Results 1 to 2 of 2

Thread: QwtDial works slowly in QWS

  1. #1
    Join Date
    Jul 2010
    Xi'an, China
    Qt products
    Qt4 Qt/Embedded
    Unix/X11 Windows

    Question QwtDial works slowly in QWS

    Hi there,

    I was trying to use QwtDial to display things under Qt for Embedded Linux. Then I found it's painfully slow to move the needle, therefore, to change a value of a dial. After searching Google I found it's not a good choice to embed QWidget-based things into QGraphicsView via QGraphicsProxyWidgetItem. Then I abandoned the Graphics View framework and straightly place a QwtDial in a single QMainWindow, but it didn't improve at all.

    Can you tell me a if there's someway to make the needle move more pliably and even in the QGraphicsView? Thanks.

    My development board is mini2440 which is based on sumsang s3c2440 arm920t cpu.
    Kernel version 2.6.31
    Cross gcc compiler version 4.1.2 with EABI support
    Kernel and userspace software are all compiled with EABI.

  2. #2
    Join Date
    Feb 2006
    Munich, Germany
    Thanked 862 Times in 811 Posts
    Qt products
    Qt3 Qt4 Qt/Embedded
    MacOS X Unix/X11 Windows

    Default Re: QwtDial works slowly in QWS

    Well, I don't believe, that QGraphicsView is the source of the problem.

    Please try to find out if painting the dial to the backing store is the reason or if it is the blitting of the backingstore to your hardware. If it is the blitting ( what I wouldn't expect ) it might help to paint the bounding rect of the previous + new needle positions only.

    What about the performance, when you disable antialiasing ( removing the line in QwtDial::paintEvent ) ? Also try to paint parts of the dial only ( also by removing lines in QwtDial::paintEvent ) - can you identify one of these parts being the bottleneck ?



Similar Threads

  1. QWTDial problem
    By zaferaltug in forum Qwt
    Replies: 2
    Last Post: 20th November 2008, 16:40
  2. Context menu works slowly on QTableWidget
    By THRESHE in forum Qt Programming
    Replies: 3
    Last Post: 13th March 2008, 20:54
  3. How Can I rewrite qwtDial Class
    By validator in forum Qwt
    Replies: 4
    Last Post: 21st February 2008, 07:25
  4. Can I Add two needle for QwtDial
    By validator in forum Qwt
    Replies: 4
    Last Post: 14th February 2008, 09:57
  5. QwtDial not exits
    By hiuao in forum Qwt
    Replies: 1
    Last Post: 23rd August 2007, 10:22


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide.