subject:"Re\: \[Interest\] Improve ListView scrolling performance \(many pictures\)"

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-13 Thread Bernhard B

@Mark: Sorry, that was probably a bit confusing. ;-)

What I meant was the following: Whenever a new batch of images are received
I resize and compress them a little bit to create thumbnails. After the
images are resized and compressed, they are added to the ListModel. That's
the part, that is still performed in the main thread.

In the delegate I am now using a QQuickAsyncImageProvider to dispatch the
painting to different threads. As the images are already correctly sized at
this point no resizing needs to be done in the image provider. So instead
of constantly resizing the images to the correct size in the image provider
I resize them once after I receive them.

The scrolling works fine now, but now the ListView lags a bit when a new
batch of images are received and processed. My initial idea was to
completely move the adding/removing (and the inital image processing) of
elements to a different thread, but I wasn't sure if that is safe. Because
in that case I would need to access the ListModel from two different
threads which probably isn't safe and won't work.

So I think my best bet is to use something like @Andy suggested and move
the QImage processing to another thread. After the image processing is done
the result gets copied back to the main thread and the image gets added to
the ListModel.

I think that's the same approach you also had in mind, right? :)

@Andy: Many thanks for the code snippet, that looks really promising. Will
definitely try that out!

Bernhard

2017-08-13 23:42 GMT+02:00 Mark Gaiser :

> Hi,
>
> I don't quite follow.
>
> First you say you implemented our suggestions (move image processing in a
> thread), then you say: "all operations are performed in the main (GUI)
> thread"... Exactly the opposite of what we've been suggesting.
>
> If i'm reading your reply correctly you're not offloading anything to a
> separate thread ;)
> Do that and the listview will feel a lot more performant.
>
>
>
> On Sun, Aug 13, 2017 at 10:40 PM, Bernhard B  wrote:
>
>> Many thanks guys!
>>
>> I just implemented your suggestions and have to say that the scrolling
>> performance definitely improved a lot. Thanks a lot for your help!
>>
>> However, as I am now doing more work (compress image + resize) before I
>> populate the Listmodel, I noticed that there is a significant lag every
>> time I fetch and process another batch of images from the server. I think
>> that's due to the fact that all operations are performed in the main (GUI)
>> thread.
>>
>> Does anyone know if it's possible to move the populating of the ListModel
>> to another thread? I am aware of the WorkerScript concept, but as far as I
>> know this only works for QML ListModel's and not for
>> QAbstractListModel-derived models. Or is the only possibility to move the
>> heavy lifiting (i.e image operations) to a separate thread and keep the
>> rest in the main thread? (as Mark suggested)
>>
>> Thanks,
>> Bernhard
>>
>>
>>
>>
>> 2017-08-11 15:54 GMT+02:00 Andy :
>>
>>> I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):
>>>
>>> void  _saveThumbnail( QImage inImage, const QString &inPath )
>>> {
>>>QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
>>> Qt::KeepAspectRatio, Qt::SmoothTransformation );
>>>
>>>QImageWriter writer( inPath, "JPEG" );
>>>
>>>writer.setQuality( 100 );
>>>writer.setOptimizedWrite( true );
>>>writer.setProgressiveScanWrite( true );
>>>
>>>writer.write( image );
>>> }
>>>
>>> It gives me decent-looking, reasonable sized thumbnails.
>>>
>>> ---
>>> Andy Maloney  //  https://asmaloney.com
>>> twitter ~ @asmaloney 
>>>
>>>
>>> On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:
>>>
 Hi Andy,

 many thanks for your response! I am also using a
 QAbstractListModel-derived class that gets exposed to the QML world which
 contains the images.

 Yesterday I started to resize the images before feeding them to the
 ListModel. According to the QML Profiler the delegate gets now created a
 little bit faster, but fast scrolling is still a little bit sluggish. Today
 I probably will play a little bit with different image codecs to see if
 those have an impact. Currently I am using *.png files often which is
 probably not the best choice.

 Thanks a lot for your input, really appreciated!

 Bernhard

 Am Freitag, 11. August 2017 schrieb Andy :

> Bernhard:
>
> I don't use QML, but in my application I use a
> QAbstractItemModel-derived class and a QTreeView-derived class to display
> image thumbnails in the view. The way I make it speedy is to save the 
> image
> as a thumbnail so the view items don't need to resize the image data at 
> all.
>
> Maybe you could save a thumbnail of an appropriate size when you're
> adding them to your model?
>
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asm

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-13 Thread Mark Gaiser

Hi,

I don't quite follow.

First you say you implemented our suggestions (move image processing in a
thread), then you say: "all operations are performed in the main (GUI)
thread"... Exactly the opposite of what we've been suggesting.

If i'm reading your reply correctly you're not offloading anything to a
separate thread ;)
Do that and the listview will feel a lot more performant.



