Merge pull request #14 from wesley5040/add_auto_resize

Figure now resizes to fit the window

changes/14.feature.rst

@@ -0,0 +1 @@
+Chart now has an ``on_draw()`` handler to ensure the chart auto-resizes.

docs/requirements_docs.txt

@@ -3,4 +3,4 @@ sphinxcontrib-spelling
 pyenchant
 sphinx-autobuild
 sphinx_rtd_theme
-sphinx_tabs==1.1.8
+sphinx_tabs

examples/chart/app.py

@@ -1,44 +1,43 @@
 import toga
 import toga_chart
 from toga.style import Pack
-from matplotlib.figure import Figure
 import numpy as np
 from toga.constants import COLUMN
 
 
-def sample_histogram():
-    np.random.seed(19680801)
-
-    # example data
-    mu = 100  # mean of distribution
-    sigma = 15  # standard deviation of distribution
-    x = mu + sigma * np.random.randn(437)
-
-    num_bins = 50
+class ExampleChartApp(toga.App):
+    def draw_chart(self, chart, figure, *args, **kwargs):
+        # example data
+        mu = 100  # mean of distribution
+        sigma = 15  # standard deviation of distribution
+        x = mu + sigma * np.random.randn(437)
 
-    f = Figure(figsize=(5, 4))
-    ax = f.add_subplot(1, 1, 1)
+        num_bins = 50
 
-    # the histogram of the data
-    n, bins, patches = ax.hist(x, num_bins, density=1)
+        ax = figure.add_subplot(1, 1, 1)
 
-    # add a 'best fit' line
-    y = ((1 / (np.sqrt(2 * np.pi) * sigma)) * np.exp(-0.5 * (1 / sigma * (bins - mu))**2))
-    ax.plot(bins, y, '--')
-    ax.set_xlabel('Value')
-    ax.set_ylabel('Probability density')
-    ax.set_title(r'Histogram: $\mu=100$, $\sigma=15$')
+        # the histogram of the data
+        n, bins, patches = ax.hist(x, num_bins, density=1)
 
-    return f
+        # add a 'best fit' line
+        y = ((1 / (np.sqrt(2 * np.pi) * sigma)) * np.exp(-0.5 * (1 / sigma * (bins - mu))**2))
+        ax.plot(bins, y, '--')
+        ax.set_xlabel('Value')
+        ax.set_ylabel('Probability density')
+        ax.set_title(r'Histogram: $\mu=100$, $\sigma=15$')
 
+        figure.tight_layout()
 
-class ExampleChartApp(toga.App):
+    def resize(self, *args, **kwargs):
+        pass
 
     def startup(self):
+        np.random.seed(19680801)
+
         # Set up main window
         self.main_window = toga.MainWindow(title=self.name)
 
-        self.chart = toga_chart.Chart(style=Pack(flex=1))
+        self.chart = toga_chart.Chart(style=Pack(flex=1), on_resize=self.resize, on_draw=self.draw_chart)
 
         self.main_window.content = toga.Box(
             children=[
@@ -47,8 +46,6 @@ def startup(self):
             style=Pack(direction=COLUMN)
         )
 
-        self.chart.draw(sample_histogram())
-
         self.main_window.show()
 
 

src/toga_chart/chart.py

@@ -2,12 +2,14 @@
 import sys
 
 from matplotlib.backend_bases import FigureCanvasBase, RendererBase
+from matplotlib.figure import Figure
 from matplotlib.path import Path
 from matplotlib.transforms import Affine2D
 
 from toga.colors import color as parse_color
 from toga.colors import rgba
 from toga.fonts import CURSIVE, FANTASY, MONOSPACE, SANS_SERIF, SERIF, Font
+from toga.handlers import wrapped_handler
 from toga.widgets.canvas import Canvas
 
 
@@ -18,24 +20,62 @@ class Chart(Canvas, FigureCanvasBase):
         id (str):  An identifier for this widget.
         style (:obj:`Style`): An optional style object. If no
             style is provided then a new one will be created for the widget.
+        on_resize (:obj:`callable`): Handler to invoke when the chart is resized.
+            The default resize handler will draw the chart on every resize;
+            generally, you won't need to override this default behavior.
+        on_draw (:obj:`callable`): Handler to invoke when the chart needs to be
+            drawn.
         factory (:obj:`module`): A python module that is capable to return a
             implementation of this class with the same name. (optional &
             normally not needed)
     """
-    def __init__(self, id=None, style=None, factory=None):
-        Canvas.__init__(self, id=id, style=style, factory=factory)
+    def __init__(self, id=None, style=None, on_resize=None, on_draw=None, factory=None):
+        if on_resize is None:
+            on_resize = self._resize
+        Canvas.__init__(self, id=id, style=style, on_resize=on_resize, factory=factory)
+        self.on_draw = on_draw
 
     def draw(self, figure):
         """Draws the matplotlib figure onto the canvas
 
         Args:
             figure (figure):  matplotlib figure to draw
         """
-        self.figure = figure
-        FigureCanvasBase.__init__(self, self.figure)
-        l, b, w, h = self.figure.bbox.bounds
+        FigureCanvasBase.__init__(self, figure)
+        l, b, w, h = figure.bbox.bounds
         renderer = ChartRenderer(self, w, h)
-        self.figure.draw(renderer)
+        figure.draw(renderer)
+
+    def _resize(self, *args, **kwargs):
+        ""
+        # 100 is the default DPI for figure at time of writing.
+        dpi = 100
+        figure = Figure(
+            figsize=(
+                self.layout.content_width / dpi,
+                self.layout.content_height / dpi
+            )
+        )
+        self.on_draw(self, figure=figure)
+        self.draw(figure)
+
+    @property
+    def on_draw(self):
+        """The handler to invoke when the canvas needs to be drawn.
+
+        Returns:
+            The handler that is invoked on canvas draw.
+        """
+        return self._on_draw
+
+    @on_draw.setter
+    def on_draw(self, handler):
+        """Set the handler to invoke when the canvas is drawn.
+
+        Args:
+            handler (:obj:`callable`): The handler to invoke when the canvas is drawn.
+        """
+        self._on_draw = wrapped_handler(self, handler)
 
 
 class ChartRenderer(RendererBase):