Fix for #10686: White line along right edge of UI on high-DPI Windows

[nethip]

This is a fix contributed by @fxb. This fix address the thin white line problem that appears just below the menu bar randomly.

[nethip]

CC @JeffryBooher @redmunds @peterflynn Please review this change.

[JeffryBooher]

Seems to work ok but the app frame is no longer drawing in the active color when activated.
My guess is that Windows isn't sending WM_ACTIVATEAPP because you're preventing the WM_ACTIVATE message from reaching the default Window Proc but I haven't debugged this to determine if that is indeed the case.

    case WM_ACTIVATEAPP:
        mIsActive = (BOOL)wParam;
        UpdateNonClientArea();
        break;
    }
    return lr;

I guess technically you could just keep track of the active state from here but I wonder if there are other things that are broken.

[nethip]

@JeffryBooher Thanks for pointing out this and proving more info! I will look into this.

[deandersson]

@nethip to be able to get the menu bar to render in the active color we can add mIsActive = (BOOL)wParam;to the WM_ACTIVATE case aswell since the rest of the function is the same.

But as @JeffryBooher pointed out what else might be broken?
MSDN has a remark about the WM_ACTIVATE message, that DefWindowProc handles keyboard focus when the window gets activated. I tried this by opening a second instance from the debug menu and when DefWindowProc doesnt run the second instance never gets keyboard focus, so you can click in the second instance and activate it but when you type it goes in the first instance..

I could not replicate this problem when switching between other processes though. I tried several variations and could not really find anything that was broken when using this fix. There are probably more variations I could try but its over midnight now.. soo nighty night! 😄

[JeffryBooher]

We should try playing around with the Window Class and make the background brush black. It's white by default. That might minimize the White Line flicker.