Draw sync?

[stephen.cheung]

Hi,

I am wondering if there is a way to continue drawing images as animation onto screen with DrawNow() / DrawDeferred()?

I am looking for way to determine the frame rate per seconds. Therefore, not sure if I should use Cperiodic to change images continues to find out the period of time?


Thanks

[Maveric]

Hi,

I am wondering if there is a way to continue drawing images as animation onto screen with DrawNow() / DrawDeferred()?

I am looking for way to determine the frame rate per seconds. Therefore, not sure if I should use Cperiodic to change images continues to find out the period of time?


Thanks

Hello Stephen,

Indeed, the DrawNow() executes the draw operation right away, while DrawDeferred() performs with a delay.
You can use this in conjunction to displaying animations. I have provided below some information that you
may find useful, please check them thru and let's continue discussion, ok?

As the draw operation is complex and heavy operation, for animation you might want to use the DrawNow.
In non-time-critical applications, but where the screen requires like 3-4 draws() for result, the framework
is able to draw the screen 4th time called. In a way delaying the draw ops to the 4th call, which brings
us to the DrawDeferred(). Actually the framework bases the operations on several factors.

When you use DrawDeferred() it will reduce actual draw work, thus increasing the speed. However, within the
animation each frame should be shown, basically requiring the use of DrawNow().

Possible having many controls in the applicationm and to be able to reflect changes of one control (e.g.
text in Label control) instead of calling DrawDeferred() you can call iLabel->DrawDeferred(). This will
result drawing in only Label control and not all of the other controls. You would have increased performance
this way.

btw. related Known issue:
http://wiki.forum.nokia.com/index.ph...60_5th_Edition

According to "Developing Series 60 Applications" by Leigh Edwards, p243:

DrawDeferred() adds a draw request to the current Window Server buffer, to be sent to the Window Server once the buffer is full.

DrawNow() does the same as DrawDeferred(), but then forces a flush of the command buffer.

He also goes on to say that overusing DrawNow() is inefficient and should be avoided.

Link to a wiki article on: "How_to_use_CPeriodic_for_a_steady_stream_of_ticks"

http://wiki.forum.nokia.com/index.ph...tream_of_ticks

Check this out too...
http://discussion.forum.nokia.com/fo...p/t-87079.html

Best Regards,