Graphic layers focus

[shakenov-chinga]

Please, refer to #406

[ubruhin]

Hi @shakenov-chinga,

I just tried it out, this is really an awesome feature! 😃

Regarding your comment at #408 (comment):

I weren't able to find any connection between PrimitivePathGraphicsItem and Board. It can be hard-coded, passing Board instance via constructor, but all of my inner self is refusing to do so smiley.

Yeah that shouldn't be done, PrimitivePathGraphicsItem is in the librepcbcommon library which must not have a dependency to librepcbproject, where Board is located.

But I just had another idea: If the focused layer would be a property of the GraphicsLayer class, all graphics items no longer need the dependency to Board to determine the focused layer. Basically following things would need to be done:

• GraphicsLayer needs an additional property, e.g. called mIsActive or so (similar to mIsVisible). Per default, all layers are set as active.
• To also avoid the hardcoded color of unfocused layers, GraphicsLayer could also have a new property mColorInactive, similar to mColorHighlighted (for simplicity, the same color can be used for all layers, but theoretically we have the option to use individual colors).
• If the user wants to focus on one specific layer, the board layer stack sets all layers to inactive, except the layer which should be focused. All graphics items are repainted automatically because they are registered to the graphics layers and thus get notified about the activity change.
• With this concept, it would even be possible to focus on multiple layers, for example by pressing CTRL or SHIFT while selecting layers in the layer dock. This would be nice for example to focus on all layers which are printed on silkscreen (outlines/names/values) to see how the whole silkscreen looks like.

What do you think about this?