Metrics: Added a node showing windows in submission order and showing the Begin() stack.

docs/CHANGELOG.txt

@@ -71,6 +71,7 @@ Other Changes:
   (an additional ItemSpacing.y was declared, affecting scrollbar range).
 - Drag and Drop: BeginDragDropSource() with ImGuiDragDropFlags_SourceAllowNullID doesn't lose
   tooltip when scrolling. (#143)
+- Metrics: Added a node showing windows in submission order and showing the Begin() stack.
 - Misc: Added missing ImGuiMouseCursor_NotAllowed cursor for software rendering (when the
   io.MouseDrawCursor flag is enabled). (#4713) [@nobody-special666]
 - Misc: Fix MinGW DLL build issue (when IMGUI_API is defined). [@rokups]

imgui.cpp

@@ -1946,7 +1946,7 @@ void ImGuiStorage::BuildSortByKey()
 {
     struct StaticFunc
     {
-        static int IMGUI_CDECL PairCompareByID(const void* lhs, const void* rhs)
+        static int IMGUI_CDECL PairComparerByID(const void* lhs, const void* rhs)
         {
             // We can't just do a subtraction because qsort uses signed integers and subtracting our ID doesn't play well with that.
             if (((const ImGuiStoragePair*)lhs)->key > ((const ImGuiStoragePair*)rhs)->key) return +1;
@@ -1954,7 +1954,7 @@ void ImGuiStorage::BuildSortByKey()
             return 0;
         }
     };
-    ImQsort(Data.Data, (size_t)Data.Size, sizeof(ImGuiStoragePair), StaticFunc::PairCompareByID);
+    ImQsort(Data.Data, (size_t)Data.Size, sizeof(ImGuiStoragePair), StaticFunc::PairComparerByID);
 }
 
 int ImGuiStorage::GetInt(ImGuiID key, int default_val) const
@@ -5872,7 +5872,10 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
     // Update ->RootWindow and others pointers (before any possible call to FocusWindow)
     if (first_begin_of_the_frame)
+    {
         UpdateWindowParentAndRootLinks(window, flags, parent_window);
+        window->ParentWindowInBeginStack = parent_window_in_stack;
+    }
 
     // Process SetNextWindow***() calls
     // (FIXME: Consider splitting the HasXXX flags into X/Y components
@@ -11314,6 +11317,7 @@ static void ImeSetInputScreenPosFn_DefaultImpl(int, int) {}
 // - DebugNodeWindow() [Internal]
 // - DebugNodeWindowSettings() [Internal]
 // - DebugNodeWindowsList() [Internal]
+// - DebugNodeWindowsListByBeginStackParent() [Internal]
 //-----------------------------------------------------------------------------
 
 #ifndef IMGUI_DISABLE_METRICS_WINDOW
@@ -11536,8 +11540,27 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     }
 
     // Windows
-    DebugNodeWindowsList(&g.Windows, "Windows");
-    //DebugNodeWindowsList(&g.WindowsFocusOrder, "WindowsFocusOrder");
+    if (TreeNode("Windows", "Windows (%d)", g.Windows.Size))
+    {
+        //SetNextItemOpen(true, ImGuiCond_Once);
+        DebugNodeWindowsList(&g.Windows, "By display order");
+        DebugNodeWindowsList(&g.WindowsFocusOrder, "By focus order (root windows)");
+        if (TreeNode("By submission order (begin stack)"))
+        {
+            // Here we display windows in their submitted order/hierarchy, however note that the Begin stack doesn't constitute a Parent<>Child relationship!
+            ImVector<ImGuiWindow*>& temp_buffer = g.WindowsTempSortBuffer;
+            temp_buffer.resize(0);
+            for (int i = 0; i < g.Windows.Size; i++)
+                if (g.Windows[i]->LastFrameActive + 1 >= g.FrameCount)
+                    temp_buffer.push_back(g.Windows[i]);
+            struct Func { static int IMGUI_CDECL WindowComparerByBeginOrder(const void* lhs, const void* rhs) { return ((int)(*(const ImGuiWindow* const *)lhs)->BeginOrderWithinContext - (*(const ImGuiWindow* const*)rhs)->BeginOrderWithinContext); } };
+            ImQsort(temp_buffer.Data, (size_t)temp_buffer.Size, sizeof(ImGuiWindow*), Func::WindowComparerByBeginOrder);
+            DebugNodeWindowsListByBeginStackParent(temp_buffer.Data, temp_buffer.Size, NULL);
+            TreePop();
+        }
+
+        TreePop();
+    }
 
