Feature request: Cmd/Ctrl-Click to set Active Label from crosshair target voxel

[sambuchl]

Summary
Add a fast way to set the Active Label directly from the image pane: in Crosshair mode, Cmd (macOS) / Ctrl (Win/Linux) + Click on a voxel sets that voxel’s label as the Active Label.

Current

• Set Active Label by either:
  • Clicking a label in Segmentation Labels (left panel)
  - Pressing l to open the label menu and selecting a label.

Problem

• With many labels (e.g., hundreds of cysts in PKD), switching via panel/menu is slow and breaks flow.

Proposed:

• Gesture: In Crosshair mode, Cmd/Ctrl + Click on a voxel.
• Result: Label under cursor becomes the Active Label.
• Background/no label: Set Active Label = 0 (Clear label).
• Scope: Read-only; applies to the active segmentation layer; must not conflict with existing shortcuts.

Acceptance Criteria:

• Cmd/Ctrl + Click on a labeled voxel sets that label as Active Label.
• Clicking background sets Active Label = 0 (Clear label).
• Works in 2D views without breaking existing shortcuts.

Bonus/Feature Nice-to-Haves:

• Feedback: Brief status/toast: “Active Label: <name/id>”.
• If available, exposing a shortcuts listing in Preferences would be helpful.

[dpshamonin]

Dear developers,

I would also like to request this feature . When working with dense label lists (e.g., $\approx 50$ labels, as is common in detailed medical imaging), constantly switching the active label via the interface is highly repetitive and inefficient. This manual switching causes significant fatigue and presents an ergonomic issue, especially for users with Repetitive Strain Injury (RSI) symptoms.

Propose:

1. Alt + Left mouse click: Pick the labels under the mouse cursor as "Active label"
2. Alt + Ctrl + Left mouse click: Pick the labels under the mouse cursor as "Paint over"
3. Alt + Shift + Left mouse click: Pick the labels under the mouse cursor as "Active label " and set the "Paint over "="All labels"
4. Alt + Shift + Ctrl + Left mouse click: Pick the labels under the mouse cursor as "Active label " and set the "Paint over "="All visible labels"

Since the non-dominant hand is often already on the left side of the keyboard (e.g., near WASD) to control labels opacity, using the Alt key is highly ergonomic for right-handers.

[pyushkevich]

Thank you both for the suggestions. I endorse this feature and will try to get it into the next release. Also if anyone out there wants to take this on as a pull request, it will be greatly appreciated.From: Denis P. Shamonin ***@***.***>Date: Monday, November 17, 2025 at 7:39 AMTo: pyushkevich/itksnap ***@***.***>Cc: Subscribed ***@***.***>Subject: Re: [pyushkevich/itksnap] Feature request: Cmd/Ctrl-Click to set Active Label from crosshair target voxel (Issue #208)dpshamonin left a comment (pyushkevich/itksnap#208)Dear developers,I would also like to request this feature image.png (view on web). When working with dense label lists (e.g., $\approx 50$ labels, as is common in detailed medical imaging), constantly switching the active label via the interface is highly repetitive and inefficient. This manual switching causes significant fatigue and presents an ergonomic issue, especially for users with Repetitive Strain Injury (RSI) symptoms.Propose:Alt + Left mouse click: Pick the labels under the mouse cursor as "Active label"Alt + Ctrl + Left mouse click: Pick the labels under the mouse cursor as "Paint over"Alt + Shift + Left mouse click: Pick the labels under the mouse cursor as "Active label " and set the "Paint over "="All labels"Alt + Shift + Left mouse click: Pick the labels under the mouse cursor as "Active label " and set the "Paint over "="All visible labels"Since the non-dominant hand is often already on the left side of the keyboard (e.g., near WASD) to control labels opacity, using the Alt key is highly ergonomic for right-handers.image.png (view on web) —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you are subscribed to this thread.

[dpshamonin]

Thank you Paul, that would help a lot in the long run. The last shortcut should be:
4: Alt + Shift + Ctrl + Left mouse click: Pick the labels under the mouse cursor as "Active label " and set the "Paint over "="All visible labels"