FvwmButtons: Shrink windows when honoring Hints.

When Swallowing a window and honoring 'Hints', shrink the window
to fit the button (instead of growing it) so the window fits inside
the button and isn't cut off. Fallback to growing the window if
shrinking makes it smaller than min size.

Fixes #573

modules/FvwmButtons/misc.c

@@ -148,41 +148,41 @@ void ConstrainSize (XSizeHints *hints, int *widthp, int *heightp)
 		if (minAspectX * dheight > minAspectY * dwidth)
 		{
 			delta = makemult(
-				minAspectX * dheight / minAspectY - dwidth,
-				xinc);
-			if (dwidth + delta <= maxWidth)
+				dheight - minAspectY * dwidth / minAspectX,
+				yinc);
+			if (dheight - delta >= minHeight)
 			{
-				dwidth += delta;
+				dheight -= delta;
 			}
 			else
 			{
 				delta = makemult(
-					dheight - minAspectY*dwidth/minAspectX,
-					yinc);
-				if (dheight - delta >= minHeight)
+					minAspectX * dheight / minAspectY -
+					dwidth,	xinc);
+				if (dwidth + delta <= maxWidth)
 				{
-					dheight -= delta;
+					dwidth += delta;
 				}
 			}
 		}
 
 		if (maxAspectX * dheight < maxAspectY * dwidth)
 		{
 			delta = makemult(
-				dwidth * maxAspectY / maxAspectX - dheight,
-				yinc);
-			if (dheight + delta <= maxHeight)
+				dwidth - maxAspectX * dheight / maxAspectY,
+				xinc);
+			if (dwidth - delta >= minWidth)
 			{
-				dheight += delta;
+				dwidth -= delta;
 			}
 			else
 			{
 				delta = makemult(
-					dwidth - maxAspectX*dheight/maxAspectY,
-					xinc);
-				if (dwidth - delta >= minWidth)
+					dwidth * maxAspectY / maxAspectX -
+					dheight, yinc);
+				if (dheight + delta <= maxHeight)
 				{
-					dwidth -= delta;
+					dheight += delta;
 				}
 			}
 		}