On Sun, Aug 13, 2017 at 10:40 PM, Bernhard B  wrote:

> Many thanks guys!
>
> I just implemented your suggestions and have to say that the scrolling
> performance definitely improved a lot. Thanks a lot for your help!
>
> However, as I am now doing more work (compress image + resize) before I
> populate the Listmodel, I noticed that there is a significant lag every
> time I fetch and process another batch of images from the server. I think
> that's due to the fact that all operations are performed in the main (GUI)
> thread.
>
> Does anyone know if it's possible to move the populating of the ListModel
> to another thread? I am aware of the WorkerScript concept, but as far as I
> know this only works for QML ListModel's and not for
> QAbstractListModel-derived models. Or is the only possibility to move the
> heavy lifiting (i.e image operations) to a separate thread and keep the
> rest in the main thread? (as Mark suggested)
>
> Thanks,
> Bernhard
>
>
>
>
> 2017-08-11 15:54 GMT+02:00 Andy :
>
>> I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):
>>
>> void  _saveThumbnail( QImage inImage, const QString &inPath )
>> {
>>QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
>> Qt::KeepAspectRatio, Qt::SmoothTransformation );
>>
>>QImageWriter writer( inPath, "JPEG" );
>>
>>writer.setQuality( 100 );
>>writer.setOptimizedWrite( true );
>>writer.setProgressiveScanWrite( true );
>>
>>writer.write( image );
>> }
>>
>> It gives me decent-looking, reasonable sized thumbnails.
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney 
>>
>>
>> On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:
>>
>>> Hi Andy,
>>>
>>> many thanks for your response! I am also using a
>>> QAbstractListModel-derived class that gets exposed to the QML world which
>>> contains the images.
>>>
>>> Yesterday I started to resize the images before feeding them to the
>>> ListModel. According to the QML Profiler the delegate gets now created a
>>> little bit faster, but fast scrolling is still a little bit sluggish. Today
>>> I probably will play a little bit with different image codecs to see if
>>> those have an impact. Currently I am using *.png files often which is
>>> probably not the best choice.
>>>
>>> Thanks a lot for your input, really appreciated!
>>>
>>> Bernhard
>>>
>>>
>>> Am Freitag, 11. August 2017 schrieb Andy :
>>>
 Bernhard:

 I don't use QML, but in my application I use a
 QAbstractItemModel-derived class and a QTreeView-derived class to display
 image thumbnails in the view. The way I make it speedy is to save the image
 as a thumbnail so the view items don't need to resize the image data at 
 all.

 Maybe you could save a thumbnail of an appropriate size when you're
 adding them to your model?

 ---
 Andy Maloney  //  https://asmaloney.com
 twitter ~ @asmaloney 


 On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B 
 wrote:

> Hi Vlad,
>
> you mean the QQuickAsyncImageProvider? That one sounds really
> promising. Will definitely try that out. Many thanks for the suggestion!
>
> Bernhard
>
> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>
>> threaded image provider might help
>>
>> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
>> wrote:
>>
>>> Hi,
>>>
>>> yesterday, I also tried to replace the Base64ImageProvider approach
>>> with a subclassed QQuickPaintedItem which paints the image in it's paint
>>> method. I imagined that this approach might be faster es no bade64 
>>> decoding
>>> needs to be done. But unfortunately it looks like as it's performing 
>>> even
>>> worse that way.
>>>
>>> Bernhard
>>>
>>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>>
 Hi,

 I would need some help from you guys on how to improve the
 ListView's performance. The problem is, that scrolling through my 
 ListView
 sometimes feels a little bit sluggish.

 If I only display some text in the ListView's delegate I can scroll
 smoothly through my list. But as soon as there is a picture in the
 ListView's delegate I notice that I can't scroll smoothly through my 
 list
 anymore. That's especially noticable if I try to scroll fast through my
 list. Every time I hit a picture while scrolling through the list I 
 can see
 t

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-13 Thread Andy

Yes - it's possible to move QImage processing to another thread. I've used
QtConcurrent::run() to resize and write several images concurrently.

void SomeClass::_writeImage( QImage inImage, const QString &inPath )
{
   QFuture  future = QtConcurrent::run( [this, inImage, inPath] () {
  QImage   image = inImage;

  int   width = image.width();
  int   height = image.height();

  width += (width % 2);
  height += (height % 2);

  if ( (width != image.width()) || (height != image.height()) )
  {
 image = image.scaled( width, height, Qt::IgnoreAspectRatio,
Qt::SmoothTransformation );
  }

  QImageWriter   imageWriter( inPath );

  if ( !imageWriter.write( image) )
  {
 // error
  }
   } );

   mFutureList.append( future );
}

... later on


   for ( auto future : mFutureList )
   {
  future.waitForFinished();
   }


If you need to monitor the QFuture to do something when it's done, take a
look at QFutureWatcher: https://doc.qt.io/qt-5/qfuturewatcher.html

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney 


On Sun, Aug 13, 2017 at 4:40 PM, Bernhard B  wrote:

