gl2d known limitations

[etpinard]

A list of known limitations in gl2d graphs in comparison with svg2d feature set:

• image export isn't reliable (meaning gl2d graphs have no image test support)
• scatter mode: 'text' (for text charts) is not available
• 'free' axes and 'overlaying' axes are not available. But subplots, insets, shared axes work. Hurdles: free axes with custom 'position' would need an option to make a gap between the data-box and the axis in gl-plot2d, overlaying axes would need more logic around when to show grid lines, scene backgroud color and have hover events propagate down. ✅ Fixed with regl.
• data-reference annotations/shapes are not available (paper-reference annotations/shapes work)
• fill options tonexty, tonexty, and toself are not avaliable (tozerox and tozeroy work) ✅ Fixed with regl.
• the marker.symbol is pretty good since v1.28.0 but not on-par with svg ✅ Fixed with regl.
• px-specified line.dash are not available
• no line.shape: 'spline' update: 'hv', 'vh', 'hvh', 'vhv' added in Scattergl improvements for: fill tozero with bad values fix, fills layering fix, add some line.shape values #3087
• axis titles are not centered (positioning algo does not consider text width)
• tick marks don't support \n (most common in date axes)
• axes don't support decreasing (custom or with autorange: 'reversed') ranges. ✅ Fixed with regl.
• hovermode x and y are not available (toggling hover on/off in modebar works). ✅ Fixed with regl.
• no support for axis fixedrange (would need to tweak gl-select-box). ✅ Fixed with regl.
• double click and shift click interactions are not supported. ✅ Fixed with regl.
• cartesian + gl2d subplot on the same graph are not supported. ✅ Fixed with regl.
• plotly_hover, plotly_unhover and plotly_click are not emitted [done in Hover / unhover events on the 2d WebGL plots #994]
• setting hoverinfo to 'none' should disable the hover spikes. ✅ Fixed with regl.
• a hover spikes sometimes appears prematurely after initial Plotly.plot call
• select box and lasso selections are not supported
• single-axis zoom/pan and corner zoom interactions are not supported
• zoom-box doesn't follow cursor outside the plot bounds (i.e. no cover slip). ✅ Fixed with regl.