Popup: Improved handling of (erroneously) repeating calls to OpenPopup() to not fully close/re-open the popup so its child popups won't get closed. (#1497, #1533, #1865).

Followup/fix the change made in deab2ab015

CHANGELOG.txt

@@ -49,6 +49,7 @@ Other Changes:
  - BeginDragDropSource(): Offset tooltip position so it is off the mouse cursor, but also closer to it than regular tooltips, and not clamped by viewport. (#1739)
  - BeginDragDropTarget(): Added ImGuiDragDropFlags_AcceptNoPreviewTooltip flag to request hiding the drag source tooltip from the target site. (#143)
  - BeginCombo(), BeginMainMenuBar(), BeginChildFrame(): Temporary style modification are restored at the end of BeginXXX instead of EndXXX, to not affect tooltips and child windows.
+ - Popup: Improved handling of (erroneously) repeating calls to OpenPopup() to not fully close/re-open the popup so its child popups won't get closed. (#1497, #1533, #1865).
  - InputTextMultiline(): Fixed double navigation highlight when scrollbar is active. (#787)
  - InputText(): Fixed Undo after pasting large amount of text (Redo will still fail when undo buffers are exhausted, but text won't be corrupted).
  - ImFontAtlas: Added GetGlyphRangesChineseSimplifiedCommon() helper that returns a list of ~2500 most common Simplified Chinese characters. (#1859) [@JX-Master, @ocornut]

imgui.cpp

@@ -5111,16 +5111,19 @@ void ImGui::OpenPopupEx(ImGuiID id)
     }
     else
     {
-        // Close child popups if any
-        g.OpenPopupStack.resize(current_stack_size + 1);
-
         // Gently handle the user mistakenly calling OpenPopup() every frame. It is a programming mistake! However, if we were to run the regular code path, the ui
         // would become completely unusable because the popup will always be in hidden-while-calculating-size state _while_ claiming focus. Which would be a very confusing
         // situation for the programmer. Instead, we silently allow the popup to proceed, it will keep reappearing and the programming error will be more obvious to understand.
         if (g.OpenPopupStack[current_stack_size].PopupId == id && g.OpenPopupStack[current_stack_size].OpenFrameCount == g.FrameCount - 1)
+        {
             g.OpenPopupStack[current_stack_size].OpenFrameCount = popup_ref.OpenFrameCount;
+        }
         else
+        {
+            // Close child popups if any, then flag popup for open/reopen
+            g.OpenPopupStack.resize(current_stack_size + 1);
             g.OpenPopupStack[current_stack_size] = popup_ref;
+        }
 
         // When reopening a popup we first refocus its parent, otherwise if its parent is itself a popup it would get closed by ClosePopupsOverWindow().
         // This is equivalent to what ClosePopupToLevel() does.