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SnapFix UDF - prevent Windows 10 from molesting your non-resizable GUI

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following this discussion in the GUI H&S forum:

this UDF attempts to provide an easy fix for the issue in Windows 10 Snap feature, that wrongly resizes a window when dragged way off-screen.

the issue is apparent for non-resizable windows, when the Snap feature is turned OFF.


How To Test

on a Windows 10 machine (also tested on a VM), disable the Snap feature (right-click the desktop > Display settings > Multitasking).

download the UDF and the example into the same folder, and run the example. it will create 4 windows which you can drag around to see how they react (and a MsgBox you can confirm to close the example script):

1. "Default" - drag this over the top of the screen (use the "drag" label) and see that it is being incorrectly resized.

2. "SnapFix" - this window uses the UDF to demonstrate that the issue is resolved.

3. "SnapFix_NoTitleBar" - this window demonstrates that the issue is resolved even for windows without a title bar

4. "SnapFix_PopUp" -  this window demonstrates that the $WS_POPUP style alone is NOT WORKING properly! must be combined with $WS_BORDER or $WS_THICKFRAME to work.


How To Use

first, the UDF needs to be included and initialized. add this at the top of your script:

#include <SnapFix.au3>


to enable the UDF for you GUI (multiple GUI's supported, not all your GUI's must be fixed), add this line after creating a GUI:


where $hGUI is the GUI handle as returned by GUICreate()






What Next

as described above, $WS_POPUP alone is not working. an override is suggested, but perhaps a solution exists.

the UDF sets some global conditions: it changes the default GUI resize mode, and registers the window message WM_SIZE, so if your script registers the WM_SIZE message for its own purposes, then in your registered function, you must call the internal UDF function __SnapFix_WM_SIZE(), like this:

Func MY_WM_SIZE($hWnd, $iMsg, $wParam, $lParam)
    __SnapFix_WM_SIZE($hWnd, $iMsg, $wParam, $lParam)
    ; your original function contents here
EndFunc   ;==>MY_WM_SIZE


the global conditions are not thoroughly tested, so use with caution!


Edited by orbs
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Thank you @orbs  for your work in putting this UDF together. I'm happy to hear about your workaround.  Just a couple of questions:

  1. Will this have any effect on our GUI's under the previous versions of Windows?
  2. Will we need to code for first checking the OS Version before implementing a "snapfix"?

Thank you.

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this UDF has no apparent effect on Windows 7, as well as on Windows 10 with Snap set to ON. (well, more precisely, it mimics the expected behavior, which occurs anyways). the effect of this UDF is only apparent on Windows 10 with Snap set to OFF.

not tested on the following versions of Windows:



8.1 Update 1

8.1 Update 1 mark 1

8.1 Update 1 mark 1 RC1

8.1 Update 1 mark 1 RC1.1

8.1 Update 1 mark 1 RC1.1 HotFix 1

...and the rest of the Windows 8 series.


EDIT: reminder: do NOT "SnapFix" your GUI if it is resizable. only non-resizable GUI should use SnapFix.


Edited by orbs
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