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Drag and drop multiple payloads and WM_DROPFILES demo #9044

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51 changes: 51 additions & 0 deletions backends/imgui_impl_win32.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -799,6 +799,51 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandlerEx(HWND hwnd, UINT msg, WPA
bd->WantUpdateHasGamepad = true;
#endif
return 0;

case WM_DROPFILES:
{
// Process dropped files
HDROP hDrop = (HDROP)wParam;
UINT fileCount = ::DragQueryFile(hDrop, 0xFFFFFFFF, nullptr, 0);

// Start drag and drop operation with external source flag
ImGuiContext* ctx = ImGui::GetCurrentContext();
if (ctx != nullptr)
{
ImGuiPayload& payload = ctx->DragDropPayload;
if (!payload.SourceId)
{
// Begin drag drop source with external flag
ImGui::BeginDragDropSource(ImGuiDragDropFlags_SourceExtern);

// Add payload for each dropped file
for (UINT i = 0; i < fileCount; i++)
{
// Get file path
wchar_t filePath[MAX_PATH];
::DragQueryFile(hDrop, i, filePath, MAX_PATH);

// Convert to UTF-8
int utf8Length = ::WideCharToMultiByte(CP_UTF8, 0, filePath, -1, nullptr, 0, nullptr, nullptr);
if (utf8Length > 0)
{
std::vector<char> utf8FilePath(utf8Length);
::WideCharToMultiByte(CP_UTF8, 0, filePath, -1, utf8FilePath.data(), utf8Length, nullptr, nullptr);

// Add payload item with file path
ImGui::AddDragDropPayload("DND_FILE_PATH", utf8FilePath.data(), utf8FilePath.size() - 1);
}
}

// End drag drop source
ImGui::EndDragDropSource();
}
}

// Release drop handle
::DragFinish(hDrop);
return 0;
}
}
return 0;
}
Expand Down Expand Up @@ -962,6 +1007,12 @@ void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd)
}
}

void ImGui_ImplWin32_EnableDragDropAcceptFiles(void* hwnd, bool enabled)
{
IM_ASSERT(hwnd != NULL);
::DragAcceptFiles((HWND)hwnd, enabled ? TRUE : FALSE);
}

//---------------------------------------------------------------------------------------------------------

#if defined(__GNUC__)
Expand Down
1 change: 1 addition & 0 deletions backends/imgui_impl_win32.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,5 +49,6 @@ IMGUI_IMPL_API float ImGui_ImplWin32_GetDpiScaleForMonitor(void* monitor); //
// - Use to enable alpha compositing transparency with the desktop.
// - Use together with e.g. clearing your framebuffer with zero-alpha.
IMGUI_IMPL_API void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd); // HWND hwnd
IMGUI_IMPL_API void ImGui_ImplWin32_EnableDragDropAcceptFiles(void* hwnd, bool enabled); // HWND hwnd

#endif // #ifndef IMGUI_DISABLE
79 changes: 64 additions & 15 deletions imgui.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14697,6 +14697,44 @@ void ImGui::EndDragDropSource()
}

// Use 'cond' to choose to submit payload on drag start or every frame
bool ImGui::AddDragDropPayload(const char* type, const void* data, size_t data_size)
{
ImGuiContext& g = *GImGui;
ImGuiPayload& payload = g.DragDropPayload;

IM_ASSERT(type != NULL);
IM_ASSERT(ImStrlen(type) < IM_ARRAYSIZE(ImGuiPayloadItem::DataType) && "Payload type can be at most 32 characters long");
IM_ASSERT((data != NULL && data_size > 0) || (data == NULL && data_size == 0));
IM_ASSERT(payload.SourceId != 0); // Not called between BeginDragDropSource() and EndDragDropSource()
IM_ASSERT(payload.DataFrameCount != -1); // SetDragDropPayload() must be called first

// Create new payload item
ImGuiPayloadItem item;
ImStrncpy(item.DataType, type, IM_ARRAYSIZE(item.DataType));

// Copy data
if (data_size > 0)
{
// Store in heap
void* item_data = g.DragDropPayloadBufHeap.Data + g.DragDropPayloadBufHeap.Size;
g.DragDropPayloadBufHeap.resize(g.DragDropPayloadBufHeap.Size + (int)data_size);
memcpy(item_data, data, data_size);
item.Data = item_data;
item.DataSize = (int)data_size;
}
else
{
item.Data = NULL;
item.DataSize = 0;
}

