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While in X-ray display, selection made via lasso select does not display properly
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Description

System Information
Operating system: Darwin-18.5.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 560X OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.8.38

Blender Version
Broken: version: 2.80 (sub 51), branch: master, commit date: 2019-03-27 13:26, hash: rB2d34420648e5
Worked: (optional)

Short description of error
While in X-ray display, selection made via lasso select does not display properly

Exact steps for others to reproduce the error
1 - Create a new general Blender file using the General template
2 - Delete everything in the scene
3 - Create a monkey mesh
4 - Turn on x-ray display
5 - Enter edit mode and make sure you're in vertex mode (I'm supplying a .blend file that starts at this state)


6 - Lasso select (ctrl-right drag) part of Suzanne (say, the chin)
7 - Observe that nothing appears to be selected
8 - Enter circle select (C)
9 - Left drag the circle to any vertex
10 - Observe that the lasso select actually worked but was just not displaying

~chuck

Event Timeline

This problem also occurs in edge select mode or face select mode. So in step 5 above, it is not essential to be in vertex select mode.

I suspect this is related to the selection changes but did not try to find the commit.

From what I can tell, lasso select does not work the first time after rotating the view. Then if you do it a second time it works. As if the depth buffer is not updated or something.

It does seem depth buffer related in some cases. Another symptom I just found. In the same .blend file I sent, try the following:

  1. Turn off x-ray display
  2. In edit mode select all with A
  3. Observe that only some of the selected faces are highlighted (it looks like there is some z-fighting going on)
  4. Rotate the view with middle mouse drag
  5. Observe faces flickering as highlight is only intermittently displayed
  6. Release the middle mouse
  7. Observe that only some of the selected faces are highlighted

This is after a rebuild (a couple of hours after the one I originally reported from). Not sure if this is new or I simply didn't notice it before.

I don't know which commit resulted in this regression, but it's not related to the recent changes in the selection.
The problem is in the do_lasso_select_mesh function. The data.is_changed variable is not always set to update the mesh.
The solution is simple, but it might be good to investigate which commit has brought this problem.