Goal

There are two very different implementations of the clone brush in Blender. Each with their own disadvantages.

In the image editor it is essentially just a brush that can use a stencil texture (Including the texture you're painting).:

• Cloning is with the purpose of cloning from the view, with the same zoom & rotation. This is hard to do with a stencil.
• You need to choose a texture first, which is redundant since you would want yo use the same one you are painting.
• The stencil is very visually obstructive.

The texture paint mode which uses the 3D cursor position to sample the colors to clone:

• The 3D cursor is fixed in place, which makes repeated strokes very difficult. The needed default behaviour is to have the cloning target follow the brush cursor.
• The 3D cursor is a point in 3D space. Ideally the cloning target should be screen based.
• The cloning is also being tiled in an unpredictable way

Proposal

There are established standards that we can follow for a more intuitive behaviour of the clone brush.

Basic Behaviour

We should follow the design of Krita for the new Clone brush. There you have the main brush cursor and a clone target cursor:

• The clone target can be set anywhere on the screen and stay there until the the next brush stroke.
• For each following brush stroke the clone target follows the movement of the brush and ends on a new screen location.
• After the first stroke the clone target will also follow the brush movement even without doing a stroke.
• Once a new clone target is set on the screen it will stick to that position again until the next stroke.

Picking a target

Picking a clone target should not be tied to the 3D cursor and related shortcuts. A more intuitive and standard approach is to use the shortcut S for color picking.
An eyedropper button should then also be added to the brush settings to use instead of the shortcut.

It should also be possible to set a fixed clone target that won't move on repeated strokes.
By default that is the less desired behaviour but it can be useful when cloning a specific spot multiple times.
While this can be a setting in the brush, It can also be included via holding Ctrl while holding S to set the target.

Painting in 3D

It's important that the colors are always picked from the screen view and painted via the view plane.
But the brush itself should be able to have a spherical falloff. Projection painting should not be strictly required.

It could also be very intuitive to pick a clone target in 3D space instead of a fixed point on the screen.
This would then allow to target a certain surface and still rotate the viewport to get the correct angle before painting.
This needs to be tested though which approach is more intuitive. Supporting both could is also an option.