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ENH: support x/y-axis zoom #30543

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ENH: support x/y-axis zoom #30543

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b63a782
feat: support x/y-axis zoom
LangQi99 Sep 10, 2025
f8583e0
Update lib/matplotlib/backend_bases.py
LangQi99 Sep 12, 2025
0a744f0
Update lib/matplotlib/backend_bases.py
LangQi99 Sep 12, 2025
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3 changes: 2 additions & 1 deletion doc/release/next_whats_new/scroll_to_zoom.rst
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Expand Up @@ -2,7 +2,8 @@ Zooming using mouse wheel
~~~~~~~~~~~~~~~~~~~~~~~~~

``Ctrl+MouseWheel`` can be used to zoom in the plot windows.
Additionally, ``x+MouseWheel`` zooms only the x-axis and ``y+MouseWheel`` zooms only the y-axis.

The zoom focusses on the mouse pointer, and keeps the aspect ratio of the axes.
The zoom focusses on the mouse pointer. With ``Ctrl``, the axes aspect ratio is kept; with ``x`` or ``y``, only the respective axis is scaled.

Zooming is currently only supported on rectilinear Axes.
21 changes: 16 additions & 5 deletions lib/matplotlib/backend_bases.py
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Expand Up @@ -2592,7 +2592,7 @@ def scroll_handler(event, canvas=None, toolbar=None):
# is required for interactive navigation.
return

if event.key == "control": # zoom towards the mouse position
if event.key in {"control", "x", "X", "y", "Y"}: # zoom towards the mouse position
toolbar.push_current()

xmin, xmax = ax.get_xlim()
Expand All @@ -2604,10 +2604,21 @@ def scroll_handler(event, canvas=None, toolbar=None):
x, y = ax.transScale.transform((event.xdata, event.ydata))

scale_factor = 0.85 ** event.step
new_xmin = x - (x - xmin) * scale_factor
new_xmax = x + (xmax - x) * scale_factor
new_ymin = y - (y - ymin) * scale_factor
new_ymax = y + (ymax - y) * scale_factor
# Determine which axes to scale based on key
zoom_x = event.key in {"control", "x", "X"}
zoom_y = event.key in {"control", "y", "Y"}

if zoom_x:
new_xmin = x - (x - xmin) * scale_factor
new_xmax = x + (xmax - x) * scale_factor
else:
new_xmin, new_xmax = xmin, xmax

if zoom_y:
new_ymin = y - (y - ymin) * scale_factor
new_ymax = y + (ymax - y) * scale_factor
else:
new_ymin, new_ymax = ymin, ymax

inv_scale = ax.transScale.inverted()
(new_xmin, new_ymin), (new_xmax, new_ymax) = inv_scale.transform(
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