Can't drag Markdown preview to start a new editor group

[gregvanl]

• VSCode Version: 1.12 Insiders
• OS Version: Windows 7, 10

Steps to Reproduce:

1. With a single editor group, open a Markdown file, then Markdown: Open Preview (Ctrl+Shift+V)
2. Now try to drag the markdown preview to the side to start a new editor group

The drop is blocked.

If you select another file and then try to drag the markdown preview with only the tabbed heading, it works.

[bpasero]

@gregvanl does it work in 1.11?

[gregvanl]

@bpasero Yes, this is a regression from 1.11.

[bpasero]

@mjbvz I see that dragging the tab over the markdown preview turns the mouse icon into a "drop not allowed" cursor. This could either be the Electron update, or changes we did to the webview within (e.g. context-isolation). A quick test to disable context isolation though did not help. Were there other changes that could have an impact? E.g. CSP settings?

[dtgriscom]

Confirmed in VSC 1.19.1 (1.19.1) on OS X 10.10.5: you can't start a new edit group by dragging a Markdown preview to the right edge of the screen.

[HPLegion]

Problem persists in VSCode 1.21.1 (Win10)

[IgorKrupenja]

I cannot repro this with VSCode 1.28.2.