"""
image viewer extension: uses fixed-size thumbnail buttons for uniform layout, and 
adds scrolling for large image sets by displaying thumbs in a canvas widget with
scroll bars;  requires PIL to view image formats such as JPEG, and reuses thumbs 
maker and single photo viewer in viewer_thumbs.py;  caveat/to do: this could also
scroll popped-up images that are too large for the screen, and are cropped on 
Windows as is;  see PyPhoto later in Chapter 11 for a much more complete version;
"""

import sys, math
from tkinter import *
from PIL.ImageTk import PhotoImage
from viewer_thumbs import makeThumbs, ViewOne

def viewer(imgdir, kind=Toplevel, numcols=None, height=300, width=300):
    """
    use fixed-size buttons, scrollable canvas;
    sets scrollable (full) size, and places thumbs at absolute x,y 
    coordinates in canvas;  caveat: assumes all thumbs are same size
    """
    win = kind()
    win.title('Simple viewer: ' + imgdir)
    quit = Button(win, text='Quit', command=win.quit, bg='beige')
    quit.pack(side=BOTTOM, fill=X)

    canvas = Canvas(win, borderwidth=0)
    vbar = Scrollbar(win)
    hbar = Scrollbar(win, orient='horizontal')

    vbar.pack(side=RIGHT,  fill=Y)                  # pack canvas after bars
    hbar.pack(side=BOTTOM, fill=X)                  # so clipped first
    canvas.pack(side=TOP, fill=BOTH, expand=YES)

    vbar.config(command=canvas.yview)               # call on scroll move
    hbar.config(command=canvas.xview)
    canvas.config(yscrollcommand=vbar.set)          # call on canvas move
    canvas.config(xscrollcommand=hbar.set)
    canvas.config(height=height, width=width)       # init viewable area size
                                                    # changes if user resizes
    thumbs = makeThumbs(imgdir)                     # [(imgfile, imgobj)]
    numthumbs = len(thumbs)
    if not numcols:
        numcols = int(math.ceil(math.sqrt(numthumbs)))  # fixed or N x N
    numrows = int(math.ceil(numthumbs / numcols))       # 3.x true div

    linksize = max(thumbs[0][1].size)                   # (width, height)
    fullsize = (0, 0,                                   # upper left  X,Y
        (linksize * numcols), (linksize * numrows) )    # lower right X,Y
    canvas.config(scrollregion=fullsize)                # scrollable area size

    rowpos = 0
    savephotos = []
    while thumbs:
        thumbsrow, thumbs = thumbs[:numcols], thumbs[numcols:]
        colpos = 0
        for (imgfile, imgobj) in thumbsrow:
            photo   = PhotoImage(imgobj)
            link    = Button(canvas, image=photo)
            handler = lambda savefile=imgfile: ViewOne(imgdir, savefile)
            link.config(command=handler, width=linksize, height=linksize)
            link.pack(side=LEFT, expand=YES)
            canvas.create_window(colpos, rowpos, anchor=NW,
                    window=link, width=linksize, height=linksize)
            colpos += linksize
            savephotos.append(photo)
        rowpos += linksize
    return win, savephotos

if __name__ == '__main__':
    imgdir = 'images' if len(sys.argv) < 2 else sys.argv[1]
    main, save = viewer(imgdir, kind=Tk)
    main.mainloop()