> Many thanks guys!
>
> I just implemented your suggestions and have to say that the scrolling
> performance definitely improved a lot. Thanks a lot for your help!
>
> However, as I am now doing more work (compress image + resize) before I
> populate the Listmodel, I noticed that there is a significant lag every
> time I fetch and process another batch of images from the server. I think
> that's due to the fact that all operations are performed in the main (GUI)
> thread.
>
> Does anyone know if it's possible to move the populating of the ListModel
> to another thread? I am aware of the WorkerScript concept, but as far as I
> know this only works for QML ListModel's and not for
> QAbstractListModel-derived models. Or is the only possibility to move the
> heavy lifiting (i.e image operations) to a separate thread and keep the
> rest in the main thread? (as Mark suggested)
>
> Thanks,
> Bernhard
>
>
>
>
> 2017-08-11 15:54 GMT+02:00 Andy :
>
>> I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):
>>
>> void  _saveThumbnail( QImage inImage, const QString &inPath )
>> {
>>QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
>> Qt::KeepAspectRatio, Qt::SmoothTransformation );
>>
>>QImageWriter writer( inPath, "JPEG" );
>>
>>writer.setQuality( 100 );
>>writer.setOptimizedWrite( true );
>>writer.setProgressiveScanWrite( true );
>>
>>writer.write( image );
>> }
>>
>> It gives me decent-looking, reasonable sized thumbnails.
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney 
>>
>>
>> On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:
>>
>>> Hi Andy,
>>>
>>> many thanks for your response! I am also using a
>>> QAbstractListModel-derived class that gets exposed to the QML world which
>>> contains the images.
>>>
>>> Yesterday I started to resize the images before feeding them to the
>>> ListModel. According to the QML Profiler the delegate gets now created a
>>> little bit faster, but fast scrolling is still a little bit sluggish. Today
>>> I probably will play a little bit with different image codecs to see if
>>> those have an impact. Currently I am using *.png files often which is
>>> probably not the best choice.
>>>
>>> Thanks a lot for your input, really appreciated!
>>>
>>> Bernhard
>>>
>>>
>>> Am Freitag, 11. August 2017 schrieb Andy :
>>>
 Bernhard:

 I don't use QML, but in my application I use a
 QAbstractItemModel-derived class and a QTreeView-derived class to display
 image thumbnails in the view. The way I make it speedy is to save the image
 as a thumbnail so the view items don't need to resize the image data at 
 all.

 Maybe you could save a thumbnail of an appropriate size when you're
 adding them to your model?

 ---
 Andy Maloney  //  https://asmaloney.com
 twitter ~ @asmaloney 


 On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B 
 wrote:

> Hi Vlad,
>
> you mean the QQuickAsyncImageProvider? That one sounds really
> promising. Will definitely try that out. Many thanks for the suggestion!
>
> Bernhard
>
> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>
>> threaded image provider might help
>>
>> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
>> wrote:
>>
>>> Hi,
>>>
>>> yesterday, I also tried to replace the Base64ImageProvider approach
>>> with a subclassed QQuickPaintedItem which paints the image in it's paint
>>> method. I imagined that this approach might be faster es no bade64 
>>> decoding
>>> needs to be done. But unfortunately it looks like as it's performing 
>>> even
>>> worse that way.
>>>
>>> Bernhard
>>

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-13 Thread Vlad Stelmahovsky

you should avoid any time consuming ops in his thread

On Aug 13, 2017 22:40, "Bernhard B"  wrote:

> Many thanks guys!
>
> I just implemented your suggestions and have to say that the scrolling
> performance definitely improved a lot. Thanks a lot for your help!
>
> However, as I am now doing more work (compress image + resize) before I
> populate the Listmodel, I noticed that there is a significant lag every
> time I fetch and process another batch of images from the server. I think
> that's due to the fact that all operations are performed in the main (GUI)
> thread.
>
> Does anyone know if it's possible to move the populating of the ListModel
> to another thread? I am aware of the WorkerScript concept, but as far as I
> know this only works for QML ListModel's and not for
> QAbstractListModel-derived models. Or is the only possibility to move the
> heavy lifiting (i.e image operations) to a separate thread and keep the
> rest in the main thread? (as Mark suggested)
>
> Thanks,
> Bernhard
>
>
>
>
> 2017-08-11 15:54 GMT+02:00 Andy :
>
>> I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):
>>
>> void  _saveThumbnail( QImage inImage, const QString &inPath )
>> {
>>QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
>> Qt::KeepAspectRatio, Qt::SmoothTransformation );
>>
>>QImageWriter writer( inPath, "JPEG" );
>>
>>writer.setQuality( 100 );
>>writer.setOptimizedWrite( true );
>>writer.setProgressiveScanWrite( true );
>>
>>writer.write( image );
>> }
>>
>> It gives me decent-looking, reasonable sized thumbnails.
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney 
>>
>>
>> On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:
>>
>>> Hi Andy,
>>>
>>> many thanks for your response! I am also using a
>>> QAbstractListModel-derived class that gets exposed to the QML world which
>>> contains the images.
>>>
>>> Yesterday I started to resize the images before feeding them to the
>>> ListModel. According to the QML Profiler the delegate gets now created a
>>> little bit faster, but fast scrolling is still a little bit sluggish. Today
>>> I probably will play a little bit with different image codecs to see if
>>> those have an impact. Currently I am using *.png files often which is
>>> probably not the best choice.
>>>
>>> Thanks a lot for your input, really appreciated!
>>>
>>> Bernhard
>>>
>>>
>>> Am Freitag, 11. August 2017 schrieb Andy :
>>>
 Bernhard:

 I don't use QML, but in my application I use a
 QAbstractItemModel-derived class and a QTreeView-derived class to display
 image thumbnails in the view. The way I make it speedy is to save the image
 as a thumbnail so the view items don't need to resize the image data at 
 all.

 Maybe you could save a thumbnail of an appropriate size when you're
 adding them to your model?

