My English is poor, this is Google Translate.
4.4.3 beta 1 When drawing a thin line, the line is broken.
Brush Tip → Auto→Mask Type:Default & Diameter 1.00 px
Brush Tip → Auto→Mask Type:Soft & Diameter 1.00 px
Brush Tip → Auto→Mask Type:Gaussian & Diameter 1.00 px
I think the soft and Gaussian thin lines are not correct. 
These pictures are drawn by the mouse.
I get those results with 4.4.2.
Are your results from 4.4.3 beta1 different from 4.4.2?
The result is not surprising for 1px diameter.
It can be made ‘better’ by removing Anti-alias and enabling Sharpness:
It also sounds related to 433603 – Brush strokes are dashed/jagged when very low pressure is applied to create near 1px width strokes – which I also think isn’t a regression.
I use 1px to help illustrate this problem.
Actual painting will…
Soft
Gaussian
Look at the left, the line is broken.
Can you show comparison results using 4.4.2?
This is related.
Not so bad by default.
default
The problem still exists.Look at the left.
4.4.2 also has this problem.
default
Soft
Gaussian
200% size can be seen clearly.
The upper stroke is with 4.4.3 beta 1 and the lower stroke is with 4.4.2.
Using Basic-5 Size with Diameter of 5 px and Gaussian Mask with Shape as Circle:
Differences at the left are due to manual pressure control uncertainty.
I don’t think this is a regression from 4.4.2
Whether or not it should happen is a different question.
The bug report linked to above has a proposal for improving the appearance.
The first 1px picture was drawn using the mouse.
Whether you use a mouse or a pen, the thin line will be broken.
I think it has nothing to do with pressure control.
This looks like bad pressure connection from the tablet. Or maybe very low levels to detect such low pressure on it.
Same with the mouse. 
So your saying you got pressure issues on your mouse too?
I find this very strange because there is working 1px brushes and you can draw with any brush that has size from 40 or 100px down to 1px width on low pressure if not smaller so small it becomes. Krita’s brush tip scaling is good.
Those blops are your tablet pressure being bad last time I tested this for another user with a similar problem.
I will do those brush combinations in a couple of minutes and double check.
Nah, that is a bug. (I used a mouse for everything here).
Take the Basic Flow brush and make sure to uncheck all dynamics (which means Flow and apparently Rotation). Open a new image 100x20 pixels. Put the size of the brush 0.8 px. You can use Line Tool since it’s easy, but using the Freehand Brush Tool in a similar way will show you the same issue.
Results:
Then if you change the brush tip to Soft, the opaque parts will look a bit better but there will still be gaps and the horizontal line will still be invisible:
Brush tip Default has much more intuitive math, the line is contiguous:
The “Gaussian” with the exact same settings on 800x160px and 6.4px of brush size gives you this effect:
Default one (the Soft one is a bit softer by default).
If I set up Soft to have similar Fade (nearly full circle) as others, the effect is again the same as in Gaussian:
For Rectangular shape, for the Gaussian the results are very similar, for Soft they are terrible (on this picture both lines were around the same length as every other line in the images above, from the edge to the edge):
Yes I have very similar results, these are mine on 4.4.2 with a tablet and I haven’t done on the beta yet even. But I guess it might not be better than this.
Turning off the Alias and lowering the spacing closer to zero helps the lines to appear more. It makes sense to a certain degree but not enough to make blops on lines.
Yes I noticed that too and I am a bit surprised with the result.
Is it also a regression? If so, we need to fix this before we release 4.4.3
No, it was already like that in 4.2.9. I think it’s a relatively old issue, but I haven’t checked any older versions.
I tested more carefully how the dab rendering behaves (after all it was I who adapted them to the vectorized form).
In this case you are reaching the limit of the algorithm maths we use within the size you have to work with. The maths of soft and gaussian dab calculation do suffer from reduced resolution. In this case the calculation of the fade effect on such small sizes will frequently be on either the on or the off state, with no in-betweens. We cannot escape this, unless we have especial cases for dabs so small.
In other words, the brush tip (the dab) is so small, less than a pixel, that calculating the fade grandient in one pixel space is not enough to get smooth results. This is why it doesn’t work the same as the example with resizing the image: for dab calculation we use the pixel size of the dab, so even if the algorhitm can make the correct gradient, we simple do not have enough pixel resolution on the dab to show it.
Afair dab generation does not work at the sub-pixel level, but I may be wrong.
However the broken line does not make sense to me. Dab generation is independent from the Line algorithm and afaik that one works with sub-pixel values just fine.
This is Google Translate.
Thank you for your clarification.
But even if it is 1 pixel, disconnection will also occur.
1 pixel size, when using the mouse, the same disconnection will occur under soft and Gaussian.
At this time, the size is fixed at 1 pixel, and there will be no less than 1 pixel, but the line is also broken.
1 pixel size, when using the mouse, there will be no disconnection by default.
The mouse is only used to eliminate pen pressure interference.
