Support downloading of plot files

Makefile

@@ -191,7 +191,6 @@ root/.built: \
 	( \
 		cd root/lib/python$(PYMINOR); \
 		rm -fr `cat ../../../remove_modules.txt`; \
-		rm encodings/cp*.py; \
 		rm encodings/mac_*.py; \
 		find . -name "*.wasm.pre" -type f -delete ; \
 		find -type d -name __pycache__ -prune -exec rm -rf {} \; \

matplotlib/patches/reduce_cpp_exceptions.patch

+diff --git a/src/_path_wrapper.cpp b/src/_path_wrapper.cpp
+index 354097557..2fd90adb9 100644
+--- a/src/_path_wrapper.cpp
++++ b/src/_path_wrapper.cpp
+@@ -437,23 +437,25 @@ static PyObject *Py_affine_transform(PyObject *self, PyObject *args, PyObject *k
+         return NULL;
+     }
+ 
+-    try {
+-        numpy::array_view<double, 2> vertices(vertices_obj);
++    PyArrayObject* vertices_arr = (PyArrayObject *)PyArray_ContiguousFromAny(vertices_obj, NPY_DOUBLE, 1, 2);
++    if (vertices_arr == NULL) {
++        return NULL;
++    }
++
++    if (PyArray_NDIM(vertices_arr) == 2) {
++        numpy::array_view<double, 2> vertices(vertices_arr);
+         npy_intp dims[] = { (npy_intp)vertices.size(), 2 };
+         numpy::array_view<double, 2> result(dims);
+         CALL_CPP("affine_transform", (affine_transform_2d(vertices, trans, result)));
++        Py_DECREF(vertices_arr);
++        return result.pyobj();
++    } else { // PyArray_NDIM(vertices_arr) == 1
++        numpy::array_view<double, 1> vertices(vertices_arr);
++        npy_intp dims[] = { (npy_intp)vertices.size() };
++        numpy::array_view<double, 1> result(dims);
++        CALL_CPP("affine_transform", (affine_transform_1d(vertices, trans, result)));
++        Py_DECREF(vertices_arr);
+         return result.pyobj();
+-    } catch (py::exception &) {
+-        PyErr_Clear();
+-        try {
+-            numpy::array_view<double, 1> vertices(vertices_obj);
+-            npy_intp dims[] = { (npy_intp)vertices.size() };
+-            numpy::array_view<double, 1> result(dims);
+-            CALL_CPP("affine_transform", (affine_transform_1d(vertices, trans, result)));
+-            return result.pyobj();
+-        } catch (py::exception &) {
+-            return NULL;
+-        }
+     }
+ }
+ 
+diff --git a/src/numpy_cpp.h b/src/numpy_cpp.h
+index 2218078ae..cddbcb659 100644
+--- a/src/numpy_cpp.h
++++ b/src/numpy_cpp.h
+@@ -398,6 +398,15 @@ class array_view : public detail::array_view_accessors<array_view, T, ND>
+         m_strides = strides;
+     }
+ 
++    array_view(PyArrayObject *arr)
++    {
++        m_arr = arr;
++        Py_XINCREF(arr);
++        m_shape = PyArray_DIMS(m_arr);
++        m_strides = PyArray_STRIDES(m_arr);
++        m_data = (char *)PyArray_BYTES(m_arr);
++    }
++
+     array_view(npy_intp shape[ND]) : m_arr(NULL), m_shape(NULL), m_strides(NULL), m_data(NULL)
+     {
+         PyObject *arr = PyArray_SimpleNew(ND, shape, type_num_of<T>::value);
+@@ -456,18 +465,18 @@ class array_view : public detail::array_view_accessors<array_view, T, ND>
+                 m_data = NULL;
+                 m_shape = zeros;
+                 m_strides = zeros;
+-		if (PyArray_NDIM(tmp) == 0 && ND == 0) {
+-		    m_arr = tmp;
+-		    return 1;
+-		}
++                if (PyArray_NDIM(tmp) == 0 && ND == 0) {
++                    m_arr = tmp;
++                    return 1;
++                }
+             }
+-	    if (PyArray_NDIM(tmp) != ND) {
+-		PyErr_Format(PyExc_ValueError,
+-			     "Expected %d-dimensional array, got %d",
+-			     ND,
+-			     PyArray_NDIM(tmp));
+-		Py_DECREF(tmp);
+-		return 0;
++            if (PyArray_NDIM(tmp) != ND) {
++                PyErr_Format(PyExc_ValueError,
++                             "Expected %d-dimensional array, got %d",
++                             ND,
