class/Widget/geometry.c: Allow reconfiguring grid cells

[HaraldJoerg]

I just added a comment to commit 81d941c. This commit fixes the segfault for "mixed" widget configuration, but also prohibits calling grid_configure twice for the same cell. The docs say:

If any of the slaves are already managed by the geometry manager then any unspecified options for them retain their previous values rather than receiving default values.

I was actually using that capability: In my application I configure the grid rows from top to bottom. In each row, the cells immediately get their col assigned. Only after the last row is defined, I assign the row attribute from top to bottom. The Prima grid rows are numbered from bottom to top, so I need to know the number of rows before assigning the row value for the topmost row.

If there is a technical reason for the extra check, please reject the PR. The sentence in the documentation should be removed, and I'll reorder my code so that I can set row and column in one go.

[dk]

That check is needed actually if the slave to be checked in in a packer or a placer. I just committed exactly that

[HaraldJoerg]

Your fix c254fe0 does the trick, thank you!