Add DragSource and DropTarget for dragging files and text in and out of windows

Author: lijy91

CMakeLists.txt

@@ -32,6 +32,7 @@ add_subdirectory(examples/url_opener_c_example)
 add_subdirectory(examples/window_c_example)
 add_subdirectory(examples/window_example)
 add_subdirectory(examples/window_drag_session_example)
+add_subdirectory(examples/drag_drop_example)
 add_subdirectory(examples/desktop_features_example)
 
 if(BUILD_TESTING)

examples/drag_drop_example/CMakeLists.txt

@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.10)
+
+project(drag_drop_example VERSION 0.0.1 LANGUAGES CXX)
+
+# Set C++ standard
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Add example program
+add_executable(drag_drop_example
+  "main.cpp"
+)
+
+# Link main library
+target_link_libraries(drag_drop_example PRIVATE nativeapi)
+
+# Set example program properties
+set_target_properties(drag_drop_example PROPERTIES
+  OUTPUT_NAME "drag_drop_example"
+)
+
+# Set example program compile options (macOS only)
+if(APPLE)
+    set_source_files_properties("main.cpp"
+    PROPERTIES
+    COMPILE_FLAGS "-x objective-c++"
+  )
+endif()

examples/drag_drop_example/main.cpp

@@ -0,0 +1,113 @@
+#include <cstdio>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include "nativeapi.h"
+
+using nativeapi::DragOperation;
+using nativeapi::DragSource;
+using nativeapi::DragSourceEndedEvent;
+using nativeapi::DropTarget;
+using nativeapi::DropTargetDroppedEvent;
+using nativeapi::DropTargetEnteredEvent;
+using nativeapi::DropTargetExitedEvent;
+using nativeapi::DropTargetMovedEvent;
+using nativeapi::RunApp;
+using nativeapi::Window;
+using nativeapi::WindowFocusedEvent;
+using nativeapi::WindowManager;
+
+namespace {
+
+const char* OperationName(DragOperation operation) {
+  switch (operation) {
+    case DragOperation::Copy:
+      return "copy";
+    case DragOperation::Move:
+      return "move";
+    case DragOperation::Link:
+      return "link";
+    case DragOperation::None:
+      break;
+  }
+  return "none";
+}
+
+}  // namespace
+
+// Drag and drop without any UI toolkit.
+//
+// - Drop files or text from a file manager or editor onto the "Drop here"
+//   window; every event is printed.
+// - Press inside the "Drag me" window (not on its title bar) and keep dragging
+//   to drag a text file out of it, into a file manager or the "Drop here"
+//   window. There is no widget to press on, so the window becoming focused
+//   stands in for the mouse-down.
+int main() {
+  WindowManager& window_manager = WindowManager::GetInstance();
+
+  auto drop_window = std::make_shared<Window>();
+  drop_window->SetTitle("Drop here");
+  drop_window->SetSize({480, 320}, false);
+  drop_window->Center();
+
+  auto source_window = std::make_shared<Window>();
+  source_window->SetTitle("Drag me");
+  source_window->SetSize({240, 160}, false);
+  auto position = drop_window->GetPosition();
+  source_window->SetPosition({position.x + 520, position.y});
+  source_window->Show();
+
+  std::cout << "Drop target supported: " << DropTarget::IsSupported()
+            << ", drag source supported: " << DragSource::IsSupported() << std::endl;
+
+  auto target = std::make_shared<DropTarget>(drop_window);
+  target->AddListener<DropTargetEnteredEvent>([](const DropTargetEnteredEvent& event) {
+    auto p = event.GetPosition();
+    std::cout << "Entered at (" << p.x << ", " << p.y << ")" << std::endl;
+  });
+  target->AddListener<DropTargetMovedEvent>([](const DropTargetMovedEvent& event) {
+    auto p = event.GetPosition();
+    std::cout << "Moved to (" << p.x << ", " << p.y << ")" << std::endl;
+  });
+  target->AddListener<DropTargetExitedEvent>([](const DropTargetExitedEvent&) {
+    std::cout << "Exited" << std::endl;
+  });
+  target->AddListener<DropTargetDroppedEvent>([](const DropTargetDroppedEvent& event) {
+    auto p = event.GetPosition();
+    std::cout << "Dropped at (" << p.x << ", " << p.y << ")" << std::endl;
+    for (const auto& path : event.GetFilePaths()) {
+      std::cout << "  file: " << path << std::endl;
+    }
+    if (!event.GetText().empty()) {
+      std::cout << "  text: " << event.GetText() << std::endl;
+    }
+  });
+  std::cout << "Drop target active: " << target->IsActive() << std::endl;
+  auto content = drop_window->GetContentBounds();
+  std::cout << "Drop content at (" << content.x << ", " << content.y << ")" << std::endl;
+
+  // A file to drag out.
+  auto file = std::filesystem::temp_directory_path() / "nativeapi-drag-drop-example.txt";
+  std::ofstream(file) << "Dragged out of drag_drop_example.\n";
+
+  auto source = std::make_shared<DragSource>();
+  source->SetFilePaths({file.string()});
+  source->SetText("Hello from drag_drop_example");
+  source->AddListener<DragSourceEndedEvent>([](const DragSourceEndedEvent& event) {
+    std::cout << "Drag ended: " << OperationName(event.GetOperation()) << std::endl;
+  });
+
+  window_manager.AddListener<WindowFocusedEvent>([&](const WindowFocusedEvent& event) {
+    if (event.GetWindowId() != source_window->GetId() || source->IsDragging()) {
+      return;
+    }
+    if (source->StartDragging(source_window)) {
+      std::cout << "Dragging " << file.string() << std::endl;
+    }
+  });
+
+  std::cout << "Drop something on \"Drop here\", or press inside \"Drag me\" and drag."
+            << std::endl;
+  return RunApp(drop_window);
+}

include/nativeapi.h

@@ -12,6 +12,8 @@
 #include "../src/dialog.h"
 #include "../src/display.h"
 #include "../src/display_manager.h"
+#include "../src/drag_source.h"
+#include "../src/drop_target.h"
 #include "../src/file_dialog.h"
 #include "../src/foundation/color.h"
 #include "../src/foundation/geometry.h"
@@ -46,6 +48,8 @@
 #include "../src/capi/dialog_c.h"
 #include "../src/capi/display_c.h"
 #include "../src/capi/display_manager_c.h"
+#include "../src/capi/drag_source_c.h"
+#include "../src/capi/drop_target_c.h"
 #include "../src/capi/file_dialog_c.h"
 #include "../src/capi/geometry_c.h"
 #include "../src/capi/image_c.h"

src/CMakeLists.txt

@@ -100,5 +100,5 @@ elseif(APPLE)
 elseif(CMAKE_SYSTEM_NAME STREQUAL "OHOS")
     target_link_libraries(nativeapi PUBLIC hilog_ndk.z)
 elseif(WIN32)
-    target_link_libraries(nativeapi PUBLIC user32 shell32 comctl32 dwmapi gdiplus crypt32 advapi32 version)
+    target_link_libraries(nativeapi PUBLIC user32 shell32 ole32 uuid comctl32 dwmapi gdiplus crypt32 advapi32 version)
 endif ()