[Bug]: Colorbar with drawedges=True and extend='both' does not draw edges at extremities #22864

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1. oscargus

   added

   topic: color/colorbar

   on Apr 20, 2022
2. oscargus commented on Apr 20, 2022

   

   oscargus

   on Apr 20, 2022

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   Fixed in #22865
3. timhoffm

   closed this as completedin #22865on Jun 15, 2022
4. QuLogic

   added this to the v3.6.0 milestone on Jun 15, 2022
5. QuLogic commented on Jun 15, 2022

   

   QuLogic

   on Jun 15, 2022

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   @oscargus running the example from the OP on main, I see a boundary on the left side, but not the right side.
6. QuLogic

   reopened this on Jun 15, 2022
7. QuLogic

   modified the milestones: v3.6.0, v3.5.3 on Jun 15, 2022
8. oscargus commented on Aug 3, 2022

   

   oscargus

   on Aug 3, 2022

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   Sorry for not getting back to this until now. I can just confirm your observation. However,

   In [3]: cbar.dividers.get_segments()
   Out[3]: 
   [array([[0., 0.],
           [0., 1.]]),
    array([[1., 0.],
           [1., 1.]]),
    array([[2., 0.],
           [2., 1.]]),
    array([[3., 0.],
           [3., 1.]]),
    array([[4., 0.],
           [4., 1.]]),
    array([[5., 0.],
           [5., 1.]]),
    array([[6., 0.],
           [6., 1.]]),
    array([[7., 0.],
           [7., 1.]]),
    array([[8., 0.],
           [8., 1.]]),
    array([[9., 0.],
           [9., 1.]])]
   

   So the right-most line is definitely included, not just drawn,,.

   For the svg and pdf output, the first and last line are about half the width of the other lines. I am wondering if maybe there is something strange with the positioning.

   Looking at the png, it is clear that the right-most tick is actually positioned what seems like a bit too far to the right:
   
   So maybe the line is rendered below the extend patch? I am not really sure how to get around this?
9. tacaswell commented on Aug 4, 2022

   

   tacaswell

   on Aug 4, 2022

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   @QuLogic and I talked about this on our checkin today. We think the solution is to turn off clipping on the dividers.

   import matplotlib as mpl
   import numpy as np
   import matplotlib.pyplot as plt  
   from matplotlib.colors import from_levels_and_colors
   
   my_cmap = mpl.cm.viridis
   bounds = np.arange(10)
   nb_colors = len(bounds) + 1
   colors = my_cmap(np.linspace(100, 255, nb_colors).astype(int))
   my_cmap, my_norm = from_levels_and_colors(bounds, colors, extend='both')
   
   plt.figure(figsize=(5, 1))
   ax = plt.subplot(111)
   cbar = mpl.colorbar.ColorbarBase(ax, cmap=my_cmap, norm=my_norm, orientation='horizontal', drawedges=True)
   plt.subplots_adjust(left=0.05, bottom=0.4, right=0.95, top=0.9)
   cbar.dividers.set_lw(5)
   cbar.dividers.set_clip_on(False)  # drop this line and you see the lines cut in half at the edges.
   plt.show()
   
10. tacaswell commented on Aug 4, 2022

    

    tacaswell

    on Aug 4, 2022

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    and in the Agg case there is definitly an issues with low dpi and pixel snapping.
11. QuLogic

    added 2 commits that reference this issue on Aug 4, 2022

    Don't clip colorbar dividers

    ...

    This issue will close once commit 298a23f is merged into the 'main' branch.

    298a23f

    Don't clip colorbar dividers

    ...

    This issue will close once commit 8fa6bd5 is merged into the 'main' branch.

    8fa6bd5
12. tacaswell

    closed this as completedin #23549on Aug 9, 2022
13. oscargus

    added a commit that references this issue on Aug 10, 2022

    Don't clip colorbar dividers

    ...

    This issue will close once commit dcf7c0b is merged into the 'main' branch.

    dcf7c0b