++                             PyArray_NDIM(tmp));
++                Py_DECREF(tmp);
++                return 0;
+             }
+ 
+             /* Copy some of the data to the view object for faster access */
+diff --git a/src/py_converters.cpp b/src/py_converters.cpp
+index cc235df2e..9119df6b6 100644
+--- a/src/py_converters.cpp
++++ b/src/py_converters.cpp
+@@ -158,45 +158,36 @@ int convert_rect(PyObject *rectobj, void *rectp)
+         rect->x2 = 0.0;
+         rect->y2 = 0.0;
+     } else {
+-        try
+-        {
+-            numpy::array_view<const double, 2> rect_arr(rectobj);
++        PyArrayObject *rect_arr = (PyArrayObject *)PyArray_ContiguousFromAny(
++                rectobj, NPY_DOUBLE, 1, 2);
++        if (rect_arr == NULL) {
++            return 0;
++        }
+ 
+-            if (rect_arr.dim(0) != 2 || rect_arr.dim(1) != 2) {
++        if (PyArray_NDIM(rect_arr) == 2) {
++            if (PyArray_DIM(rect_arr, 0) != 2 ||
++                PyArray_DIM(rect_arr, 1) != 2) {
+                 PyErr_SetString(PyExc_ValueError, "Invalid bounding box");
++                Py_DECREF(rect_arr);
+                 return 0;
+             }
+ 
+-            rect->x1 = rect_arr(0, 0);
+-            rect->y1 = rect_arr(0, 1);
+-            rect->x2 = rect_arr(1, 0);
+-            rect->y2 = rect_arr(1, 1);
+-        }
+-        catch (py::exception &)
+-        {
+-            PyErr_Clear();
+-
+-            try
+-            {
+-                numpy::array_view<const double, 1> rect_arr(rectobj);
+-
+-                if (rect_arr.dim(0) != 4) {
+-                    PyErr_SetString(PyExc_ValueError, "Invalid bounding box");
+-                    return 0;
+-                }
+-
+-                rect->x1 = rect_arr(0);
+-                rect->y1 = rect_arr(1);
+-                rect->x2 = rect_arr(2);
+-                rect->y2 = rect_arr(3);
+-            }
+-            catch (py::exception &)
+-            {
++        } else {  // PyArray_NDIM(rect_arr) == 1
++            if (PyArray_DIM(rect_arr, 0) != 4) {
++                PyErr_SetString(PyExc_ValueError, "Invalid bounding box");
++                Py_DECREF(rect_arr);
+                 return 0;
+             }
+         }
+-    }
+ 
++        double *buff = (double *)PyArray_DATA(rect_arr);
++        rect->x1 = buff[0];
++        rect->y1 = buff[1];
++        rect->x2 = buff[2];
++        rect->y2 = buff[3];
++
++        Py_DECREF(rect_arr);
++    }
+     return 1;
+ }
+ 
+@@ -336,27 +327,26 @@ int convert_trans_affine(PyObject *obj, void *transp)
+         return 1;
+     }
+ 
+-    try
+-    {
+-        numpy::array_view<const double, 2> matrix(obj);
++    PyArrayObject *array = (PyArrayObject *)PyArray_ContiguousFromAny(obj, NPY_DOUBLE, 2, 2);
++    if (array == NULL) {
++        return 0;
++    }
+ 
+-        if (matrix.dim(0) == 3 && matrix.dim(1) == 3) {
+-            trans->sx = matrix(0, 0);
+-            trans->shx = matrix(0, 1);
+-            trans->tx = matrix(0, 2);
++    if (PyArray_DIM(array, 0) == 3 && PyArray_DIM(array, 1) == 3) {
++        double *buffer = (double *)PyArray_DATA(array);
++        trans->sx = buffer[0];
++        trans->shx = buffer[1];
++        trans->tx = buffer[2];
+ 
+-            trans->shy = matrix(1, 0);
+-            trans->sy = matrix(1, 1);
+-            trans->ty = matrix(1, 2);
++        trans->shy = buffer[3];
++        trans->sy = buffer[4];
++        trans->ty = buffer[5];
+ 
+-            return 1;
+-        }
+-    }
+-    catch (py::exception &)
+-    {
+-        return 0;
++        Py_DECREF(array);
++        return 1;
+     }
+ 
++    Py_DECREF(array);
+     PyErr_SetString(PyExc_ValueError, "Invalid affine transformation matrix");
+     return 0;
+ }

