xfwm appears to ignore changes to WM_NORMAL_HINTS after mapping

[Sam Varshavchik]

Currently I have an application window that, according to xprop(1), has the  
following properties:

WM_NORMAL_HINTS(WM_SIZE_HINTS):
        program specified minimum size: 89 by 277
        program specified maximum size: 1912 by 277

So, the application window claims that its horizontal size can be adjusted,  
and its vertical size is fixed. So I should be able to resize this  
application window horizontally.
  
If I prepare to grab either the left or the right border with the pointer,  
immediately upon hovering over the border xfwm (4.12) changes the mouse icon  
to an arrow in the appropriate direction, supposedly indicating that the  
application window can, indeed, be resized.

However, as soon as I actually grab the appropriate border, the mouse icon  
changes to a hand, and instead of resizing the application window, xfwm4  
drags the entire window, changing its position, but keeping its existing  
size the same.

It appears to me that xfwm4 reads WM_NORMAL_HINTS only when the application  
window gets mapped. At the time this application window got mapped, its  
WM_NORMAL_HINTS indicated a fixed size, with minimum and maximum width being  
the same (about the middle of this range). But after the window got mapped,  
my application updated its WM_NORMAL_HINTS to the values shown above.

If I change the application to indicate an adjustable horizontal range  
before the window gets mapped, xfwm4 will let me resize the application  
window normally.

I have not done enough experimentation to determine whether or not xfwm pays  
attention to updated WM_NORMAL_HINTS, as long as the initial values, when  
mapped, indicate an adjustable size (meaning that this occurs only if the  
initial WM_NORMAL_HINTS, upon mapping, reported a fixed size).

Does this look like a bug, or am I failing to implement some parts of icccm  
that prod the WM to look at WM_NORMAL_HINTS again?
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