// https://github.com/vassvik/imgui_docking_minimal/
//
// This is free and unencumbered software released into the public domain.
//
// Anyone is free to copy, modify, publish, use, compile, sell, or
// distribute this software, either in source code form or as a compiled
// binary, for any purpose, commercial or non-commercial, and by any
// means.
//
// In jurisdictions that recognize copyright laws, the author or authors
// of this software dedicate any and all copyright interest in the
// software to the public domain. We make this dedication for the benefit
// of the public at large and to the detriment of our heirs and
// successors. We intend this dedication to be an overt act of
// relinquishment in perpetuity of all present and future rights to this
// software under copyright law.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
// For more information, please refer to <http://unlicense.org>

#include <new> // placement new

namespace ImGui
{
	struct DockContext
	{
		enum Slot_
		{
			Slot_Left,
			Slot_Right,
			Slot_Top,
			Slot_Bottom,
			Slot_Tab,

			Slot_Float,
			Slot_None
		};

		enum EndAction_
		{
			EndAction_None,
			EndAction_Panel,
			EndAction_End,
			EndAction_EndChild
		};

		enum Status_
		{
			Status_Docked,
			Status_Float,
			Status_Dragged
		};

		struct Dock
		{
			Dock()
				: id(0)
				, label(NULL)
				, next_tab(NULL)
				, prev_tab(NULL)
				, parent(NULL)
				, pos(0, 0)
				, size(-1, -1)
				, active(true)
				, status(Status_Float)
				, opened(false)
			{
				location[0] = 0;
				children[0] = children[1] = NULL;
			}

			~Dock()
			{
				MemFree(label);
			}

			ImVec2 getMinSize() const
			{
				if (!children[0]) return ImVec2(16, 16 + GetTextLineHeightWithSpacing());

				ImVec2 s0 = children[0]->getMinSize();
				ImVec2 s1 = children[1]->getMinSize();
				return isHorizontal() ? ImVec2(s0.x + s1.x, ImMax(s0.y, s1.y))
					: ImVec2(ImMax(s0.x, s1.x), s0.y + s1.y);
			}

			bool isHorizontal() const
			{
				return children[0]->pos.x < children[1]->pos.x;
			}

			void setParent(Dock* dock)
			{
				parent = dock;
				for (Dock* tmp = prev_tab; tmp; tmp = tmp->prev_tab) tmp->parent = dock;
				for (Dock* tmp = next_tab; tmp; tmp = tmp->next_tab) tmp->parent = dock;
			}

			Dock& getSibling()
			{
				IM_ASSERT(parent);
				if (parent->children[0] == &getFirstTab()) return *parent->children[1];
				return *parent->children[0];
			}

			Dock& getFirstTab()
			{
				Dock* tmp = this;
				while (tmp->prev_tab) tmp = tmp->prev_tab;
				return *tmp;
			}

			void setActive()
			{
				active = true;
				for (Dock* tmp = prev_tab; tmp; tmp = tmp->prev_tab) tmp->active = false;
				for (Dock* tmp = next_tab; tmp; tmp = tmp->next_tab) tmp->active = false;
			}

			bool isContainer() const
			{
				return children[0] != NULL;
			}

			void setChildrenPosSize(const ImVec2& _pos, const ImVec2& _size)
			{
				ImVec2 s = children[0]->size;
				if (isHorizontal())
				{
					s.y = _size.y;
					s.x = (float)int(
							_size.x * children[0]->size.x / (children[0]->size.x + children[1]->size.x));
					if (s.x < children[0]->getMinSize().x)
					{
						s.x = children[0]->getMinSize().x;
					}
					else if (_size.x - s.x < children[1]->getMinSize().x)
					{
						s.x = _size.x - children[1]->getMinSize().x;
					}
					children[0]->setPosSize(_pos, s);

					s.x = _size.x - children[0]->size.x;
					ImVec2 p = _pos;
					p.x += children[0]->size.x;
					children[1]->setPosSize(p, s);
				}
				else
				{
					s.x = _size.x;
					s.y = (float)int(
							_size.y * children[0]->size.y / (children[0]->size.y + children[1]->size.y));
					if (s.y < children[0]->getMinSize().y)
					{
						s.y = children[0]->getMinSize().y;
					}
					else if (_size.y - s.y < children[1]->getMinSize().y)
					{
						s.y = _size.y - children[1]->getMinSize().y;
					}
					children[0]->setPosSize(_pos, s);

					s.y = _size.y - children[0]->size.y;
					ImVec2 p = _pos;
					p.y += children[0]->size.y;
					children[1]->setPosSize(p, s);
				}
			}

			void setPosSize(const ImVec2& _pos, const ImVec2& _size)
			{
				size = _size;
				pos = _pos;
				for (Dock* tmp = prev_tab; tmp; tmp = tmp->prev_tab)
				{
					tmp->size = _size;
					tmp->pos = _pos;
				}
				for (Dock* tmp = next_tab; tmp; tmp = tmp->next_tab)
				{
					tmp->size = _size;
					tmp->pos = _pos;
				}

				if (!isContainer()) return;
				setChildrenPosSize(_pos, _size);
			}

			ImU32   id;
			char*   label;
			Dock*   next_tab;
			Dock*   prev_tab;
			Dock*   parent;
			ImVec2  pos;
			ImVec2  size;
			bool    active;
			Status_ status;
			bool    opened;

			Dock* children[2];
			char  location[16];
			int   last_frame;
			int   invalid_frames;
			bool  first;
		};

		typedef ImVector<Dock*> DockVector;
		DockVector m_docks;
		ImVec2 m_drag_offset;
		Dock* m_current;
		int m_last_frame;
		EndAction_ m_end_action;

		DockContext()
			: m_current(NULL)
			, m_last_frame(0)
		{
		}

		~DockContext()
		{
		}

		Dock& getDock(const char* label, bool opened)
		{
			ImU32 id = ImHash(label, 0);
			for (int i = 0; i < m_docks.size(); ++i)
			{
				if (m_docks[i]->id == id) return *m_docks[i];
			}

			Dock* new_dock = (Dock*)MemAlloc(sizeof(Dock));
			IM_PLACEMENT_NEW(new_dock) Dock();
			m_docks.push_back(new_dock);
			new_dock->label = ImStrdup(label);
			IM_ASSERT(new_dock->label);
			new_dock->id = id;
			new_dock->setActive();
			new_dock->status = Status_Float;
			new_dock->pos = ImVec2(0, 0);
			new_dock->size = GetIO().DisplaySize;
			new_dock->opened = opened;
			new_dock->first = true;
			new_dock->last_frame = 0;
			new_dock->invalid_frames = 0;
			new_dock->location[0] = 0;
			return *new_dock;
		}

		void putInBackground()
		{
			ImGuiWindow* win = GetCurrentWindow();
			ImGuiContext& g = *GImGui;
			if (g.Windows[0] == win) return;

			for (int i = 0; i < g.Windows.Size; i++)
			{
				if (g.Windows[i] == win)
				{
					for (int j = i - 1; j >= 0; --j)
					{
						g.Windows[j + 1] = g.Windows[j];
					}
					g.Windows[0] = win;
					break;
				}
			}
		}

		void splits()
		{
			if (GetFrameCount() == m_last_frame)
			{
				return;
			}

			m_last_frame = GetFrameCount();

			putInBackground();

			ImU32 color = GetColorU32(ImGuiCol_Button);
			ImU32 color_hovered = GetColorU32(ImGuiCol_ButtonHovered);
			ImDrawList* draw_list = GetWindowDrawList();
			ImGuiIO& io = GetIO();
			for (int i = 0; i < m_docks.size(); ++i)
			{
				Dock& dock = *m_docks[i];
				if (!dock.isContainer())
				{
					continue;
				}

				PushID(i);
				if (!IsMouseDown(0))
				{
					dock.status = Status_Docked;
				}

