Popups: Fix b17b2fb (#4936)

imgui.cpp

@@ -6073,6 +6073,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     {
         // Initialize
         const bool window_is_child_tooltip = (flags & ImGuiWindowFlags_ChildWindow) && (flags & ImGuiWindowFlags_Tooltip); // FIXME-WIP: Undocumented behavior of Child+Tooltip for pinned tooltip (#1345)
+        const bool window_just_appearing_after_hidden_for_resize = (window->HiddenFramesCannotSkipItems > 0);
         window->Active = true;
         window->HasCloseButton = (p_open != NULL);
         window->ClipRect = ImVec4(-FLT_MAX, -FLT_MAX, +FLT_MAX, +FLT_MAX);
@@ -6234,6 +6235,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             SetWindowPos(window, window->SetWindowPosVal - window->Size * window->SetWindowPosPivot, 0); // Position given a pivot (e.g. for centering)
         else if ((flags & ImGuiWindowFlags_ChildMenu) != 0)
             window->Pos = FindBestWindowPosForPopup(window);
+        else if ((flags & ImGuiWindowFlags_Popup) != 0 && !window_pos_set_by_api && window_just_appearing_after_hidden_for_resize)
+            window->Pos = FindBestWindowPosForPopup(window);
         else if ((flags & ImGuiWindowFlags_Tooltip) != 0 && !window_pos_set_by_api && !window_is_child_tooltip)
             window->Pos = FindBestWindowPosForPopup(window);
 
@@ -9417,6 +9420,10 @@ ImVec2 ImGui::FindBestWindowPosForPopup(ImGuiWindow* window)
             r_avoid = ImRect(parent_window->Pos.x + horizontal_overlap, -FLT_MAX, parent_window->Pos.x + parent_window->Size.x - horizontal_overlap - parent_window->ScrollbarSizes.x, FLT_MAX);
         return FindBestWindowPosForPopupEx(window->Pos, window->Size, &window->AutoPosLastDirection, r_outer, r_avoid, ImGuiPopupPositionPolicy_Default);
     }
+    if (window->Flags & ImGuiWindowFlags_Popup)
+    {
+        return FindBestWindowPosForPopupEx(window->Pos, window->Size, &window->AutoPosLastDirection, r_outer, ImRect(window->Pos, window->Pos), ImGuiPopupPositionPolicy_Default); // Ideally we'd disable r_avoid here
+    }
     if (window->Flags & ImGuiWindowFlags_Tooltip)
     {
         // Position tooltip (always follows mouse)