// Add item to payload
payload.Items.push_back(item);

// Return whether the payload has been accepted
return (g.DragDropAcceptFrameCount == g.FrameCount) || (g.DragDropAcceptFrameCount == g.FrameCount - 1);
}

bool ImGui::SetDragDropPayload(const char* type, const void* data, size_t data_size, ImGuiCond cond)
{
ImGuiContext& g = *GImGui;
Expand All @@ -14705,35 +14743,39 @@ bool ImGui::SetDragDropPayload(const char* type, const void* data, size_t data_s
cond = ImGuiCond_Always;

IM_ASSERT(type != NULL);
IM_ASSERT(ImStrlen(type) < IM_ARRAYSIZE(payload.DataType) && "Payload type can be at most 32 characters long");
IM_ASSERT(ImStrlen(type) < IM_ARRAYSIZE(ImGuiPayloadItem::DataType) && "Payload type can be at most 32 characters long");
IM_ASSERT((data != NULL && data_size > 0) || (data == NULL && data_size == 0));
IM_ASSERT(cond == ImGuiCond_Always || cond == ImGuiCond_Once);
IM_ASSERT(payload.SourceId != 0); // Not called between BeginDragDropSource() and EndDragDropSource()

if (cond == ImGuiCond_Always || payload.DataFrameCount == -1)
{
// Copy payload
ImStrncpy(payload.DataType, type, IM_ARRAYSIZE(payload.DataType));
// Clear existing payload items
payload.Items.clear();
g.DragDropPayloadBufHeap.resize(0);
if (data_size > sizeof(g.DragDropPayloadBufLocal))

// Create first payload item
ImGuiPayloadItem item;
ImStrncpy(item.DataType, type, IM_ARRAYSIZE(item.DataType));

// Copy data
if (data_size > 0)
{
// Store in heap
g.DragDropPayloadBufHeap.resize((int)data_size);
payload.Data = g.DragDropPayloadBufHeap.Data;
memcpy(payload.Data, data, data_size);
}
else if (data_size > 0)
{
// Store locally
memset(&g.DragDropPayloadBufLocal, 0, sizeof(g.DragDropPayloadBufLocal));
payload.Data = g.DragDropPayloadBufLocal;
memcpy(payload.Data, data, data_size);
item.Data = g.DragDropPayloadBufHeap.Data;
memcpy(item.Data, data, data_size);
item.DataSize = (int)data_size;
}
else
{
payload.Data = NULL;
item.Data = NULL;
item.DataSize = 0;
}
payload.DataSize = (int)data_size;

// Add item to payload and set as current for backward compatibility
payload.Items.push_back(item);
payload.CurrentItem = &payload.Items[0];
}
payload.DataFrameCount = g.FrameCount;

Expand Down Expand Up @@ -14868,6 +14910,13 @@ const ImGuiPayload* ImGui::AcceptDragDropPayload(const char* type, ImGuiDragDrop
RenderDragDropTargetRectForItem(r);
}

// Set current item for backward compatibility
payload.CurrentItem = NULL;
if (type != NULL)
payload.CurrentItem = payload.GetItemByType(type);
else if (!payload.Items.empty())
payload.CurrentItem = &payload.Items[0];

