multi-key shortcuts with different modifiers in each don't work

[amosbird]

Description

commands.addKeyBinding({
    selector: '.jp-Notebook.jp-mod-editMode',
    keys: ['Ctrl C', 'Shift P'], // <<--- doesn't work
    command: 'paste-above-cell-and-edit'
});

commands.addKeyBinding({
    selector: '.jp-Notebook.jp-mod-editMode',
    keys: ['Ctrl C', 'Ctrl P'], // <<--- works
    command: 'paste-above-cell-and-edit'
});


{
    "shortcuts": [
                {
            "command": "notebook:extend-marked-cells-above",
            "keys": [
                "Ctrl Shift D", "Ctrl Shift F"  // works too
            ],
            "selector": ".jp-Notebook:focus"
        },
    ]
}

@telamonian mentioned in gitter that "It looks like we don't support multi-key shortcuts in which you have to change modifier keys."

[jasongrout]

Did you happen to try with the latest 2.0 beta? There has been some work recently with the keyboard shortcut processing.

[amosbird]

Not yet, can I grab 2.0 beta via pip install?

[jasongrout]

Yes, pip install --pre jupyterlab.

[amosbird]

Hmm, is this expected error?

ModuleNotFoundError: Module not found: Error: Can't resolve 'vega-embed' in '/home/amos/.local/share/jupyter/lab/staging/node_modules/@jupyterlab/vega5-extension/lib'
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/webpack/lib/Compilation.js:925:10
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/webpack/lib/NormalModuleFactory.js:401:22
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/webpack/lib/NormalModuleFactory.js:130:21
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/webpack/lib/NormalModuleFactory.js:224:22
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/neo-async/async.js:2830:7
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/neo-async/async.js:6877:13
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/webpack/lib/NormalModuleFactory.js:214:25
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/enhanced-resolve/lib/Resolver.js:184:12
    at /home/amos/.local/share/jupyter/lab/staging/node_modules/enhanced-resolve/lib/Resolver.js:238:5

[jasongrout]

yes, please don't try to build, that is a known problem with the beta. But you should be able to set keyboard shortcuts in the settings to test things.

[amosbird]

It still doesn't work in 2.0 beta

[markellekelly]

The problem seems to be with lumino, which doesn't currently support releasing a modifier mid-shortcut, regardless of whether you use two different modifiers. (e.g., ['Ctrl C', 'Ctrl P'] doesn't work if you press Ctrl+C, release, then press Ctrl+P.)
Currently, whenever all keys are released, keystroke is empty, causing the pending state to be cleared:
https://github.com/jupyterlab/lumino/blob/3b93496b80e1e681af112e6184ef5791c5ad06fc/packages/commands/src/index.ts#L454-L462
This means lumino stops keeping track of the keys already pressed, so a match with the existing shortcut never happens. To fix this, I think we'd also have to allow releasing all keys in the middle of other shortcuts (e.g. ['Ctrl C', 'Ctrl P']). Is this desired behavior?

[amosbird]

To fix this, I think we'd also have to allow releasing all keys in the middle of other shortcuts

I think so. And it would help make ['Ctrl C', 'Shift P'] work

[jasongrout]

I think a fix in Lumino to this would be to check right after this if the key is a modifier key, and if it is, return immeditately

https://github.com/jupyterlab/lumino/blob/8c253bea28fb9584adc65e0d5af4e6bec2d25659/packages/commands/src/index.ts#L449-L452

[jasongrout]

Looking at the code, does Lumino also have a problem with this shortcut? ['Ctrl C', 'Ctrl Shift P'], even if control is held down? I think pressing the shift for the second key would trigger the emptying the pending state?

[amosbird]

does Lumino also have a problem with this shortcut?

I don't know how to verify that.

[jasongrout]

For Lumino changes, I think it would be enough to:

1. Extend keyboard layouts to include a separate section for modifier key keycodes (or maybe we just call them ignored keycodes? the idea is that we ignore them in the processing)
2. Extend the IKeyboardLayout with functions to test if a key is ignored, perhaps isIgnoredKey to mirror isValidKey?
3. Use this function to shortcut return at https://github.com/jupyterlab/lumino/blob/8c253bea28fb9584adc65e0d5af4e6bec2d25659/packages/commands/src/index.ts#L449-L452