pstoedit objects distorted if edited with pdf2svg and vice versa

[sizmailov]

Steps to reproduce:

1. Create TexText object with pstoedit backend
2. Apply skew/rotation to TexText object
3. Open TexText object with pdf2svg backend, click "Save" button.

Affected systems:

• Ubuntu 18.04.1
  • pstoedit: 3.70-5
  • ghostscript: 9.25~dfsg+1
  • pdf2svg: 0.2.3-1
  • textext 0.8.1
  • inkscape 0.92.3
• Ubuntu 14.04.5
  • pstoedit: 3.62
  • ghostscript: 9.25~dfsg+1
  • pdf2svg: 0.2.2-1
  • textext 0.8.1
  • inkscape 0.48.4

Here is and example:

     $$\lim_{x \to 0} \frac{\sin(x)}{x} = 1$$

Edit 1: Add system info
Edit 2: Test bug on Ubuntu 14.04

[sizmailov]

The solution:
Change

textext/textext.py

Lines 1137 to 1141 in 0164a57

	old_transform = ref_node.get_attrib('transform')
	composition = st.parseTransform(old_transform, scale_transform)
	# Account for vertical flipping of pstoedit nodes when recompiled via pdf2svg and vice versa
	composition = self._check_and_fix_transform(ref_node, composition)

to

        old_transform = st.parseTransform(ref_node.get_attrib('transform'))

        # Account for vertical flipping of pstoedit nodes when recompiled via pdf2svg and vice versa
        revert_flip = ... 
        composition = st.composeTransform(old_transform, revert_flip)

        composition = st.composeTransform(scale_transform, composition)

where revert flip is [[1,0,0],[0,1,0]] if converter is same and [[1,0,0],[0,-1,0]] otherwise

I propose to change signature and name of _check_and_fix_transform to return such matrix.