2001-02-26  Gene Z. Ragan  <gzr@eazel.com>

	reviewed by: John Harper <jsh@eazel.com>

	Fixed bug 3898, selection in icon view extremely slow

	I increased the performance of drag selection of icons in a few ways.
	First, I avoid unneeded, repeated transforms of coordinates from
	world coordinates to canvas coordinates.  I also cached three freqeuently
	calculated dimensions; the icons bounds in canvas coordinates, the icons
	text bounds and canvas coordinates and the bounding rect of all emblems
	in canvas coordinates.  Instead of repeatedly calculating these values,
	have functions refer to the cached values.  In hit_test, I then do a
	quick intersection check of the drag rect with the cached values before
	proceeding to the more expensive intersection detection routines.

	* libnautilus-extensions/nautilus-icon-canvas-item.c:
	* libnautilus-extensions/nautilus-icon-canvas-item.h:
	(nautilus_icon_canvas_item_set_image), (compute_text_rectangle),
	(nautilus_icon_canvas_item_draw),
	(nautilus_icon_canvas_item_render),
	(nautilus_icon_canvas_item_bounds), (get_icon_canvas_rectangle),
	Set up the various places that we need to update our cached items.

	(nautilus_icon_canvas_item_update_bounds):
	Update our cached values.

	(hit_test), (hit_test_stretch_handle):
	Perform quick interesection checks before doing more expensive checks.

	(nautilus_icon_canvas_item_hit_test_rectangle):
	Change function to use canvas coordinates. The caller is responsible
	to do the conversion form world to canvas. This provides a large
	optimization if this routine is caled in a loop.

	* libnautilus-extensions/nautilus-icon-container.c:
	* libnautilus-extensions/nautilus-icon-container.h:
	(rubberband_select):
	Do transform of drag rect from world coordiantes to canvas canvas
	coordinates onlty once. There is no need to do this for every canvas
	item that is visted during list traversal.

	* libnautilus-extensions/nautilus-icon-dnd.c:
	(nautilus_icon_container_item_at):
	Call nautilus_icon_canvas_item_hit_test_rectangle() using coordinate
	converted to canvas coordinates.