Future-proof Chart against changing Toga Widget initialization (#194)

Updates API usage to match Toga 0.5, updates version specifiers to match.

Also adds an explicit matplotlib dependency, and adapts to a recent matplotlib API change.

Author: HalfWhitt

changes/194.misc.rst

@@ -0,0 +1 @@
+The initialization of Chart has been updated to be compatible with Toga 0.5.0.

examples/chart/app.py

@@ -66,16 +66,16 @@ def startup(self):
                 self.chart,
                 toga.Box(
                     children=[toga.Label("𝜇"), self.mu],
-                    style=Pack(padding=(5, 10)),
+                    style=Pack(margin=(5, 10)),
                 ),
                 toga.Box(
                     children=[toga.Label("𝜎"), self.sigma],
-                    style=Pack(padding=(5, 10)),
+                    style=Pack(margin=(5, 10)),
                 ),
                 toga.Button(
                     "Recreate data",
                     on_press=self.recreate_data,
-                    style=Pack(padding=(10, 10, 20, 10)),
+                    style=Pack(margin=(10, 10, 20, 10)),
                 ),
             ],
             style=Pack(direction=COLUMN),

pyproject.toml

@@ -37,6 +37,10 @@ classifiers = [
     "Topic :: Software Development",
     "Topic :: Software Development :: User Interfaces",
 ]
+dependencies = [
+    "matplotlib >= 3.9.0",
+    "toga-core >= 0.5.0, < 0.6.0",
+]
 
 [project.optional-dependencies]
 # Extras used by developers *of* briefcase are pinned to specific versions to
@@ -46,7 +50,7 @@ dev = [
     "pytest == 8.3.5",
     "setuptools_scm == 8.2.0",
     "tox == 4.25.0",
-    "toga-dummy >= 0.4.0",
+    "toga-dummy >= 0.5.0, < 0.6.0",
 ]
 # Docs are always built on a specific Python version; see RTD and tox config files.
 docs = [

src/toga_chart/chart.py

@@ -44,6 +44,7 @@ def __init__(
 
         super().__init__(id=id, style=style)
 
+    def _create(self):
         self._impl = self.canvas._impl
 
     @Widget.app.setter
@@ -193,13 +194,7 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
         # Math mode text must be rendered using paths.
         # Otherwise, we can use canvas-level text markup.
         if ismath:
-            path, transform = self._get_text_path_transform(
-                x, y, s, prop, angle, ismath
-            )
-            color = gc.get_rgb()
-
-            gc.set_linewidth(0.75)
-            self.draw_path(gc, path, transform, rgbFace=color)
+            self._draw_text_as_path(gc, x, y, s, prop, angle, ismath)
         else:
             self._canvas.context.translate(x, y)
             self._canvas.context.rotate(-math.radians(angle))