 ---
 Andy Maloney  //  https://asmaloney.com
 twitter ~ @asmaloney 


 On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B 
 wrote:

> Hi Vlad,
>
> you mean the QQuickAsyncImageProvider? That one sounds really
> promising. Will definitely try that out. Many thanks for the suggestion!
>
> Bernhard
>
> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>
>> threaded image provider might help
>>
>> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
>> wrote:
>>
>>> Hi,
>>>
>>> yesterday, I also tried to replace the Base64ImageProvider approach
>>> with a subclassed QQuickPaintedItem which paints the image in it's paint
>>> method. I imagined that this approach might be faster es no bade64 
>>> decoding
>>> needs to be done. But unfortunately it looks like as it's performing 
>>> even
>>> worse that way.
>>>
>>> Bernhard
>>>
>>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>>
 Hi,

 I would need some help from you guys on how to improve the
 ListView's performance. The problem is, that scrolling through my 
 ListView
 sometimes feels a little bit sluggish.

 If I only display some text in the ListView's delegate I can scroll
 smoothly through my list. But as soon as there is a picture in the
 ListView's delegate I notice that I can't scroll smoothly through my 
 list
 anymore. That's especially noticable if I try to scroll fast through my
 list. Every time I hit a picture while scrolling through the list I 
 can see
 that there is a noticable delay until the picture is fully loaded. My
 assumption is, that those pictures are the reason why he scrolling 
 feels so
 sluggish.

 My application currently works like this:

 * load 20 pictures via REST (pictures are base64 encoded)
 * populate list

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-13 Thread Bernhard B

Many thanks guys!

I just implemented your suggestions and have to say that the scrolling
performance definitely improved a lot. Thanks a lot for your help!

However, as I am now doing more work (compress image + resize) before I
populate the Listmodel, I noticed that there is a significant lag every
time I fetch and process another batch of images from the server. I think
that's due to the fact that all operations are performed in the main (GUI)
thread.

Does anyone know if it's possible to move the populating of the ListModel
to another thread? I am aware of the WorkerScript concept, but as far as I
know this only works for QML ListModel's and not for
QAbstractListModel-derived models. Or is the only possibility to move the
heavy lifiting (i.e image operations) to a separate thread and keep the
rest in the main thread? (as Mark suggested)

Thanks,
Bernhard




2017-08-11 15:54 GMT+02:00 Andy :

> I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):
>
> void  _saveThumbnail( QImage inImage, const QString &inPath )
> {
>QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
> Qt::KeepAspectRatio, Qt::SmoothTransformation );
>
>QImageWriter writer( inPath, "JPEG" );
>
>writer.setQuality( 100 );
>writer.setOptimizedWrite( true );
>writer.setProgressiveScanWrite( true );
>
>writer.write( image );
> }
>
> It gives me decent-looking, reasonable sized thumbnails.
>
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney 
>
>
> On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:
>
>> Hi Andy,
>>
>> many thanks for your response! I am also using a
>> QAbstractListModel-derived class that gets exposed to the QML world which
>> contains the images.
>>
>> Yesterday I started to resize the images before feeding them to the
>> ListModel. According to the QML Profiler the delegate gets now created a
>> little bit faster, but fast scrolling is still a little bit sluggish. Today
>> I probably will play a little bit with different image codecs to see if
>> those have an impact. Currently I am using *.png files often which is
>> probably not the best choice.
>>
>> Thanks a lot for your input, really appreciated!
>>
>> Bernhard
>>
>>
>> Am Freitag, 11. August 2017 schrieb Andy :
>>
>>> Bernhard:
>>>
>>> I don't use QML, but in my application I use a
>>> QAbstractItemModel-derived class and a QTreeView-derived class to display
>>> image thumbnails in the view. The way I make it speedy is to save the image
>>> as a thumbnail so the view items don't need to resize the image data at all.
>>>
>>> Maybe you could save a thumbnail of an appropriate size when you're
>>> adding them to your model?
>>>
>>> ---
>>> Andy Maloney  //  https://asmaloney.com
>>> twitter ~ @asmaloney 
>>>
>>>
>>> On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B  wrote:
>>>
 Hi Vlad,

 you mean the QQuickAsyncImageProvider? That one sounds really
 promising. Will definitely try that out. Many thanks for the suggestion!

 Bernhard

 Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :

> threaded image provider might help
>
> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
> wrote:
>
>> Hi,
>>
>> yesterday, I also tried to replace the Base64ImageProvider approach
>> with a subclassed QQuickPaintedItem which paints the image in it's paint
>> method. I imagined that this approach might be faster es no bade64 
>> decoding
>> needs to be done. But unfortunately it looks like as it's performing even
>> worse that way.
>>
>> Bernhard
>>
>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>
>>> Hi,
>>>
>>> I would need some help from you guys on how to improve the
>>> ListView's performance. The problem is, that scrolling through my 
>>> ListView
>>> sometimes feels a little bit sluggish.
>>>
>>> If I only display some text in the ListView's delegate I can scroll
>>> smoothly through my list. But as soon as there is a picture in the
>>> ListView's delegate I notice that I can't scroll smoothly through my 
>>> list
>>> anymore. That's especially noticable if I try to scroll fast through my
>>> list. Every time I hit a picture while scrolling through the list I can 
>>> see
>>> that there is a noticable delay until the picture is fully loaded. My
>>> assumption is, that those pictures are the reason why he scrolling 
>>> feels so
>>> sluggish.
>>>
>>> My application currently works like this:
>>>
>>> * load 20 pictures via REST (pictures are base64 encoded)
>>> * populate list model
>>> * the Image component in the delegate uses a Base64ImageProvider
>>> (self written) to access the model's base64 encoded content and displays
>>> the image
>>> * if the user scrolls past a threshold another batch of base64
>>> encoded pictures

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-11 Thread Andy

I've been using jpeg - something like this (where MAX_THUMB_DIM is 60):

void  _saveThumbnail( QImage inImage, const QString &inPath )
{
   QImage   image = inImage.scaled( MAX_THUMB_DIM, MAX_THUMB_DIM,
Qt::KeepAspectRatio, Qt::SmoothTransformation );

   QImageWriter writer( inPath, "JPEG" );

   writer.setQuality( 100 );
   writer.setOptimizedWrite( true );
   writer.setProgressiveScanWrite( true );

   writer.write( image );
}

It gives me decent-looking, reasonable sized thumbnails.

