InfiniteLine: Fix bounding box for differing x and y ranges

Previously, the same pixel -> local transform was used for both
direction, which breaks if the displayed coordinate range is not
the same for both axes.

pyqtgraph/graphicsItems/InfiniteLine.py

@@ -301,27 +301,27 @@ class InfiniteLine(GraphicsObject):
         if vr is None:
             return QtCore.QRectF()
 
-        ## add a 4-pixel radius around the line for mouse interaction.
+        # Compute width of area around line to use for mouse interaction, in
+        # pixels (at least 4 for thin lines).
+        penWidth = max(self.pen.width() / 2, self.hoverPen.width() / 2)
+        padding = max(4, self._maxMarkerSize + penWidth) + 1
 
-        px = self.pixelLength(direction=Point(1,0), ortho=True)  ## get pixel length orthogonal to the line
-        if px is None:
-            px = 0
-        pw = max(self.pen.width() / 2, self.hoverPen.width() / 2)
-        w = max(4, self._maxMarkerSize + pw) + 1
-        w = w * px
-        br = QtCore.QRectF(vr)
-        br.setBottom(-w)
-        br.setTop(w)
+        br = QtCore.QRectF()
+
+        orthoPadding = padding * (self.pixelLength(direction=Point(1,0), ortho=True) or 0)
+        br.setBottom(-orthoPadding)
+        br.setTop(orthoPadding)
+
+        paraPadding = padding * (self.pixelLength(direction=Point(1,0)) or 0)
+        length = vr.width()
+        left = vr.left() + length * self.span[0]
+        right = vr.left() + length * self.span[1]
+        br.setLeft(left - paraPadding)
+        br.setRight(right + paraPadding)
 
-        length = br.width()
-        left = br.left() + length * self.span[0]
-        right = br.left() + length * self.span[1]
-        br.setLeft(left)
-        br.setRight(right)
         br = br.normalized()
 
         vs = self.getViewBox().size()
-        
         if self._bounds != br or self._lastViewSize != vs:
             self._bounds = br
             self._lastViewSize = vs

pyqtgraph/graphicsItems/tests/test_InfiniteLine.py

@@ -46,6 +46,47 @@ def test_InfiniteLine():
     assert not br.containsPoint(pos + 7 * px, QtCore.Qt.OddEvenFill)
 
 
+def test_InfiniteLine_scaled_bounding_box():
+    # Make plot with unequal axis ranges.
+    plt = pg.plot()
+    plt.setXRange(0, 1)
+    plt.setYRange(0, 1e-3)
+    plt.resize(400, 400)
+
+    QtTest.QTest.qWaitForWindowShown(plt)
+    QtTest.QTest.qWait(100)
+
+    # Vertical line.
+    vline = pg.InfiniteLine(angle=90)
+    vline.setPos(0.5)
+    plt.addItem(vline)
+
+    # Make sure there is some padding around the line...
+    vbr = vline.mapToScene(vline.boundingRect())
+    def contains(rect, x, y):
+        return rect.containsPoint(pg.Point(x, y), QtCore.Qt.OddEvenFill)
+    assert contains(vbr, 221, -1)
+    assert contains(vbr, 229, 381)
+
+    # ... but not too much.
+    assert not contains(vbr, 221, -10)
+    assert not contains(vbr, 210, -1)
+    assert not contains(vbr, 229, 390)
+    assert not contains(vbr, 240, 381)
+
+    # Same for horizontal line.
+    hline = pg.InfiniteLine(angle=0)
+    hline.setPos(0.5e-3)
+    plt.addItem(hline)
+    hbr = hline.mapToScene(hline.boundingRect())
+    assert contains(hbr, 47, 185)
+    assert contains(hbr, 403, 194)
+    assert not contains(hbr, 47, 175)
+    assert not contains(hbr, 37, 185)
+    assert not contains(hbr, 413, 194)
+    assert not contains(hbr, 403, 204)
+
+
 def test_mouseInteraction():
     plt = pg.plot()
     plt.scene().minDragTime = 0  # let us simulate mouse drags very quickly.