Created attachment 147821 [details]
Shape with arcTo, that is wrongly rendered
Open attached document. Notice, the first slide seems to be empty. But the Navigator shows, that there is an element. The second slide has an image, how the shape is rendered in PowerPoint.
Created attachment 147822 [details]
custoomshapeproperties.cxx lines 240 and 2241 look very suspicious to me. If I comment them out, the shape is rendered correctly.
If the viewBox is forced to width=0 and height=0 here, the members nCoordWidthG and nCoordHeightG will become zero too by ApplyShapeAttributes() later on. And thus members nCoordWidth and nCoordHeight become zero too in EnhancedCustomShape2d::SetPathSize() in EnhancedCustomShape2d.cxx.
But I'm not familiar with pptx import and cannot estimate, whether such change would break something in other areas.
Confirmed using LO 188.8.131.52 / Windows 7.
The mentioned lines were added in the following commit.
author Muthu Subramanian <firstname.lastname@example.org> 2013-12-27 19:59:22 +0530
committer Muthu Subramanian <email@example.com> 2013-12-27 19:59:22 +0530
fdo#72998: Custom shapes have improper size.
Ah, then first a better solution for bug 72998 has to be found. The current "trick" to force viewBox to "0 0 0 0" is also reason for bug 76334.