diff --git a/imgui.cpp b/imgui.cpp
index e65a74ec..62923d40 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -1145,6 +1145,7 @@ ImGuiIO::ImGuiIO()
     DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
 
     // Miscellaneous configuration options
+    ConfigViewportsNoParent = false;
 #ifdef __APPLE__
     ConfigMacOSXBehaviors = true;  // Set Mac OS X style defaults based on __APPLE__ compile time flag
 #else
@@ -5201,7 +5202,11 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 viewport_flags |= ImGuiViewportFlags_NoDecoration;
 
             // We can overwrite viewport flags using ImGuiWindowClass (advanced users)
-            window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId ? window->WindowClass.ParentViewportId : IMGUI_VIEWPORT_DEFAULT_ID;
+            // We don't default to the main viewport because.
+            if (window->WindowClass.ParentViewportId)
+                window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId;
+            else
+                window->Viewport->ParentViewportId = g.IO.ConfigViewportsNoParent ? 0 : IMGUI_VIEWPORT_DEFAULT_ID;
             if (window->WindowClass.ViewportFlagsOverrideMask)
                 viewport_flags = (viewport_flags & ~window->WindowClass.ViewportFlagsOverrideMask) | (window->WindowClass.ViewportFlagsOverrideValue & window->WindowClass.ViewportFlagsOverrideMask);
 
@@ -5476,6 +5481,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         {
             window->Viewport->PlatformRequestClose = false;
             g.NavWindowingToggleLayer = false; // Assume user mapped PlatformRequestClose on ALT-F4 so we disable ALT for menu toggle. False positive not an issue.
+            //IMGUI_DEBUG_LOG("Window '%s' PlatformRequestClose\n", window->Name);
             *p_open = false;
         }
 
@@ -10307,7 +10313,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         static void NodeViewport(ImGuiViewportP* viewport)
         {
             ImGui::SetNextTreeNodeOpen(true, ImGuiCond_Once);
-            if (ImGui::TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->Window ? viewport->Window->Name : "N/A"))
+            if (ImGui::TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Parent: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->ParentViewportId, viewport->Window ? viewport->Window->Name : "N/A"))
             {
                 ImGuiWindowFlags flags = viewport->Flags;
                 ImGui::BulletText("Pos: (%.0f,%.0f), Size: (%.0f,%.0f), Monitor: %d, DpiScale: %.0f%%", viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y, viewport->PlatformMonitor, viewport->DpiScale * 100.0f);
diff --git a/imgui.h b/imgui.h
index 8154df6e..168cca32 100644
--- a/imgui.h
+++ b/imgui.h
@@ -1266,6 +1266,7 @@ struct ImGuiIO
 
     // Miscellaneous configuration options
     bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by back-end implementations.
+    bool        ConfigViewportsNoParent;        // = false          // By default, viewports are marked with ParentViewportId = <main_viewport>, expecting the platform back-end to setup a parent/child relationship between the OS windows (some back-end may ignore this). Set to true if you want the default to be 0, then all viewports will be top-level OS windows.
     bool        ConfigMacOSXBehaviors;          // = defined(__APPLE__) // OS X style: Text editing cursor movement using Alt instead of Ctrl, Shortcuts using Cmd/Super instead of Ctrl, Line/Text Start and End using Cmd+Arrows instead of Home/End, Double click selects by word instead of selecting whole text, Multi-selection in lists uses Cmd/Super instead of Ctrl (was called io.OptMacOSXBehaviors prior to 1.63)
     bool        ConfigInputTextCursorBlink;     // = true           // Set to false to disable blinking cursor, for users who consider it distracting. (was called: io.OptCursorBlink prior to 1.63)
     bool        ConfigWindowsResizeFromEdges;   // = true           // Enable resizing of windows from their edges and from the lower-left corner. This requires (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors) because it needs mouse cursor feedback. (This used to be the a per-window ImGuiWindowFlags_ResizeFromAnySide flag)
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index 664d93f6..5440e40d 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -327,6 +327,9 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the decoration right away).");
             ImGui::CheckboxFlags("io.ConfigFlags: ViewportsNoMerge", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsNoMerge);
             ImGui::SameLine(); ShowHelpMarker("All floating windows will always create their own viewport and platform window.");
+            ImGui::Checkbox("io.ConfigViewportNoParent", &io.ConfigViewportsNoParent);
+            ImGui::SameLine(); ShowHelpMarker("By default, viewports are marked with ParentViewportId = <main_viewport>, expecting the platform back-end to setup a parent/child relationship between the OS windows (some back-end may ignore this). Set to true if you want the default to be 0, then all viewports will be top-level OS windows.");
+
             ImGui::Checkbox("io.ConfigInputTextCursorBlink", &io.ConfigInputTextCursorBlink);
             ImGui::SameLine(); ShowHelpMarker("Set to false to disable blinking cursor, for users who consider it distracting");
             ImGui::Checkbox("io.ConfigWindowsResizeFromEdges", &io.ConfigWindowsResizeFromEdges);