				ImVec2 dsize(0, 0);
				SetCursorScreenPos(dock.children[1]->pos);
				ImVec2 min_size0 = dock.children[0]->getMinSize();
				ImVec2 min_size1 = dock.children[1]->getMinSize();
				if (dock.isHorizontal())
				{
					InvisibleButton("split", ImVec2(3, dock.size.y));
					if (dock.status == Status_Dragged) dsize.x = io.MouseDelta.x;
					dsize.x = -ImMin(-dsize.x, dock.children[0]->size.x - min_size0.x);
					dsize.x = ImMin(dsize.x, dock.children[1]->size.x - min_size1.x);
				}
				else
				{
					InvisibleButton("split", ImVec2(dock.size.x, 3));
					if (dock.status == Status_Dragged) dsize.y = io.MouseDelta.y;
					dsize.y = -ImMin(-dsize.y, dock.children[0]->size.y - min_size0.y);
					dsize.y = ImMin(dsize.y, dock.children[1]->size.y - min_size1.y);
				}
				ImVec2 new_size0 = dock.children[0]->size + dsize;
				ImVec2 new_size1 = dock.children[1]->size - dsize;
				ImVec2 new_pos1 = dock.children[1]->pos + dsize;
				dock.children[0]->setPosSize(dock.children[0]->pos, new_size0);
				dock.children[1]->setPosSize(new_pos1, new_size1);

				if (IsItemHovered() && IsMouseClicked(0))
				{
					dock.status = Status_Dragged;
				}

				draw_list->AddRectFilled(
						GetItemRectMin(), GetItemRectMax(), IsItemHovered() ? color_hovered : color);
				PopID();
			}
		}

		void checkNonexistent()
		{
			int frame_limit = ImMax(0, ImGui::GetFrameCount() - 2);
			for (DockVector::iterator it = m_docks.begin(), itEnd = m_docks.end(); it != itEnd; ++it)
			{
				Dock* dock = *it;
				if (dock->isContainer()) continue;
				if (dock->status == Status_Float) continue;
				if (dock->last_frame < frame_limit)
				{
					++dock->invalid_frames;
					if (dock->invalid_frames > 2)
					{
						doUndock(*dock);
						dock->status = Status_Float;
					}
					return;
				}
				dock->invalid_frames = 0;
			}
		}

		void beginPanel()
		{
			ImGuiWindowFlags flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize |
				ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoCollapse |
				ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoScrollbar |
				ImGuiWindowFlags_NoScrollWithMouse | ImGuiWindowFlags_ShowBorders | 
				ImGuiWindowFlags_NoBringToFrontOnFocus;
			Dock* root = getRootDock();
			if (root)
			{
				SetNextWindowPos(root->pos);
				SetNextWindowSize(root->size);
			}
			else
			{
				SetNextWindowPos(ImVec2(0, 0));
				SetNextWindowSize(GetIO().DisplaySize);
			}
			ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0);
			Begin("###DockPanel", NULL, flags);
			splits();

			checkNonexistent();
		}

		void endPanel()
		{
			End();
			ImGui::PopStyleVar();
		}

		// Doesn't use input??
		Dock* getDockAt(const ImVec2& /*pos*/) const
		{
			for (int i = 0; i < m_docks.size(); ++i)
			{
				Dock& dock = *m_docks[i];
				if (dock.isContainer()) continue;
				if (dock.status != Status_Docked) continue;
				if (IsMouseHoveringRect(dock.pos, dock.pos + dock.size, false))
				{
					return &dock;
				}
			}

			return NULL;
		}

		static ImRect getDockedRect(const ImRect& rect, Slot_ dock_slot)
		{
			ImVec2 half_size = rect.GetSize() * 0.5f;
			switch (dock_slot)
			{
				default: return rect;
				case Slot_Top: return ImRect(rect.Min, rect.Min + ImVec2(rect.Max.x, half_size.y));
				case Slot_Right: return ImRect(rect.Min + ImVec2(half_size.x, 0), rect.Max);
				case Slot_Bottom: return ImRect(rect.Min + ImVec2(0, half_size.y), rect.Max);
				case Slot_Left: return ImRect(rect.Min, rect.Min + ImVec2(half_size.x, rect.Max.y));
			}
		}

