Manually building docking nodes for Editor and setting default positi…

…ons for windows.

Windows like Console and Entity Tree now default show at the bottom and left respectively. Requires manual construction of our dockspace via imgui_internal.h to ascertain the correct dock_ids.

source/Platform/Window.cpp

@@ -13,6 +13,7 @@
 #include "backends/imgui_impl_glfw.h"
 #include "backends/imgui_impl_opengl3.h"
 #include "imgui.h"
+#include "imgui_internal.h"
 #include "ImGuizmo.h"
 
 #include <iostream>
@@ -161,32 +162,54 @@ namespace Platform
 		ImGui::NewFrame();
 		ImGuizmo::BeginFrame();
 
-		{ // At the start of an ImGui frame, push a window the size of viewport to allow docking other ImGui windows to.
-			ImGui::SetNextWindowSize(size());
-			ImGui::SetNextWindowPos(ImVec2(0, 0));
-			ImGui::SetNextWindowViewport(ImGui::GetMainViewport()->ID);
+		// At the start of an ImGui frame, push a window the size of viewport to allow docking other ImGui windows to.
+		ImGuiViewport* viewport = ImGui::GetMainViewport();
+		ImGui::SetNextWindowSize(viewport->Size);
+		ImGui::SetNextWindowPos(viewport->Pos);
+		ImGui::SetNextWindowViewport(viewport->ID);
 
-			ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
-			ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
-			ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
+		ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+		ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+		ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
 
-			auto imgui_window_flags = ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoTitleBar
-				| ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove
-				| ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoBackground | ImGuiWindowFlags_NoBringToFrontOnFocus;
+		auto imgui_window_flags = ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoTitleBar
+			| ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove
+			| ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoBackground | ImGuiWindowFlags_NoBringToFrontOnFocus;
 
-			if (m_show_menu_bar) imgui_window_flags |= ImGuiWindowFlags_MenuBar;
+		if (m_show_menu_bar) imgui_window_flags |= ImGuiWindowFlags_MenuBar;
 
-			ImGui::Begin("Dockspace window", nullptr, imgui_window_flags);
+		ImGui::Begin("root_dock", nullptr, imgui_window_flags);
+		ImGui::PopStyleVar(3);
 
-			ImGui::DockSpace(ImGui::GetID("Dockspace window"), ImVec2(0.f, 0.f), ImGuiDockNodeFlags_None
-			| ImGuiDockNodeFlags_PassthruCentralNode | ImGuiDockNodeFlags_NoDockingInCentralNode);
 
-			ImGui::PopStyleVar(3);
+		ImGuiID root_dock_ID = ImGui::GetID("root_dock");
+		ImGui::DockSpace(root_dock_ID, ImVec2(0.f, 0.f), ImGuiDockNodeFlags_PassthruCentralNode | ImGuiDockNodeFlags_NoDockingInCentralNode);
+
+		static bool first_time = true;
+		if (first_time)
+		{
+			first_time = false;
+			ImGuiDockNodeFlags dockspace_flags = ImGuiDockNodeFlags_PassthruCentralNode;
+
+			// Clear the previous layout and add a root node the size of the viewport.
+			ImGui::DockBuilderRemoveNode(root_dock_ID);
+			ImGui::DockBuilderAddNode(root_dock_ID, dockspace_flags | ImGuiDockNodeFlags_DockSpace | ImGuiDockNodeFlags_NoResize | ImGuiDockNodeFlags_KeepAliveOnly);
+			ImGui::DockBuilderSetNodeSize(root_dock_ID, viewport->Size);
+
+			// Split the dockspace into 4 nodes by splitting root_dock_ID horizontally and then splitting the right node vertically.
+			ImGuiID dock_id_left, dock_id_right;
+			ImGui::DockBuilderSplitNode(root_dock_ID, ImGuiDir_Left, 0.2f, &dock_id_left, &dock_id_right);
+			ImGuiID dock_id_down, dock_id_up;
+			ImGui::DockBuilderSplitNode(dock_id_right, ImGuiDir_Down, 0.15f, &dock_id_down, &dock_id_up);
+			ImGui::DockBuilderFinish(root_dock_ID);
+
+			ASSERT_THROW(dock_id_left == 1 && dock_id_right == 2 && dock_id_up == 3 && dock_id_down == 4,
+				"Dock direction IDs are not as expected. We use these hard coded numbers for the layout of the editor with SetNextWindowDockID()! Can create a mapping if the order changes.");
 		}
 	}
 	void Window::end_ImGui_frame()
 	{
-		ImGui::End();
+		ImGui::End(); // root_dock
 		ImGui::Render();
 		ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 	}

source/UI/Console.cpp

@@ -24,9 +24,8 @@ namespace UI
 	void Console::draw(const char* title, bool* p_open)
 	{
 		static ImGuiTextFilter m_filter; // Declared statically to avoid having to include ImGui in the header.
-		ImGui::SetNextWindowSize(ImVec2(520, 600), ImGuiCond_FirstUseEver);
-		ImGui::SetNextWindowDockID(0, ImGuiCond_FirstUseEver); // Dock to the bottom of the view.
 
+		ImGui::SetNextWindowDockID(4, ImGuiCond_Once);
 		if (ImGui::Begin(title, p_open))
 		{
 			bool copy_to_clipboard = false;

source/UI/Editor.cpp

@@ -432,6 +432,7 @@ namespace UI
 	}
 	void Editor::draw_entity_tree_window()
 	{
+		ImGui::SetNextWindowDockID(1, ImGuiCond_Once);
 		if (ImGui::Begin("Entities", &m_windows_to_display.Entity))
 		{
 			auto& scene = m_scene_system.get_current_scene_entities();