Sorry, I may have been being a bit dramatic
In mpl.patches: Arrow, FancyArrow, YAArrow, FancyArrowPatch,
ConnectionPatch + annotation related artists + some classes in axisartist
which now that I look at them are not really general purpose arrow tools.
I had not been counting quiver (or barbs) or sankey.
Neil: Those are all great questions! Much of the arrow related code was
written by Joe-Joon Lee who (by having read a good deal of his code) has a
habit of writing very power but very opaque python.
I believe that the line join style is controlled by `joinstyle` on the
graphics context and it is up to the backends to implement that correctly.
Tom
On Wed, May 13, 2015 at 10:58 PM Neil Girdhar <mistersh...@gmail.com> wrote:
> Okay, I'm looking at this in more detail and there may be some design
> concerns:
>
> The arrow placement is decided without asking the arrow any questions,
> such as its bounding box. Instead, the arrow should return a bounding box
> and then the line should retreat until the bounding box no longer
> intersects the target node. Then the arrow should be placed. This doesn't
> matter so much when you have a simple arrow like this: ---->, but it's a
> big deal when you have an arrow like ----| . In this case, the sides of
> the arrow risk intersecting with the target node.
>
> I'm not keen on implementing every arrow three times: <-, ->, <->. This
> really should be handled by the code placing the arrows for many reasons:
> 1. It should also be possible to have a different arrowhead at either end
> of the line.
> 2. It should be possible to stack the arrows, for example having two heads
> one after another (to represent two kinds of relationships). This is
> another reason to be able to ask the arrowhead its length and so on.
>
> I don't understand the "monolithic" keyword. How can the arrow draw the
> line as well when it doesn't know the line style, color and so on?
>
> I think I like the design of the transmute function. I'm curious:
> ultimately, where does the mutation_size come from? Is it a global scale
> applied to the figure, or is it based on the linewidth, or?
>
> When you emit a set of lines, how are they joined? If I draw a line
> having linewidth 0.1 from the origin to (1, 0), and back to (0, 0.5), what
> happens at the tip? Are two rectangles drawn (each having width 0.1, but
> oriented differently)? Is a bevel created? A miter? Or is the tip
> rounded? Can this be controlled? See page 166 of the manual I sent
> earlier (search for tikz/line join).
>
> Best,
>
> Neil
>
> On Wed, May 13, 2015 at 10:14 PM, Neil Girdhar <mistersh...@gmail.com>
> wrote:
>
>> Thanks, it works!
>>
>> I needed to add:
>>
>> import matplotlib.patches
>>
>> to one file and
>>
>> plt.show()
>>
>> to the other.
>>
>> Any word on the locations in the code of the seven arrow drawing methods?
>>
>> I've located the arrow drawing code in tikz, and so I can start porting
>> it over. I'm curious, do we know the linewidth of the edge being decorated
>> by the arrow? To make arrows scale nicely, most of the arrow dimensions
>> are given in two pieces: an absolute value (in points for example) and a
>> line width factor. The dimension is the absolute value plus the line width
>> factor times the line width. The TikZ manual explains: "This makes it easy
>> to vary the size of an arrow tip in accordance with the line width –
>> usually a very good idea since thicker lines will need thicker arrow tips."
>>
>> Best,
>>
>> Neil
>>
>> On Wed, May 13, 2015 at 10:07 PM, Benjamin Reedlunn <breed...@gmail.com>
>> wrote:
>>
>>> Neil,
>>>
>>> I have attached code to draw the arrowhead.
>>>
>>> -Ben
>>>
>>>
>>>
>>> On May 13, 2015, at 7:44 PM, Neil Girdhar <mistersh...@gmail.com> wrote:
>>>
>>> Do you have the code that you used to draw the arrowhead? I'm up to
>>> date now on the development workflow (
>>> http://matplotlib.org/devel/gitwash/development_workflow.html), so I'm
>>> ready to start working.
>>>
>>> Thanks,
>>>
>>> Neil
>>>
>>> On Wed, May 13, 2015 at 9:10 PM, Benjamin Reedlunn <breed...@gmail.com>
>>> wrote:
>>>
>>>> Yes, I fully agree that we need to unify the many different ways to
>>>> draw arrows.