		static ImRect getSlotRect(ImRect parent_rect, Slot_ dock_slot)
		{
			ImVec2 size = parent_rect.Max - parent_rect.Min;
			ImVec2 center = parent_rect.Min + size * 0.5f;
			switch (dock_slot)
			{
				default: return ImRect(center - ImVec2(20, 20), center + ImVec2(20, 20));
				case Slot_Top: return ImRect(center + ImVec2(-20, -50), center + ImVec2(20, -30));
				case Slot_Right: return ImRect(center + ImVec2(30, -20), center + ImVec2(50, 20));
				case Slot_Bottom: return ImRect(center + ImVec2(-20, +30), center + ImVec2(20, 50));
				case Slot_Left: return ImRect(center + ImVec2(-50, -20), center + ImVec2(-30, 20));
			}
		}

		static ImRect getSlotRectOnBorder(ImRect parent_rect, Slot_ dock_slot)
		{
			ImVec2 size = parent_rect.Max - parent_rect.Min;
			ImVec2 center = parent_rect.Min + size * 0.5f;
			switch (dock_slot)
			{
				case Slot_Top:
					return ImRect(ImVec2(center.x - 20, parent_rect.Min.y + 10),
							ImVec2(center.x + 20, parent_rect.Min.y + 30));
				case Slot_Left:
					return ImRect(ImVec2(parent_rect.Min.x + 10, center.y - 20),
							ImVec2(parent_rect.Min.x + 30, center.y + 20));
				case Slot_Bottom:
					return ImRect(ImVec2(center.x - 20, parent_rect.Max.y - 30),
							ImVec2(center.x + 20, parent_rect.Max.y - 10));
				case Slot_Right:
					return ImRect(ImVec2(parent_rect.Max.x - 30, center.y - 20),
							ImVec2(parent_rect.Max.x - 10, center.y + 20));
				default: IM_ASSERT(false);
			}
			IM_ASSERT(false);
			return ImRect();
		}

		Dock* getRootDock()
		{
			for (int i = 0; i < m_docks.size(); ++i)
			{
				if (!m_docks[i]->parent &&
						(m_docks[i]->status == Status_Docked || m_docks[i]->children[0]))
				{
					return m_docks[i];
				}
			}
			return NULL;
		}

		bool dockSlots(Dock& dock, Dock* dest_dock, const ImRect& rect, bool on_border)
		{
			ImDrawList* canvas = GetWindowDrawList();
			ImU32 color = GetColorU32(ImGuiCol_Button);
			ImU32 color_hovered = GetColorU32(ImGuiCol_ButtonHovered);
			ImVec2 mouse_pos = GetIO().MousePos;
			for (int i = 0; i < (on_border ? 4 : 5); ++i)
			{
				ImRect r =
					on_border ? getSlotRectOnBorder(rect, (Slot_)i) : getSlotRect(rect, (Slot_)i);
				bool hovered = r.Contains(mouse_pos);

				canvas->AddRectFilled(r.Min, r.Max, hovered ? color_hovered : color);
				if (!hovered) continue;

				if (!IsMouseDown(0))
				{
					doDock(dock, dest_dock ? dest_dock : getRootDock(), (Slot_)i);
					return true;
				}
				ImRect docked_rect = getDockedRect(rect, (Slot_)i);
				canvas->AddRectFilled(docked_rect.Min, docked_rect.Max, GetColorU32(ImGuiCol_Button));
			}
			return false;
		}

		void handleDrag(Dock& dock)
		{
			Dock* dest_dock = getDockAt(GetIO().MousePos);

			Begin("##Overlay",
					NULL,
					ImVec2(0, 0),
					0.f,
					ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoMove |
					ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings |
					ImGuiWindowFlags_AlwaysAutoResize);
			ImDrawList* canvas = GetWindowDrawList();

			canvas->PushClipRectFullScreen();

			ImU32 docked_color = GetColorU32(ImGuiCol_FrameBg);
			docked_color = (docked_color & 0x00ffFFFF) | 0x80000000;
			dock.pos = GetIO().MousePos - m_drag_offset;
			if (dest_dock)
			{
				if (dockSlots(dock,
							dest_dock,
							ImRect(dest_dock->pos, dest_dock->pos + dest_dock->size),
							false))
				{
					canvas->PopClipRect();
					End();
					return;
				}
			}
			if (dockSlots(dock, NULL, ImRect(ImVec2(0, 0), GetIO().DisplaySize), true))
			{
				canvas->PopClipRect();
				End();
				return;
			}
			canvas->AddRectFilled(dock.pos, dock.pos + dock.size, docked_color);
			canvas->PopClipRect();

			if (!IsMouseDown(0))
			{
				dock.status = Status_Float;
				dock.location[0] = 0;
				dock.setActive();
			}

