[Qgis-user] Node Tool - proposing improvements

[Bernhard Ströbl]

Hi Nyall,

the reason to post this issue to the users' list was to get feedback 
from users (and developers, too). I am totally aware that a QEP would be 
appropriate but I doubt that many users are taking part in the 
discussion there.
Anyways I am going to sum up the results and create a proposal later on, 
will that do?

Bernhard

Am 27.11.2018 um 01:23 schrieb Nyall Dawson:
> On Mon, 26 Nov 2018 at 21:39, Bernhard Ströbl <bernhard.stroebl at jena.de> 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.
> 
> Hi Bernhard,
> 
> Thanks for the detailed proposal, and for taking the time to come up
> with a constructive way forward here.
> 
> Can I encourage you to copy the contents of your proposal across to
> the "QEP" repository:
> https://github.com/qgis/QGIS-Enhancement-Proposals/issues ? I think
> that's the correct channel to discuss these ideas so that the
> conversation is kept central and recorded permanently for reference.
> 
> Nyall
> 
>>
>> 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.
>> 2) Highlighting effect is disturbing.
>> 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).
>> 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).
>> 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.
>> 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.
>>
>> 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
>>
>>
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-- 
Bernhard Ströbl
Anwendungsbetreuer GIS

Kommunale Immobilien Jena
Am Anger 26
07743 Jena

Tel.: 03641 49- 5190
E-Mail: bernhard.stroebl at jena.de
Internet: www.kij.de


Kommunale Immobilien Jena
Eigenbetrieb der Stadt Jena
Werkleiter: Karl-Hermann Kliewe


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