No I know this

 But when the shape has not yet been confirmed, the handles will disappear but the angles can be changed without the handle

Only the handles disappear for no reason

@Charlie Jolly (charlie) Can you reproduce it? I cannot.

@mobin (mobin.artworks) I'm unable to reproduce the issue. Are the control points for the start and end points still visible?

No No points are visible

You should work with this tool for at least ten minutes to find out. I suggest drawing a simple character with it

Can I upload a photo or video here to show you?

Yes, more information the better.

@Charlie Jolly (charlie) Jolly (charlie)

I was able to figure out the cause of this problem!
 First, draw a few simple lines with the Curve tool and change the angles with the handles
Then select the Eraser tool and clear a section of lines with it
And now if you choose Curve again and you will notice the disappearance of the handles!
I was able to record a movie from that. How do I send it to you?

@mobin (mobin.artworks) How you sue the Eraser tool? select in he toolbar?

I cannot select the Eraser tool (I need press Enter or MMB before)...if you do that..you have confirmed the curve, so you will never get the handles again. If you get the eraser using othe rmodes, tell me how you did it.

To clarify, the primitive tools are not like tools in other softwares where you can create, delete, edit again, etc. This is not supported, maybe in future relases, but now after the creation it converts in a normal stroke and you must modify with sculpt tools or common edit tools like hand drawing strokes.

PS: You can put the video in Dropbox/Youtube, etc and put here the link.

No, you haven't noticed!

Yes, you press Enter, then select Eraser and clear a part of the line drawn with the Curve tool!

Then select the Curve tool again and start dragging.

The handles no longer exist

Ok, this give us a clue of the problem...the handles are not visible in the "next" arc

Yes that's right

Confirmed.

Not entirely sure why this is happening but if you select the draw tool then the arc tool the control points are visible again.

Yes, that's why I said that it appears for no reason and disappears again

I have seen the reason...fixing it

I have found the reason.

When you draw a primitive, by default the current brush->gpencil_tool is DRAW, so the following variable is true:

const bool is_paint_tool = (bool)((brush) && (brush->gpencil_tool == GPAINT_TOOL_DRAW));

The problem when you use the erase, the tool change to GPAINT_TOOL_ERASE and the variable above will be false.

To solve the issue, we need set the gpencil_tool to GPAINT_TOOL_DRAW for all primitives. This is the reason when you select again Draw tools, the handles back again.

@Campbell Barton (campbellbarton) How we can set this value and change the brush when select the Primitive Tools (Line, Arc, Box, Curve)? The logic would be set the same Brush used in Draw mode.

I hope you find a solution

Thank you very, very much

@mobin (mobin.artworks) Thanks to you for catching the bug and be able to reproduce it.

you're welcome. You're great because you make Blender users not alone with their problems and it makes a great sense❤?

I have seen this bug has other potential bug "inside". As the primitive is using the current brush, if the material is pinned, the primitive will use the current material and not the pinned material because the active brush is not the same used in Draw Tool.

Same bug appears when switching from 'Fill Tool' to "Primitives".

Proposed fix: D5403