Description Matthias Wienand 2013-09-19 10:38:16 EDT

Created attachment 235632 [details]
SWT snippet demonstrating the incorrect behavior.

The SWT GC (ostensibly) does not perform drawing operations when particular transformations are in-use, even if the setLineAttributes() workaround is used. The attached snippet demonstrates the incorrect behavior.

For example, the following transformation matrix leads to invisibility of drawings:

    tx.setElements(
        (float) 0.527691627751155, (float) 0.527691627751155,
        (float) -0.527691627751155, (float) 0.527691627751155,
        (float) 15.375719146431834, (float) 247.60611440956703
    );

Whereas this transformation matrix works just fine:

    tx.setElements(
        (float) 0.527691627751155, (float) 0.527691627751155,
        (float) -0.52, (float) 0.527691627751155,
        (float) 15.375719146431834, (float) 247.60611440956703
    );

The only difference (a quite small difference!) between both transformation matrices is found in the first cell of the second row.

This SWT bug is known for a long time. Nonetheless, I want to document it here so that we can find a better workaround (maybe) or at least users can find it more easily.