[Kdenlive-devel] Title rotation

[Till Theato]

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On 01/05/2010 12:39 AM, jb wrote:
> On Monday 04 January 2010 22:51:56 Till Theato wrote:
>> Rotation on all axes adds the possibility to "integrate" a title into
>> the video. You can make it look like the text was written on a object in
>> the video.
>>
>> Might this be worth advancing the syntax of kdenlive titles so it can
>> represent rotation?
> 
> Hi!
> 
> Sure, the kdenlive title syntax must be updated to support new features. 
> But you must be aware of one important issue in the design of the titler 
> module:
> 
> Kdenlive produces xml data, and then, the MLT kdenlivetitle producer (in 
> modules/qimage) creates a QGraphicsScene and loads the xml into it. 
> 
> The big problem is that using a QGraphicsScene like that in an MLT module is 
> not really supported by Qt. 
> 
> You are supposed to have a full Qt QApplication to use a QGraphicsScene, but 
> when MLT is used inside Kdenlive, we cannot create a new QApplication because 
> MLT is running in a thread of Kdenlive. 
> 
> So we re-use the QApplication from Kdenlive, but it is in a different thread 
> and that leads to some issues, for example using QPixmap crashes the MLT 
> kdenlivetitle producer...
> 
> so before going too far, I think you should first try to check that the 
> features you want to implement work inside the MLT kdenlivetitle producer...

Thanks for your background information!

The attached patch works without changes on the MLT side.

It should basically work, but there are some problems i wasn't able to fix:
Resizing rotated items with the mouse doesn't work very well.
When loading a title, the zoom of rotated items is wrong.
Help is welcome.


I'm not sure what is done in TitleWidget::slotValueChanged as it only
applies to images. Could someone please explain the calculations and
their meaning to me?


regards ttill
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