Cleanup: ED_view3d_win_to_delta & ED_view3d_calc_zfac usage

- Rename ED_view3d_win_to_delta `mval` argument to `xy_delta` as it
  as it was misleading since this is an screen-space offset not a region
  relative cursor position (typical use of the name `mval`).
  Also rename the variable passed to this function which also used the
  term `mval` in many places.
- Re-order the output argument of ED_view3d_win_to_delta last.
  use an r_ prefix for return arguments.
- Document how the `zfac` argument is intended to be used.
- Split ED_view3d_calc_zfac into two functions as the `r_flip` argument
  was only used in some special cases.

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/transform/transform.c b/source/blender/editors/transform/transform.c
index b006b13d217..67b0d5c85ac 100644
--- a/source/blender/editors/transform/transform.c
+++ b/source/blender/editors/transform/transform.c
@@ -177,8 +177,8 @@ void convertViewVec(TransInfo *t, float r_vec[3], double dx, double dy)
       r_vec[1] = dy;
     }
     else {
-      const float mval_f[2] = {(float)dx, (float)dy};
-      ED_view3d_win_to_delta(t->region, mval_f, r_vec, t->zfac);
+      const float xy_delta[2] = {(float)dx, (float)dy};
+      ED_view3d_win_to_delta(t->region, xy_delta, t->zfac, r_vec);
     }
   }
   else if (t->spacetype == SPACE_IMAGE) {