On 04/16/2015 03:55 AM, Carlos Garnacho wrote:
In gtk+/gnome we currently have the following keybindings active during DnD: - Cursor keys move the drag point, modifiers affect speed - Esc key cancels drag - Modifiers alone pick an action from the offered list
The user has to hold the mouse button down during these? That does not sound very useful. Or is it possible to start DnD with a keystroke? What happens then if the user moves the mouse or pushes the mouse button?
I really need a clearer explanation of these keystrokes. I suspect some requirements of implementing things on X are leaking into your description, and you are talking about a global handicapped-assistance api (which I agree would be done by the compositor, but applies everywhere, not just DnD).
So ok, the latter is dubious to punt to compositors, but there's basically no other choice with the 2 first ones.
It can be handled by either the source or dest getting a grab and responding to the key events with some new api that manually moves the drop target. In fact there is a lot of proposed things for the grab to be able to completely control the cursor position, this would be another one.
I do agree that making Esc cause the compositor to cancel a grab unconditionally is an acceptable idea. If you don't have to hold down the mouse to do DnD, or if there is no position on the screen that you can drop without anything happening, then this is necessary.
It does seem like the source getting the keyboard drag is consistent, and match how dragging any other part of the source's ui works.
However I think it will work better for the destination to get the grab. This is because the destination has a more complex job, including actions that the source does not need to distinguish (insert vs replace, link vs copy), and if there is a popup menu to let the user choose the action they will think it is part of the destination and it would look far better if it was drawn with the destination's style, and user preferences for it are set on the destination.
So during a DnD the keyboard focus should be (in effect) point-to-type. I don't think it should get mouse enter/exit/move events, instead the drag enter/exit/move would replace them. There will unfortunately have to be a keyboard focus-in event as that is the only way to communicate the current keymap to the client (it may be useful to add an event for that as there already is the problem where the compositor eats keystrokes, but can't tell the client about the new keymap without a fake exit/enter).
I think both the source and destination should be able to modify the cursor. If the destination says it will accept the drop then it is it's job to update the cursor, as it may modify it to show clearly what will happen (for instance it may update it's own display to show the result of the drop, and change the cursor to just the pointer). If it says it won't, then the source sets the cursor to it's default version. Race conditions with this idea need to be solved...
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