From 1d85cf8def68f86928518cd7427f1c7031419922 Mon Sep 17 00:00:00 2001
From: djowel <djowel@gmail.com>
Date: Tue, 10 Oct 2023 19:42:53 +0800
Subject: [PATCH] MacOS drag and drop support

---
 lib/host/macos/base_view.mm        | 56 ++++++++++++++++++++++++++++++
 lib/include/elements/base_view.hpp | 13 +++++++
 2 files changed, 69 insertions(+)

diff --git a/lib/host/macos/base_view.mm b/lib/host/macos/base_view.mm
index 90c5ef1e9..33573dc09 100755
--- a/lib/host/macos/base_view.mm
+++ b/lib/host/macos/base_view.mm
@@ -210,6 +210,7 @@ @interface ELEMENTS_VIEW_CLASS : NSView <NSTextInputClient>
 
    bool                             _text_inserted;
 }
+
 @end
 
 @compatibility_alias ElementsView ELEMENTS_VIEW_CLASS;
@@ -251,6 +252,8 @@ - (void) elements_init : (ph::base_view*) view_
 
    [self setPostsBoundsChangedNotifications : YES];
    _text_inserted = false;
+
+   [self registerForDraggedTypes:@[NSPasteboardTypeURL]];
 }
 
 - (void) dealloc
@@ -668,6 +671,59 @@ -(void) windowDidResignKey : (NSNotification*) notification
    _view->end_focus();
 }
 
+-(void) makeDropInfo : (id <NSDraggingInfo>) sender : (ph::drop_info*) info
+{
+   auto pos = [sender draggingLocation];
+   pos = [self convertPoint : pos fromView : nil];
+
+   NSPasteboard* pasteboard = [sender draggingPasteboard];
+   NSDictionary* options = @{NSPasteboardURLReadingFileURLsOnlyKey:@YES};
+   NSArray* urls = [pasteboard   readObjectsForClasses:@[[NSURL class]]
+                                 options:options];
+   const NSUInteger count = [urls count];
+   if (count)
+   {
+      info->where = ph::point{ float(pos.x), float(pos.y) };
+      for (NSUInteger i = 0; i < count; ++i)
+         info->paths.push_back([urls[i] fileSystemRepresentation]);
+   }
+}
+
+- (BOOL)performDragOperation : (id <NSDraggingInfo>) sender
+{
+   ph::drop_info info;
+   [self makeDropInfo : sender : &info];
+   if (info.paths.size())
+   {
+      if (_view->drop(info))
+         return YES;
+   }
+   return NO;
+}
+
+- (BOOL)wantsPeriodicDraggingUpdates
+{
+   return YES;
+}
+
+- (NSDragOperation)draggingEntered : (id <NSDraggingInfo>) sender
+{
+   ph::drop_info info;
+   [self makeDropInfo : sender : &info];
+   if (info.paths.size())
+      _view->track_drop(info);
+   return NSDragOperationGeneric;
+}
+
+- (NSDragOperation)draggingUpdated : (id<NSDraggingInfo>) sender
+{
+   ph::drop_info info;
+   [self makeDropInfo : sender : &info];
+   if (info.paths.size())
+      _view->track_drop(info);
+   return NSDragOperationGeneric;
+}
+
 @end // @implementation ElementsView
 
 namespace cycfi { namespace elements
diff --git a/lib/include/elements/base_view.hpp b/lib/include/elements/base_view.hpp
index 2752fce11..93eb06a04 100644
--- a/lib/include/elements/base_view.hpp
+++ b/lib/include/elements/base_view.hpp
@@ -279,6 +279,12 @@ namespace cycfi { namespace elements
       int               modifiers;
    };
 
+   struct drop_info
+   {
+      std::vector<fs::path>   paths;
+      point                   where;
+   };
+
    ////////////////////////////////////////////////////////////////////////////
    // The base view base class
    ////////////////////////////////////////////////////////////////////////////
@@ -315,6 +321,8 @@ namespace cycfi { namespace elements
       virtual bool         text(text_info const& info);
       virtual void         begin_focus();
       virtual void         end_focus();
+      virtual void         track_drop(drop_info const& info);
+      virtual bool         drop(drop_info const& info);
       virtual void         poll();
 
       virtual void         refresh();
@@ -341,6 +349,11 @@ namespace cycfi { namespace elements
    inline bool base_view::text(text_info const& /* info */) { return false; }
    inline void base_view::begin_focus() {}
    inline void base_view::end_focus() {}
+   inline void base_view::track_drop(drop_info const& /*info*/) {}
+   inline bool base_view::drop(drop_info const& /*info*/)
+   {
+      return false;
+   }
    inline void base_view::poll() {}
 
    ////////////////////////////////////////////////////////////////////////////