Fix IsWindowAppearing() from returning true twice in most cases. (#3982, #1497, #1061)

docs/CHANGELOG.txt

@@ -41,6 +41,7 @@ Other Changes:
 
 - Scrolling: Fix scroll tracking with e.g. SetScrollHereX/Y() when WindowPadding < ItemSpacing.
 - Scrolling: Fix scroll snapping on edge of scroll region when both scrollbars are enabled.
+- Window: Fix IsWindowAppearing() from returning true twice in most cases. (#3982, #1497, #1061)
 - Tables: Expose TableSetColumnEnabled() in public api. (#3935)
 - TabBar: Fixed mouse reordering with very fast movements (e.g. crossing multiple tabs in a single
   frame and then immediately standling still (would only affect automation/bots). [@rokups]

imgui.cpp

@@ -5703,14 +5703,13 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
     // Update the Appearing flag
     bool window_just_activated_by_user = (window->LastFrameActive < current_frame - 1);   // Not using !WasActive because the implicit "Debug" window would always toggle off->on
-    const bool window_just_appearing_after_hidden_for_resize = (window->HiddenFramesCannotSkipItems > 0);
     if (flags & ImGuiWindowFlags_Popup)
     {
         ImGuiPopupData& popup_ref = g.OpenPopupStack[g.BeginPopupStack.Size];
         window_just_activated_by_user |= (window->PopupId != popup_ref.PopupId); // We recycle popups so treat window as activated if popup id changed
         window_just_activated_by_user |= (window != popup_ref.Window);
     }
-    window->Appearing = (window_just_activated_by_user || window_just_appearing_after_hidden_for_resize);
+    window->Appearing = window_just_activated_by_user;
     if (window->Appearing)
         SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
 
@@ -5967,6 +5966,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 window->Pos = parent_window->DC.CursorPos;
         }
 
+        const bool window_just_appearing_after_hidden_for_resize = (window->HiddenFramesCannotSkipItems > 0);
         const bool window_pos_with_pivot = (window->SetWindowPosVal.x != FLT_MAX && window->HiddenFramesCannotSkipItems == 0);
         if (window_pos_with_pivot)
             SetWindowPos(window, window->SetWindowPosVal - window->Size * window->SetWindowPosPivot, 0); // Position given a pivot (e.g. for centering)