QTextDocument and insertImage

[bunjee]

Hey there,

I'm using a QTextDocument and QTextCursor::insertImage.
The goal is to remplace : - ) keywords by a :) in the text document.



ZePictureWidget * test = new ZePictureWidget("zeData/zeSmileys/Crying.png");
document()->addResource(QTextDocument::ImageResource, QUrl("test"), test->getPixmap());


//================================================== ===========================
//================================================== ===========================

void ZeSmileyController::scanSmiley(QTextDocument & textDocument,
const QString & smiley,
const QString & path)
{
QTextCursor textCursor;
textCursor = textDocument.find(smiley);
while (textCursor.isNull() == false)
{
textCursor.deleteChar();
textCursor.insertImage("test");

textCursor = textDocument.find(smiley);
}
}

Unfortunately when replacing 100 smileys it's very slow, it's like the Cursor is reloading the smileys over and over again.

Any idea?

[wysota]

Take a look at QTextDocument::addResource.

[bunjee]

1.
ZePictureWidget * test = new ZePictureWidget("zeData/zeSmileys/Crying.png");
2.
document()->addResource(QTextDocument::ImageResource, QUrl("test"), test->getPixmap());

I've already used that, did I miss something?

[wysota]

Oh, no... sorry, I read your post too fast and missed the first chunk of code. Did you try profiling the code to find the bottleneck?

[bunjee]

//================================================== ===========================
//================================================== ===========================

void ZeSmileyController::InsertSmiley(QTextDocument & textDocument)
{
ZeLog::get()->AddLine("ZeSmileyController - insertSmiley\n");

QMapIterator<QString, QString> i(mSmileyMap);

while (i.hasNext())
{
i.next();
scanSmiley(textDocument, i.key(), i.value());
}
}

//================================================== ===========================
//================================================== ===========================

void ZeSmileyController::scanSmiley(QTextDocument & textDocument,
const QString & smiley,
const QString & path)
{
QTextCursor textCursor;
textCursor = textDocument.find(smiley);
while (textCursor.isNull() == false)
{
textCursor.insertImage(path); // <<< THIS IS SLOW

textCursor = textDocument.find(smiley);
}
}

Yes : textCursor.insertImage(path); is the line slowing down everything.

[wysota]

How about profiling deeper - going into Qt code too?

[jpn]

Do you replace several smileys at time? Perhaps you should break the QTextDocument-QTextEdit relation meanwhile? I guess QTextEdit ends up doing a lot of unnecessary updates upon every change to the document.

[bunjee]

Yes I'm doing a lot of smiley replacement at a time, since I'm progressively refreshing a text bubble as if somebody was typing on the keyboard.

how would you break the QTextDocument-QTextEdit relation meanwhile?

Thanks.

[jpn]

Whatever it takes to make QTextEdit ignorant of those updates. Block signals, remove and set the document back or modify a copy of the document. Also, make sure you have things like undo-redo-stack disabled.

[wysota]

It might be wise to replace the smileys as the user is typing the text - this way you replace only one at the time and only check the current paragraph instead of the whole text that gets bigger and bigger as one types. If you work on a document which already exists, be sure to replace the smileys before you associate the text with a widget as J-P suggests - this way the text will not have to be relaid again and again.

[bunjee]

Thanks jpn and wysota,

This implementation is working way faster :


//================================================== ===========================
//================================================== ===========================

void ZeParagraphWidget::setHtml(const QString & text, bool smiley)
{
//QTextEdit::setHtml(text);

QTextDocument * temp = document()->clone();

temp->setHtml(text);
if (smiley)
{
ZeSmileyController::get()->InsertSmiley(*temp);
setDocument(temp);
}
emit paragraphUpdate();
}

I don't seem to have to delete my old document after doing a setDocument, do you confirm on that ?

[jpn]

I don't seem to have to delete my old document after doing a setDocument, do you confirm on that ?
As a practice, you could open src/gui/widgets/qtextedit.cpp and confirm it yourself. It's wonderful to have sources, isn't it?

PS. src/gui/text/qtextcontrol.cpp ;)

[wysota]

A general rule is that a widget or other component will delete the object it doesn't use anymore if it is its child in terms of QObject hierarchy.

[bunjee]

And Qt doc confirms this :


void QTextEdit::setDocument ( QTextDocument * document )
Makes document the new document of the text editor.
The parent QObject of the provided document remains the owner of the object. If the current document is a child of the text editor, then it is deleted.
See also document().