[Qgis-user] Node Tool - proposing improvements

Tue Nov 27 06:51:22 PST 2018

Bernhard Ströbl wrote
> Dear all,
> 
> I want to apologize, this has become an extremely long mail...
> 
> A lot of discussion has been going on about the recent reimplementation 
> of the node tool in QGIS 3.
> 
> I see two reasons for this:
> 1) The way the tool works is very different from the way it used to work 
> in QGIS 2:
> a) in QGIS 2 it was choose feature - choose node(s) - do something 
> whereas in QGIS 3 it is choose node - do something
> b) to move a node was click - (keep pressed) - move - release which was 
> changed to click - release - move - click - release
> 2) There have been several bugs (as could be expected with a new 
> implementation). These, however, were used to question the whole feature 
> (most of the bugs are fixed now).
> 
> Apart from bugs and people not being used to the new tool the critics 
> concentrate around:
> 1) Probably most annoying: Mouse movements for choosing an existing 
> vertex/adding a new vertex at the middle of the line are not well 
> defined (especially important if features and its vertices are very 
> close together). Imagine a polygon surrounded (or even worse: 
> overlapped) by others, now try to click a particular vertex. You will 
> fail if always the neighbouring polygon is highlighted. The workaround 
> is to select the vertex with a mouse window while its feature is 
> highlighted (or previously select the feature e.g. with the 
> Select-Feature tool). For overlapping features it is even harder.

I agree with the perplexities;
In fact the clicks have increased significantly compared to 
the version of QGIS2(where a user may add a vertex anywhere and not just in
the middle of the segment...),
this new behavior, during a day long editing session it translates into
about 1-2 hours 
spent to moving vertices from the center of the segment to the desired
position.

> 2) Highlighting effect is disturbing.

The vertex highlight is not only disturbing, 
but It seems Impossible to hold it for example when zooming in or out, 
then te user can easily lose the knowledge of the polygon he was editing 
(time spent to find the desired polygon)

> 3) Adding a new vertex puts the new vertex on the mouse ready to be 
> moved but user has no intention to move it but to leave it where it has 
> been added (e.g. for topological reasons).

this also translates into time spent trying to figure out how to reposition
the vertex

> 4) Vertices are not visible all the time but only when the feature is 
> highlighted. This can make choosing a particular vertex difficult (see 
> also 1).

I would suggest going back to keeping the highlight fixed 
once the interested polygon has been selected with keeping the vertices
always clearly visible until a user's new instruction

> 5) It is easy to accidentally add or move a vertex because the most 
> intuitive way of selecting something is to click it. But when you click 
> a vertex/segment/cross while being highlighted you are already on your 
> way to move it.

this is another disappointing behavior, the selection of the vertices
happens only passing with the mouse on the polygon 
but, 
in a polygon with thousands of vertices it is almost impossible to choose
the one or those need to edit if the vertices 
do not remain highlighted (where the vertices are on polygon? The user
should select them randomly? How much time is lost to find the right ones to
edit?)

> 6) The behaviour is not consistent:
> a) If you want to move _one_ vertex, try to grab it when it is 
> highlighted then move it; if you want to move several vertices, first 
> select them, then click them, then move them.
> b) If you want to delete a vertex, try to grab it when it is 
> highlighted; if you want to delete a segment, do not try to grab it when 
> it is highlighted but select its two vertices and delete them.

nothing to add here, the incongruity speaks for itself (in my opinion, the
users they must know clearly and visually the exact position of the vertexes
in a polygon when they need to edit them)

> The German user group thinks that the points raised above are valid, 
> even if all pending bugs are fixed. The node tool is still not perfect 
> (it wasn't in QGIS 2 either).
> 
> So we propose a change in the way the node tool works and would like to 
> hear other users' s opinions.
> While the click - move - click change has valid reasons (use advance 
> digitizing panel, pan or zoom map while moving vertices) the dropping of 
> the first choose feature - then choose vertex workflow to immediately 
> move a vertex has no real reasoning (except that it is less clicks in 
> those cases where the node can be easily grabbed in the first place). 
> But this new workflow is the main cause for the problems listed above.
> 
> Therefore we would like to see the old workflow reimplemented with some 
> of the new ideas added plus some new ingredients. This is the draft for 
> how the tool might work in the future:
> 
> 1) While the mouse is moved around features are highlighted to indicate 
> they can be edited. Furthermore eventual vertices, segments or crosses 
> are highlighted, too (as in QGIS 3).
> 2) While a feature is being highlighted, it can be chosen with a left 
> click (new).
> 3) If the user makes a right click instead, another (adjacent) feature 
> is highlighted and can be chosen with a subsequent left click and so on 
> (new).
> 4) As soon as a feature is chosen, the Vertex-Editor panel is opened (as 
> in QGIS 2).
> 5) A chosen feature is the only feature whose vertices can be edited at 
> that point* (as in QGIS 2). The chosen feature and all its vertices stay 
> visible until the end of this feature's editing session (as in QGIS 2). 
> If a vertex was highlighted it is immediately selected, if a segment was 
> highlighted, its two vertices are immediately selected, if the middle of 
> a segment was highlighted with a cross a new vertex is created there and 
> immediately selected (new).
> 6) A vertex is selected by left clicking on it (as in QGIS 2).
> 7) Several vertices are selected by using a mouse window (as in QGIS 2 
> and 3).
> 8) A click on a segment selects its two vertices (as in QGIS 2).
> 9) Vertices can be selected via the Vertex-Editor panel, too (as was in 
> QGIS 2)
> 10) Every new vertex selection clears any previuos selection except if 
> Crtl is pressed which adds the new selection to the current if vertices 
> were not selected or subtracts them from the current selection if they 
> were selected (as in QGIS 2).
> 11) Selected vertices can be deleted (as in QGIS 2 and 3).
> 12) Selected vertices can be moved by clicking either of them, thus the 
> vertex (the vertices) are attached to the mouse and can be dropped with 
> another left click (as in QGIS 3). A right click aborts the moving 
> operation but the vertices are still selected (new).
> 13) A new vertex can be created by double clicking on any segment (as in 
> QGIS 2 and 3), the new vertex is immediately selected (new).
> 14) A right click ends the chosen feature's editing session, if another 
> feature is within reach it is immediately highlighted, continue as in 1) 
> (new).
> 14b) To be discussed: Left clicking another feature immediately chooses 
> this feature (as in QGIS 2).
> 
> * topological editing is still posssible, of course
> 
> We see the following advantages in this approach:
> 1) The new quick editing possibilities are preserved, there is just one 
> additional click (compared to current QGIS 3) to move an existing vertex 
> or segment or to create and immediately move a new vertex.
> 2) It is easier to create a new vertex in place.
> 3) It is a lot easier to graphically choose the feature to edit.
> 4) The highlighting indicates, which feature will be chosen by an 
> immediate click, no surprises for the user.
> 5) It is easier to graphically select the vertices to edit.
> 6) The workflow is always the same: Choose feature - select vertices - 
> do something with them.
> 7) The workflow is consistent with creating a new feature (right click 
> to finish editing).
> 8) The application is more consistent because graphically selecting 
> vertices works the exact same way as graphically selecting features with 
> the Select-features tool.
> 
> I appreciate your feedback
> 
> Bernhard

I hope these will be possible by adding suggestion and/or reimplementing
useful behaviors for selecting highlight and editing vertex listed above, 
because these are the main causes of the difficulty of use 
and the loss of ergonomics compared to QGIS2

Regards

Antonio

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Antonio
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