Keybinding to set a new label doesn't work consistently

[melissawm]

🐛 Bug Report

After creating a labels layer, I observed that the m keybinding does not behave consistently.

💡 Steps to Reproduce

Create a labels layer.

• If the layer is selected, the m keybinding will either do nothing or select another layer wiht a name that starts with the letter m;
• If the paintbrush, fill bucket or polygon tools are selected, the m keybinding doesn't do anything;
• If the paintbrush has been used in the canvas, the m keybinding correctly adds 1 to the label control and a new label is selected and can be used to paint.

💡 Expected Behavior

The m keybinding should increase the label number in all those situations.

🌎 Environment

napari: 0.5.0a2.dev486+g4d60a7ce
Platform: Linux-6.1.64-1-MANJARO-x86_64-with-glibc2.38
System: Manjaro Linux
Python: 3.11.6 | packaged by conda-forge | (main, Oct 3 2023, 10:40:35) [GCC 12.3.0]
Qt: 5.15.2
PyQt5: 5.15.10
NumPy: 1.26.2
SciPy: 1.11.4
Dask: 2023.11.0
VisPy: 0.14.1
magicgui: 0.8.0
superqt: 0.6.1
in-n-out: 0.1.9
app-model: 0.2.2
npe2: 0.7.3

OpenGL:

• GL version: 4.6 (Compatibility Profile) Mesa 23.1.9-manjaro1.1
• MAX_TEXTURE_SIZE: 16384

Screens:

• screen 1: resolution 1920x1080, scale 1.0
• screen 2: resolution 1920x1080, scale 1.0

Settings path:

• /home/melissa/.config/napari/napari-dev_f5bfbd9c5d96bcb503f816d91f8db95d3b6d554f/settings.yaml
  Plugins:
• napari: 0.5.0a2.dev486+g4d60a7ce (77 contributions)
• napari-console: 0.0.9 (0 contributions)
• napari-svg: 0.1.10 (2 contributions)

💡 Additional Context

No response

[dalthviz]

Hi there, just in case, gave this a check and seems like the related logic for that shortcut is at

napari/napari/layers/labels/_labels_key_bindings.py

Lines 70 to 78 in e6a454e

	@register_label_action(
	trans._(
	"Set the currently selected label to the largest used label plus one."
	),
	)
	def new_label(layer: Labels):
	"""Set the currently selected label to the largest used label plus one."""
	layer.selected_label = np.max(layer.data) + 1

Seems like it depends on the layer data to work (which I guess is the reason why it only works when you painted something). Also, maybe that is the reason why there are a couple of other shortcuts which change the current selected label regardless of layer data (- to decrease and = to increase)?

[psobolewskiPhD]

Sorry I missed this!!
Daniel is right m doesn't increase the label number, it sets it to the next unused number. So if there are no labels painted then max+1 will return 1 which is the first label (0 is background/erase).
Likewise, if you paint with 1, hit m to get 2 then hitting m again won't do anything, because it's already at max+1.
So I would say this is not a bug, but it might be worth considering a Notification in these cases just not sure how to phrase it, maybe like:
Largest label already selected or something?

[melissawm]

Oh that makes sense, yes! A warning sounds very reasonable. Thanks!

[dalthviz]

So something like this could work?:

@register_label_action(
    trans._(
        "Set the currently selected label to the largest used label plus one."
    ),
)
def new_label(layer: Labels):
    """Set the currently selected label to the largest used label plus one."""
    new_selected_label = np.max(layer.data) + 1
    if layer.selected_label == new_selected_label:
        warnings.warn(
            trans._(
                "Largest label already selected",
            )
        )
    else:
        layer.selected_label = new_selected_label

A preview:

Let me know if such an approach could be worthy to submit a PR :)

[psobolewskiPhD]

Yeah that's exactly what I was thinking, only using show_info

napari/napari/utils/notifications.py

Line 359 in d507dd6

def show_info(message: str):

see also:

napari/napari/layers/points/_points_key_bindings.py

Lines 66 to 78 in d507dd6

	def select_all_in_slice(layer: Points):
	new_selected = set(layer._indices_view[: len(layer._view_data)])
	# If all visible points are already selected, deselect the visible points
	if new_selected & layer.selected_data == new_selected:
	layer.selected_data = layer.selected_data - new_selected
	show_info(
	trans._(
	"Deselected all points in this slice, use Shift-A to deselect all points on the layer. ({n_total} selected)",
	n_total=len(layer.selected_data),
	deferred=True,
	)
	)

It has a different icon in the notification, versus warning.