rendering individual elements of drawings ...

[Marco Cecchetti]

Hi Armin,


Il 09/07/24 22:26, Michael Meeks ha scritto:
> Hi Armin,
> 
>      Currently we're in a bit of a rush; but we have some code that can 
> render individual elements of a slide; and I believe we're currently 
> doing this by rendering via to a GDI meta-file and then re-rendering to 
> pixels.
> 
>      I would expect that we could do this rather better in future by 
> rendering with primitives directly to an outputdevice of some kind.
> 
>      Would appreciate a quick poke at Marco's code to see how easy that 
> is to do - at least if it doesn't slow us down coding time-wise =)
> 
>      Marco - do you have some pointers ?

I'm trying to subdivide a slide in layers and render them separately: 
background, master page objects, static shapes, animated shapes, etc.
In order to do so I adapted the rendering code in the slideshow module 
which uses GDI meta-file.
For instance in 
https://git.libreoffice.org/core/+/refs/heads/distro/collabora/co-24.04/slideshow/source/engine/slide/slideimpl.cxx, 
you can see LOKSlideRenderer::createLayerBitmap and 
LOKSlideRenderer::renderLayerBitmapImpl methods. In the latter the call 
to pBitmap->draw(pDevicePixelCanvas) resolves in executing meta actions 
belonging to a gdi meta-file. In the end it is the same done for 
rendering the bitmap when the slideshow is running in Impress: 
https://git.libreoffice.org/core/+/refs/heads/distro/collabora/co-24.04/slideshow/source/engine/slide/slideimpl.cxx#942.
I'm not sure at which stage this GDI meta-file is generated and if it's 
possible to render an XShape instance in another way. In fact the 
slideshow module is very isolated wrt the other LibreOffice modules.

Thanks,
   Marco