Inkscape

How can I edit LPE, not object geometry?

Asked by Windell Oskay

After applying a live path effect (LPE) to a given shape, it sometimes seems like the "edit paths by node" tool is only interested in letting me edit the shape of the object-- it does not seem to show the control handles for the LPE.

Is there a command or tool that I can pick that will force Inkscape to let me edit the LPE, not the object geometry?

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Best su_v (suv-lp) said : 		#1

Not all live path effects do have a) parameters to be edited (e.g. the Spiro path effect) or b) handles to edit the path effect parameters on-canvas. If the path effect has parameters, you can always edit or access them in the path effect editor (menu 'Path > Path Effect Editor') - either numerically or by clicking on the 'Node-edit' icon (e.g. for bend paths or patterns) there.

If the parameters of an LPE can be edited on canvas, you can access them from within the node tool: the 4th icon from the right on the controls bar ("Show next editable path effect parameter") allows editing the handles of path effect parameters (and cycling through all parameters - e.g. access all 4 bend paths, one by one, of the Envelope path effect).

There are keyboard shortcuts defined for LPEs, but I'm not sure if they work with all keyboard layouts/platforms (on my Mac with de_CH keyboard layout 'Ctrl+Shift+7' doesn't - because 'Shift+7' is '/', but 'Ctrl+Shift+&' works fine):
Ctrl+Shift+& Open path effect editor dialog
Ctrl+Shift+7 Open path effect editor dialog
7 Edit next path effect parameter

Some things to consider:
- If a path uses a stack of path effects, the shortcut '7' (or the corresponding icon on the node tool controls bar) apparently always accesses either the last LPE applied or the one selected in the path effect editor.
- Sometimes the handles might be out of sight: the pattern of the 'Pattern along path' effect is located in the upper left corner of the page (but can be dragged closer to the path affected by selecting all nodes and dragging the path as known from the normal node-editing)
- If a parameter like a bend path or pattern has been linked (not pasted) to another path, you need to edit the original path and the change will be live-updated for the path using said path effect.

Maybe you can describe in more details with which path effect you have difficulties accessing the parameter handles? Do you work with path effects on groups or on single paths? Do you use stacks of path effects (multiple effects applied to the same path or group)?

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su_v (suv-lp) said : 		#2

The introduction to path effects in the manual also includes a summary about on-canvas editing of path effect parameters (called 'control paths' there), in the second half of the page:
<http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Paths-LivePathEffects.html>

Note that some minor details might have changed in 0.48 (due to the re-factored node tool).

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vwanweb (vwanweb) said : 		#3

Its not clear in your description which path effect you are using and how you are applying it. Are you using the Path Menu >Path >Path Effect Editor...?

I will provide feedback based the path effect editor...

zoom to a level where you can see the outline of the Page Border.

Draw a curvey line using the Bezier tool with these settings, set via the Tool Controls Bar. (the bar just above the canvas). Draw your path at the TOP LEFT corner of the page border.

Using the BEZIER TOOL (Shift+F6, b) in SPIRO MODE, with a SHAPE of TRIANGLE IN.

Once you have drawn the spiro path, open the >Path >Path Effect Editor... dialog.

there are THREE sections to the effect editor dialog
1. Apply New Effect
2.Effect LIst
3.Current Effect

In the CURRENT EFFECT area Click on the PATTERN ALONG PATH effect.
Now click the 1st icon of the top row setting titled "PATTERN SOURCE" .
The source pattern will be on your canvas just above the top left corner of the inkscape page border and will have a STROKE COLORING of GREEN. You can now edit the SOURCE like any other path, add nodes, lines to curves, rotation scale etc.

The GREEN paths are the visual settings letting us know we are manipulating the "EFFECT'S VECTORS" and not the actual PATH VECTORS... Hope this makes sense and helps you out.

If not I would suggest you provide more detail on what exact path effect you are using and how you are applying it. As the >Extensions menu has some path based effects that can be applied vs. the >Path >Path Effect Editor...

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Windell Oskay (windell) said : 		#4

Thank you ~suv.

The particular case is with a Hatches (rough) LPE. I have taken a path object, applied the LPE (once), and then (with the edit paths by node tool) I can edit the hatch with the handles.

In either case, with it editable or not, the "Show next editable path effect parameter" tool says that there are no editable parameters.

Update: I have found the problem, which was that the control handles were simply "out of sight."

I am unsure how the handles could get so far away. With the LPE settings as they were, usually the handles are all very close to center, but none of the four were visible.

And, thank you again for the hint.

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Windell Oskay (windell) said : 		#5

Thanks ~suv, that solved my question.

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su_v (suv-lp) said : 		#6

Did you copy and paste the path effect(s) from another object?

I can see that the handles are offset for both objects at the right end in the sample you attached to bug #657139. It can also be reproduced in a new drawing when copying and pasting a path effect to a second object: the objects are now sharing the same path effect definition and the handles are displayed at the location where the path effect was first added.

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Windell Oskay (windell) said : 		#7

I did copy and paste the path effect, but only as an attempt to solve this problem, so I do not *think* that it was the original cause, but I cannot prove it one way or another.

(I did generate the example file for the bug report at the same time that I was struggling with this issue, but I do believe that that bug is real and independent of my failure to locate the handles.)

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su_v (suv-lp) said : 		#8

Yes, the bug can be reproduced and has no relation to the display of the handles. I'm just not yet sure if it is an unsupported feature (-> wishlist) or a bug (broken path effect) ;)

Similar issues can be observed when using a path for the hatch effect with several levels of self-intersections (but only one sub-path): the hatched areas vary seemingly at random when dragging a node (changing the size of level of an intersecting region) or one of the parameter handles (knots) and only sometimes correspond to filled areas rendered without the path effect applied.