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Fix Screengrab DPI scaling on Windows 10 version 1607+ #4000

merged 3 commits into from Sep 30, 2019


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@nulano nulano commented Jul 31, 2019

Fixes #2438 and its duplicates #3432, #3626 for Windows 10 version 1607+ (Anniversary Update).

This PR uses SetThreadDpiAwarenessContext to temporarily make Python DPI aware. This function returns the previous awareness context, which is then used to restore the old value, thus avoiding problems with other parts of Python. It was added in Windows 10 version 1607, which is why it is called dynamically.

The issue is not fixed for older versions of Windows. This is not a big problem for Windows 7, as very few people use DPI scaling there. Windows 8 and Windows 10 pre-1607 are now out of standard support by Microsoft.

src/display.c Outdated
@@ -329,6 +331,9 @@ PyImaging_GrabScreenWin32(PyObject* self, PyObject* args)
HDC screen, screen_copy;
DWORD rop;
PyObject* buffer;
HANDLE dpiAwareness;
HMODULE user32 = LoadLibraryA("User32.dll");
Func_SetThreadDpiAwarenessContext SetThreadDpiAwarenessContext_function;
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@nulano nulano Jul 31, 2019

Can someone suggest a better name here? This the best I could do but it's ridiculously long.

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@hugovk hugovk Sep 26, 2019

At least it's descriptive! :)

nulano and others added 2 commits Aug 12, 2019
* Load User32 after possible return

* Removed unused setting of variable
@aclark4life aclark4life added this to New Issues in Pillow Sep 12, 2019
hugovk approved these changes Sep 26, 2019
@radarhere radarhere merged commit aaf2c42 into python-pillow:master Sep 30, 2019
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@hugovk hugovk commented Sep 30, 2019

PR 4000! 🍰

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3 participants