You can align layers horizontally or vertically. When aligning layers, Corel Painter calculates the "destination" point for alignment. For example, if you align layers to the left, the destination is the leftmost point of all selected layers. If you align horizontally to the center, the destination is the midpoint between the leftmost edge and the rightmost edge of the selected layers.
Next, Corel Painter aligns the corresponding edge of each selected layer’s bounding box with the destination point. For example, if you align layers to the left, each layer is moved so that the left edge of its bounding box lines up with the destination point. If you align horizontally to the center, each layer is moved so that the horizontal midpoint of its bounding box lines up with the destination point.
The left edge of the image is the leftmost point of all the layers (left). The layers are aligned horizontally to the left so that all the layers line up with the leftmost point (right).