Mouse Event: Drag

[SqrtRyan]

When selecting text with the mouse (by clicking and dragging in a prompt-toolkit text editing field), I noticed that it doesn't render the selected text as highlighted until after I release the mouse button. (Editors like vim and micro both highlight the text as you drag your mouse, whereas prompt-toolkit doesn't seem to have a handler event for when you're click-dragging the mouse). Is it possible to add this functionality? I would be willing to help

[SqrtRyan]

How do I mark this as a feature request? Also where would I go looking if I wanted to create this myself as a pull request (@jonathan, I'd be willing to help)

[jonathanslenders]

For this, be prepared to dig in the source code.
This would require a couple of changes, I think, but I can be wrong:

1. After a mouse down event, we probably have to tell the terminal to report all mouse move events.
2. handle the input coming from mouse move events.
3. After a mouse up event, tell the terminal to stop reporting mouse move events.

Telling the terminal to do something is probably in the Output classes. The vt100 one is here: https://github.com/prompt-toolkit/python-prompt-toolkit/blob/master/prompt_toolkit/output/vt100.py

The mouse handlers can be found here: https://github.com/prompt-toolkit/python-prompt-toolkit/blob/master/prompt_toolkit/key_binding/bindings/mouse.py#L23

These mouse handlers call the handlers that were registered by the UI controls. For the BufferControl, you can find it here: https://github.com/prompt-toolkit/python-prompt-toolkit/blob/master/prompt_toolkit/layout/controls.py#L821
You have to create a MouseEventType.MOUSE_MOVE enum value, and handle that here.

I'm not sure if all terminals support this. It would require some testing to be sure it doesn't break something else. Ideally, we should also support Windows.