diff --git a/imgui.cpp b/imgui.cpp
index 0dd930bd4..dc418eba3 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -1826,7 +1826,6 @@ ImGuiWindow::ImGuiWindow(const char* name)
     ID = ImHash(name, 0);
     IDStack.push_back(ID);
     Flags = 0;
-    OrderWithinParent = 0;
     PosFloat = Pos = ImVec2(0.0f, 0.0f);
     Size = SizeFull = ImVec2(0.0f, 0.0f);
     SizeContents = SizeContentsExplicit = ImVec2(0.0f, 0.0f);
@@ -1845,6 +1844,8 @@ ImGuiWindow::ImGuiWindow(const char* name)
     SkipItems = false;
     Appearing = false;
     CloseButton = false;
+    BeginOrderWithinParent = -1;
+    BeginOrderWithinContext = -1;
     BeginCount = 0;
     PopupId = 0;
     AutoFitFramesX = AutoFitFramesY = -1;
@@ -2271,7 +2272,7 @@ void ImGui::NewFrame()
 
     // Initialize on first frame
     if (!g.Initialized)
-        ImGui::Initialize();
+        Initialize();
 
     SetCurrentFont(GetDefaultFont());
     IM_ASSERT(g.Font->IsLoaded());
@@ -2279,6 +2280,7 @@ void ImGui::NewFrame()
     g.Time += g.IO.DeltaTime;
     g.FrameCount += 1;
     g.TooltipOverrideCount = 0;
+    g.WindowsActiveCount = 0;
     g.OverlayDrawList.Clear();
     g.OverlayDrawList.PushTextureID(g.IO.Fonts->TexID);
     g.OverlayDrawList.PushClipRectFullScreen();
@@ -2497,8 +2499,8 @@ void ImGui::NewFrame()
 
     // Create implicit window - we will only render it if the user has added something to it.
     // We don't use "Debug" to avoid colliding with user trying to create a "Debug" window with custom flags.
-    ImGui::SetNextWindowSize(ImVec2(400,400), ImGuiCond_FirstUseEver);
-    ImGui::Begin("Debug##Default");
+    SetNextWindowSize(ImVec2(400,400), ImGuiCond_FirstUseEver);
+    Begin("Debug##Default");
 }
 
 static void* SettingsHandlerWindow_ReadOpen(ImGuiContext&, const char* name)
@@ -2785,7 +2787,7 @@ static int ChildWindowComparer(const void* lhs, const void* rhs)
         return d;
     if (int d = (a->Flags & ImGuiWindowFlags_Tooltip) - (b->Flags & ImGuiWindowFlags_Tooltip))
         return d;
-    return (a->OrderWithinParent - b->OrderWithinParent);
+    return (a->BeginOrderWithinParent - b->BeginOrderWithinParent);
 }
 
 static void AddWindowToSortedBuffer(ImVector<ImGuiWindow*>& out_sorted_windows, ImGuiWindow* window)
@@ -3359,7 +3361,7 @@ void ImGui::CalcListClipping(int items_count, float items_height, int* out_items
 static ImGuiWindow* FindHoveredWindow(ImVec2 pos)
 {
     ImGuiContext& g = *GImGui;
-    for (int i = g.Windows.Size-1; i >= 0; i--)
+    for (int i = g.Windows.Size - 1; i >= 0; i--)
     {
         ImGuiWindow* window = g.Windows[i];
         if (!window->Active)
@@ -3598,7 +3600,8 @@ bool ImGui::IsItemClicked(int mouse_button)
 
 bool ImGui::IsAnyItemHovered()
 {
-    return GImGui->HoveredId != 0 || GImGui->HoveredIdPreviousFrame != 0;
+    ImGuiContext& g = *GImGui;
+    return g.HoveredId != 0 || g.HoveredIdPreviousFrame != 0;
 }
 