g.DragDropAcceptFrameCount = g.FrameCount;
if ((g.DragDropSourceFlags & ImGuiDragDropFlags_SourceExtern) && g.DragDropMouseButton == -1)
payload.Delivery = was_accepted_previously && (g.DragDropSourceFrameCount < g.FrameCount);
Expand Down
28 changes: 23 additions & 5 deletions imgui.h
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Original file line number Diff line number Diff line change
Expand Up @@ -967,11 +967,13 @@ namespace ImGui
// - An item can be both drag source and drop target.
IMGUI_API bool BeginDragDropSource(ImGuiDragDropFlags flags = 0); // call after submitting an item which may be dragged. when this return true, you can call SetDragDropPayload() + EndDragDropSource()
IMGUI_API bool SetDragDropPayload(const char* type, const void* data, size_t sz, ImGuiCond cond = 0); // type is a user defined string of maximum 32 characters. Strings starting with '_' are reserved for dear imgui internal types. Data is copied and held by imgui. Return true when payload has been accepted.
IMGUI_API bool AddDragDropPayload(const char* type, const void* data, size_t sz); // Add another payload item to the current drag and drop operation. Return true when payload has been accepted.
IMGUI_API void EndDragDropSource(); // only call EndDragDropSource() if BeginDragDropSource() returns true!
IMGUI_API bool BeginDragDropTarget(); // call after submitting an item that may receive a payload. If this returns true, you can call AcceptDragDropPayload() + EndDragDropTarget()
IMGUI_API const ImGuiPayload* AcceptDragDropPayload(const char* type, ImGuiDragDropFlags flags = 0); // accept contents of a given type. If ImGuiDragDropFlags_AcceptBeforeDelivery is set you can peek into the payload before the mouse button is released.
IMGUI_API void EndDragDropTarget(); // only call EndDragDropTarget() if BeginDragDropTarget() returns true!
IMGUI_API const ImGuiPayload* GetDragDropPayload(); // peek directly into the current payload from anywhere. returns NULL when drag and drop is finished or inactive. use ImGuiPayload::IsDataType() to test for the payload type.
IMGUI_API bool AddDragDropPayload(const char* type, const void* data, size_t sz); // Add another payload item to the current drag and drop operation. Return true when payload has been accepted.

// Disabling [BETA API]
// - Disable all user interactions and dim items visuals (applying style.DisabledAlpha over current colors)
Expand Down Expand Up @@ -2654,26 +2656,42 @@ struct ImGuiSizeCallbackData
ImVec2 DesiredSize; // Read-write. Desired size, based on user's mouse position. Write to this field to restrain resizing.
};

// Data payload item for Drag and Drop operations
struct ImGuiPayloadItem
{
void* Data; // Data (copied and owned by dear imgui)
int DataSize; // Data size
char DataType[32 + 1]; // Data type tag (short user-supplied string, 32 characters max)

ImGuiPayloadItem() { Clear(); }
void Clear() { Data = NULL; DataSize = 0; memset(DataType, 0, sizeof(DataType)); }
bool IsDataType(const char* type) const { return strcmp(type, DataType) == 0; }
};

// Data payload for Drag and Drop operations: AcceptDragDropPayload(), GetDragDropPayload()
struct ImGuiPayload
{
// Members
void* Data; // Data (copied and owned by dear imgui)
int DataSize; // Data size
ImVector<ImGuiPayloadItem> Items; // Multiple payload items
const ImGuiPayloadItem* CurrentItem; // Current item for backward compatibility

// [Internal]
ImGuiID SourceId; // Source item id
ImGuiID SourceParentId; // Source parent id (if available)
int DataFrameCount; // Data timestamp
char DataType[32 + 1]; // Data type tag (short user-supplied string, 32 characters max)
bool Preview; // Set when AcceptDragDropPayload() was called and mouse has been hovering the target item (nb: handle overlapping drag targets)
bool Delivery; // Set when AcceptDragDropPayload() was called and mouse button is released over the target item.

ImGuiPayload() { Clear(); }
void Clear() { SourceId = SourceParentId = 0; Data = NULL; DataSize = 0; memset(DataType, 0, sizeof(DataType)); DataFrameCount = -1; Preview = Delivery = false; }
bool IsDataType(const char* type) const { return DataFrameCount != -1 && strcmp(type, DataType) == 0; }
void Clear() { SourceId = SourceParentId = 0; Items.clear(); CurrentItem = NULL; DataFrameCount = -1; Preview = Delivery = false; }
bool IsDataType(const char* type) const { for (int i = 0; i < Items.Size; i++) if (Items[i].IsDataType(type)) return true; return false; }
const ImGuiPayloadItem* GetItemByType(const char* type) const { for (int i = 0; i < Items.Size; i++) if (Items[i].IsDataType(type)) return &Items[i]; return NULL; }
bool IsPreview() const { return Preview; }
bool IsDelivery() const { return Delivery; }
// Backward compatibility
const void* GetData() const { return CurrentItem ? CurrentItem->Data : NULL; }
int GetDataSize() const { return CurrentItem ? CurrentItem->DataSize : 0; }
const char* GetDataType() const { return CurrentItem ? CurrentItem->DataType : NULL; }
};

//-----------------------------------------------------------------------------
Expand Down