[graf2d] Fix Setting window size in batch mode

[rlalik]

The current implementation doesn't make sense at all? Was it some accidentally committed code?

@linev It was your commit? Was it mistake?

771c44692bcb graf2d/gpad/src/TCanvas.cxx (Sergey Linev      2023-07-06 16:42:42 +0200 2151)    if (fBatch && !IsWeb())
d023aecbdda4 graf2d/gpad/src/TCanvas.cxx (Sergey Linev      2020-05-04 19:06:00 +0200 2152)       SetCanvasSize((ww + fCw) / 2, (wh + fCh) / 2);
d023aecbdda4 graf2d/gpad/src/TCanvas.cxx (Sergey Linev      2020-05-04 19:06:00 +0200 2153)    else if (fCanvasImp)
d023aecbdda4 graf2d/gpad/src/TCanvas.cxx (Sergey Linev      2020-05-04 19:06:00 +0200 2154)       fCanvasImp->SetWindowSize(ww, wh);

• tested changes locally
• updated the docs (if necessary)

[linev]

@rlalik

No, this kind of calculation was there since a while. See:

https://github.com/root-project/root/blob/v6-24-00-patches/graf2d/gpad/src/TCanvas.cxx#L2201

I only add special handling for web case

[linev]

I have no idea why code looks like this but I prefer not to touch it.
SetWindowSize has no real meaning for the batch - one should use SetCanvasSize instead.

[rlalik]

Well, in the batch mode there is indeed no window but this code changes the canvas size. And I would say, for compatibility reasons, should work properly. Otherwise macro run in batch mode will produce wrongly sized canvases.

[ferdymercury]

related: #11004 and c3de92f