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney 


On Fri, Aug 11, 2017 at 9:36 AM, Bernhard B  wrote:

> Hi Andy,
>
> many thanks for your response! I am also using a
> QAbstractListModel-derived class that gets exposed to the QML world which
> contains the images.
>
> Yesterday I started to resize the images before feeding them to the
> ListModel. According to the QML Profiler the delegate gets now created a
> little bit faster, but fast scrolling is still a little bit sluggish. Today
> I probably will play a little bit with different image codecs to see if
> those have an impact. Currently I am using *.png files often which is
> probably not the best choice.
>
> Thanks a lot for your input, really appreciated!
>
> Bernhard
>
>
> Am Freitag, 11. August 2017 schrieb Andy :
>
>> Bernhard:
>>
>> I don't use QML, but in my application I use a QAbstractItemModel-derived
>> class and a QTreeView-derived class to display image thumbnails in the
>> view. The way I make it speedy is to save the image as a thumbnail so the
>> view items don't need to resize the image data at all.
>>
>> Maybe you could save a thumbnail of an appropriate size when you're
>> adding them to your model?
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney 
>>
>>
>> On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B  wrote:
>>
>>> Hi Vlad,
>>>
>>> you mean the QQuickAsyncImageProvider? That one sounds really promising.
>>> Will definitely try that out. Many thanks for the suggestion!
>>>
>>> Bernhard
>>>
>>> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>>>
 threaded image provider might help

 On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
 wrote:

> Hi,
>
> yesterday, I also tried to replace the Base64ImageProvider approach
> with a subclassed QQuickPaintedItem which paints the image in it's paint
> method. I imagined that this approach might be faster es no bade64 
> decoding
> needs to be done. But unfortunately it looks like as it's performing even
> worse that way.
>
> Bernhard
>
> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>
>> Hi,
>>
>> I would need some help from you guys on how to improve the ListView's
>> performance. The problem is, that scrolling through my ListView sometimes
>> feels a little bit sluggish.
>>
>> If I only display some text in the ListView's delegate I can scroll
>> smoothly through my list. But as soon as there is a picture in the
>> ListView's delegate I notice that I can't scroll smoothly through my list
>> anymore. That's especially noticable if I try to scroll fast through my
>> list. Every time I hit a picture while scrolling through the list I can 
>> see
>> that there is a noticable delay until the picture is fully loaded. My
>> assumption is, that those pictures are the reason why he scrolling feels 
>> so
>> sluggish.
>>
>> My application currently works like this:
>>
>> * load 20 pictures via REST (pictures are base64 encoded)
>> * populate list model
>> * the Image component in the delegate uses a Base64ImageProvider
>> (self written) to access the model's base64 encoded content and displays
>> the image
>> * if the user scrolls past a threshold another batch of base64
>> encoded pictures is fetched from the server
>>
>> I also found this document: http://doc.qt.io/qt-
>> 5/qtquick-performance.html#rendering and tried to apply as much as
>> possible. In detail I applied the following changes:
>>
>> * removed complex bindings from delegate
>> * set sourceSize property for Image
>> * increased cacheBuffer a bit
>> * profiled with QML profiler and improved a few things
>>
>> But still, the ListView feels a bit sluggish. The strange thing is,
>> that it's most noticable on Android whereas on Windows and iOs it is 
>> better.
>>
>> Does anyone have an idea on how to improve that?
>>
>>
>> Any help is really appreciated.
>> Thanks a lot!
>>
>
> ___
> Interest mailing list
> Interest@qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>
>


 --
 Best regards,
 Vlad

>>>
>>> ___
>>> Interest mailing l

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-11 Thread Mark Gaiser

You need to do the "heavy" image operations in a separate thread!
Copy the result back to the main thread and feed it to QML.
You should not do any more operations on it once it lives in the main
thread (no resize, scale, colorize, whatever) as you will notice that
during scrolling.

