WIP: Try to make tkagg blitting threadsafe

richardsheridan · richardsheridan · commit 0dcdd21abacb · 2020-10-24T07:59:06.000-04:00
current status: doesn't crash but also doesn't draw
when called from a thread
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -123,6 +123,7 @@ def __init__(self, figure, master=None, resize_callback=None):
             width=w, height=h, borderwidth=0, highlightthickness=0)
         self._tkphoto = tk.PhotoImage(
             master=self._tkcanvas, width=w, height=h)
+        self._findphoto_name = self._tkcanvas.register(self._findphoto)
         self._tkcanvas.create_image(w//2, h//2, image=self._tkphoto)
         self._resize_callback = resize_callback
         self._tkcanvas.bind("<Configure>", self.resize)
@@ -178,6 +179,37 @@ def resize(self, event):
             int(width / 2), int(height / 2), image=self._tkphoto)
         self.resize_event()
 
+    def _findphoto(self):
+        return _tkagg.findphoto(self._tkphoto.tk.interpaddr(), str(self._tkphoto))
+
+    def blit(self, bbox=None):
+        """
+        Blit *aggimage* to *photoimage*.
+
+        *offsets* is a tuple describing how to fill the ``offset`` field of the
+        ``Tk_PhotoImageBlock`` struct: it should be (0, 1, 2, 3) for RGBA8888 data,
+        (2, 1, 0, 3) for little-endian ARBG32 (i.e. GBRA8888) data and (1, 2, 3, 0)
+        for big-endian ARGB32 (i.e. ARGB8888) data.
+
+        If *bbox* is passed, it defines the region that gets blitted.
+        """
+        data = np.asarray(self.renderer._renderer)
+        height, width = data.shape[:2]
+        dataptr = (height, width, data.ctypes.data)
+        if bbox is not None:
+            (x1, y1), (x2, y2) = bbox.__array__()
+            x1 = max(math.floor(x1), 0)
+            x2 = min(math.ceil(x2), width)
+            y1 = max(math.floor(y1), 0)
+            y2 = min(math.ceil(y2), height)
+            bboxptr = (x1, x2, y1, y2)
+        else:
+            self._tkphoto.blank()
+            bboxptr = (0, width, 0, height)
+        # photoptr = self._findphoto()  # Thread unsafe
+        photoptr = self._master.tk.call(self._findphoto_name)  # Thread safe
+        _tkagg.photoputblock(photoptr, dataptr, (0, 1, 2, 3), bboxptr)  # ???
+
     def draw_idle(self):
         # docstring inherited
         if not self._idle:
diff --git a/lib/matplotlib/backends/backend_tkagg.py b/lib/matplotlib/backends/backend_tkagg.py
@@ -1,4 +1,3 @@
-from . import _backend_tk
 from .backend_agg import FigureCanvasAgg
 from ._backend_tk import (
     _BackendTk, FigureCanvasTk, FigureManagerTk, NavigationToolbar2Tk)
@@ -7,11 +6,7 @@
 class FigureCanvasTkAgg(FigureCanvasAgg, FigureCanvasTk):
     def draw(self):
         super().draw()
-        _backend_tk.blit(self._tkphoto, self.renderer._renderer, (0, 1, 2, 3))
-
-    def blit(self, bbox=None):
-        _backend_tk.blit(
-            self._tkphoto, self.renderer._renderer, (0, 1, 2, 3), bbox=bbox)
+        self.blit()
 
 
 @_BackendTk.export
diff --git a/src/_tkagg.cpp b/src/_tkagg.cpp
@@ -89,8 +89,71 @@ static PyObject *mpl_tk_blit(PyObject *self, PyObject *args)
     }
 }
 
+static PyObject *mpl_tk_findphoto(PyObject *self, PyObject *args)
+{
+    Tcl_Interp *interp;
+    char const *photo_name;
+    Tk_PhotoHandle photo;
+    if (!PyArg_ParseTuple(args, "O&s:findphoto",convert_voidptr, &interp, &photo_name)) {
+        goto exit;
+    }
+    if (!(photo = TK_FIND_PHOTO(interp, photo_name))) {
+        PyErr_SetString(PyExc_ValueError, "Failed to extract Tk_PhotoHandle");
+        goto exit;
+    }
+exit:
+    if (PyErr_Occurred()) {
+        return NULL;
+    } else {
+        return PyLong_FromVoidPtr((void *)photo);
+    }
+}
+
+static PyObject *mpl_tk_photoputblock(PyObject *self, PyObject *args)
+{
+    int height, width;
+    unsigned char *data_ptr;
+    int o0, o1, o2, o3;
+    int x1, x2, y1, y2;
+    Tk_PhotoHandle photo;
+    Tk_PhotoImageBlock block;
+    if (!PyArg_ParseTuple(args, "O&(iiO&)(iiii)(iiii):photoputblock",
+                          convert_voidptr, &photo,
+                          &height, &width, convert_voidptr, &data_ptr,
+                          &o0, &o1, &o2, &o3,
+                          &x1, &x2, &y1, &y2)) {
+        goto exit;
+    }
+    if (0 > y1 || y1 > y2 || y2 > height || 0 > x1 || x1 > x2 || x2 > width) {
+        PyErr_SetString(PyExc_ValueError, "Attempting to draw out of bounds");
+        goto exit;
+    }
+
+    Py_BEGIN_ALLOW_THREADS
+    block.pixelPtr = data_ptr + 4 * ((height - y2) * width + x1);
+    block.width = x2 - x1;
+    block.height = y2 - y1;
+    block.pitch = 4 * width;
+    block.pixelSize = 4;
+    block.offset[0] = o0;
+    block.offset[1] = o1;
+    block.offset[2] = o2;
+    block.offset[3] = o3;
+    TK_PHOTO_PUT_BLOCK_NO_COMPOSITE(
+        photo, &block, x1, height - y2, x2 - x1, y2 - y1);
+    Py_END_ALLOW_THREADS
+exit:
+    if (PyErr_Occurred()) {
+        return NULL;
+    } else {
+        Py_RETURN_NONE;
+    }
+}
+
 static PyMethodDef functions[] = {
     { "blit", (PyCFunction)mpl_tk_blit, METH_VARARGS },
+    { "findphoto", (PyCFunction)mpl_tk_findphoto, METH_VARARGS },
+    { "photoputblock", (PyCFunction)mpl_tk_photoputblock, METH_VARARGS },
     { NULL, NULL } /* sentinel */
 };
 