 bool ImGui::IsAnyItemActive()
@@ -3914,8 +3917,9 @@ bool ImGui::BeginPopupContextItem(const char* str_id, int mouse_button)
     ImGuiWindow* window = GImGui->CurrentWindow;
     ImGuiID id = str_id ? window->GetID(str_id) : window->DC.LastItemId; // If user hasn't passed an ID, we can use the LastItemID. Using LastItemID as a Popup ID won't conflict!
     IM_ASSERT(id != 0);                                                  // However, you cannot pass a NULL str_id if the last item has no identifier (e.g. a Text() item)
-    if (IsMouseClicked(mouse_button) && IsItemHovered(ImGuiHoveredFlags_AllowWhenBlockedByPopup))
-        OpenPopupEx(id, true);
+    if (IsMouseClicked(mouse_button))
+        if (IsItemHovered(ImGuiHoveredFlags_AllowWhenBlockedByPopup))
+            OpenPopupEx(id, true);
     return BeginPopupEx(id, ImGuiWindowFlags_AlwaysAutoResize);
 }
 
@@ -4448,7 +4452,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         //    window->RootNavWindow = window->RootNavWindow->ParentWindow;
 
         window->Active = true;
-        window->OrderWithinParent = 0;
+        window->BeginOrderWithinParent = 0;
+        window->BeginOrderWithinContext = g.WindowsActiveCount++;
         window->BeginCount = 0;
         window->ClipRect = ImVec4(-FLT_MAX,-FLT_MAX,+FLT_MAX,+FLT_MAX);
         window->LastFrameActive = current_frame;
@@ -4570,7 +4575,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Position child window
         if (flags & ImGuiWindowFlags_ChildWindow)
         {
-            window->OrderWithinParent = parent_window->DC.ChildWindows.Size;
+            window->BeginOrderWithinParent = parent_window->DC.ChildWindows.Size;
             parent_window->DC.ChildWindows.push_back(window);
         }
         if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !window_pos_set_by_api)
@@ -6685,6 +6690,7 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     button_flags |= ImGuiButtonFlags_PressedOnDragDropHold;
     if (flags & ImGuiTreeNodeFlags_OpenOnDoubleClick)
         button_flags |= ImGuiButtonFlags_PressedOnDoubleClick | ((flags & ImGuiTreeNodeFlags_OpenOnArrow) ? ImGuiButtonFlags_PressedOnClickRelease : 0);
+
     bool hovered, held, pressed = ButtonBehavior(interact_bb, id, &hovered, &held, button_flags);
     if (pressed && !(flags & ImGuiTreeNodeFlags_Leaf))
     {
@@ -6774,7 +6780,6 @@ bool ImGui::CollapsingHeader(const char* label, bool* p_open, ImGuiTreeNodeFlags
         ImGuiContext& g = *GImGui;
         float button_sz = g.FontSize * 0.5f;
         ImGuiItemHoveredDataBackup last_item_backup;
-        last_item_backup.Backup();
         if (CloseButton(window->GetID((void*)(intptr_t)(id+1)), ImVec2(ImMin(window->DC.LastItemRect.Max.x, window->ClipRect.Max.x) - g.Style.FramePadding.x - button_sz, window->DC.LastItemRect.Min.y + g.Style.FramePadding.y + button_sz), button_sz))
             *p_open = false;
         last_item_backup.Restore();
diff --git a/imgui.h b/imgui.h
index b44f39369..6bbf2df58 100644
--- a/imgui.h
+++ b/imgui.h
@@ -79,8 +79,8 @@ typedef int ImGuiMouseCursor;       // enum: a mouse cursor identifier
 typedef int ImGuiStyleVar;          // enum: a variable identifier for styling  // enum ImGuiStyleVar_
 typedef int ImDrawCornerFlags;      // flags: for ImDrawList::AddRect*() etc.   // enum ImDrawCornerFlags_
 typedef int ImGuiColorEditFlags;    // flags: for ColorEdit*(), ColorPicker*()  // enum ImGuiColorEditFlags_
-typedef int ImGuiDragDropFlags;     // flags: for *DragDrop*()                  // enum ImGuiDragDropFlags_
 typedef int ImGuiColumnsFlags;      // flags: for *Columns*()                   // enum ImGuiColumnsFlags_