On Fri, Aug 11, 2017 at 3:36 PM, Bernhard B  wrote:

> Hi Andy,
>
> many thanks for your response! I am also using a
> QAbstractListModel-derived class that gets exposed to the QML world which
> contains the images.
>
> Yesterday I started to resize the images before feeding them to the
> ListModel. According to the QML Profiler the delegate gets now created a
> little bit faster, but fast scrolling is still a little bit sluggish. Today
> I probably will play a little bit with different image codecs to see if
> those have an impact. Currently I am using *.png files often which is
> probably not the best choice.
>
> Thanks a lot for your input, really appreciated!
>
> Bernhard
>
>
> Am Freitag, 11. August 2017 schrieb Andy :
>
>> Bernhard:
>>
>> I don't use QML, but in my application I use a QAbstractItemModel-derived
>> class and a QTreeView-derived class to display image thumbnails in the
>> view. The way I make it speedy is to save the image as a thumbnail so the
>> view items don't need to resize the image data at all.
>>
>> Maybe you could save a thumbnail of an appropriate size when you're
>> adding them to your model?
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney 
>>
>>
>> On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B  wrote:
>>
>>> Hi Vlad,
>>>
>>> you mean the QQuickAsyncImageProvider? That one sounds really promising.
>>> Will definitely try that out. Many thanks for the suggestion!
>>>
>>> Bernhard
>>>
>>> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>>>
 threaded image provider might help

 On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
 wrote:

> Hi,
>
> yesterday, I also tried to replace the Base64ImageProvider approach
> with a subclassed QQuickPaintedItem which paints the image in it's paint
> method. I imagined that this approach might be faster es no bade64 
> decoding
> needs to be done. But unfortunately it looks like as it's performing even
> worse that way.
>
> Bernhard
>
> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>
>> Hi,
>>
>> I would need some help from you guys on how to improve the ListView's
>> performance. The problem is, that scrolling through my ListView sometimes
>> feels a little bit sluggish.
>>
>> If I only display some text in the ListView's delegate I can scroll
>> smoothly through my list. But as soon as there is a picture in the
>> ListView's delegate I notice that I can't scroll smoothly through my list
>> anymore. That's especially noticable if I try to scroll fast through my
>> list. Every time I hit a picture while scrolling through the list I can 
>> see
>> that there is a noticable delay until the picture is fully loaded. My
>> assumption is, that those pictures are the reason why he scrolling feels 
>> so
>> sluggish.
>>
>> My application currently works like this:
>>
>> * load 20 pictures via REST (pictures are base64 encoded)
>> * populate list model
>> * the Image component in the delegate uses a Base64ImageProvider
>> (self written) to access the model's base64 encoded content and displays
>> the image
>> * if the user scrolls past a threshold another batch of base64
>> encoded pictures is fetched from the server
>>
>> I also found this document: http://doc.qt.io/qt-
>> 5/qtquick-performance.html#rendering and tried to apply as much as
>> possible. In detail I applied the following changes:
>>
>> * removed complex bindings from delegate
>> * set sourceSize property for Image
>> * increased cacheBuffer a bit
>> * profiled with QML profiler and improved a few things
>>
>> But still, the ListView feels a bit sluggish. The strange thing is,
>> that it's most noticable on Android whereas on Windows and iOs it is 
>> better.
>>
>> Does anyone have an idea on how to improve that?
>>
>>
>> Any help is really appreciated.
>> Thanks a lot!
>>
>
> ___
> Interest mailing list
> Interest@qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>
>


 --
 Best regards,
 Vlad

>>>
>>> ___
>>> Interest mailing list
>>> Interest@qt-project.org
>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>
>>>
>>
> ___
> Interest mailing list
> Interest@qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>
>
__

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-11 Thread Bernhard B

Hi Andy,

many thanks for your response! I am also using a QAbstractListModel-derived
class that gets exposed to the QML world which contains the images.

Yesterday I started to resize the images before feeding them to the
ListModel. According to the QML Profiler the delegate gets now created a
little bit faster, but fast scrolling is still a little bit sluggish. Today
I probably will play a little bit with different image codecs to see if
those have an impact. Currently I am using *.png files often which is
probably not the best choice.

Thanks a lot for your input, really appreciated!

Bernhard

Am Freitag, 11. August 2017 schrieb Andy :

> Bernhard:
>
> I don't use QML, but in my application I use a QAbstractItemModel-derived
> class and a QTreeView-derived class to display image thumbnails in the
> view. The way I make it speedy is to save the image as a thumbnail so the
> view items don't need to resize the image data at all.
>
> Maybe you could save a thumbnail of an appropriate size when you're adding
> them to your model?
>
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney 
>
>
> On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B  > wrote:
>
>> Hi Vlad,
>>
>> you mean the QQuickAsyncImageProvider? That one sounds really promising.
>> Will definitely try that out. Many thanks for the suggestion!
>>
>> Bernhard
>>
>> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>>
>>> threaded image provider might help
>>>
>>> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B 
>>> wrote:
>>>
 Hi,

 yesterday, I also tried to replace the Base64ImageProvider approach
 with a subclassed QQuickPaintedItem which paints the image in it's paint
 method. I imagined that this approach might be faster es no bade64 decoding
 needs to be done. But unfortunately it looks like as it's performing even
 worse that way.

 Bernhard

 Am Mittwoch, 9. August 2017 schrieb Bernhard B :

