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FIX: when creating a canvas from a Figure use original dpi#30750
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When we upscale the DPI for high-dpi screens we stash the original dpi and thenset the figure dpi to the scaled version. If the same Figure instance isrepeatedly passed to a Canvas that support hi-dpi it would go into a loop wherethe scaled DPI is treated as the original dpi and infinitely increases.By grabbing `fig._original_dpi` (which we stash for exactly this reason) we canavoid this loop.closesmatplotlib#26380
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anntzer commentedNov 13, 2025
Maybe related to#27224? (I didn't actually check) |
The issue is that we reset the dpi but did not re-compute any of thebounding boxes derived from the dpi leading to the initial redraw eventsto use the wrong physical size on the screen.Closesmatplotlib#27224
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tacaswell commentedNov 14, 2025
I found a clean place to test the second fix. |
timhoffm approved these changesNov 15, 2025
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PR summary
When we upscale the DPI for high-dpi screens we stash the original dpi and then set the figure dpi to the scaled version. If the same Figure instance is repeatedly passed to a Canvas that support hi-dpi it would go into a loop where the scaled DPI is treated as the original dpi and infinitely increases.
By grabbing
fig._original_dpi(which we stash for exactly this reason) we can avoid this loop.closes#26380
This is a slightly more general version of what we had already done to support re-attaching Figures to pyplot.
This is covered by the tests for dpi ratio tests we added as part of re-attaching to Figures to pyplot (which my first version of this broke so I'm sure it is being hit).
There is a case that we should move the "re run with device ratio 1" logic into
CanvasBase, but any backend that does support scaling will take care of re-scaling the canvas on display so setting it back to 1 inCanvasBase.__init__seems like it will always be redundent for users and we have a hook to explicitly clean it up when we remove the Figure from pyplot.I suspect there is still a few more iterations before we have covered all the stress-cases on this, but this is another step in the right direction.
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