Fixes #3: ZeroDivisionError when shrinking PlotWidget below its min width

Author: PierreRaybaut

plotpy/plot/base.py

@@ -2172,17 +2172,22 @@ def get_plot_limits(
         return x0, x1, y0, y1
 
     # ---- Image scale/aspect ratio -related API -------------------------------
-    def get_current_aspect_ratio(self) -> float:
+    def get_current_aspect_ratio(self) -> float | None:
         """Return current aspect ratio
 
         Returns:
-            float: the current aspect ratio
+            The current aspect ratio or None if the aspect ratio cannot be computed
+            (this happens when the plot has been shrunk to a size so that the
+            width is zero)
         """
         dx = self.axisScaleDiv(self.X_BOTTOM).range()
         dy = self.axisScaleDiv(self.Y_LEFT).range()
         h = self.canvasMap(self.Y_LEFT).pDist()
         w = self.canvasMap(self.X_BOTTOM).pDist()
-        return fabs((h * dx) / (w * dy))
+        try:
+            return fabs((h * dx) / (w * dy))
+        except ZeroDivisionError:
+            return None
 
     def get_aspect_ratio(self) -> float:
         """Return aspect ratio
@@ -2220,7 +2225,9 @@ def apply_aspect_ratio(self, full_scale: bool = False) -> None:
         if not self.isVisible():
             return
         current_aspect = self.get_current_aspect_ratio()
-        if abs(current_aspect - self.__aspect_ratio) < self.EPSILON_ASPECT_RATIO:
+        if current_aspect is None or (
+            abs(current_aspect - self.__aspect_ratio) < self.EPSILON_ASPECT_RATIO
+        ):
             return
         ymap = self.canvasMap(self.Y_LEFT)
         xmap = self.canvasMap(self.X_BOTTOM)

plotpy/tests/features/test_manager.py

@@ -8,6 +8,7 @@
 # guitest: show
 
 from guidata.qthelpers import qt_app_context, win32_fix_title_bar_background
+from qtpy import QtCore as QC
 from qtpy import QtWidgets as QW
 
 from plotpy.builder import make
@@ -45,6 +46,12 @@ def __init__(self, parent):
     def register_tools(self):
         self.manager.register_all_image_tools()
 
+    def minimumSizeHint(self):
+        """Override QWidget method"""
+        # The purpose of this reimplementation is to trigger the issue #3
+        # (see https://github.com/PlotPyStack/PlotPy/issues/3)
+        return QC.QSize(150, 100)
+
 
 class Window(QW.QMainWindow):
     def __init__(self):
@@ -75,5 +82,19 @@ def test_manager():
         win.show()
 
 
+def test_resize_to_minimum_width():
+    """Testing resize window to minimum width"""
+    # This test was failing at the time of Issue #3
+    # (see https://github.com/PlotPyStack/PlotPy/issues/3)
+    with qt_app_context(exec_loop=False):
+        win = Window()
+        win.show()
+        width = 350
+        while width > win.minimumWidth():
+            width -= 1
+            win.resize(width, 100)
+
+
 if __name__ == "__main__":
     test_manager()
+    # test_resize_to_minimum_width()