Looks nice.

I'll try to set some time aside next week to have a good look at the
code and hopefully merge it.

Tav

On Sat, 2017-04-22 at 04:27 -0700, Yale Zhang wrote:
> Rotate should be useful. I think most people find it easier to draw
> vertical lines than horizontal since there's less wrist motion.
>
> I've updated my touchscreen code to support canvas rotation. Anyone
> want to use it?
>
> https://youtu.be/-8v1EVKqcaM
>
> transform math:
> https://1drv.ms/u/s!AngRQgSreBCehTiw0R_rGV7gxQIP
>
> A couple of notes:
> *awkward coordinate system - Why is the canvas completely off the
> screen when rotation=0, offset=0? It seems the window's Y axis points
> down while the document's Y axis points up?
>
> * why is a positive rotation counter clockwise? In a left handed
> coordinate system, it should be clockwise.
>
> *I couldn't figure out how to set the rotation, zoom, and offset
> using
> the functions in the desktop class (scroll_to_point(),
> zoom_absolute_keep_point() and had to access the private affine
> matrix
> directly. Calling those functions in sequence seems to add unwanted
> offsets on top of each other instead of letting me set the offset
> directly.
>
> *had to roll back r15548 or else touch screen events get lost
> somehow.
>
> * I couldn't figure out how to use the GTK gesture classes (which are
> probably more robust), so wrote my own code for detecting zoom,
> rotate, and scroll gestures. When I tried, the gesture classes
> weren't
> receiving any events. 2nd, it seems only 2 finger rotation and zoom
> gestures are recognized, but not 2 finger scrolling. There is a 1
> finger scroll gesture.
>
> -Yale
>
> On Tue, Apr 4, 2017 at 8:35 PM, Raghavendra Kamath
> <raghu@...3496...> wrote:
> > Hi Tav,
> >
> > On 2017 Mar 30 13:29:23, Tavmjong Bah wrote:
> > >
> > > Hi,
> > >
> > > I've just checked in code to quickly preview canvas rotation.
> > > Like
> > > Jabier's code, it is triggered by Ctrl-Middle-Mouse-Button. It
> > > lacks
> > > all the fancy graphics of Jabier's version. Some of this can be
> > > added
> > > back if there is user demand. There is certainly some tweaking to
> > > do.
> > >
> > > I also implemented canvas flip (Horizontal and Vertical). This is
> > > not
> > > in the GUI yet. Flipping can be bound to keys (not done by
> > > default
> > > since there are few keys free).
> > >
> > > So here is a summary of what you can do:
> > >
> > >
> > > * Rotate canvas
> > >  - Via GUI spin-entry box:
> > >    * Directly enter a number.
> > >    * Mouse up/down to change by ±1°.
> > >    * Click on + or − to change by ±1°.
> > >    * Left click to open pop-up.
> > >  - Via Key shortcut
> > >    * Inkscape Preferences->Interface->Keyboard Shortcuts, View
> > >     - Rotate Clockwise          (Recommended: 'Shift-(')
> > >     - Rotate Counter-Clockwise  (Recommended: 'Shift-)')
> > >     - Rotate 0                  (Recommended: '0')
> > >    * Uses /options/rotateincrement/value for step size if set.
> > >  - Via Ctrl-Middle-Mouse-Button.
> > >     Drag cursor keeping Middle-Mouse-Button down to rotate.
> > >     Release mouse button to end.
> > >    * No auxilary key: ±1°.
> > >    * Shift: ±15°.
> > >    * Alt: arbitrary rotation.
> > >    * Shift + Ctrl: reset to zero.
> > >
> > > * Flip canvas
> > >  - Via Key shortcut
> > >    * Inkscape Preferences->Interface->Keyboard Shortcuts, View
> > >     - Flip Horizontal  (Recommended: 'Shift-H')
> > >     - Flip Vertical    (Recommended: 'Shift-V')
> > >     - Flip None
> >
> > Thank you very much for the work. The shortcut keys are great now
> > :)
> >
> >
> > --
> > Raghavendra Kamath
> > Illustrator
> > raghukamath.com
> >
> > -----------------------------------------------------------------
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>

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