2003-05-05  Michael Natterer  <mitch@gimp.org>

	* app/display/gimpdisplayshell-scale.[ch]
	(gimp_display_shell_scale_zoom_fraction): new utility function
	which takes GimpZoomType and zooms "scalesrc" and "scaledest".
	(gimp_display_shell_scale_calc_fraction): new utility function
	which takes an exact double scale factor and calculates "scalesrc"
	and "scaledest".

	(gimp_display_shell_scale): use the first.
	(gimp_display_shell_scale_fit): use the second.

	* app/tools/gimpmagnifytool.[ch]: use the first to click-zoom and
	the second to area-zoom. Fixes bug #112115. Removed zoom_in() and
	zoom_out() utiliy functions. Removed "GimpZoomType op" from the
	GimpMagnifyTool struct. Cleanup.