Allow Artists to show pixel data in cursor display #3989
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| @@ -2791,6 +2791,12 @@ def mouse_move(self, event): | |||
| except (ValueError, OverflowError): | |||
| pass | |||
| else: | |||
| ax = event.inaxes | |||
| artists = ax.artists + ax.images + ax.lines | |||
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Should also look at ax.collections (that is where things like scatter live) and maybe ax.patches
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and the order should be ax.collections + ax.patches + ax.lines + ax.artists + ax.images to match the order used for sorting out the rendering order in Axes.draw (around https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/axes/_base.py#L1993 images are special cased around line 2030).
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They then get ordered by zorder anyway: https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/axes/_base.py#L2036
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Ok then. So how to handle composite images? It does not seem feasible to recreate the composite every time.
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The AxesImage could composite the specific pixel on demand.
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I think to first order, just ignore the compositing and use the top image.
The in-place compositing is only for some of the vector backends which can't do it them selves (ex pdf) to try and save space (so you don't have multiple overlapping images) but it leads to other bugs as all images get smashed to the same zorder relative to the other lines etc. In Agg (which backs all but 3 (gtkcairo, macsox and windows) of the interactive backends) the whole if _do_composite block is skipped and the compsiting is taken care of at the c++ layer.
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How's that? I noticed |
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However, it looks like |
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Probably worth having a top-level module for useful event handlers, which I think we greatly reduce the threshold to get people using the event system. @WeatherGod @joferkington thoughts? Yes to separate PR for re-ordering |
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I think we do need to handle compositing. For instance, if I run this example, I get the Zdata for the overlay layer. How about just checking for |
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Well, the more I think about it the more I agree that the top image should get priority. The canny value really is the point of the example. |
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Added |
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Do I still "need revision"? |
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Looks good to me. I am a tad wary of the I would like @WeatherGod to weigh in. |
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What do you mean "does not use |
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Meaning it should be a static method? |
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Either way I think it belongs in the class so it can be overridden. |
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Yes, it is an instance method which does not refer to it's instance and I can't think of a use case where you would want to (but I may just have poor imagination). I thought about suggesting to move it to |
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I'd worry that adding a |
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This also needs an entry in https://github.com/matplotlib/matplotlib/tree/master/doc/users/whats_new |
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Done. |
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@matplotlib/developers Can this get eyes from someone else but me? This addresses a long standing and frequent feature request in a pleasingly general way. |
| """ | ||
| Get the zdata for a given event, as a string message | ||
| """ | ||
| return '' |
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Why do you want to use a string for this? Shouldn't "data" always be numeric?
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This allows the Artist to control the display of numbers, similar to the existing ax.format_coord.
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I agree with @efiring on this one. I can think of a lot of use cases (e.g. interactive sampling) where it would be very convenient to access a "raw" value. Returning a numerical value would make this method useful for a lot more than just display.
You already have a separate method for the formatting, so it's only slightly more verbose to flip the function calls on their head and make the displayed string using artist.format_zdata(artist.get_zdata()). In my opinion, this would be a better approach overall.
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Ha! I originally meant to do that...
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@joferkington again. Sorry to pester, but I see you are doing OSS stuff today and would like your feed back on this 😄 |
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@tacaswell - Absolutely! Sorry I've been so out-of-touch with things lately, as well. |
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ENH: Allow Artists to show pixel data in cursor display
Also adds implementation for
AxesImage. Closes #3984.Inspired by mpldatacursor.