Continuous grab is broken 2.92.0 Alpha macOS #82870

System Information
Operating system: Darwin-19.6.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 455 OpenGL Engine ATI Technologies Inc. 4.1 ATI-3.10.18

Blender Version
Broken: version: 2.92.0 Alpha, Fri, Nov 20, 14:41, 96995b2343.
Worked: ~

Short description of error
When the cursor crosses the editor border, the value jumps/doubles.
It doesn't matter if it's a tablet, mouse, or trackpad.

This problem is also present in previous versions (at least in 2.83 it definitely is)
but after 96200110eb it began to happen all the time.

Actually there is a report for Windows #59836, but it's set to just todo.

continuous-grab-issue.mov

Here's what I see, this is a normal case:

GHOST x_mouse 558
GHOST x_accum 0 
GHOST warped_x_mouse 558 
WM    event.x 1116

GHOST x_mouse 559
GHOST x_accum 0 
GHOST warped_x_mouse 1 
WM    event.x 1118

GHOST x_mouse 1
GHOST x_accum 558 
GHOST warped_x_mouse 1 
WM    event.x 1118

And this is the wrong one:

GHOST x_mouse 558
GHOST x_accum 0 
GHOST warped_x_mouse 558 

WM    event.x 1116

GHOST x_mouse 559
GHOST x_accum 0 
GHOST warped_x_mouse 1 

GHOST x_mouse 559
GHOST x_accum 558 <--- !!!
GHOST warped_x_mouse 1 

WM    event.x 1118
WM    event.x 2234

CC @brecht

Added subscribers: @brecht, @jenkm

I mean, it seems that the value accumulates but the cursor position is not updated,
and at the next event, the previous cursor position is used and the position is again accumulated.

Added subscriber: @mano-wii

It seems to be a high priority issue.
I can't reproduce the problem on windows, in fact it seems to be MacOS specific.

Added subscriber: @PrototypeNM1

I don't have time to look into this. @PrototypeNM1 or @jenkm worked on this and they would be the ones to look into a fix. If there is no quick fix, it's best to revert the patch until this issue is fixed.

Also @jenkm, as a developer you can triage the bug immediately and set appropriate tags, confirmation status and priority.

The equivalent Windows Ghost code tells the OS to update the mouse cursor position, then skips issuing a Ghost event as the OS will issue a new cursor move event with corrected position.

I think what's happening is that after wrapping/accumulating there remains stale mouse events in the OS event queue that previously would have been overwritten before the next event is issued. The only reason this hasn't surfaced on Windows is because inbetween mouse events aren't handled, only tablets.

@brecht It was much better with these, (note 2.91 also has a similar regression, but less noticeable).

--- a/intern/ghost/intern/GHOST_SystemCocoa.mm
+++ b/intern/ghost/intern/GHOST_SystemCocoa.mm
@@ -1590,7 +1590,7 @@ - (void)windowWillClose:(NSNotification *)notification
         }
         case GHOST_kGrabWrap:  // Wrap cursor at area/window boundaries
         {
-          NSPoint mousePos = [event locationInWindow];
+          NSPoint mousePos = [cocoawindow mouseLocationOutsideOfEventStream];
           GHOST_TInt32 x_mouse = mousePos.x;
           GHOST_TInt32 y_mouse = mousePos.y;
           GHOST_Rect bounds, windowBounds, correctedBounds;

9e85812acc

Also I think the navigation gizmos needs to use GHOST_kGrabHide not GHOST_kGrabWrap, this will completely fix the problem for them.

Changed status from 'Needs Triage' to: 'Confirmed'

OK, I found a third similar report #74918 and there was a fix for Linux d6fd03616e.
I will try to do the similar thing (use a time stamp and delay) for Mac.

And the fourth #75528.
And probably these, too #67362 #39144.

This issue was referenced by 9306e01b10

Added subscriber: @seanr

I can confirm that @jenkm's fix in D9662 works well. 2.92 was utterly unusable without it, but it now appears to be performing even better than it did previously with the fix.

Changed status from 'Confirmed' to: 'Resolved'

Added subscriber: @AgentSam-2

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Continuous grab is broken 2.92.0 Alpha macOS #82870