How to do a toolbar in Dear ImGui.

toolbar.cpp

// How to do a toolbar in Dear ImGui.

const float toolbarSize = 50;

void DockSpaceUI()
{
	ImGuiViewport* viewport = ImGui::GetMainViewport();
	ImGui::SetNextWindowPos(viewport->Pos + ImVec2(0, toolbarSize));
	ImGui::SetNextWindowSize(viewport->Size - ImVec2(0, toolbarSize));
	ImGui::SetNextWindowViewport(viewport->ID);
	ImGuiWindowFlags window_flags = 0
		| ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking
		| ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse
		| ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove
		| ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;

	ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
	ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
	ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
	ImGui::Begin("Master DockSpace", NULL, window_flags);
	ImGuiID dockMain = ImGui::GetID("MyDockspace");
	
	// Save off menu bar height for later.
	menuBarHeight = ImGui::GetCurrentWindow()->MenuBarHeight();

	ImGui::DockSpace(dockMain);
	ImGui::End();
	ImGui::PopStyleVar(3);
}

void ToolbarUI()
{
	ImGuiViewport* viewport = ImGui::GetMainViewport();
	ImGui::SetNextWindowPos(ImVec2(viewport->Pos.x, viewport->Pos.y + menuBarHeight));
	ImGui::SetNextWindowSize(ImVec2(viewport->Size.x, toolbarSize));
	ImGui::SetNextWindowViewport(viewport->ID);

	ImGuiWindowFlags window_flags = 0
		| ImGuiWindowFlags_NoDocking 
		| ImGuiWindowFlags_NoTitleBar 
		| ImGuiWindowFlags_NoResize 
		| ImGuiWindowFlags_NoMove 
		| ImGuiWindowFlags_NoScrollbar 
		| ImGuiWindowFlags_NoSavedSettings
		;
	ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0);
	ImGui::Begin("TOOLBAR", NULL, window_flags);
	ImGui::PopStyleVar();
  
	ImGui::Button("Toolbar goes here", ImVec2(0, 37));
  
	ImGui::End();
}

void ProgramUI()
{
	DockSpaceUI();
	ToolbarUI();
}