			End();
		}

		void fillLocation(Dock& dock)
		{
			if (dock.status == Status_Float) return;
			char* c = dock.location;
			Dock* tmp = &dock;
			while (tmp->parent)
			{
				*c = getLocationCode(tmp);
				tmp = tmp->parent;
				++c;
			}
			*c = 0;
		}

		void doUndock(Dock& dock)
		{
			if (dock.prev_tab)
				dock.prev_tab->setActive();
			else if (dock.next_tab)
				dock.next_tab->setActive();
			else
				dock.active = false;
			Dock* container = dock.parent;

			if (container)
			{
				Dock& sibling = dock.getSibling();
				if (container->children[0] == &dock)
				{
					container->children[0] = dock.next_tab;
				}
				else if (container->children[1] == &dock)
				{
					container->children[1] = dock.next_tab;
				}

				bool remove_container = !container->children[0] || !container->children[1];
				if (remove_container)
				{
					if (container->parent)
					{
						Dock*& child = container->parent->children[0] == container
							? container->parent->children[0]
							: container->parent->children[1];
						child = &sibling;
						child->setPosSize(container->pos, container->size);
						child->setParent(container->parent);
					}
					else
					{
						if (container->children[0])
						{
							container->children[0]->setParent(NULL);
							container->children[0]->setPosSize(container->pos, container->size);
						}
						if (container->children[1])
						{
							container->children[1]->setParent(NULL);
							container->children[1]->setPosSize(container->pos, container->size);
						}
					}
					for (int i = 0; i < m_docks.size(); ++i)
					{
						if (m_docks[i] == container)
						{
							m_docks.erase(m_docks.begin() + i);
							break;
						}
					}
					container->~Dock();
					MemFree(container);
				}
			}
			if (dock.prev_tab) dock.prev_tab->next_tab = dock.next_tab;
			if (dock.next_tab) dock.next_tab->prev_tab = dock.prev_tab;
			dock.parent = NULL;
			dock.prev_tab = dock.next_tab = NULL;
		}

		void drawTabbarListButton(Dock& dock)
		{
			if (!dock.next_tab) return;

			ImDrawList* draw_list = GetWindowDrawList();
			if (InvisibleButton("list", ImVec2(16, 16)))
			{
				OpenPopup("tab_list_popup");
			}
			if (BeginPopup("tab_list_popup"))
			{
				Dock* tmp = &dock;
				while (tmp)
				{
					bool dummy = false;
					if (Selectable(tmp->label, &dummy))
					{
						tmp->setActive();
					}
					tmp = tmp->next_tab;
				}
				EndPopup();
			}

			bool hovered = IsItemHovered();
			ImVec2 min = GetItemRectMin();
			ImVec2 max = GetItemRectMax();
			ImVec2 center = (min + max) * 0.5f;
			ImU32 text_color = GetColorU32(ImGuiCol_Text);
			ImU32 color_active = GetColorU32(ImGuiCol_FrameBgActive);
			draw_list->AddRectFilled(ImVec2(center.x - 4, min.y + 3),
					ImVec2(center.x + 4, min.y + 5),
					hovered ? color_active : text_color);
			draw_list->AddTriangleFilled(ImVec2(center.x - 4, min.y + 7),
					ImVec2(center.x + 4, min.y + 7),
					ImVec2(center.x, min.y + 12),
					hovered ? color_active : text_color);
		}

		bool tabbar(Dock& dock, bool close_button)
		{
			float tabbar_height = 2 * GetTextLineHeightWithSpacing();
			ImVec2 size0(dock.size.x, tabbar_height);
			bool tab_closed = false;

			SetCursorScreenPos(dock.pos);
			char tmp[20];
			ImFormatString(tmp, IM_ARRAYSIZE(tmp), "tabs%d", (int)dock.id);
			if (BeginChild(tmp, size0, true))
			{
				Dock* dock_tab = &dock;

