Creating a new drawing device based on QPaintEngine + QPaintDevice ...

Yuri34

Good day !

Ooo! Thank you so much for the tip on the options for counseling ! I will try ...

As for debugging the code and getting a clearer picture of how Qt classes work - yes , of course ! That 's what I 'm doing ! But so far the results are insignificant ! :)

But in any case - thank you for your advice !!!

Sincerely, Yuri.

Yuri34

Good day !

And so ! :)
Part of my weekend was devoted to trying to solve my puzzle ! :)

As a result :

it is clear that SVG prevents my code from converting files - this is transform="translate(... ...)" ! Files where there are no transformations , as they were the success that I had from the very beginning ! :)
But I am absolutely sure that this is just because I use the methods of the Qt Paint System classes poorly ! Since when working with , for example , QImage , the same files are drawn perfectly !
I became even more convinced that it is necessary to seek competent help from specialists who work with SVG and can advise on the methods of the Qt Paint System classes or understand the source code. :)))
I looked very carefully at the ICS resource! Judging by the information on their website, they are just VERY competent in Qt (just cool)! And of course I wrote to them ! I even signed up for a free QML course :), but unfortunately I have not yet received an answer both to the desire to learn from them and to the question I asked! I'll be waiting...
And finally - special thanks to SGaist - for advising me the ICS resource! And in general for the reaction to my questions ! :)

Sincerely, Yuri.

Yuri34

Good day !

Can one of my colleagues tell me how to properly overload the methods virtual void QPaintEngine::updateState(const QPaintEngineState &state) and virtual int QPaintDevice::metric(PaintDeviceMetric metric) const ?

Or where can I see examples of their overload ?

Sincerely, Yuri.

JonB

@Yuri34 said in Creating a new drawing device based on QPaintEngine + QPaintDevice ...:

properly overload the methods

Do you mean overload? Overload means write a new version of the QPaintEngine::updateState() method which takes different parameters from the current one. In which case you just write that. Is this what you want?

Or did you mean override instead? Override means write your own version of the existing virtual methods with the same parameters as the existing one. Is that actually what you want? In which case:

// in yourclass.h
class YourClass : public QPaintEngine
{
    virtual void updateState(const QPaintEngineState &state) override;
}

// in yourclass.cpp
void YourClass::updateState(const QPaintEngineState &state)
{
    ...
    // and if you need to call the original base class implementation
    QPaintEngine::updateState(state);
    ...
}

Yuri34

Oh, thanks !

Apparently I explained it incorrectly ! :)
What is overloading and how syntactically it is formed in c++/Qt, I perfectly imagine!
I am interested in what and what is initialized in the virtual methods I mentioned ?

In order not to insert pieces of code here, I will mention once again the link to the repo-gitlab - https://gitlab.com/z34x/codemaker.git !

::metric() at the end of the file - FCPaintDevice
::updateState() at the end of the file - FCPaintEngine

I 'm doing exactly wrong !!!

My question is how to properly design these virtual methods so that the svg file is parsed correctly ? :)

Moreover, pay attention to the virtual void QPaintEngine::updateState(const QPaintEngine State &state) = 0 ! abstract method !!!

Sincerely, Yuri.

Yuri34

Good day !

Ooook ! :)
It seems like the problem is not frequent for developers or not relevant !

Best regards, Yuri.

Yuri34

The next question ...

Is there a method in the Qt Painting System classes that allows you to determine the intersection of primitives when drawing on QPaintDevice ?

Best regards, Yuri.

Yuri34

OooK!
I'll answer myself (maybe it's interesting to someone besides me) !
Of course there is - intersect(..)/intersected(..) !!!

Best regards, Yuri.

Yuri34

I have one more question ! :)
Who knows how the QPaintDevice scaling system works ?
It is the theory that interests me !
I don't understand what needs to be done to implement full-fledged scaling except overloading and implementing my own instance of QPaintDevice::metric(..) !

Best regards, Yuri.

Yuri34

Good afternoon!

Who can help with understanding how to work with QPaintDevice::metric(..) ?
I have already read and tried everything that is written in the documentation, of course ! :)

QPaintDevice::PdmWidth: - width in svg storage units; (as far as I understand in pixels) (we take from QSvgRenderer::defaultDevice(..))
QPaintDevice::PdmHeight: - height similarly
QPaintDevice::PdmWidthMM: - width in mm (we take from QSvgRenderer::viewBox(..))
QPaintDevice::PdmHeightMM: - height is similar
QPaintDevice::PdmNumColors: - the number of colors for the device being created (a constant from the device requirements) - let it be, for example, 16
QPaintDevice::PdmDepth: - the number of bit planes (by docks) - it's not clear here - it's a bit per color or something Incomprehensible
QPaintDevice::PdmDpiX: - dpi X logical - it's not clear to me here!!!
QPaintDevice::PdmPhysicalDpiX: - dpi X physical - similarly!!!
QPaintDevice::PdmDpiY: - dpi Y logical - similar !!!
QPaintDevice::PdmPhysicalDpiY: - dpi Y physical - similar !!!
QPaintDevice::pdmdevicepixelratio: - the ratio of what to what is Incomprehensible
QPaintDevice::PdmDevicePixelRatioScaled: - similar!!!

I 'm sure I don 't understand the idea that is embedded in class management ! If someone has experience working with this method and , accordingly, with the class , I will be very grateful for any hints !

Sincerely, Yuri.
PS: It is clear that you can write your crutches to this class and make it generate what you need ! But I would like to understand exactly the logic that the developers laid down.