When rotating X's display orientation on the fly
using xrandr -o left|normal|inverted|right command, following transitions are performed with
black screen delay effect i.e. the display becomes
black for a moment then displays rotated screen. The following transitions are performed with a delay
a black screen is shown with ~1 second duration, then
rotated screen appears normal > right|left inverted > normal|left|right left > normal|inverted right > normal|inverted The following transitions are performed smoothly with
no delays, i.e. "immediately" normal > inverted left > right right > left
Reason of the problem Most time consuming code while rotating the display orientation
with xrandr is
ret = crtc->funcs->set_mode_major(crtc, mode, rotation, x, y); intel video drivers function call. This call is located in
hw/xfree86/modes/xf86Crtc.c file in xf86CrtcSetModeTransform
function. HW Platforms: Graphics : Intel GMA 3150 graphics Graphics : Intel Graphics Media Accelerator (GMA) 950
Corresponding bug is opened in Xservers's intel video drivers
project
https://bugs.freedesktop.org/show_bug.cgi?id=31313