>>>>
>>>> Neil, in case an example would be helpful for you, I have attached a
>>>> module that includes a custom arrowhead class. The arrowhead class works
>>>> with the with the ax.annotate() method. (I like the annotate method
>>>> because it allows me to easily mix and match coordinate systems for arrow
>>>> placement.) As you can see in the attached pdf, the custom arrowhead
>>>> doesn't include fancy Bezier curves, but that could be added.
>>>>
>>>> -Ben
>>>>
>>>>
>>>>
>>>> On May 13, 2015, at 2:54 PM, Thomas Caswell <tcasw...@gmail.com> wrote:
>>>>
>>>> The other thing that should be done is to unify the (I think 7?!?)
>>>> unique ways to draw arrows in mpl.
>>>>
>>>> On Wed, May 13, 2015 at 4:52 PM Neil Girdhar <mistersh...@gmail.com>
>>>> wrote:
>>>>
>>>>> Yes, I just noticed that as well. That's how the tikz pgf code looks
>>>>> (a sequence of line_to and curve_to commands and so on) so it should be
>>>>> easy to port over the various shapes.
>>>>>
>>>>> On Wed, May 13, 2015 at 4:49 PM, Eric Firing <efir...@hawaii.edu>
>>>>> wrote:
>>>>>
>>>>>> On 2015/05/13 10:12 AM, Neil Girdhar wrote:
>>>>>>
>>>>>>> If you want to make arrowheads look at all decent, they really need
>>>>>>> to
>>>>>>> be enclosed in Bezier curves. See the diagram here:
>>>>>>>
>>>>>>
>>>>>> Mpl paths support Bezier curves.
>>>>>> http://matplotlib.org/api/path_api.html?highlight=bezier
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> http://tex.stackexchange.com/questions/150289/how-do-you-accomplish-stealth-with-the-new-arrows-meta/230965#230965
>>>>>>>
>>>>>>> The first two look like garbage. The last one is the only one that
>>>>>>> looks good imho.
>>>>>>>
>>>>>>
>>>>>> That depends on the application, and the observer.
>>>>>
>>>>>
>>>>> Sure, but I may as well port them all of the tikz arrowheads over
>>>>> since most of the work would be figuring out how to do it.
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>> Eric
>>>>>>
>>>>>>
>>>>>>> Best,
>>>>>>>
>>>>>>> Neil
>>>>>>>
>>>>>>> On Wed, May 13, 2015 at 4:09 PM, Eric Firing <efir...@hawaii.edu
>>>>>>> <mailto:efir...@hawaii.edu>> wrote:
>>>>>>>
>>>>>>> On 2015/05/13 9:36 AM, Neil Girdhar wrote:
>>>>>>>
>>>>>>> I don't know matplotlib well enough (yet) to know what the
>>>>>>> change would
>>>>>>> consist of.
>>>>>>>
>>>>>>> I suggest you take a look at the beautiful tikz manual:
>>>>>>> http://pgf.sourceforge.net/pgf_CVS.pdf
>>>>>>>
>>>>>>>
>>>>>>> Very helpful, thank you.
>>>>>>>
>>>>>>>
>>>>>>> The arrows.meta on page 201–212 are really well-designed and
>>>>>>> beautiful.
>>>>>>>
>>>>>>> Compare this with matplotlib's custom arrows:
>>>>>>>
>>>>>>> http://stackoverflow.com/questions/16968007/custom-arrow-style-for-matplotlib-pyplot-annotate
>>>>>>>
>>>>>>> How do I make tikz's arrowheads available for all backends?
>>>>>>>
>>>>>>>
>>>>>>> My guess offhand is that this is a matter of using the mpl API.
>>>>>>> I
>>>>>>> don't think we would want to add all of these types and options
>>>>>>> to
>>>>>>> the mpl core; but a toolkit might be ideal for this. The mpl
>>>>>>> API,
>>>>>>> which generates the same results for all backends, is quite
>>>>>>> complete
>>>>>>> and flexible. Things like arrowheads are Patch objects, and you
>>>>>>> can
>>>>>>> specify any path you want. The main trick is figuring out how to
>>>>>>> handle transforms--what kind of coordinates should the path be
>>>>>>> specifying? How should things scale as a figure is reshaped and
>>>>>>> resized?
>>>>>>>
>>>>>>> For many of these types you could also use mpl Line2D objects,
>>>>>>> for
>>>>>>> which several properties including cap style can be specified.
>>>>>>> Not
>>>>>>> all of the TikZ options would be available, but perhaps enough.
>>>>>>>
>>>>>>> Eric
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
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>>>
>>>
>>>
>>
>
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