QTextList constructor question

['milimoj]

Ok. Then I'm missing something or I'm looking in wrong direction.
Please, help me where to start from? I just don't see it

What classes should I look for to implement my own widget with scene with multiple QGraphicTextItems and other graphic items on it. I clearly can see how to implement that when I have only one QGraphictextitems, but when I wanth to use more then one item in scene everything goes to hell.

For instance what clases to start from for my first question: to create multilayer numerized bullet list that propagates numbering through all items in scene an to be able to catch when text blocks in any of lists in any of documents are changed, removed, moved, added, inserted... to list... so I can refresh numeration. I just don't see anything that can help me. What class to use to controll QTextBlocks in more then one QGraphictextitems?
Can I use some standard Qt class for bullets and numbering or I must insert symbols to text by my self and control them, and what to use to insert graphic symbols (I guess some QFrames.... with bullets or e.g. 1.1.2. text ) in front of text in block.

Example:

Document 1:

1. Text something...
1.1.2 Some nested text
....
....

Document 2:

2. Text somenting 2
2.1 Nested text in 2
.....

I know I'm boring but I am stuck with this and documentation and examples are hard to find for this case.

Thanks, for help

[anda_skoa]

Please, help me where to start from?

If the documentation or examples doesn't cover something, the source of Qt itself an numerous FOSS projects using Qt are available for studying.

For instance what clases to start from for my first question: to create multilayer numerized bullet list that propagates numbering through all items in scene an to be able to catch when text blocks in any of lists in any of documents are changed, removed, moved, added, inserted... to list... so I can refresh numeration.

Your first question was why there is no constructor in QTextList.
For that new question you could look into modelling the data in a list or tree and displaying each item.

What class to use to controll QTextBlocks in more then one QGraphictextitems?

Most classes can have multiple instances. If you find a class that allows you to manipulate text in one graphics item, the same should be true for any other text item.

Cheers,
_

['milimoj]

Yes. We have pushed the subject to my question from other post. Sorry for that, but this is interesting subject.... at least for me and I have a headache because of it.

Ok. I had idea of creating a tree of my own classes too but I do not understand how to keep list of "some kind of pointers" to paragraphs (I must be abale to catch when someone change something in paragraph in any of documents on scene - as I need to prevent deleting og bullet simbols, update numbering...). As I understood QTextBlock objects does not exists all the time. They are created when neaded for representation of information about paragraph (- correct me if I am wrong, please -) and I can not keep pointers to these objects. Is there any class object that represent paragraph that is always accesable and can be reimplemented.

Only thing I could think of is to create QTextBlockGroup in each of Documents on scene and to keep pointers to them in my class outside the documents. Then, I should use connections to blockRemoved, blockInserted... signals from QTextBlockGroup-s.... But this semas to be very ugly programming. Is there some other way?

Thanks for your patience, again

[anda_skoa]

What part of your application is using the QTextDocument API to change the data?
Can't you just add signalling there?

Cheers,
_

['milimoj]

What part of your application is using the QTextDocument API to change the data?
Can't you just add signalling there?

Cheers,
_

Yes I can. Problem is that I must use some of existing clases for textblock control in QTextDocument and then again catch signals in some extern class to provide "real" logic for text parsing. In the end this will be my solution. That should work but solution is "ugly" for my taste.
If only there was some class similar to QTextBlock with signals it would be easier and much less coding.


@wysota
Thanks for replay. I will take a look in QAbstractTextDocumentLayout documentation, but code is already present and I'm not sure if I'll be able to change it much. I just wanted to add bullet list functionality to it, with nesting of numbering lists.

[wysota]

Ok. I had idea of creating a tree of my own classes too but I do not understand how to keep list of "some kind of pointers" to paragraphs

There is no need to develop your own set of classes. The problem is not here -- QTextDocument and family is a set of classes for keeping the data related to text documents and you can extend it with your own subclasses. Your problem seems to rather be with rendering. Thus it seems likely that you should implement a custom text layout engine (see QAbstractTextDocumentLayout) which uses existing QTextDocument infrastructure.

['milimoj]

There is no need to develop your own set of classes. The problem is not here -- QTextDocument and family is a set of classes for keeping the data related to text documents and you can extend it with your own subclasses. Your problem seems to rather be with rendering. Thus it seems likely that you should implement a custom text layout engine (see QAbstractTextDocumentLayout) which uses existing QTextDocument infrastructure.

You are right. I have looked at the QAbstractTextDocumentLayout documentation and it seams that I should implement my own TextList class which will return desired textItems and reimplement QAbstractTextDocumentLayout. But, if I was confused with relations between QTextDocument and QGraphicTextItem then I'm lost here. From source code it seams like I must use something like my own drawListItem method in QAbstractTextDocumentLayout for drawing list items, but that is part of QTextDocumentLayoutPrivate and I can't reimplement it. How should I do this? As I can see there are only few virtual methods in QAbstractTextDocumentLayout.

[wysota]

QTextObjectInterface for each object type will provide a method for rendering that object in the document.

['milimoj]

Ok.

1. I have to create my own class similar to QTextList, which will take care of QTextBlocks added into list and about list style, indent.... That class should be reimplemented QTextBlockGroup and QTextObjectInterface .
2. Then I should implement drawObject(...) of that class where I would draw some bullet characters in front of selected QTextBlock (like in drawListItem() from QTextDocumentLayoutPrivate) and add selected blocks into QTextBlockGroup.
3. On the end register that class as handler for my object type in document constructor.

4. Now.... When "create bullet list" button is triggered how I should activate that drawObject, and how to call it again to re-draw bullet character when text from text block is moved, deleted....?
I do not see how I should redraw all bullets in list when block is deleted, and how to prevent editing of bullet characters from application (e.g. inserting SPACE-s before bullet symbol).
Also, how to delete bullets when "create bullet list" button is toggled to off if bullets are edited?

This approach still seams wrong to me. As I can see in QTextDocumentLayout source code, bullet drawing is called from drawBlock function.

['milimoj]

@wysota
Thanks for help. QTextObjectInterface was right choice. It is not easy to implement all functionality I need but it is the correct way to do it. I had to do a lot of coding but this seams to be a solution I need.

I must notice few things here :

1. Documentation for Qt is really bad. There should be more examples, especially for more complex usage. I had to look a lot of code examples on the net and still could not find examples of how to use all functions from class in the way they could be used.
We need more instructions about what will happen when some parameter is set, changed.... What signals shall be emited... Who will take the control... What fields in view shall be repainted... I had to read dozens of pages just to use one function from class, because in class documentation I found only few words about that functions. Please add tabs for more explanation and examples in documentation.

2. It seems that a too little new functionality are added to existing classes with new releases of Qt. All of this job could be done in few minutes if only QTextList class had function for setStartValue(int), which seems to be so natural. In fact I took a look in source code of QTextDocumentLayout and QTextList and souch expansion is a trivial job. Just one offset to add when counting index if block in list.

Again, thanks for help