[usdrecord] Prevent Qt window from showing

[pmintus-atvi]

Description of Issue

usdrecord creates a glWidget window that it hides after displaying it. On Windows, this causes the window to show up for a split second and then disappear. The window doesn't just cause a visual artifact, it also steals input focus since the window is created top-level. When usdrecord is used in a batch process, these windows blink into existence and flood the user's desktop.

Steps to Reproduce

1. Execute usdrecord

System Information (OS, Hardware)

Windows 10 20H2

Package Versions

21.05

[pmintus]

I plan on submitting a fix for this.

[jtran56]

Filed as internal issue #USD-6701

[tallytalwar]

Instead of doing a widget->show and then widget->hide, we can simply set the gl context to be current, which will NOT make the qt widget show up. Note that we simply need to record the framebuffer in an image and do not want to show the gl widget.
This change prevents the usdrecord window from being displayed for a split second. An change has been made for the same internally and should go out in the next dev branch push.