Fix: Online-host list column-toggle leaves ghost artifact after last column

CListCtrlEx::OnEraseBkgnd (with m_bSkipEraseBkgnd) only erases the empty
area below the last item, not the horizontal strip right of the last
column (the ~20px scrollbar reserve AdjustColumnWidths always leaves).
Changing the column count via SetColumnVisible/ToggleColumnVisibility
redistributed widths but never repainted with background erase, so stale
pixels from the previous last column lingered next to the new one (e.g.
after "TLS") until a tab switch or minimize/restore forced a full redraw.

Mirror the proven OnSize needRefresh path: temporarily lift the
skip-erase flag and issue a full RedrawWindow with
RDW_ERASE|RDW_INVALIDATE|RDW_ALLCHILDREN|RDW_UPDATENOW after each
visibility change.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/CListCtrlEx.cpp

@@ -160,6 +160,9 @@ void CListCtrlEx::SetColumnVisible(int nCol, BOOL bVisible)
         if (m_Columns[nCol].CanHide || bVisible) {  // 不允许隐藏的列只能设为可见
             m_Columns[nCol].Visible = bVisible;
             AdjustColumnWidths();
+            // 列数变化后完整重绘（含背景擦除），否则最后一列右侧会残留旧列残影。
+            ScopedEraseBkgnd scope(*this);
+            RedrawWindow(NULL, NULL, RDW_ERASE | RDW_INVALIDATE | RDW_ALLCHILDREN | RDW_UPDATENOW);
         }
     }
 }
@@ -230,6 +233,11 @@ void CListCtrlEx::ToggleColumnVisibility(int nColumn)
 
     // 重新调整列宽
     AdjustColumnWidths();
+
+    // 列数变化后完整重绘（含背景擦除），否则最后一列（TLS 等）右侧会残留旧列残影。
+    // 与 OnSize 中 needRefresh 分支相同的处理：临时放行背景擦除 + 全量 RedrawWindow。
+    ScopedEraseBkgnd scope(*this);
+    RedrawWindow(NULL, NULL, RDW_ERASE | RDW_INVALIDATE | RDW_ALLCHILDREN | RDW_UPDATENOW);
 }
 
 void CListCtrlEx::LoadColumnVisibility()