QT

[hujieyc]

I am using QT and need your help: I use the QCanvas class to draw the graphic. I use a big map as the background and some horizontal lines from the left of the screen to the right of the screen are on top. These lines cross the whole screen. The QCanvasItem
class provides z index to separate the layer. I use it and it succeed.
BUT this program is costly for the system, it takes up nearly the whole CPU resource. I doubt that when I redraw these lines the
background map is redrawed automatic. Does anyone know any way to redraw these lines and keep the background unchanged?------That is the reason I study “overlay” recently. If you have any good way, please show it to me with details.

[amendola]

This is Off Topic,

do an QCanvas::drawArea(x,y,w,h) to update the the area that the lines are in. Also, don’t update the whole canvas so much use the function is “QCanvas::setUpdatePeriod(int ms)” to set the refresh rate of the canvas.

This really is a Qt question, and there are lots of resources for finding the answer to Qt specific stuff. Look here:
http://doc.trolltech.com/3.1/

I was really interested in hearing about you having some success with the OpenGL overlays within the Qt Framework. What happened?

Jamie

[This message has been edited by amendol (edited 02-13-2003).]

[This message has been edited by amendol (edited 02-13-2003).]

[This message has been edited by amendol (edited 02-13-2003).]

[hujieyc]

I am failed to run the overlay example, so I have never seen that either.