为何包含Ribbon的宿主窗口不应使用CS_HREDRAW与CS_VREDRAW样式？

Great catch—this is one of those underdocumented Ribbon implementation details that trips up a lot of developers, so I’m glad you asked about it! Let’s break down why the SimpleRibbon sample avoids those two window class styles:

First, let’s anchor this to the code you’re examining: when registering the window class that hosts the Ribbon, the sample intentionally excludes CS_HREDRAW and CS_VREDRAW from the class style flags. Here’s the key reasoning behind this choice:

• The Ribbon handles its own optimized redraws
  The Windows Ribbon framework has built-in logic to calculate layout changes and only redraw the specific parts of the UI that need updating when the window resizes. If you enable CS_HREDRAW/CS_VREDRAW, the system will force a full redraw of the entire window every time its width or height changes. This is redundant for the Ribbon and can introduce unnecessary flicker or performance overhead, especially with complex layouts (like galleries, contextual tabs, or dynamic control groups).

• They conflict with the Ribbon’s clipping and invalidation logic
  The Ribbon uses child windows and custom clipping regions to manage its UI elements. When those two styles are active, the system triggers a full invalidation of the parent window’s client area. This disrupts the Ribbon’s targeted invalidation rules, leading to visual glitches—such as parts of the ribbon failing to update correctly, or unexpected artifacts appearing during resizing.

• It’s a de facto framework best practice
  Even though MSDN doesn’t explicitly document this, it’s an unwritten guideline from the Ribbon development team. The framework is designed to handle dynamic layout changes independently, so letting the system take over full redraws undermines its optimized design. The sample code follows internal rules that never made it into public documentation.

If you were to test adding those styles back into the sample, you’d likely notice increased flicker during window resizing, and possibly odd rendering issues in the ribbon itself—particularly if you’re using dynamic controls that adjust based on window size.

内容的提问来源于stack exchange，提问作者fabspro