				ImDrawList* draw_list = GetWindowDrawList();
				ImU32 color = GetColorU32(ImGuiCol_FrameBg);
				ImU32 color_active = GetColorU32(ImGuiCol_FrameBgActive);
				ImU32 color_hovered = GetColorU32(ImGuiCol_FrameBgHovered);
				ImU32 text_color = GetColorU32(ImGuiCol_Text);
				ImU32 text_color_disabled = GetColorU32(ImGuiCol_TextDisabled);
				float line_height = GetTextLineHeightWithSpacing();
				float tab_base;

				drawTabbarListButton(dock);

				while (dock_tab)
				{
					SameLine(0, 15);

					const char* text_end = FindRenderedTextEnd(dock_tab->label);
					ImVec2 size1(CalcTextSize(dock_tab->label, text_end).x, line_height);
					if (InvisibleButton(dock_tab->label, size1))
					{
						dock_tab->setActive();
					}

					if (IsItemActive() && IsMouseDragging())
					{
						m_drag_offset = GetMousePos() - dock_tab->pos;
						doUndock(*dock_tab);
						dock_tab->status = Status_Dragged;
					}

					bool hovered = IsItemHovered();
					ImVec2 pos = GetItemRectMin();
					size1.x += 20 + GetStyle().ItemSpacing.x;

					tab_base = pos.y;

					draw_list->AddRectFilled(pos+ImVec2(-8.0f, 0.0),
							pos+size1,
							hovered ? color_hovered : (dock_tab->active ? color_active : color));
					draw_list->AddText(pos, text_color, dock_tab->label, text_end);

					if (dock_tab->active && close_button)
					{
						SameLine();
						tab_closed = InvisibleButton("close", ImVec2(16, 16));

						ImVec2 center = ((GetItemRectMin() + GetItemRectMax()) * 0.5f);
						draw_list->AddLine( center + ImVec2(-3.5f, -3.5f), center + ImVec2(3.5f, 3.5f), text_color);
						draw_list->AddLine( center + ImVec2(3.5f, -3.5f), center + ImVec2(-3.5f, 3.5f), text_color);
					} else {
						if(!dock_tab->active && close_button) {
							SameLine();
							InvisibleButton("close", ImVec2(16, 16));

							ImVec2 center = ((GetItemRectMin() + GetItemRectMax()) * 0.5f);
							draw_list->AddLine( center + ImVec2(-3.5f, -3.5f), center + ImVec2(3.5f, 3.5f), text_color_disabled);
							draw_list->AddLine( center + ImVec2(3.5f, -3.5f), center + ImVec2(-3.5f, 3.5f), text_color_disabled);
						}
					}

					dock_tab = dock_tab->next_tab;
				}
				ImVec2 cp(dock.pos.x, tab_base + line_height);
				draw_list->AddLine(cp, cp + ImVec2(dock.size.x, 0), color);
			}
			EndChild();
			return tab_closed;
		}

		static void setDockPosSize(Dock& dest, Dock& dock, Slot_ dock_slot, Dock& container)
		{
			IM_ASSERT(!dock.prev_tab && !dock.next_tab && !dock.children[0] && !dock.children[1]);

			dest.pos = container.pos;
			dest.size = container.size;
			dock.pos = container.pos;
			dock.size = container.size;

			switch (dock_slot)
			{
				case Slot_Bottom:
					dest.size.y *= 0.5f;
					dock.size.y *= 0.5f;
					dock.pos.y += dest.size.y;
					break;
				case Slot_Right:
					dest.size.x *= 0.5f;
					dock.size.x *= 0.5f;
					dock.pos.x += dest.size.x;
					break;
				case Slot_Left:
					dest.size.x *= 0.5f;
					dock.size.x *= 0.5f;
					dest.pos.x += dock.size.x;
					break;
				case Slot_Top:
					dest.size.y *= 0.5f;
					dock.size.y *= 0.5f;
					dest.pos.y += dock.size.y;
					break;
				default: IM_ASSERT(false); break;
			}
			dest.setPosSize(dest.pos, dest.size);

			if (container.children[1]->pos.x < container.children[0]->pos.x ||
					container.children[1]->pos.y < container.children[0]->pos.y)
			{
				Dock* tmp = container.children[0];
				container.children[0] = container.children[1];
				container.children[1] = tmp;
			}
		}

