QNX RTOS v4 Knowledge Base
QNX RTOS v4 Knowledge Base
| Title |
Labels blinking with enabled transparency |
| Ref. No. |
QNX.000009839 |
| Category(ies) |
Development |
| Issue |
In our application multiple labels are updated and redrawn over a 16-bit bitmapped background. If transparency is enabled for the widgets, they blink off and redraw very slowly, which is unacceptable for our application.
If we turn off the transparency, it works fine, but it does not look pretty.
So, if we just use the drawtext functions, it works fine with transparency, but we need the label-widgets functionality.
Should we write our own label?
Is there any way to make the standard widget work fast with transparency?
|
| Solution |
The slow redraw when the labels are transparent is due to the fact that when the label's text changes, the image behind it must draw to repair where the old text was.
When the label background is not transparent the image does not need to draw when the label changes.
If the image was in shared memory (see PgShmemCreate() and PxLoadImage() examples in the docs) the refresh would be much quicker.
Writing your own label would not make any difference as the label draw is not what is taking the time...it is the image drawing. |
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