Starting with Windows 10 Build 1809, the Windows API call to SendMessage(hWnd, WM_GETTITLEBARINFOEX, IntPtr.Zero, ref tbi) returns nothing when two mo

  • Thread starter WinForms TeamDevExpress
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WinForms TeamDevExpress

My name is Stanislav Shchelokovskiy. I'm a software engineer representing the WinForms team at DevExpress.

Recently we were reported that our RibbonControl component doesn't display some of its visual elements. Having researched this issue, we found that it takes place because the SendMessage(hwnd, Constants.WM_GETTITLEBARINFOEX, IntPtr.Zero, ref str) API method, which is used for calculations, returns an empty structure if a target form is shown on the main display while two displays are connected.

We have created a project (sample_project) that reproduces this issue and attached it.

To reproduce this behavior, do the following:

1) Connect two displays to your machine and configurethem so that the main display is displayed on the right side as demonstrated in the image attached (see display_settings).

2) Run the project (the form should be displayed on the main display) and try to resize it. You will see that Label indicates that an empty structure is returned. Refer to the video that demonstrates the result and steps to reproduce this issue.

The expected result is that the SendMessage(hwnd, Constants.WM_GETTITLEBARINFOEX, IntPtr.Zero, ref str) API method call returns a non empty structure in this scenario.

It's important to resolve this issue because it may affect a lot of our users who use the RibbonControl component.

If you are aware of this problem, are there any workarounds available?

If necessary, we can provide more detailed information.

Thank you.

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