Implementing view and element drop support

examples/CMakeLists.txt

@@ -21,3 +21,4 @@ add_subdirectory(custom_control)
 add_subdirectory(child_window)
 add_subdirectory(sync_scrollbars)
 add_subdirectory(icons_list)
+add_subdirectory(drop_file)

examples/drop_file/CMakeLists.txt

@@ -0,0 +1,31 @@
+cmake_minimum_required(VERSION 3.9.6...3.15.0)
+project(HelloUniverse LANGUAGES C CXX)
+
+if (NOT ELEMENTS_ROOT)
+   message(FATAL_ERROR "ELEMENTS_ROOT is not set")
+endif()
+
+# Make sure ELEMENTS_ROOT is an absolute path to add to the CMake module path
+get_filename_component(ELEMENTS_ROOT "${ELEMENTS_ROOT}" ABSOLUTE)
+set (CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH};${ELEMENTS_ROOT}/cmake")
+
+# If we are building outside the project, you need to set ELEMENTS_ROOT:
+if (NOT ELEMENTS_BUILD_EXAMPLES)
+   include(ElementsConfigCommon)
+   set(ELEMENTS_BUILD_EXAMPLES OFF)
+   add_subdirectory(${ELEMENTS_ROOT} elements)
+endif()
+
+set(ELEMENTS_APP_PROJECT "DropFile")
+set(ELEMENTS_APP_TITLE "Drop File")
+set(ELEMENTS_APP_COPYRIGHT "Copyright (c) 2023 Joel de Guzman")
+set(ELEMENTS_APP_ID "com.cycfi.drop-file")
+set(ELEMENTS_APP_VERSION "1.0")
+
+set(ELEMENTS_APP_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp)
+set(ELEMENTS_APP_RESOURCES ${CMAKE_CURRENT_SOURCE_DIR}/resources/space.jpg)
+
+# For your custom application icon on macOS or Windows see cmake/AppIcon.cmake module
+include(AppIcon)
+include(ElementsConfigApp)
+

examples/drop_file/main.cpp

@@ -0,0 +1,59 @@
+/*=============================================================================
+   Copyright (c) 2016-2020 Joel de Guzman
+
+   Distributed under the MIT License (https://opensource.org/licenses/MIT)
+=============================================================================*/
+#include <elements.hpp>
+
+using namespace cycfi::elements;
+
+using cycfi::artist::rgba;
+
+// Main window background color
+auto constexpr bkd_color = rgba(35, 35, 37, 255);
+auto background = box(bkd_color);
+
+int main(int argc, char* argv[])
+{
+   app _app(argc, argv, "Drop File", "com.cycfi.drop-file");
+   window _win(_app.name());
+   _win.on_close = [&_app]() { _app.stop(); };
+
+   view view_(_win);
+
+   auto image_    = share(image{ "space.jpg" });
+   auto drop_box_ = share(drop_box(scroller(hold(image_))));
+
+   drop_box_->on_drop = [image_ = get(image_), &view_](drop_info const& info)
+   {
+      if (info.paths.size() == 1)  // We accept only one file
+      {
+         auto image_path = info.paths[0];
+         if (auto p = image_.lock())
+         {
+            try
+            {
+               auto img = image{image_path};
+               *p = img;
+               view_.refresh(*p);
+            }
+            catch (std::runtime_error const&)
+            {
+               // Invalid image
+               return false;
+            }
+            return true;
+         }
+      }
+      return false;
+   };
+
+   view_.content(
+      align_center_middle(label("Drop a picture here").font_size(20)),
+      margin({20, 20, 20, 20}, hold(drop_box_)),
+      share(background)
+   );
+
+   _app.run();
+   return 0;
+}

lib/host/macos/base_view.mm

@@ -689,7 +689,7 @@ -(void) makeDropInfo : (id <NSDraggingInfo>) sender : (ph::drop_info*) info
    }
 }
 
-- (BOOL)performDragOperation : (id <NSDraggingInfo>) sender
+- (BOOL) performDragOperation : (id <NSDraggingInfo>) sender
 {
    ph::drop_info info;
    [self makeDropInfo : sender : &info];
@@ -701,29 +701,37 @@ - (BOOL)performDragOperation : (id <NSDraggingInfo>) sender
    return NO;
 }
 
-- (BOOL)wantsPeriodicDraggingUpdates
+- (BOOL) wantsPeriodicDraggingUpdates
 {
    return YES;
 }
 
-- (NSDragOperation)draggingEntered : (id <NSDraggingInfo>) sender
+- (NSDragOperation) draggingEntered : (id <NSDraggingInfo>) sender
 {
    ph::drop_info info;
    [self makeDropInfo : sender : &info];
    if (info.paths.size())
-      _view->track_drop(info);
+      _view->track_drop(info, ph::cursor_tracking::entering);
    return NSDragOperationGeneric;
 }
 
-- (NSDragOperation)draggingUpdated : (id<NSDraggingInfo>) sender
+- (NSDragOperation) draggingUpdated : (id<NSDraggingInfo>) sender
 {
    ph::drop_info info;
    [self makeDropInfo : sender : &info];
    if (info.paths.size())
-      _view->track_drop(info);
+      _view->track_drop(info, ph::cursor_tracking::hovering);
    return NSDragOperationGeneric;
 }
 
