Double-click (fast tap) of tablet pen when editing a path do not add node.

Related to or duplicate of bug #559140 “On canvas node adding doesnt work anymore”?
Also mentioned in bug #624277 “XInput settings stored” (as secondary issue).

Maybe bug #559140 needs to be reopened (it was closed as 'Invalid' by the reporter - apparently the problem no longer occured after resetting the preferences…)?

Note:

1. I have found this bug on a fresh, not used upgrade of Inkscape. During tests I did wiped out whole ~/config/inkscape folder to be sure there is no "dead" settings. I also inspected preferences.xml file looking for tablet specific settings which may be related to click/double-click/drag recognition. I did not found any.

2. I played a bit again with 0.47 to check how does the "click/drag threshold" setting affects mouse and how does it affect tablet.

 First this is not exactly true what I have written earlier. If this value is large it is easy to click on a segment of curve to select it (both adjacent nodes are selected). The double click inserts node. If this setting is zero doing the same requires exact accuracy. Normally if cursor is in a mode allowing selection of a segment and inserting a node it changes to a "hand". If "mouse-click/drag" threshold is zero, it just flickers when it is _exactly_ over the line segment. So in my opinion this option does not only control how to recognize click from drag but also controls "grab" ability when editing nodes. When moving objects (but not editing them) "grab sensitivity" seems to not control anything while "click/drag" do control how far one needs to move cursor to drag an object. But still, in node edit it also controls when cursor changes into a "hand".

The "click/drag threshold" set for mouse also applies to a tablet - when I do set it to zero (my hand+tablet has a 2..3 pixels jitter) it is impossible to do a thing with a path.

3. I did upgrade again to 0.48 and focused on nodes selection and "cursor changes to hand" case. To my surprise it worked as expected, till I killed all copies started prior the upgrade. After a clean restart of Inkscape the faulty behavior returned.

So I did change "click/drag threshold" to zero. This time even with a mouse I wasn't able to change cursor from arrow to hand when in node edit mode. So this is a first difference between 0.47 - 0.48. Then I tested if I can see any influence of "grab sensitivity" - as in 0.47 I can't see it. So I set "click/drag threshold" back to reasonable value.

When moving cursor with a tablet cursor do change to a hand the same way as with a mouse. With a single tap I'm able to select a path segment. I'm also able to drag it. But not to insert a point by double fast tap.
So the same way as in 0.47 the "click/drag threshold" does affect both mouse and tablet.

I moved to "Input devices" section. My tablet is a "Bamboo" with a pen only with tap, pressure and two buttons.. A generic driver reports however a plenty of other elements: eraser, finger and a set of buttons. I noticed however that all wacom elements are disabled. Well... I'm pretty sure I enabled them... Since I do not use pressure sensitivity I didn't notice any change in behavior. Ok, my wrong - I did enable a pen and verified that there was no pressure sensitivity earlier and now it is working.

It do NOT affect bug reported. In screen mode double tap still is not working. In window mode... well... I could not figure out how the heck window mode works - on my system in window mode cursor shown on screen is far off from the point when drawing takes place. It s...

I have found the same problem using Inkscape 0.48.1 on Windows Vista 32 bit (SP2 I think - recently updated) using a Wacom Bamboo Pen tablet. I have to click on the add node icon.

Clive Catterall

I can confirm the bug with Inkscape 0.48.1 in Debian Testing and 0.48.2 in Linux Mint 12 with Genius Pensketch and Wacom Bamboo tablets respectively.
Both 64 bit, both Gnome3 (3.0.1 and 3.2).

I found a workaround (doesn't solve the problem but makes possible adding nodes with tablet): Pressing CTRL+ALT and tapping once on the path with the tip of the pen adds a node in that exact position.

Changing
- Bug status to 'Confirmed' based on multiple user reports
- Bug Importance to 'Low' (for now) since two alternative methods to insert nodes exist (the regression does not completely preventing tablet users from inserting new nodes in the node tool context).