Pressing "End" when selecting multiplle cells does not expand selection

[krassowski]

When navigating notebook Up an Down arrows move us one cell up or down; pressing Home or End quickly scrolls up to the beginning or end of the notebokok.

If we select cells in a notebook, we can extend the selection down with Shift + Down or reduce it with Shift + Up (and vice versa when going up from the starting cell).

However, Shift + End does not select all the cells until the end of the notebook (and Shift + Home does not select cells till the begining).

Expected behavior
I would expect the Shift + Home/End to select all cell in specified direction, just as if I were repeating Shift + Up/Down until reaching the begining/end of he notebook.

Desktop (please complete the following information):

• OS: Ubuntu 19.04
• Browser: Chrome 70+
• JupyterLab: 1.0.1

[ian-r-rose]

I think this is a nice idea @krassowski (though I would expect this behavior on PageUp and PageDown, rather than Home and End, which is how my text editor behaves).

I think this would be a good issue for an advanced new contributor.
One would add new commands to the command registry to select all above/below, mimicking these commands:

jupyterlab/packages/notebook-extension/src/index.ts

Lines 1446 to 1467 in 079115d

	commands.addCommand(CommandIDs.extendAbove, {
	label: 'Extend Selection Above',
	execute: args => {
	const current = getCurrent(args);
	if (current) {
	return NotebookActions.extendSelectionAbove(current.content);
	}
	},
	isEnabled
	});
	commands.addCommand(CommandIDs.extendBelow, {
	label: 'Extend Selection Below',
	execute: args => {
	const current = getCurrent(args);
	if (current) {
	return NotebookActions.extendSelectionBelow(current.content);
	}
	},
	isEnabled
	});

The notebook actions extendSelectionAbove and extendSelectionBelow could be enhanced to take an option for whether to extend just one cell, multiple cells, or to the top/bottom:

jupyterlab/packages/notebook/src/actions.tsx

Lines 718 to 766 in 079115d

	/**
	* Extend the selection to the cell above.
	*
	* @param notebook - The target notebook widget.
	*
	* #### Notes
	* This is a no-op if the first cell is the active cell.
	* The new cell will be activated.
	*/
	export function extendSelectionAbove(notebook: Notebook): void {
	if (!notebook.model || !notebook.activeCell) {
	return;
	}
	// Do not wrap around.
	if (notebook.activeCellIndex === 0) {
	return;
	}
	const state = Private.getState(notebook);
	notebook.mode = 'command';
	notebook.extendContiguousSelectionTo(notebook.activeCellIndex - 1);
	Private.handleState(notebook, state, true);
	}
	/**
	* Extend the selection to the cell below.
	*
	* @param notebook - The target notebook widget.
	*
	* #### Notes
	* This is a no-op if the last cell is the active cell.
	* The new cell will be activated.
	*/
	export function extendSelectionBelow(notebook: Notebook): void {
	if (!notebook.model || !notebook.activeCell) {
	return;
	}
	// Do not wrap around.
	if (notebook.activeCellIndex === notebook.widgets.length - 1) {
	return;
	}
	const state = Private.getState(notebook);
	notebook.mode = 'command';
	notebook.extendContiguousSelectionTo(notebook.activeCellIndex + 1);
	Private.handleState(notebook, state, true);
	}

Then one would add a keyboard shortcut that checks for the up/down arrows and pageup/pagedown/home/end:

jupyterlab/packages/notebook-extension/schema/tracker.json

Lines 80 to 99 in 079115d

	{
	"command": "notebook:extend-marked-cells-above",
	"keys": ["Shift ArrowUp"],
	"selector": ".jp-Notebook:focus"
	},
	{
	"command": "notebook:extend-marked-cells-above",
	"keys": ["Shift K"],
	"selector": ".jp-Notebook:focus"
	},
	{
	"command": "notebook:extend-marked-cells-below",
	"keys": ["Shift ArrowDown"],
	"selector": ".jp-Notebook:focus"
	},
	{
	"command": "notebook:extend-marked-cells-below",
	"keys": ["Shift J"],
	"selector": ".jp-Notebook:focus"
	},

[jasongrout]

Fixed in #7177