How to mirror a whole layer, not just brush and eraser

[default4a1g3fiil39y]

Hi. I'm designing a logo and using a mix of brush, rectangle/ellipse tool, and so on, but the symmetry tool only applies to brush and eraser tools. Is there a way to somehow make a smart layer that is a copy of another layer, just mirrored/rotated? I want the symmetry to apply to all the pixels of a layer.

[c.pfaffenbichler]

Convert the Layers to one Smart Object, cmd-J, Edit > Transform > Flip Horizontal, apply a Layer Mask to the top one. 

Edit: If transparency is relevant both instances may have to be masked or a different approach (with a knockout layer) employed. 

[default4a1g3fiil39y]

Thanks for the answer! I'm not good with smart objects/layer masks though... Do you mean that I start with two normal layers > select both and convert to smart object > ctrl+j > transform > apply layer mask? How do I apply layer mask? When I press ctrl+j with the smart object selected it just makes a raster copy of the layer independent from the first layer.

I don't mean that I want to copy-paste the drawing and then rotate it on another layer... I want to be able to edit the pixels in one layer and have those changes also reflected on a second layer, which is a flipped copy.

[c.pfaffenbichler]

When I press ctrl+j with the smart object selected it just makes a raster copy of the layer independent from the first layer.

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Because you have an active Selection. 

How do I apply layer mask?

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Create a Selection and click the »Add layer mask«-button in the Layers Panel or use Layer > Layer Mask > Reveal Selection 

Could you please post screenshots with the pertinent Panels (Toolbar, Layers, Options Bar, …) visible? 

[default4a1g3fiil39y]

Also, I can't transform a smart object, it says I need to convert it to raster first.

[c.pfaffenbichler]

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@default4a1g3fiil39y wrote:

Also, I can't transform a smart object, it says I need to convert it to raster first.

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You appear to have an active Selection. Deselect (cmd-D).