Version/Branch of Dear ImGui:

Version: v1.79 WIP
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_opengl3.cpp + imgui_impl_glfw.cpp
Compiler: MSVC v142 - Visual Studio 2019 (not entirely sure about msvc version, should be irrelevant though)
Operating System: Windows 10 Pro; Version: 10.0.19042 Build 19042

My Issue/Question:

I have a weird issue using an ImGui::InputText in a dockspace window. I have a Properties Window containing the InputText. When the Properties Window isn't docked, the InputText works perfectly fine. However, if I dock my Properties Window, I cannot input anything. If I click on the InputText, it immediately seems to lose focus, because I start dragging the window (even though I set the flag that you can only drag a window by its title bar).
In the video, you can see how I cannot use the InputText if the window is docked, then I drag the window out of the dockspace, grabbing it by the input text (which shouldnt be possible). When the window is undocked, the InputText works.

Screenshots/Video

here's a youtube link, because the file was too big
https://www.youtube.com/watch?v=fRXyaAJel1A

Standalone, minimal, complete and verifiable example:

First of all, you need to create a dockspace window (I did it like this):

static bool open = true;

static ImGuiDockNodeFlags dockspace_flags = ImGuiDockNodeFlags_None;

ImGuiWindowFlags window_flags = ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking;

ImGuiViewport* viewport = ImGui::GetMainViewport();
ImGui::SetNextWindowPos(viewport->GetWorkPos());
ImGui::SetNextWindowSize(viewport->GetWorkSize());
ImGui::SetNextWindowViewport(viewport->ID);

window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
window_flags |= ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus;

ImGui::Begin("DockSpace Demo", &open, window_flags);

ImGuiID dockspace_id = ImGui::GetID("MyDockSpace");
ImGui::DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags);

I have those config flags set:

ImGuiIO& io = ImGui::GetIO(); (void)io;
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;       // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;           // Enable Docking
io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows

io.ConfigWindowsMoveFromTitleBarOnly = true;

Then, create a Properties Window like this:

ImGui::Begin("Properties");

static char tagBuffer[256];

memset(tagBuffer, '\0', sizeof(tagBuffer));
strcpy_s(tagBuffer, sizeof(tagBuffer), "Test");

if (ImGui::InputText("", tagBuffer, sizeof(tagBuffer)))
{
    // ...
}

ImGui::End();

Now dock the Properties window to the dockspace, and you should see that you can't input anything.