dragdrop file work

1 files changed, 106 insertions, 0 deletions

diff --git a/src/windows/DropManager.h b/src/windows/DropManager.h
new file mode 100644
index 0000000..32b6922
--- /dev/null
+++ b/src/windows/DropManager.h
@@ -0,0 +1,106 @@
+#pragma once
+
+#include "platform.h"
+
+#include <oleidl.h>
+
+// create a class inheriting from IDropTarget
+class DropManager : public IDropTarget
+{
+public:
+	//--- implement the IUnknown parts
+	// you could do this the proper way with InterlockedIncrement etc,
+	// but I've left out stuff that's not exactly necessary for brevity
+	ULONG AddRef()  { return 1; }
+	ULONG Release() { return 0; }
+
+	// we handle drop targets, let others know
+	HRESULT QueryInterface(REFIID riid, void **ppvObject)
+	{
+		if (riid == IID_IDropTarget)
+		{
+			*ppvObject = this;	// or static_cast<IUnknown*> if preferred
+			// AddRef() if doing things properly
+                        // but then you should probably handle IID_IUnknown as well;
+			return S_OK;
+		}
+
+		*ppvObject = NULL;
+		return E_NOINTERFACE;
+	};
+
+
+	//--- implement the IDropTarget parts
+
+	// occurs when we drag files into our applications view
+	HRESULT DragEnter(IDataObject *pDataObj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect)
+	{
+		// TODO: check whether we can handle this type of object at all and set *pdwEffect &= DROPEFFECT_NONE if not;
+
+		// do something useful to flag to our application that files have been dragged from the OS into our application
+		//...
+		dragdrop_data.is_dragging_file = true;
+
+		// trigger MouseDown for button 1 within ImGui
+		//...
+
+		*pdwEffect &= DROPEFFECT_COPY;
+		return S_OK;
+	}
+
+	// occurs when we drag files out from our applications view
+	HRESULT DragLeave() { 
+		dragdrop_data.is_dragging_file = false;
+		return S_OK; 
+		}
+
+	// occurs when we drag the mouse over our applications view whilst carrying files (post Enter, pre Leave)
+	HRESULT DragOver(DWORD grfKeyState, POINTL pt, DWORD *pdwEffect)
+	{
+		// trigger MouseMove within ImGui, position is within pt.x and pt.y
+		// grfKeyState contains flags for control, alt, shift etc
+		//...
+
+		*pdwEffect &= DROPEFFECT_COPY;
+		return S_OK;
+	}
+
+	// occurs when we release the mouse button to finish the drag-drop operation
+	HRESULT Drop(IDataObject *pDataObj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect)
+	{
+		dragdrop_data.is_dragging_file = false;
+		// grfKeyState contains flags for control, alt, shift etc
+
+		// render the data into stgm using the data description in fmte
+		FORMATETC fmte = { CF_HDROP, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
+		STGMEDIUM stgm;
+
+		if (SUCCEEDED(pDataObj->GetData(&fmte, &stgm)))
+		{
+			HDROP hdrop = (HDROP)stgm.hGlobal; // or reinterpret_cast<HDROP> if preferred
+			UINT file_count = DragQueryFile(hdrop, 0xFFFFFFFF, NULL, 0);
+
+			// We only accept 1 file for now..
+			for (UINT i = 0; i < 1; i++)
+			{
+				TCHAR szFile[MAX_PATH];
+				UINT cch = DragQueryFile(hdrop, i, szFile, MAX_PATH);
+				if (cch > 0 && cch < MAX_PATH)
+				{
+					WideCharToMultiByte(CP_UTF8,0,szFile,-1,(LPSTR)dragdrop_data.path, MAX_INPUT_LENGTH, NULL, NULL);
+				}
+			}
+
+			// we have to release the data when we're done with it
+			ReleaseStgMedium(&stgm);
+			
+			dragdrop_data.did_drop = true;
+		}
+
+		// trigger MouseUp for button 1 within ImGui
+		//...
+
+		*pdwEffect &= DROPEFFECT_COPY;
+		return S_OK;
+	}
+};
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