Fixed ParentWindow setup which broke Modal windows (fix c65124f415)

imgui.cpp

@@ -2387,10 +2387,7 @@ void ImGui::NewFrame()
     if (ImGuiWindow* modal_window = GetFrontMostModalRootWindow())
     {
         g.ModalWindowDarkeningRatio = ImMin(g.ModalWindowDarkeningRatio + g.IO.DeltaTime * 6.0f, 1.0f);
-        ImGuiWindow* window = g.HoveredRootWindow;
-        while (window && window != modal_window)
-            window = window->ParentWindow;
-        if (!window)
+        if (g.HoveredRootWindow && !IsWindowChildOf(g.HoveredRootWindow, modal_window))
             g.HoveredRootWindow = g.HoveredWindow = NULL;
     }
     else
@@ -4341,7 +4338,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
 
     // Parent window is latched only on the first call to Begin() of the frame, so further append-calls can be done from a different window stack
-    ImGuiWindow* parent_window = first_begin_of_the_frame ? ((flags & ImGuiWindowFlags_ChildWindow) && !g.CurrentWindowStack.empty() ? g.CurrentWindowStack.back() : NULL) : window->ParentWindow;
+    ImGuiWindow* parent_window = first_begin_of_the_frame ? ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Popup)) && !g.CurrentWindowStack.empty() ? g.CurrentWindowStack.back() : NULL) : window->ParentWindow;
     IM_ASSERT(parent_window != NULL || !(flags & ImGuiWindowFlags_ChildWindow));
 
     // Add to stack

imgui_internal.h

@@ -746,7 +746,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiStorage            StateStorage;
     float                   FontWindowScale;                    // Scale multiplier per-window
     ImDrawList*             DrawList;
-    ImGuiWindow*            ParentWindow;                       // If we are a child window, this is pointing to our parent.
+    ImGuiWindow*            ParentWindow;                       // If we are a child _or_ popup window, this is pointing to our parent. Otherwise NULL.
     ImGuiWindow*            RootWindow;                         // Generally point to ourself. If we are a child window, this is pointing to the first non-child parent window.
     ImGuiWindow*            RootNonPopupWindow;                 // Generally point to ourself. Used to display TitleBgActive color and for selecting which window to use for NavWindowing