> Hi,
>
> I would need some help from you guys on how to improve the ListView's
> performance. The problem is, that scrolling through my ListView sometimes
> feels a little bit sluggish.
>
> If I only display some text in the ListView's delegate I can scroll
> smoothly through my list. But as soon as there is a picture in the
> ListView's delegate I notice that I can't scroll smoothly through my list
> anymore. That's especially noticable if I try to scroll fast through my
> list. Every time I hit a picture while scrolling through the list I can 
> see
> that there is a noticable delay until the picture is fully loaded. My
> assumption is, that those pictures are the reason why he scrolling feels 
> so
> sluggish.
>
> My application currently works like this:
>
> * load 20 pictures via REST (pictures are base64 encoded)
> * populate list model
> * the Image component in the delegate uses a Base64ImageProvider (self
> written) to access the model's base64 encoded content and displays the 
> image
> * if the user scrolls past a threshold another batch of base64 encoded
> pictures is fetched from the server
>
> I also found this document: http://doc.qt.io/qt-
> 5/qtquick-performance.html#rendering and tried to apply as much as
> possible. In detail I applied the following changes:
>
> * removed complex bindings from delegate
> * set sourceSize property for Image
> * increased cacheBuffer a bit
> * profiled with QML profiler and improved a few things
>
> But still, the ListView feels a bit sluggish. The strange thing is,
> that it's most noticable on Android whereas on Windows and iOs it is 
> better.
>
> Does anyone have an idea on how to improve that?
>
>
> Any help is really appreciated.
> Thanks a lot!
>

 ___
 Interest mailing list
 Interest@qt-project.org
 http://lists.qt-project.org/mailman/listinfo/interest


>>>
>>>
>>> --
>>> Best regards,
>>> Vlad
>>>
>>
>> ___
>> Interest mailing list
>> Interest@qt-project.org
>> 
>> http://lists.qt-project.org/mailman/listinfo/interest
>>
>>
>
___
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-11 Thread Andy

Bernhard:

I don't use QML, but in my application I use a QAbstractItemModel-derived
class and a QTreeView-derived class to display image thumbnails in the
view. The way I make it speedy is to save the image as a thumbnail so the
view items don't need to resize the image data at all.

Maybe you could save a thumbnail of an appropriate size when you're adding
them to your model?

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney 

On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B  wrote:

> Hi Vlad,
>
> you mean the QQuickAsyncImageProvider? That one sounds really promising.
> Will definitely try that out. Many thanks for the suggestion!
>
> Bernhard
>
> Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :
>
>> threaded image provider might help
>>
>> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B  wrote:
>>
>>> Hi,
>>>
>>> yesterday, I also tried to replace the Base64ImageProvider approach with
>>> a subclassed QQuickPaintedItem which paints the image in it's paint method.
>>> I imagined that this approach might be faster es no bade64 decoding needs
>>> to be done. But unfortunately it looks like as it's performing even worse
>>> that way.
>>>
>>> Bernhard
>>>
>>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>>
 Hi,

 I would need some help from you guys on how to improve the ListView's
 performance. The problem is, that scrolling through my ListView sometimes
 feels a little bit sluggish.

 If I only display some text in the ListView's delegate I can scroll
 smoothly through my list. But as soon as there is a picture in the
 ListView's delegate I notice that I can't scroll smoothly through my list
 anymore. That's especially noticable if I try to scroll fast through my
 list. Every time I hit a picture while scrolling through the list I can see
 that there is a noticable delay until the picture is fully loaded. My
 assumption is, that those pictures are the reason why he scrolling feels so
 sluggish.

 My application currently works like this:

 * load 20 pictures via REST (pictures are base64 encoded)
 * populate list model
 * the Image component in the delegate uses a Base64ImageProvider (self
 written) to access the model's base64 encoded content and displays the 
 image
 * if the user scrolls past a threshold another batch of base64 encoded
 pictures is fetched from the server

 I also found this document: http://doc.qt.io/qt-
 5/qtquick-performance.html#rendering and tried to apply as much as
 possible. In detail I applied the following changes:

 * removed complex bindings from delegate
 * set sourceSize property for Image
 * increased cacheBuffer a bit
 * profiled with QML profiler and improved a few things

 But still, the ListView feels a bit sluggish. The strange thing is,
 that it's most noticable on Android whereas on Windows and iOs it is 
 better.

 Does anyone have an idea on how to improve that?

 Any help is really appreciated.
 Thanks a lot!

>>>
>>> ___
>>> Interest mailing list
>>> Interest@qt-project.org
>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>
>>>
>>
>>
>> --
>> Best regards,
>> Vlad
>>
>
> ___
> Interest mailing list
> Interest@qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>
>
___
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-11 Thread Bernhard B

Hi Vlad,

you mean the QQuickAsyncImageProvider? That one sounds really promising.
Will definitely try that out. Many thanks for the suggestion!

Bernhard

Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :

> threaded image provider might help
>
> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B  > wrote:
>
>> Hi,
>>
>> yesterday, I also tried to replace the Base64ImageProvider approach with
>> a subclassed QQuickPaintedItem which paints the image in it's paint method.
>> I imagined that this approach might be faster es no bade64 decoding needs
>> to be done. But unfortunately it looks like as it's performing even worse
>> that way.
>>
>> Bernhard
>>
>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>
>>> Hi,
>>>
>>> I would need some help from you guys on how to improve the ListView's
>>> performance. The problem is, that scrolling through my ListView sometimes
>>> feels a little bit sluggish.
>>>
>>> If I only display some text in the ListView's delegate I can scroll
>>> smoothly through my list. But as soon as there is a picture in the
>>> ListView's delegate I notice that I can't scroll smoothly through my list
>>> anymore. That's especially noticable if I try to scroll fast through my
>>> list. Every time I hit a picture while scrolling through the list I can see
>>> that there is a noticable delay until the picture is fully loaded. My
>>> assumption is, that those pictures are the reason why he scrolling feels so
>>> sluggish.
>>>
>>> My application currently works like this:
>>>
>>> * load 20 pictures via REST (pictures are base64 encoded)
>>> * populate list model
>>> * the Image component in the delegate uses a Base64ImageProvider (self
>>> written) to access the model's base64 encoded content and displays the image
>>> * if the user scrolls past a threshold another batch of base64 encoded
>>> pictures is fetched from the server
>>>
>>> I also found this document: http://doc.qt.io/qt-
>>> 5/qtquick-performance.html#rendering and tried to apply as much as
>>> possible. In detail I applied the following changes:
>>>
>>> * removed complex bindings from delegate
>>> * set sourceSize property for Image
>>> * increased cacheBuffer a bit
>>> * profiled with QML profiler and improved a few things
>>>
>>> But still, the ListView feels a bit sluggish. The strange thing is, that
>>> it's most noticable on Android whereas on Windows and iOs it is better.
>>>
>>> Does anyone have an idea on how to improve that?
>>>
>>>
>>> Any help is really appreciated.
>>> Thanks a lot!
>>>
>>
>> ___
>> Interest mailing list
>> Interest@qt-project.org
>> 
>> http://lists.qt-project.org/mailman/listinfo/interest
>>
>>
>
>
> --
> Best regards,
> Vlad
>
___
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-10 Thread Vlad Stelmahovsky