		void doDock(Dock& dock, Dock* dest, Slot_ dock_slot)
		{
			IM_ASSERT(!dock.parent);
			if (!dest)
			{
				dock.status = Status_Docked;
				dock.setPosSize(ImVec2(0, 0), GetIO().DisplaySize);
			}
			else if (dock_slot == Slot_Tab)
			{
				Dock* tmp = dest;
				while (tmp->next_tab)
				{
					tmp = tmp->next_tab;
				}

				tmp->next_tab = &dock;
				dock.prev_tab = tmp;
				dock.size = tmp->size;
				dock.pos = tmp->pos;
				dock.parent = dest->parent;
				dock.status = Status_Docked;
			}
			else if (dock_slot == Slot_None)
			{
				dock.status = Status_Float;
			}
			else
			{
				Dock* container = (Dock*)MemAlloc(sizeof(Dock));
				IM_PLACEMENT_NEW(container) Dock();
				m_docks.push_back(container);
				container->children[0] = &dest->getFirstTab();
				container->children[1] = &dock;
				container->next_tab = NULL;
				container->prev_tab = NULL;
				container->parent = dest->parent;
				container->size = dest->size;
				container->pos = dest->pos;
				container->status = Status_Docked;
				container->label = ImStrdup("");

				if (!dest->parent)
				{
				}
				else if (&dest->getFirstTab() == dest->parent->children[0])
				{
					dest->parent->children[0] = container;
				}
				else
				{
					dest->parent->children[1] = container;
				}

				dest->setParent(container);
				dock.parent = container;
				dock.status = Status_Docked;

				setDockPosSize(*dest, dock, dock_slot, *container);
			}
			dock.setActive();
		}

		void rootDock(const ImVec2& pos, const ImVec2& size)
		{
			Dock* root = getRootDock();

			// martin: make sure we have a root dock
			if (!root)
				root = &getDock("Root", true);

			root->status = Status_Docked;

			ImVec2 min_size = root->getMinSize();
			ImVec2 requested_size = size;
			root->setPosSize(pos, ImMax(min_size, requested_size));
		}

		void setDockActive()
		{
			IM_ASSERT(m_current);
			if (m_current) m_current->setActive();
		}

		static Slot_ getSlotFromLocationCode(char code)
		{
			switch (code)
			{
				case '1': return Slot_Left;
				case '2': return Slot_Top;
				case '3': return Slot_Bottom;
				default: return Slot_Right;
			}
		}

		static char getLocationCode(Dock* dock)
		{
			if (!dock) return '0';

			if (dock->parent->isHorizontal())
			{
				if (dock->pos.x < dock->parent->children[0]->pos.x) return '1';
				if (dock->pos.x < dock->parent->children[1]->pos.x) return '1';
				return '0';
			}
			else
			{
				if (dock->pos.y < dock->parent->children[0]->pos.y) return '2';
				if (dock->pos.y < dock->parent->children[1]->pos.y) return '2';
				return '3';
			}
		}

		void tryDockToStoredLocation(Dock& dock)
		{
			if (dock.status == Status_Docked) return;

			Dock* tmp = getRootDock();
			if (!tmp) return;

			Dock* prev = NULL;
			char* c = dock.location + strlen(dock.location) - 1;
			while (c >= dock.location && tmp)
			{
				prev = tmp;
				tmp = *c == getLocationCode(tmp->children[0]) ? tmp->children[0] : tmp->children[1];
				if(tmp) --c;
			}
			if (tmp && tmp->children[0]) tmp = tmp->parent;
			doDock(dock, tmp ? tmp : prev, tmp && !tmp->children[0] ? Slot_Tab : getSlotFromLocationCode(*c));
		}

		bool begin(const char* label, bool* opened, ImGuiWindowFlags extra_flags)
		{
			Dock& dock = getDock(label, !opened || *opened);
			// martin: tweak docking for better defaults
			if (!dock.opened || (!opened || *opened)) tryDockToStoredLocation(dock);
			dock.last_frame = ImGui::GetFrameCount();
			if (strcmp(dock.label, label) != 0)
			{
				MemFree(dock.label);
				dock.label = ImStrdup(label);
			}

			m_end_action = EndAction_None;