     // DrawLists
     int drawlist_count = 0;
@@ -12161,7 +12184,6 @@ void ImGui::DebugNodeWindowsList(ImVector<ImGuiWindow*>* windows, const char* la
 {
     if (!TreeNode(label, "%s (%d)", label, windows->Size))
         return;
-    Text("(In front-to-back order:)");
     for (int i = windows->Size - 1; i >= 0; i--) // Iterate front to back
     {
         PushID((*windows)[i]);
@@ -12171,6 +12193,24 @@ void ImGui::DebugNodeWindowsList(ImVector<ImGuiWindow*>* windows, const char* la
     TreePop();
 }
 
+// FIXME-OPT: This is technically suboptimal, but it is simpler this way.
+void ImGui::DebugNodeWindowsListByBeginStackParent(ImGuiWindow** windows, int windows_size, ImGuiWindow* parent_in_begin_stack)
+{
+    for (int i = 0; i < windows_size; i++)
+    {
+        ImGuiWindow* window = windows[i];
+        if (window->ParentWindowInBeginStack != parent_in_begin_stack)
+            continue;
+        char buf[20];
+        ImFormatString(buf, IM_ARRAYSIZE(buf), "[%04d] Window", window->BeginOrderWithinContext);
+        //BulletText("[%04d] Window '%s'", window->BeginOrderWithinContext, window->Name);
+        DebugNodeWindow(window, buf);
+        Indent();
+        DebugNodeWindowsListByBeginStackParent(windows + i + 1, windows_size - i - 1, window);
+        Unindent();
+    }
+}
+
 //-----------------------------------------------------------------------------
 // [SECTION] OTHER DEBUG TOOLS (ITEM PICKER, STACK TOOL)
 //-----------------------------------------------------------------------------

imgui_internal.h

@@ -2026,6 +2026,7 @@ struct IMGUI_API ImGuiWindow
     ImDrawList*             DrawList;                           // == &DrawListInst (for backward compatibility reason with code using imgui_internal.h we keep this a pointer)
     ImDrawList              DrawListInst;
     ImGuiWindow*            ParentWindow;                       // If we are a child _or_ popup _or_ docked window, this is pointing to our parent. Otherwise NULL.
+    ImGuiWindow*            ParentWindowInBeginStack;
     ImGuiWindow*            RootWindow;                         // Point to ourself or first ancestor that is not a child window. Doesn't cross through popups/dock nodes.
     ImGuiWindow*            RootWindowPopupTree;                // Point to ourself or first ancestor that is not a child window. Cross through popups parent<>child.
     ImGuiWindow*            RootWindowForTitleBarHighlight;     // Point to ourself or first ancestor which will display TitleBgActive color when this window is active.
@@ -2784,6 +2785,7 @@ namespace ImGui
     IMGUI_API void          DebugNodeWindow(ImGuiWindow* window, const char* label);
     IMGUI_API void          DebugNodeWindowSettings(ImGuiWindowSettings* settings);
     IMGUI_API void          DebugNodeWindowsList(ImVector<ImGuiWindow*>* windows, const char* label);
+    IMGUI_API void          DebugNodeWindowsListByBeginStackParent(ImGuiWindow** windows, int windows_size, ImGuiWindow* parent_in_begin_stack);
     IMGUI_API void          DebugNodeViewport(ImGuiViewportP* viewport);
     IMGUI_API void          DebugRenderViewportThumbnail(ImDrawList* draw_list, ImGuiViewportP* viewport, const ImRect& bb);