Description Javier Martin 2020-07-01 07:59:16 EDT

Created attachment 283470 [details]
Output of example program showing widths and column types, in Windows and Mac

When a column is manually resized in a Table widget handled by TableColumnLayout in macOS, _all_ columns stop resizing.

This seems to be caused by the implementation of JFace TableColumnLayout and its parent AbstractColumnLayout. When they get a column resize event, they do the following:

1. If there is already an "update in process", return
2. If the column being resized was expandable (it had ColumnWeightData), make it fixed (ColumnPixelData)
3. Recompute the size of all other columns
4. Set the "update in process" flag to TRUE
5. Set the new sizes through setColumnWidths, which calls TableColumn.setWidth
6. Unsetting the "update in process" flag

This relies on the assumption that the Resize events caused by point 5 will come _before_ point 6. This does happen in Windows, but not in macOS, _at least_ since version 4.11 of Eclipse and up to 4.16. Instead, the events are parsed _afterwards_ when "update in process" is again FALSE, which causes every single column to go through point 2... which makes all columns fixed in size as soon as the first manual resize happens.

NOTE: I've marked this as a bug in JFace because it's the immediate cause, but that code is 13 years old, so this might also be a symptom of a bug/change in SWT for macOS.