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Allow a reference point to be specified for interactive zooming #211

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cpietsch opened this issue Jul 12, 2020 · 7 comments · May be fixed by #212
Open

Allow a reference point to be specified for interactive zooming #211

cpietsch opened this issue Jul 12, 2020 · 7 comments · May be fixed by #212
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@cpietsch
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cpietsch commented Jul 12, 2020 •
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In d3 v3 there used to be a zoom.center() to adjust the target point while zooming via mousewheel / touch. Basically you could define a (center) target and when the user does a zoom input the zoom would steer in that direction. This was useful to avoid zooming into dead space of a scatter plot.

I made a workaround for this feature by modifying the zoom transform in the zoom callback and @Fil made a nice hack to override the mouse position

Probably the location to add this feature would be here somewhere here. Instead of using the mouse position we could use a reference point which needs to be declared before.
@Fil Fil added the feature label Jul 12, 2020
@mbostock
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Sounds reasonable. These are supported in the programmatic interface #178 #184, but not yet in the wheel and dblclick listeners.

d3-zoom/src/zoom.js

Line 219 in c609de4

p = mouse(this);

d3-zoom/src/zoom.js

Line 284 in c609de4

p0 = mouse(this),

Presumably we could allow a function or a constant, and have it default to d3.mouse (d3.pointer in d3-selection@2) for the current behavior.
@cpietsch
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It could be also used for the touch input.
Suggesting zoom.reference(point/function) that replaces the centroid function for non interactive zoom and mouse for interactive zoom ? Or just have one interface for the interactive reference.
Fil added a commit that referenced this issue Jul 13, 2020
@Fil
zoom.center() defines a center function for the reference point of th…
aa8323f 
…e zoom; defaults to d3.pointer

fixes #211
@Fil Fil linked a pull request Jul 13, 2020 that will close this issue
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@Fil
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Fil commented Jul 13, 2020

More remarks after a first (failed) attempt:

scatterplot example:

  • for the wheel input:
    • changing the center should only be done once at the start of the gesture—otherwise when wheeling "out" we get jittering (the movement gravitates to a triangle's circumcenter, and the reference point jumps between the three vertices of that triangle).
    • when wheeling out, it's better not to set the center
  • for the touch input, the gesture feels weird when the reference point is not between the two touches. I'd rather not have it at all.
  • for the programmatic zoomIn button, I added the same logic

complete example now at https://observablehq.com/d/9035ed7049aaa8c6

target example:

  • the following sequence does not work properly: mousedown, wheel, then translate (the transform "jumps" when translating)

(issue visible at https://bl.ocks.org/mbostock/6226534, which is d3v3)

notebook example with d3@6 (alpha) at https://observablehq.com/d/48ff4a64c477cc79
Fil added a commit that referenced this issue Jul 13, 2020
@Fil
zoom.center() defines a center function for the reference point of th…
14ab156 
…e wheel event; defaults to d3.pointer

fixes #211
Fil added a commit that referenced this issue Jul 13, 2020
@Fil
fix the mousedown-wheel-translate issue
f76063d 
(see comment #211 (comment))
@cpietsch
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Wow, nice work! Looks like the issue is quite interwoven.
The scatterplot example works great. One suggestion would be to use event.deltaY < 0 for the wheel-in detection.
The sequence on d3v3 is working fine with my Firefox, but on the d3@6 notebook it swallow some translations (only if I move very fast).
@filipinascimento
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Hey any updates on that? I think Fil's PR does not work anymore with the latest d3. Having the center functionality would be great for data snap on zoom and for some pseudo-3D interactions.
@ptgamr
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ptgamr commented May 30, 2023

I am in desparate need for this center() function
Fil added a commit that referenced this issue May 30, 2023
@Fil
zoom.center() defines a center function for the reference point of th…
df77d81 
…e wheel event; defaults to d3.pointer

fixes #211
Fil added a commit that referenced this issue May 30, 2023
@Fil
fix the mousedown-wheel-translate issue
3afbe2a 
(see comment #211 (comment))
@Fil
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Fil commented May 30, 2023

I've refreshed #212 (there was a small conflict on README.md), and upgraded the test notebooks.
@tomatenhans tomatenhans mentioned this issue Sep 11, 2023
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@Fil @cpietsch @mbostock @filipinascimento @ptgamr