			if (dock.first && opened) *opened = dock.opened;
			dock.first = false;
			if (opened && !*opened)
			{
				if (dock.status != Status_Float)
				{
					fillLocation(dock);
					doUndock(dock);
					dock.status = Status_Float;
				}
				dock.opened = false;
				return false;
			}
			dock.opened = true;

			m_end_action = EndAction_Panel;
			beginPanel();

			m_current = &dock;
			if (dock.status == Status_Dragged) handleDrag(dock);

			bool is_float = dock.status == Status_Float;

			if (is_float)
			{
				SetNextWindowPos(dock.pos);
				SetNextWindowSize(dock.size);
				bool ret = Begin(label,
						opened,
						dock.size,
						-1.0f,
						ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_ShowBorders | extra_flags);
				m_end_action = EndAction_End;
				dock.pos = GetWindowPos();
				dock.size = GetWindowSize();

				ImGuiContext& g = *GImGui;

				if (g.ActiveId == GetCurrentWindow()->MoveId && g.IO.MouseDown[0])
				{
					m_drag_offset = GetMousePos() - dock.pos;
					doUndock(dock);
					dock.status = Status_Dragged;
				}
				return ret;
			}

			if (!dock.active && dock.status != Status_Dragged) return false;

			m_end_action = EndAction_EndChild;

			PushStyleColor(ImGuiCol_Border, ImVec4(0, 0, 0, 0));
			PushStyleColor(ImGuiCol_BorderShadow, ImVec4(0, 0, 0, 0));
			float tabbar_height = GetTextLineHeightWithSpacing();
			if (tabbar(dock.getFirstTab(), opened != NULL))
			{
				fillLocation(dock);
				*opened = false;
			}
			ImVec2 pos = dock.pos;
			ImVec2 size = dock.size;
			pos.y += tabbar_height + GetStyle().WindowPadding.y;
			size.y -= tabbar_height + GetStyle().WindowPadding.y;

			SetCursorScreenPos(pos);
			ImGuiWindowFlags flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize |
				ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoCollapse |
				ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoBringToFrontOnFocus |
				extra_flags;
			char tmp[256];
			strcpy(tmp, label);
			strcat(tmp, "_docked"); // to avoid https://github.com/ocornut/imgui/issues/713
			bool ret = BeginChild(tmp, size, true, flags);
			PopStyleColor();
			PopStyleColor();
			return ret;
		}

		void end()
		{
			if (m_end_action == EndAction_End)
			{
				End();
			}
			else if (m_end_action == EndAction_EndChild)
			{
				PushStyleColor(ImGuiCol_Border, ImVec4(0, 0, 0, 0));
				PushStyleColor(ImGuiCol_BorderShadow, ImVec4(0, 0, 0, 0));
				EndChild();
				PopStyleColor();
				PopStyleColor();
			}
			m_current = NULL;
			if (m_end_action > EndAction_None) endPanel();
		}

		int getDockIndex(Dock* dock)
		{
			if (!dock) return -1;

			for (int i = 0; i < m_docks.size(); ++i)
			{
				if (dock == m_docks[i]) return i;
			}

			IM_ASSERT(false);
			return -1;
		}

		Dock* getDockByIndex(int idx)
		{
			return idx < 0 ? NULL : m_docks[(int)idx];
		}
	};

	static DockContext* s_dock = NULL;

	IMGUI_API void InitDockContext()
	{
		void* ptr = ImGui::MemAlloc(sizeof(DockContext) );
		s_dock = new(ptr) DockContext;
	}

	IMGUI_API void ShutdownDockContext()
	{
		s_dock->~DockContext();
		ImGui::MemFree(s_dock);
		s_dock = NULL;
	}

	IMGUI_API void RootDock(const ImVec2& pos, const ImVec2& size)
	{
		s_dock->rootDock(pos, size);
	}

	IMGUI_API bool BeginDock(const char* label, bool* opened, ImGuiWindowFlags extra_flags)
	{
		return s_dock->begin(label, opened, extra_flags);
	}

	IMGUI_API void EndDock()
	{
		s_dock->end();
	}

	IMGUI_API void SetDockActive()
	{
		s_dock->setDockActive();
	}

} // namespace ImGui