+typedef int ImGuiDragDropFlags;     // flags: for *DragDrop*()                  // enum ImGuiDragDropFlags_
 typedef int ImGuiComboFlags;        // flags: for BeginCombo()                  // enum ImGuiComboFlags_
 typedef int ImGuiFocusedFlags;      // flags: for IsWindowFocused()             // enum ImGuiFocusedFlags_
 typedef int ImGuiHoveredFlags;      // flags: for IsItemHovered() etc.          // enum ImGuiHoveredFlags_
@@ -627,7 +627,7 @@ enum ImGuiHoveredFlags_
     ImGuiHoveredFlags_RootWindow                    = 1 << 1,   // IsWindowHovered() only: Test from root window (top most parent of the current hierarchy)
     ImGuiHoveredFlags_AllowWhenBlockedByPopup       = 1 << 2,   // Return true even if a popup window is normally blocking access to this item/window
     //ImGuiHoveredFlags_AllowWhenBlockedByModal     = 1 << 3,   // Return true even if a modal popup window is normally blocking access to this item/window. FIXME-TODO: Unavailable yet.
-    ImGuiHoveredFlags_AllowWhenBlockedByActiveItem  = 1 << 4,   // Return true even if an active item is blocking access to this item/window
+    ImGuiHoveredFlags_AllowWhenBlockedByActiveItem  = 1 << 4,   // Return true even if an active item is blocking access to this item/window. Useful for Drag and Drop patterns.
     ImGuiHoveredFlags_AllowWhenOverlapped           = 1 << 5,   // Return true even if the position is overlapped by another window
     ImGuiHoveredFlags_RectOnly                      = ImGuiHoveredFlags_AllowWhenBlockedByPopup | ImGuiHoveredFlags_AllowWhenBlockedByActiveItem | ImGuiHoveredFlags_AllowWhenOverlapped
 };
diff --git a/imgui_internal.h b/imgui_internal.h
index 16b71bad3..5c0705ad7 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -183,7 +183,7 @@ enum ImGuiButtonFlags_
     ImGuiButtonFlags_AllowItemOverlap       = 1 << 6,   // require previous frame HoveredId to either match id or be null before being usable, use along with SetItemAllowOverlap()
     ImGuiButtonFlags_DontClosePopups        = 1 << 7,   // disable automatically closing parent popup on press // [UNUSED]
     ImGuiButtonFlags_Disabled               = 1 << 8,   // disable interactions
-    ImGuiButtonFlags_AlignTextBaseLine      = 1 << 9,   // vertically align button to match text baseline (ButtonEx() only)
+    ImGuiButtonFlags_AlignTextBaseLine      = 1 << 9,   // vertically align button to match text baseline - ButtonEx() only // FIXME: Should be removed and handled by SmallButton(), not possible currently because of DC.CursorPosPrevLine
     ImGuiButtonFlags_NoKeyModifiers         = 1 << 10,  // disable interaction if a key modifier is held
     ImGuiButtonFlags_NoHoldingActiveID      = 1 << 11,  // don't set ActiveId while holding the mouse (ImGuiButtonFlags_PressedOnClick only)
     ImGuiButtonFlags_PressedOnDragDropHold  = 1 << 12   // press when held into while we are drag and dropping another item (used by e.g. tree nodes, collapsing headers)
@@ -207,8 +207,8 @@ enum ImGuiColumnsFlags_
 enum ImGuiSelectableFlagsPrivate_
 {
     // NB: need to be in sync with last value of ImGuiSelectableFlags_
-    ImGuiSelectableFlags_Menu               = 1 << 3,
-    ImGuiSelectableFlags_MenuItem           = 1 << 4,
+    ImGuiSelectableFlags_Menu               = 1 << 3,   // -> PressedOnClick
+    ImGuiSelectableFlags_MenuItem           = 1 << 4,   // -> PressedOnRelease
     ImGuiSelectableFlags_Disabled           = 1 << 5,
     ImGuiSelectableFlags_DrawFillAvailWidth = 1 << 6
 };
@@ -439,6 +439,7 @@ struct ImGuiContext
     ImVector<ImGuiWindow*>  WindowsSortBuffer;
