Orientation changed with changedisplaysettingsex is not kept in mind after a reboot

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In an own small software tool, we change the orientation according to user input. It works well, with one exception. After a reboot always the landscape orientation is restored.

Here are the essential lines of code, that we use:

mode.dmDisplayOrientation = portrait ? DMDO_270 : DMDO_DEFAULT;
ChangeDisplaySettingsEx(device.DeviceName, &mode, NULL, CDS_UPDATEREGISTRY | CDS_RESET | CDS_GLOBAL, NULL);

How can I figure out, the reason for the described problem?

What I have tried:

I read MSDN documentation. Changed the main monitor (2 monitors are conected to the PC). ....

Posted 15-Jul-19 4:13am

Member 14068019

Updated 15-Jul-19 5:24am

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Richard MacCutchan 15-Jul-19 11:36am

You are not checking the return value so it is impossible to guess whether it was successful at changing the registry.

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#realJSOP · Answer 1 · 2019-07-15T04:59:00

Solution 1

USE.THE.DEBUGGER.

If you can't use the tools you have on hand, you will NOT succeed as a programmer.

Posted 15-Jul-19 4:59am

#realJSOP

Dave Kreskowiak · Answer 2 · 2019-07-15T05:24:00

Solution 2

NEVER perform a calculation and the assignment in a single line.

Break the calculation out into it own variable, then use the value in that variable to make the assignment. This makes it far easier to debug the code instead of guessing at the result of the calculation.

Posted 15-Jul-19 5:24am

Dave Kreskowiak