use crate::foundation::{id, nil, NSInteger, NSString, NO, NSURL, YES};
 
 #[cfg(feature = "appkit")]