src/wasm_backend.py

+import base64
+import io
+
 from matplotlib.backends import backend_agg
 from matplotlib.backend_bases import _Backend
 from matplotlib import backend_bases, _png
@@ -6,7 +9,6 @@ from js import iodide
 from js import document
 from js import window
 from js import ImageData
-from js import Uint8ClampedArray
 
 
 class FigureCanvasWasm(backend_agg.FigureCanvasAgg):
@@ -167,7 +169,7 @@ _FONTAWESOME_ICONS = {
     'forward': 'fa-arrow-right',
     'zoom_to_rect': 'fa-search-plus',
     'move': 'fa-arrows',
-    'download': 'download',
+    'download': 'fa-download',
     None: None,
 }
 
@@ -178,21 +180,57 @@ class NavigationToolbar2Wasm(backend_bases.NavigationToolbar2):
 
     def get_element(self):
         div = document.createElement('span')
+
+        def add_spacer():
+            span = document.createElement('span')
+            span.style.minWidth = '16px'
+            span.textContent = '\u00a0'
+            div.appendChild(span)
+
         for text, tooltip_text, image_file, name_of_method in self.toolitems:
             if image_file in _FONTAWESOME_ICONS:
                 if image_file is None:
-                    span = document.createElement('span')
-                    span.style.minWidth = 16
-                    span.style.textContent = ' '
-                    div.appendChild(span)
+                    add_spacer()
                 else:
                     button = document.createElement('button')
                     button.classList.add('fa')
                     button.classList.add(_FONTAWESOME_ICONS[image_file])
                     button.addEventListener('click', getattr(self, name_of_method))
                     div.appendChild(button)
+
+        for filetype in ('png', 'svg', 'pdf'):
+            button = document.createElement('button')
+            button.classList.add('fa')
+            button.textContent = filetype
+            button.addEventListener('click', getattr(self, 'download_' + filetype))
+            div.appendChild(button)
+
         return div
 
+    def download_png(self, event):
+        self.download('png', 'image/png')
+
+    def download_svg(self, event):
+        self.download('svg', 'image/svg+xml')
+
+    def download_pdf(self, event):
+        self.download('pdf', 'application/pdf')
+
+    def download(self, format, mimetype):
+        element = document.createElement('a')
+        data = io.BytesIO()
+        try:
+            self.canvas.figure.savefig(data, format=format)
+        except Exception as e:
+            raise
+        element.setAttribute('href', 'data:{};base64,{}'.format(
+            mimetype, base64.b64encode(data.getvalue()).decode('ascii')))
+        element.setAttribute('download', 'plot.{}'.format(format))
+        element.style.display = 'none'
+        document.body.appendChild(element)
+        element.click()
+        document.body.removeChild(element)
+
     def set_message(self, message):
         self.canvas.set_message(message)
 

test/test_matplotlib.py

@@ -7,3 +7,15 @@ def test_matplotlib(selenium):
     )
     assert img.startswith('data:image/png;base64,')
     assert len(img) == 26766
+
+
+def test_svg(selenium):
+    selenium.load_package("matplotlib")
+    selenium.run("from matplotlib import pyplot as plt")
+    selenium.run("x = plt.plot([1,2,3])")
+    selenium.run("import io")
+    selenium.run("fd = io.BytesIO()")
+    selenium.run("plt.savefig(fd, format='svg')")
+    content = selenium.run("fd.getvalue().decode('utf8')")
+    assert len(content) == 15752
+    assert content.startswith("<?xml")