Unnecessary code and decoration with :after prevents dnd

[usernamehw]

Issue Type: Bug

1. Have unused variable in the first line of the file const asdf = 0; (any line tbh, just an example)
2. Create decoration on the same line with the after property specified

const decorationType = vscode.window.createTextEditorDecorationType({
	isWholeLine: true,
});
const decorationOptions: vscode.DecorationOptions = {
	range: new vscode.Range(0, 0, 0, 0),
	renderOptions: {
		after: {
			contentText: 'random',
		},
	},
};
editor.setDecorations(decorationType, [decorationOptions]);

3. Try to drag-n-drop text to that line

If I reference that variable (remove unused status) - then dnd works fine again.

VS Code version: Code - Insiders 1.39.0-insider (55825e9, 2019-09-10T05:25:22.729Z)
OS version: Windows_NT x64 10.0.18362

[alexdima]

I can reproduce. I cannot drop on the line:

[rebornix]

Weird bug. While mouseDownAndMove, the mouse event target is span <- span <- view line <- view lines <- .... However once it stops, the last cached mouse event target is span <- span <- view line <- null when dropping in above case. The mouse target somehow gets unconnected from view lines.

[alexdima]

@rebornix That might happen because the line gets redrawn. In that case, the line becomes orphaned. I think the line might get redrawn due to inline decorations getting added/removed as drop feedback or as hover range feedback.

[KapitanOczywisty]

@rebornix @alexdima Since this is pretty annoying bug when using Error Lens extension, I spend some time and found what exactly is wrong. Basically lines with after decorator are redrawn because lineDecorations has the same elements, but in different order. I'm pretty sure order is messed by DragAndDropController._onEditorMouseDrag combined with some other regular task, but this is not important for the actual fix.

Meanwhile event used for drop target is gathered when mouse is still on the move

vscode/src/vs/editor/browser/controller/mouseHandler.ts

Line 302 in f74e473

this._lastMouseEvent = e;

and the render cycle passes before this event is used

vscode/src/vs/editor/browser/controller/mouseHandler.ts

Line 359 in f74e473

const position = this._findMousePosition(this._lastMouseEvent!, true);

---

To fix this, lineDecorations have to be sorted here: (before condition here):

vscode/src/vs/editor/common/viewLayout/viewLineRenderer.ts

Line 130 in 29e9717

this.lineDecorations = lineDecorations;

Or this function has to ignore elements order

vscode/src/vs/editor/common/viewLayout/lineDecorations.ts

Lines 31 to 43 in 29e9717

	public static equalsArr(a: LineDecoration[], b: LineDecoration[]): boolean {
	const aLen = a.length;
	const bLen = b.length;
	if (aLen !== bLen) {
	return false;
	}
	for (let i = 0; i < aLen; i++) {
	if (!LineDecoration._equals(a[i], b[i])) {
	return false;
	}
	}
	return true;
	}

I've tested both options in DevTools and this fixes issue. Since this is rather crucial part of code I'll leave proper implementation to you.

[alexdima]

To verify:

• package.json:

{
    "publisher": "alex",
    "name": "80666",
    "version": "1.0.0",
    "engines": {
        "vscode": "^1.0.0"
    },
    "main": "main.js",
    "activationEvents": ["*"]
}

• main.js:

const vscode = require('vscode');

exports.activate = function() {
    const decorationType = vscode.window.createTextEditorDecorationType({
        isWholeLine: true,
    });
    const decorationOptions = {
        range: new vscode.Range(2, 1000, 2, 1000),
        renderOptions: {
            after: {
                contentText: 'random',
            },
        },
    };
    vscode.window.activeTextEditor.setDecorations(decorationType, [decorationOptions]);
}

• file.ts:

function x() {
    const asdf = 0;
}

[github-actions]

This bug has been fixed in to the latest release of VS Code Insiders!

@usernamehw, you can help us out by confirming things are working as expected in the latest Insiders release. If things look good, please leave a comment with the text /verified to let us know. If not, please ensure you're on version ac165d7 of Insiders (today's or later - you can use Help: About in the command palette to check), and leave a comment letting us know what isn't working as expected.

Happy Coding!

[usernamehw]

/verified Tested by using Error Lens extension decorations