/* * (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 pixel n_v = number of views per image, i.e. NumViewsPerImage. W_i = width of one image = n_v * W_v n_i = number of images W_t = the overall width of all images = n_i * W_i = n_i * n_v * W_v Define 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 * | | | | * * | | | | * * | | | | * * | | +-----------------------+-------***********-----+-----------------------+ ^ ^ ^ ^ !| !! ! | ! ! | ! ! +-sbPos-+ ! ! ! ! !! Where sbPos = LongScrollBar.getValue() The 2 methods componentResized() and checkToRedrawImage() are related. Whatever strategy/criteria that checkToRedrawImage() adopts to redraw one 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 the viewport 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 more than 3 images allows more time for the image to be redrawn before user notices 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_init and 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 multiple images 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() may need one more variable( compared to 1 image buffer case ) to recreate the image buffer[] when the component listener(i.e. the one implements componentResized()) is invoked. The extra variable specifies the relative location of the viewport in the _current_image_.
