Follow ImGui dockspace pattern for demo hub

Author: jslee02

python/demo_hub/gui/app.py

@@ -129,8 +129,33 @@ def _render(state: GuiState) -> None:  # pragma: no cover - manual UI
 
 
 def _dockspace_fullscreen() -> None:
-    dock_flags = imgui.DockNodeFlags_.passthru_central_node
-    return imgui.dock_space_over_viewport(0, None, dock_flags, None)
+    # Follow Dear ImGui's recommended fullscreen dockspace pattern.
+    dockspace_flags = imgui.DockNodeFlags_.none
+    window_flags = (
+        imgui.WindowFlags_.no_title_bar
+        | imgui.WindowFlags_.no_collapse
+        | imgui.WindowFlags_.no_resize
+        | imgui.WindowFlags_.no_move
+        | imgui.WindowFlags_.no_bring_to_front_on_focus
+        | imgui.WindowFlags_.no_nav_focus
+        | imgui.WindowFlags_.no_docking
+    )
+    viewport = imgui.get_main_viewport()
+    imgui.set_next_window_pos(viewport.pos)
+    imgui.set_next_window_size(viewport.size)
+    imgui.set_next_window_viewport(viewport.id_)
+    imgui.push_style_var(imgui.StyleVar_.window_rounding, 0.0)
+    imgui.push_style_var(imgui.StyleVar_.window_border_size, 0.0)
+    imgui.push_style_var(imgui.StyleVar_.window_padding, (0.0, 0.0))
+    if dockspace_flags & imgui.DockNodeFlags_.passthru_central_node:
+        window_flags |= imgui.WindowFlags_.no_background
+
+    imgui.begin("MainDockSpaceHost", flags=window_flags)
+    imgui.pop_style_var(3)
+    dockspace_id = imgui.get_id("MainDockSpace")
+    imgui.dock_space(dockspace_id, (0.0, 0.0), dockspace_flags)
+    imgui.end()
+    return dockspace_id
 
 
 def main(argv: list[str] | None = None) -> None: