/* *  (C) 2001 by Argonne National Laboratory *      See COPYRIGHT in top-level directory. *//* *  @author  Anthony Chan */Multiple Images-------- ------Assume there are 3 different images, NumImages, in the view object of the viewport.  Each image is an integral multiple wider than viewport,i.e. each image is NumViewsPerImage multiple of width of viewport.Define the following quantities:W_v = width of viewport( visible part of the view ) in pixeln_v = number of views per image, i.e. NumViewsPerImage.W_i = width of one image    = n_v * W_vn_i = number of imagesW_t = the overall width of all images    = n_i * W_i    = n_i * n_v * W_vDefine the __current__ image to be the one when the viewport is __totally__ within it.  Since viewport.getViewPosition() returns view.getValue()which starts at the 1st image.          imgs[prev]               imgs[curr]              imgs[next]   +-----------------------+-------***********-----+-----------------------+   |                       |       *         *     |                       |   |                       |       *  vport  *     |                       |   |                       |       *         *     |                       |   |                       |       *         *     |                       |   |                       |       *         *     |                       |   +-----------------------+-------***********-----+-----------------------+   ^                       ^       ^         ^    !<-------- W_i -------->|       !<- W_v ->!    !                       |       !   !                       |       !   !                       +-sbPos-+   !                               !   !                               !   !<------ view.getValue() ------>!Where sbPos = LongScrollBar.getValue()The 2 methods componentResized() and checkToRedrawImage() are related.Whatever strategy/criteria that checkToRedrawImage() adopts to redrawone of the images will affect how componentResized() works, vice versa.checkToRedrawImage()--------------------Since image is considered __current_image__ when the viewport is __totally__ within the image, so checkToRedrawImage() should be called after the check  for current_image has been changed.  This probably should be done in theviewport code.  1st, there should be a variable called current image index,say cur_img_idx.   If there are 3 images used as circular image buffer[], labeled as 0, 1 & 2, cur_img_idx should be initialized to the middle index,i.e. 1.  In principle, the number of images used in the circular image buffer[] is required to be an odd number, i.e. 1, 3, 5, ....  The viewport should be set at the middle of the middle image initially.  Using morethan 3 images allows more time for the image to be redrawn before usernotices the existence of image buffer[] if the redraw is done on a separate thread.  The cost of too many images used in the buffer[] is longer initialization process and long resizing time.  The tView_init/tView_final of the viewport should be set to tGlobal_init/tGlobal_final respectively.  2nd, when the scrollbar is moved by the user, the tView_init/tView_final should be checked constantly to see if they have __completely__ moved out of the _current_image_( this should probably be done by either a ChangeListener or LongAdjustmentListener of the time_model ).  If tView_initand tView_final are both moved out of the current_image completely, the index cur_img_idx should be updated to reflect the change.  Then one of the multipleimages should be redrawn.  The image being redrawn should be at the other end of where the viewport is moved to.componentResized()------------------Because of how checkToRedrawImage() should work, componenetResized() mayneed one more variable( compared to 1 image buffer case ) to recreate theimage buffer[] when the component listener(i.e. the one implementscomponentResized()) is invoked.  The extra variable specifies the relativelocation of the viewport in the _current_image_.