O, I get it! Thank you for your explanation! <br><br><br><div class="gmail_quote">On Wed, Apr 27, 2011 at 8:22 PM, Dave Hylands <span dir="ltr"><<a href="mailto:dhylands@gmail.com">dhylands@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi Philip,<br>
<br>
Replying to all this time.<br>
<div class="im"><br>
On Wed, Apr 27, 2011 at 4:24 PM, siqiao chen <<a href="mailto:siqiaochen@gmail.com">siqiaochen@gmail.com</a>> wrote:<br>
</div><div class="im">> Hello, Could I ask how do I enable double buffer support in FrameBuffer<br>
> device?<br>
> I think I could manually increase xres_virtual/yres_virtual to 2 times of<br>
> the display size in video driver and swap xoffset/yoffset after VSync. But<br>
> could I know if this is the right way to do double buffering or this<br>
> function is already built-in?<br>
<br>
</div><div><div></div><div class="h5">You're on the right track. You only need to double xres_virtual or<br>
yres_virtual, not both.<br>
<br>
Let's suppose that your display is 800x480. Then your display driver<br>
needs to size the framebuffer to be 800x960, and you'd use<br>
FBIOPAN_DISPLAY to toggle between 0,0 and 0,480.<br>
<br>
The driver has to support the double sized framebuffer and the pan<br>
command (or maybe you can modify yoffset directly? I haven't tried<br>
this approach myself).<br>
<br>
--<br>
Dave Hylands<br>
Shuswap, BC, Canada<br>
<a href="http://www.davehylands.com" target="_blank">http://www.davehylands.com</a><br>
</div></div></blockquote></div><br>