+- (void) draggingExited : (id <NSDraggingInfo>) sender
+{
+   ph::drop_info info;
+   [self makeDropInfo : sender : &info];
+   if (info.paths.size())
+      _view->track_drop(info, ph::cursor_tracking::leaving);
+}
+
 @end // @implementation ElementsView
 
 namespace cycfi { namespace elements

lib/include/elements/base_view.hpp

@@ -321,7 +321,7 @@ 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 void         track_drop(drop_info const& info, cursor_tracking status);
       virtual bool         drop(drop_info const& info);
       virtual void         poll();
 
@@ -349,7 +349,7 @@ 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 void base_view::track_drop(drop_info const& /*info*/, cursor_tracking /* status */) {}
    inline bool base_view::drop(drop_info const& /*info*/)
    {
       return false;

lib/include/elements/element.hpp

@@ -11,6 +11,7 @@
 #include <elements/element/composite.hpp>
 #include <elements/element/child_window.hpp>
 #include <elements/element/dial.hpp>
+#include <elements/element/drop.hpp>
 #include <elements/element/dynamic_list.hpp>
 #include <elements/element/floating.hpp>
 #include <elements/element/flow.hpp>

lib/include/elements/element/composite.hpp

@@ -65,6 +65,9 @@ namespace cycfi { namespace elements
       void                    focus(std::size_t index);
       virtual void            reset();
 
+      void                    track_drop(context const& ctx, drop_info const& info, cursor_tracking status) override;
+      bool                    drop(context const& ctx, drop_info const& info) override;
+
    // Composite
 
       using weak_element_ptr = std::weak_ptr<elements::element>;

lib/include/elements/element/drop.hpp

@@ -0,0 +1,83 @@
+/*=============================================================================
+   Copyright (c) 2016-2020 Joel de Guzman
+
+   Distributed under the MIT License [ https://opensource.org/licenses/MIT ]
+=============================================================================*/
+#if !defined(ELEMENTS_DROP_OCOBER_11_2023)
+#define ELEMENTS_DROP_OCOBER_11_2023
+
+#include <elements/element/proxy.hpp>
+#include <functional>
+
+namespace cycfi { namespace elements
+{
+   template <typename Subject>
+   class drop_box : public proxy<Subject>
+   {
+   public:
+
+      using base_type = proxy<Subject>;
+      using on_drop_function = std::function<bool(drop_info const& info)>;
+
+                              drop_box(Subject subject);
+      void                    draw(context const& ctx) override;
+      bool                    wants_control() const override;
+
+      void                    track_drop(context const& ctx, drop_info const& info, cursor_tracking status) override;
+      bool                    drop(context const& ctx, drop_info const& info) override;
+
+      on_drop_function        on_drop = [](drop_info const&){ return false; };
+
+   private:
+
+      bool                    _is_tracking = false;
+   };
+
+   template <typename Subject>
+   drop_box<Subject>::drop_box(Subject subject)
+    : proxy<Subject>{std::move(subject)}
+   {}
+
+   template <typename Subject>
+   inline void drop_box<Subject>::draw(context const& ctx)
+   {
+      proxy<Subject>::draw(ctx);
+      if (_is_tracking)
+      {
+         auto& cnv = ctx.canvas;
+         auto& bounds = ctx.bounds;
+         cnv.stroke_style(get_theme().indicator_hilite_color.opacity(0.5));
+         cnv.line_width(2.0);
+         cnv.add_rect(bounds);
+         cnv.stroke();
+      }
+   }
+
+   template <typename Subject>
+   inline bool drop_box<Subject>::wants_control() const
+   {
+      return true;
+   }
+
+   template <typename Subject>
+   inline void drop_box<Subject>::track_drop(context const& ctx, drop_info const& /*info*/, cursor_tracking status)
+   {
+      auto new_is_tracking = status != cursor_tracking::leaving;
+      if (new_is_tracking != _is_tracking)
+      {
+         _is_tracking = new_is_tracking;
+         ctx.view.refresh(ctx.bounds);
+      }
+   }
+
+   template <typename Subject>
+   inline bool drop_box<Subject>::drop(context const& ctx, drop_info const& info)
+   {
+      bool r = on_drop(info);
+      _is_tracking = false;
+      ctx.view.refresh(ctx.bounds);
+      return r;
+   }
+}}
+
+#endif

lib/include/elements/element/element.hpp

@@ -60,6 +60,9 @@ namespace cycfi { namespace elements
       virtual element const*  focus() const;
       virtual element*        focus();
 
+      virtual void            track_drop(context const& ctx, drop_info const& info, cursor_tracking status);
+      virtual bool            drop(context const& ctx, drop_info const& info);
+
       enum tracking { none, begin_tracking, while_tracking, end_tracking };
 
    protected:

lib/include/elements/element/indirect.hpp

@@ -71,6 +71,10 @@ namespace cycfi { namespace elements
       void                    end_focus() override;
       element const*          focus() const override;
       element*                focus() override;
+
+      void                    track_drop(context const& ctx, drop_info const& info, cursor_tracking status) override;
+      bool                    drop(context const& ctx, drop_info const& info) override;
+
    };
 
    struct indirect_base : element
@@ -268,6 +272,18 @@ namespace cycfi { namespace elements
       return this->get().focus();
    }
 
+   template <typename Base>
+   inline void indirect<Base>::track_drop(context const& ctx, drop_info const& info, cursor_tracking status)
+   {
+      this->get().track_drop(ctx, info, status);
+   }
+
+   template <typename Base>
+   inline bool indirect<Base>::drop(context const& ctx, drop_info const& info)
+   {
+      return this->get().drop(ctx, info);
+   }
+
    ////////////////////////////////////////////////////////////////////////////
    // reference (inline) implementation
    ////////////////////////////////////////////////////////////////////////////