randr1.3 primary output using?

[FloraGui at viatech.com.cn]

Dear All:

    Recently I am using RandR1.3, I found a little confuse with RandR1.3
primary output definition.

    What is this parameter for?

 

    I use the command

 xrandr  --output  VGA  --primary 

    I found if the VGA occupied the IGA2, after using the command line
it occupied IGA1, see the info from xrandr --verbose 

    Before command 

        Screen 0: minimum 320 x 200, current 1024 x 768, maximum 2048 x
2048

VGA connected 1024x768+0+0 (0x3e) normal (normal left inverted right x
axis y axis) 352mm x 264mm

        Identifier: 0x3a

        Timestamp:  584354

        Subpixel:   unknown

        Clones:    

        CRTC:       0

        CRTCs:      0 1

        EDID_DATA:

                00ffffffffffff005a63133501010101

                320d01031d241bbe2abbb8a352469824

                0f484cffff8081998159714f6159a94f

                c140c940d140863d00c05100304040a0

                130060081100001e000000ff00333543

                3033353030303238300a000000fd0032

                b41e6118000a202020202020000000fc

                00473930662b0a2020202020202000bb

        TV connected 1024x768+0+0 (0x49) normal (normal left inverted
right x axis y axis) 0mm x 0mm

        Identifier: 0x3d

        Timestamp:  584354

        Subpixel:   unknown

        Clones:    

        CRTC:       1

        CRTCs:      0 1

    After command

         Screen 0: minimum 320 x 200, current 1024 x 768, maximum 2048 x
2048

CRT connected 1024x768+0+0 (0x3e) normal (normal left inverted right x
axis y axis) 352mm x 264mm

        Identifier: 0x3a

        Timestamp:  584354

        Subpixel:   unknown

        Clones:    

        CRTC:       1

        CRTCs:      1 0

        EDID_DATA:

                00ffffffffffff005a63133501010101

                320d01031d241bbe2abbb8a352469824

                0f484cffff8081998159714f6159a94f

                c140c940d140863d00c05100304040a0

                130060081100001e000000ff00333543

                3033353030303238300a000000fd0032

                b41e6118000a202020202020000000fc

                00473930662b0a2020202020202000bb

        TV connected 1024x768+0+0 (0x49) normal (normal left inverted
right x axis y axis) 0mm x 0mm

        Identifier: 0x3d

        Timestamp:  584354

        Subpixel:   unknown

        Clones:    

        CRTC:       0

        CRTCs:      1 0

 

    In my opinion, because the crtc is changed we need to redraw the
screen, but actually the screen do not redraw, so I now is a little
confused about the function of this command? what is the right behavior
of the command?

    Thanks!

 
Best Regards

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