问题
I working on a simple paint program. It seemed Qt (and KDE) would be a easy way to implement it. I find Qt quite easy to work with, but now I have hit a problem.
When I draw something in my program the mouse skips if I move the mouse to fast.
like this:
It susposed to be like one long string.
I'm using mouseMoveEvent() to draw a pixel to my image when the left mouse button is pressed down. I have called setMouseTracking(true); so the event should be called as long as I move the mouse.
void camoMaker::mouseMoveEvent(QMouseEvent *ev) { if(ev->state()==Qt::LeftButton) { QPoint mPoint=ev->pos(); mPoint.setX(mPoint.x()-80); drawPoint(mPoint); } } camoMaker is the main widget.
drawPoint() draws a pixel on both a internal QImage and using QPainter on a QWidget thats the drawing area.
It seems to me that either mouseMoveEvent() isn't called for every pixel the mouse moves or that the mouse actually just skips some pixel.
I understand that it might just how it works and not Qt fault but X11 or how the OS handle mouse position/input.
If so how would I go about to fix it, should I try to interpolate from 2 points that gets registered?
回答1:
Mouse events don't occur for each pixel as the mouse moves, on most operating systems. The message handlers (including KDE/linux) repeatedly show mouse movements, but pixels will often be skipped.
You'll need to track the last pixel location, and either draw a line, or add extra points in between the last position and the current position.
回答2:
You're right - windowing systems don't deliver a mouse move event for every pixel. You need to interpolate a line between the pixels for which you get events.
来源：https://stackoverflow.com/questions/1219827/qt-mouse-skipping-not-updating-every-pixel-mousemoveevent