[Interest] QPrintPreviewWidget

[Dan Allen]

Hi Bill,

I agree, however when the print is quite complex it makes the GUI very 
unresponsive.

Painting into an off screen image is not GUI related. The print preview 
could show something like "Generating Preview" while a background thread 
generates it and then show it when it's ready for example. This would 
prevent the GUI from seeming unresponsive to the user. I wasn't sure if 
there was a current method to do something like this.

Thanks,

Dan Allen.


On 01/04/17 13:43, william.crocker at analog.com wrote:
> On 04/01/2017 03:41 AM, Dan Allen wrote:
>> Hi,
>>
>> Could anyone tell me if it's possible to paint into a 
>> QPrintPreviewWidget in
>> another thread, and if so, how?
>>
>> I have created a class to perform printing and this runs in another 
>> thread.
>> When used for printing it works fine.  However when used for the 
>> print preview,
>> nothing is shown unless I force the signal to either 
>> Qt::DirectConnection (i.e.
>> use the GUI thread) or Qt ::BlockingQueuedConnection (i.e. block the 
>> GUI thread).
>>
> Dan:
>
> Conventional wisdom, if not the rule of law, states that all GUI activity
> should be done from the main thread. You may just be experiencing
> the Qt library enforcing this rule.
>
> Bill
>
>> Thanks,
>>
>> Dan Allen.
>>
>>
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