     ImVector<ImGuiWindow*>  CurrentWindowStack;
     ImGuiStorage            WindowsById;
+    int                     WindowsActiveCount;
     ImGuiWindow*            CurrentWindow;                      // Being drawn into
     ImGuiWindow*            NavWindow;                          // Nav/focused window for navigation
     ImGuiWindow*            HoveredWindow;                      // Will catch mouse inputs
@@ -550,6 +551,7 @@ struct ImGuiContext
         Time = 0.0f;
         FrameCount = 0;
         FrameCountEnded = FrameCountRendered = -1;
+        WindowsActiveCount = 0;
         CurrentWindow = NULL;
         NavWindow = NULL;
         HoveredWindow = NULL;
@@ -723,7 +725,6 @@ struct IMGUI_API ImGuiWindow
     char*                   Name;
     ImGuiID                 ID;                                 // == ImHash(Name)
     ImGuiWindowFlags        Flags;                              // See enum ImGuiWindowFlags_
-    int                     OrderWithinParent;                  // Order within immediate parent window, if we are a child window. Otherwise 0.
     ImVec2                  PosFloat;
     ImVec2                  Pos;                                // Position rounded-up to nearest pixel
     ImVec2                  Size;                               // Current size (==SizeFull or collapsed title bar size)
@@ -748,6 +749,8 @@ struct IMGUI_API ImGuiWindow
     bool                    SkipItems;                          // Set when items can safely be all clipped (e.g. window not visible or collapsed)
     bool                    Appearing;                          // Set during the frame where the window is appearing (or re-appearing)
     bool                    CloseButton;                        // Set when the window has a close button (p_open != NULL)
+    int                     BeginOrderWithinParent;             // Order within immediate parent window, if we are a child window. Otherwise 0.
+    int                     BeginOrderWithinContext;            // Order within entire imgui context. This is mostly used for debugging submission order related issues.
     int                     BeginCount;                         // Number of Begin() during the current frame (generally 0 or 1, 1+ if appending via multiple Begin/End pairs)
     ImGuiID                 PopupId;                            // ID in the popup stack when this window is used as a popup/menu (because we use generic Name/ID for recycling)
     int                     AutoFitFramesX, AutoFitFramesY;
@@ -809,8 +812,9 @@ struct ImGuiItemHoveredDataBackup
     ImRect      LastItemRect;
     bool        LastItemRectHoveredRect;
 
-    void Backup()  { ImGuiWindow* window = GImGui->CurrentWindow; LastItemId = window->DC.LastItemId; LastItemRect = window->DC.LastItemRect; LastItemRectHoveredRect = window->DC.LastItemRectHoveredRect; }
-    void Restore() { ImGuiWindow* window = GImGui->CurrentWindow; window->DC.LastItemId = LastItemId; window->DC.LastItemRect = LastItemRect; window->DC.LastItemRectHoveredRect = LastItemRectHoveredRect; }
+    ImGuiItemHoveredDataBackup() { Backup(); }
+    void Backup()        { ImGuiWindow* window = GImGui->CurrentWindow; LastItemId = window->DC.LastItemId; LastItemRect = window->DC.LastItemRect; LastItemRectHoveredRect = window->DC.LastItemRectHoveredRect; }
+    void Restore() const { ImGuiWindow* window = GImGui->CurrentWindow; window->DC.LastItemId = LastItemId; window->DC.LastItemRect = LastItemRect; window->DC.LastItemRectHoveredRect = LastItemRectHoveredRect; }
 };
 
 //-----------------------------------------------------------------------------