Add file drop functionality

Adds the ability to drag and drop files from windows in order to attempt
to execute them

src/xenia/ui/ui_event.h

@@ -26,6 +26,18 @@ class UIEvent {
   Window* target_ = nullptr;
 };
 
+class FileDropEvent : public UIEvent {
+ public:
+  FileDropEvent(Window* target, wchar_t* filename)
+      : UIEvent(target), filename_(filename) {}
+  ~FileDropEvent() override = default;
+
+  wchar_t* filename() const { return filename_; }
+
+ private:
+  wchar_t* filename_ = nullptr;
+};
+
 class KeyEvent : public UIEvent {
  public:
   KeyEvent(Window* target, int key_code, int repeat_count, bool prev_state)

src/xenia/ui/window.cc

@@ -213,6 +213,11 @@ void Window::OnPaint(UIEvent* e) {
   }
 }
 
+void Window::OnFileDrop(FileDropEvent* e) {
+  on_file_drop(e);
+  ForEachListener([e](auto listener) { listener->OnFileDrop(e); });
+}
+
 void Window::OnVisible(UIEvent* e) {
   ForEachListener([e](auto listener) { listener->OnVisible(e); });
 }

src/xenia/ui/window.h

@@ -102,6 +102,7 @@ class Window {
   Delegate<UIEvent*> on_painting;
   Delegate<UIEvent*> on_paint;
   Delegate<UIEvent*> on_painted;
+  Delegate<FileDropEvent*> on_file_drop;
 
   Delegate<KeyEvent*> on_key_down;
   Delegate<KeyEvent*> on_key_up;
@@ -128,6 +129,7 @@ class Window {
   virtual void OnResize(UIEvent* e);
   virtual void OnLayout(UIEvent* e);
   virtual void OnPaint(UIEvent* e);
+  virtual void OnFileDrop(FileDropEvent* e);
 
   virtual void OnVisible(UIEvent* e);
   virtual void OnHidden(UIEvent* e);

src/xenia/ui/window_listener.h

@@ -31,6 +31,7 @@ class WindowListener {
   virtual void OnPainting(UIEvent* e) {}
   virtual void OnPaint(UIEvent* e) {}
   virtual void OnPainted(UIEvent* e) {}
+  virtual void OnFileDrop(UIEvent* e) {}
 
   virtual void OnVisible(UIEvent* e) {}
   virtual void OnHidden(UIEvent* e) {}

src/xenia/ui/window_win.cc

@@ -101,6 +101,8 @@ bool Win32Window::OnCreate() {
 
   // Enable DWM elevation.
   EnableMMCSS();
+  // Enable file dragging from external sources
+  DragAcceptFiles(hwnd_, true);
 
   ShowWindow(hwnd_, SW_SHOWNORMAL);
   UpdateWindow(hwnd_);
@@ -378,6 +380,21 @@ LRESULT Win32Window::WndProc(HWND hWnd, UINT message, WPARAM wParam,
   }
 
   switch (message) {
+    case WM_DROPFILES: {
+      TCHAR lpszFile[MAX_PATH] = {0};
+      UINT uFiles = 0;
+      HDROP hDrop = (HDROP)wParam;
+      // Get number of files dropped
+      uFiles = DragQueryFile(hDrop, -1, NULL, NULL);
+
+      // Only getting first file dropped (other files ignored)
+      if (DragQueryFile(hDrop, 0, lpszFile, MAX_PATH)) {
+        auto e = FileDropEvent(this, lpszFile);
+        OnFileDrop(&e);
+      }
+
+      DragFinish(hDrop);
+    } break;
     case WM_NCCREATE:
       break;
     case WM_CREATE: