Dock window on first open

[caxapexac]

Version/Branch of Dear ImGui:

Version: 1.86
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: webGL
Compiler: em++
Operating System: V8

My Issue/Question:

DockBuilder: #2109 (comment)
ImGuiCond: #2554 (comment)

How to use it together?

Example:
I have button 'open window_X' which sets window_X flag to true
I need to have window_X docked at the right side of my root docking space and use 20% of screen if it was opened for the first time
Just like ImGuiCond_FirstUseEver

So in my mind it will be:

ImGuiID window_X_id = ImGui::DockBuilderSplitNode(dock_main_id, ImGuiDir_Left, 0.10f, NULL, &dock_main_id, ImGuiCond_FirstUseEver);
ImGui::DockBuilderDockWindow("Window_X", window_X_id , ImGuiCond_FirstUseEver);

or something like this

Are there any workarounds?

[MStachowicz]

Hey @ocornut, I managed to implement a solution to this problem. I manually construct my dock nodes as such (ImGui v 1.89.5):

ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();

// 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));

auto imgui_window_flags = ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoTitleBar
	| ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove
	| ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoBackground | ImGuiWindowFlags_NoBringToFrontOnFocus;

ImGui::Begin("root_dock", nullptr, imgui_window_flags);
ImGui::PopStyleVar(3);

ImGuiID dockspace_id = ImGui::GetID("root_dock");
ImGui::DockSpace(dockspace_id, ImVec2(0.f, 0.f), ImGuiDockNodeFlags_PassthruCentralNode | ImGuiDockNodeFlags_AutoHideTabBar | ImGuiDockNodeFlags_NoDockingInCentralNode);

static bool first_time = true;
if (first_time)
{
	first_time = false;
	ImGuiDockNodeFlags dockspace_flags = ImGuiDockNodeFlags_PassthruCentralNode | ImGuiDockNodeFlags_AutoHideTabBar;

	ImGui::DockBuilderRemoveNode(dockspace_id); // clear any previous layout
	ImGui::DockBuilderAddNode(dockspace_id, dockspace_flags | ImGuiDockNodeFlags_DockSpace);
	ImGui::DockBuilderSetNodeSize(dockspace_id, viewport->Size);

	// Split the dockspace into 2 nodes -- DockBuilderSplitNode takes in the following args in the following order
	ImGuiID dock_id_left, dock_id_right;
	ImGui::DockBuilderSplitNode(dockspace_id, ImGuiDir_Left, 0.2f, &dock_id_left, &dock_id_right);
	LOG("dock_id_left: {} dock_id_right: {}", 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);
	LOG("dock_id_down: {} dock_id_up: {}", dock_id_down, dock_id_up);

	ImGui::DockBuilderFinish(dock_id_up);
}

dock_id_left is set to 1, further along I create a window as such, asking it to dock to the left node from above on first use:

ImGui::SetNextWindowDockID(1, ImGuiCond_FirstUseEver);

if (ImGui::Begin("Entities", &m_windows_to_display.Entity))
{
    ...
}

This works perfectly on first run. On second run, the saved window DockId is reset and the window is floating using the exact size and pos of the original dock node 1.

Any ideas why the saved .ini DockId=0x00000001,0 for [Window][Entities] is reset on second launch?

FYI if I dont set a condition and force the DockId every run, it is correctly docked on launch evert time:

ImGui::SetNextWindowDockID(1, 0);

[MStachowicz]

UPDATE
By using:
ImGui::SetNextWindowDockID(1, ImGuiCond_Once);

I am able to have the windows dock correctly on first run AND on successive runs they are not undocked and hovering with the same pos and size as above. This does mean that every single launch the layout is reset for the windows since this doesn't match the ImGuiCond_FirstUseEver functionality I'm looking for but it feels less buggy so will go with this for now.

(ImGui v 1.89.5)