threaded image provider might help

On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B  wrote:

> Hi,
>
> yesterday, I also tried to replace the Base64ImageProvider approach with a
> subclassed QQuickPaintedItem which paints the image in it's paint method. I
> imagined that this approach might be faster es no bade64 decoding needs to
> be done. But unfortunately it looks like as it's performing even worse that
> way.
>
> Bernhard
>
> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>
>> Hi,
>>
>> I would need some help from you guys on how to improve the ListView's
>> performance. The problem is, that scrolling through my ListView sometimes
>> feels a little bit sluggish.
>>
>> If I only display some text in the ListView's delegate I can scroll
>> smoothly through my list. But as soon as there is a picture in the
>> ListView's delegate I notice that I can't scroll smoothly through my list
>> anymore. That's especially noticable if I try to scroll fast through my
>> list. Every time I hit a picture while scrolling through the list I can see
>> that there is a noticable delay until the picture is fully loaded. My
>> assumption is, that those pictures are the reason why he scrolling feels so
>> sluggish.
>>
>> My application currently works like this:
>>
>> * load 20 pictures via REST (pictures are base64 encoded)
>> * populate list model
>> * the Image component in the delegate uses a Base64ImageProvider (self
>> written) to access the model's base64 encoded content and displays the image
>> * if the user scrolls past a threshold another batch of base64 encoded
>> pictures is fetched from the server
>>
>> I also found this document: http://doc.qt.io/qt-
>> 5/qtquick-performance.html#rendering and tried to apply as much as
>> possible. In detail I applied the following changes:
>>
>> * removed complex bindings from delegate
>> * set sourceSize property for Image
>> * increased cacheBuffer a bit
>> * profiled with QML profiler and improved a few things
>>
>> But still, the ListView feels a bit sluggish. The strange thing is, that
>> it's most noticable on Android whereas on Windows and iOs it is better.
>>
>> Does anyone have an idea on how to improve that?
>>
>>
>> Any help is really appreciated.
>> Thanks a lot!
>>
>
> ___
> Interest mailing list
> Interest@qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>
>


-- 
Best regards,
Vlad
___
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest

Re: [Interest] Improve ListView scrolling performance (many pictures)

2017-08-10 Thread Bernhard B

Hi,

yesterday, I also tried to replace the Base64ImageProvider approach with a
subclassed QQuickPaintedItem which paints the image in it's paint method. I
imagined that this approach might be faster es no bade64 decoding needs to
be done. But unfortunately it looks like as it's performing even worse that
way.

Bernhard

Am Mittwoch, 9. August 2017 schrieb Bernhard B :

> Hi,
>
> I would need some help from you guys on how to improve the ListView's
> performance. The problem is, that scrolling through my ListView sometimes
> feels a little bit sluggish.
>
> If I only display some text in the ListView's delegate I can scroll
> smoothly through my list. But as soon as there is a picture in the
> ListView's delegate I notice that I can't scroll smoothly through my list
> anymore. That's especially noticable if I try to scroll fast through my
> list. Every time I hit a picture while scrolling through the list I can see
> that there is a noticable delay until the picture is fully loaded. My
> assumption is, that those pictures are the reason why he scrolling feels so
> sluggish.
>
> My application currently works like this:
>
> * load 20 pictures via REST (pictures are base64 encoded)
> * populate list model
> * the Image component in the delegate uses a Base64ImageProvider (self
> written) to access the model's base64 encoded content and displays the image
> * if the user scrolls past a threshold another batch of base64 encoded
> pictures is fetched from the server
>
> I also found this document: http://doc.qt.io/qt-
> 5/qtquick-performance.html#rendering and tried to apply as much as
> possible. In detail I applied the following changes:
>
> * removed complex bindings from delegate
> * set sourceSize property for Image
> * increased cacheBuffer a bit
> * profiled with QML profiler and improved a few things
>
> But still, the ListView feels a bit sluggish. The strange thing is, that
> it's most noticable on Android whereas on Windows and iOs it is better.
>
> Does anyone have an idea on how to improve that?
>
>
> Any help is really appreciated.
> Thanks a lot!
>
___
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

Re: [Interest] Improve ListView scrolling performance (many pictures)

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