[sugar] [PATCH] #447: grab/scroll key
pgf at laptop.org
Sun Jul 13 11:20:33 EDT 2008
> Brilliant work, Erik! I had a chance to play with your first working
> hand scroll, and it's beyond explanation how fun it is to be able to
> scroll around using the touchpad without aiming for a gtkScrollBar.
> For all to consider: there are two grab buttons. What if one tended to
> grab + move *objects*, and the other grabs + moves
> *scenes/backgrounds*? From what I've heard, kids tend to have a hard
> time left-clicking and dragging with their same hand (as with the
adults too. recently while demoing one of the tamtam's, it was
startling to see how much click-and-dragging was necessary (e.g.,
for a volume slider). i suppose that would quickly become a two-handed
operation. and i have no idea how or whether the grab buttons could
help this. they probably can't.
> So, for applications like Browse, both grab buttons could
> still just scroll up/down. But for graphical editors (e.g., layout
> programs, Physics, Model, anything with a scene and objects), this UI
> behavior may be a real time saver and fun to use. This would require
> giving applications the ability to process events from these two
> scroll buttons in a way that identifies them separately.
> Bravo, sir,
> On Thu, Jul 10, 2008 at 2:39 AM, Erik Garrison <erik at laptop.org> wrote:
> > Sugar devs:
> > This is a copy of my bug report for #447. I have completed a first pass
> > of the grab key implementation.
> > -Erik
> > Summary:
> > I used the grab keys to convert the touchpad into a virtual
> > mouse scrollwheel. Holding down the grab key and moving the mouse a
> > small number pixels causes a fake mouse button 4/5/6/7 press, depending
> > on the direction of motion. This approach works in all applications
> > which support mouse scroll buttons.
> > Patches:
> > The attached patch to sugar-toolkit adds glib/C-side hooks to grab an
> > ungrab the mouse, and pass motion-notify events to the python side of
> > the Sugar shell. I have packaged this patch in an rpm which should be
> > installable on an XO running a recent joyride (tested on joyride-2123).
> > (RPMS: tested but slightly older git snapshot:
> > or, untested but slightly newer git snapshot:
> > http://dev.laptop.org/~erik/rpms/sugar-toolkit-0.81.6-1.fc9.i386.rpm)
> > The attached patch to sugar (specifically keyhandler.py) adds the
> > python-side hooks required to enable the grab/scroll button
> > functionality.
> > The patches work in the following manner:
> > When the left or right grab buttons are pressed, XGrabPointer is
> > called. Subsequently, we capture all of the motion-notify events
> > which occur when the user moves the mouse, and each event hits
> > KeyHandler._motion_notify_cb() with the coordinates of the mouse.
> > After we move N pixels (currently 10) we issue a fake mouse scroll
> > button press corresponding to the direction of motion of the mouse
> > (4/5/6/7). To issue the fake button press I have found it is
> > necessary to ungrab the mouse, issue the press, and then re-grab.
> > Known issues:
> > In some cases key-releases are not registered. This is problematic
> > because without the release signal the mouse grabbing does not
> > stop and Sugar becomes entirely unusable. I have not been able to
> > establish why, but have noticed that hitting the journal view key
> > after Sugar startup before any of the other special keys
> > (registered in keyhandler.py) tends to resolve the issue for the
> > Super_L and Super_R keys (the grab buttons).
> > The mouse still scrolls around the screen, and the cursor is
> > visible during the grab. Solution: Hide the mouse; When a grab key
> > press is registered, hide the mouse by setting the cursor pixmap
> > to a blank map (and set it back when the grab key release is
> > registered).
> > Eventually, after scrolling in one direction, the mouse can move
> > out of or to the edge of the scrolling window and the scrolling
> > stops. Solution: Every time we issue a fake button press, warp the
> > mouse back to the position it was at when we first pressed the
> > grab key.
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paul fox, pgf at laptop.org
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