From 3dcbcd8bf0d0331a7bc870bbf725145e6beed069 Mon Sep 17 00:00:00 2001
From: ocornut <omarcornut@gmail.com>
Date: Thu, 19 Nov 2020 16:58:14 +0100
Subject: [PATCH] Internals: added IsWindowAbove() for use for modal/viewport
 bugfix.

---
 imgui.cpp        | 26 +++++++++++++++-----------
 imgui_internal.h |  1 +
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/imgui.cpp b/imgui.cpp
index e86a4968..83ed42f7 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -3571,17 +3571,7 @@ void ImGui::UpdateMouseMovingWindowEndFrame()
         // Find the top-most window between HoveredWindow and the top-most Modal Window.
         // This is where we can trim the popup stack.
         ImGuiWindow* modal = GetTopMostPopupModal();
-        bool hovered_window_above_modal = false;
-        if (modal == NULL)
-            hovered_window_above_modal = true;
-        for (int i = g.Windows.Size - 1; i >= 0 && hovered_window_above_modal == false; i--)
-        {
-            ImGuiWindow* window = g.Windows[i];
-            if (window == modal)
-                break;
-            if (window == g.HoveredWindow)
-                hovered_window_above_modal = true;
-        }
+        bool hovered_window_above_modal = g.HoveredWindow && IsWindowAbove(g.HoveredWindow, modal);
         ClosePopupsOverWindow(hovered_window_above_modal ? g.HoveredWindow : modal, true);
     }
 }
@@ -6956,6 +6946,20 @@ bool ImGui::IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent)
     return false;
 }
 
+bool ImGui::IsWindowAbove(ImGuiWindow* potential_above, ImGuiWindow* potential_below)
+{
+    ImGuiContext& g = *GImGui;
+    for (int i = g.Windows.Size - 1; i >= 0; i--)
+    {
+        ImGuiWindow* candidate_window = g.Windows[i];
+        if (candidate_window == potential_above)
+            return true;
+        if (candidate_window == potential_below)
+            return false;
+    }
+    return false;
+}
+
 bool ImGui::IsWindowHovered(ImGuiHoveredFlags flags)
 {
     IM_ASSERT((flags & ImGuiHoveredFlags_AllowWhenOverlapped) == 0);   // Flags not supported by this function
diff --git a/imgui_internal.h b/imgui_internal.h
index f9ff8098..490fc2f3 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -2026,6 +2026,7 @@ namespace ImGui
     IMGUI_API void          UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags flags, ImGuiWindow* parent_window);
     IMGUI_API ImVec2        CalcWindowExpectedSize(ImGuiWindow* window);
     IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent);
+    IMGUI_API bool          IsWindowAbove(ImGuiWindow* potential_above, ImGuiWindow* potential_below);
     IMGUI_API bool          IsWindowNavFocusable(ImGuiWindow* window);
     IMGUI_API ImRect        GetWindowAllowedExtentRect(ImGuiWindow* window);
     IMGUI_API void          SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond = 0);