Contour plots with no colorscale should go in the legend #2880

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1. alexcjohnson

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   bugsomething brokensomething broken

   featuresomething newsomething new

   status: discussion needed

   on Aug 7, 2018
2. etpinard commented on Aug 7, 2018

   

   etpinard

   on Aug 7, 2018

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   Always give contour traces the showlegend attribute, and have it default to true for both contours.type='constraint' and contours.coloring='none' traces, false otherwise.

   I agree, this should be the default behavior. But I think the contours.coloring: 'none' part qualifies as a backward incompatible change even though contours.coloring: 'none' traces never have colorbars. So I'd vote for making showlegend: false by default whenever contours.type !== 'constraint' in v1 and change to a smarter default in v2.

   Make a way to display even contours with colorscale in the legend.

   That would be cool. Would contours.showlegend: true | false be too confusing or legendmode: 'trace' | 'contours' be better?

   We don't have a clean API for toggling contour levels, so I suspect click/double-clicking on those legend items wouldn't do anything in this iteration?

   The legend entry could either just show the line (which has a single color),

   Not if contours.coloring is set to 'lines'.

   or perhaps for consistency we fill below either using the middle color or with a gradient showing the whole colorscale.

   This one is tricky, if we want to cover all cases in one glyph, we could show a gradient corresponding to the colorscale in a rectangle and have its border follow the trace line style.That way contours.coloring: 'line' traces would have unfilled rectangles as legend items,
3. phxnsharp commented on Aug 8, 2018

   

   phxnsharp

   on Aug 8, 2018

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   @alexcjohnson Yes, looks like my coder created a colorscale that is uniform, not knowing you could do anything else. Here is the typescript that creates the trace:

         return contourDataGenerator.run(zVar.metadata.name, cancelToken)
            .then((results: IContourData) => {
   
               let trace: IPlotlyContourTrace = {
                  colorbar: {
                     exponentformat: PlotlyStdValues.STD_EXPONENT_FORMAT,
                     tickformat: PlotlyStdValues.STD_NUMBER_PRECISION,
                     title: GuiTextService.toNameAndUnitsFromVar(zVar),
                  },
                  type: 'contour',
                  x: results.x1Vals,
                  y: results.x2Vals,
                  z: results.zVals,
                  name: 'Contour: ' + GuiTextService.shortenFullVarNames(zVar.metadata.name),
                  hoverinfo: 'none',
                  contours: {
                     type: 'levels',
                     coloring: 'lines',
                     showlabels: true,
                     labelformat: PlotlyStdValues.STD_NUMBER_PRECISION,
                  },
                  colorscale: [[0, color], [1, color]],
               };
   
               return trace;
            });
   

   And to write it down for posterity, for our use case we do not require the colorscale mode combined with constraints at all. If it is available, we will make it available to our users but our defaults will always draw with contours.coloring set to 'none'.

   👍React with 👍1Reacted by Alex Johnson
4. alexcjohnson commented on Aug 15, 2018

   

   alexcjohnson

   on Aug 15, 2018

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   Further discussion needed on if and how to automatically avoid legend/colorbar overlaps

   Moved this to #420 as it would be a breaking change. The rest of this issue is handled in #2891 so closing.
5. alexcjohnson

   closed this as completedon Aug 15, 2018