Source code for metapho.imagelist

#!/usr/bin/env python3

# The objects defined in this file are to get around Python's wacky
# and unpredictable lack of true global variables.
# I utterly failed at trying to treat g_cur_imgno imported from metapho.py
# as a global when used in submodules. So instead, here's a singleton
# object that manages the image list and the pointer into it,
# so other classes never need to access the global.


cur_imgno = -1

img_list = []




[docs]
def current_image():
    try:
        return img_list[cur_imgno]
    except:
        return None





[docs]
def current_imageno():
    return cur_imgno





[docs]
def set_current_imageno(val):
    global cur_imgno
    cur_imgno= val





[docs]
def set_current_image(im):
    """Can raise ValueError if im isn't in the list"""
    global cur_imgno
    if im:
        cur_imgno = img_list.index(im)
    else:
        cur_imgno = -1



# Iterator over valid images in the imagelist


[docs]
class ImageListIterator:
    def __iter__(self):
        return self

    def __next__(self):
        try:
            advance()
            return current_image()
        except IndexError:
            raise StopIteration





[docs]
def image_list():
    return img_list





[docs]
def get_image(imgno):
    return img_list[imgno]





[docs]
def num_images():
    return len(img_list)





[docs]
def clear_images():
    # As usual, global doesn't work. But this should:
    img_list.clear()





[docs]
def num_valid_images():
    return len ([ im for im in img_list if not im.invalid ])





[docs]
def advance():
    """Increment cur_imgno by 1 if possible, else raise IndexError"""
    global cur_imgno
    if cur_imgno >= len(img_list) - 1:
        # print("Couldn't advance past", cur_imgno, "=", img_list[cur_imgno],
        #       file=sys.stderr)
        raise IndexError
    cur_imgno += 1





[docs]
def retreat():
    """Decrement cur_imgno by 1 if possible, else raise IndexError"""
    global cur_imgno
    if cur_imgno <= 0:
        # print("Couldn't retreat past", cur_imgno, "=", img_list[cur_imgno],
        #       file=sys.stderr)
        raise IndexError
    cur_imgno -= 1





[docs]
def add_images(newlist_or_img):
    """Pass either a list of MetaphoImage or a single MetaphoImage.
    """
    if type(newlist_or_img) is not list:
        newlist_or_img = [ newlist_or_img ]

    for newimg in newlist_or_img:
        # Is it a valid image? E.g. not a Tags file.
        if not newimg.invalid:
            img_list.append(newimg)


        # else:
        #     print("Skipping non-image file", newimg)



[docs]
def remove_image(img=None):
    """Remove the indicated image. If img is None, remove the current image.
       If the cur_imgno pointer was pointing to the removed image,
       leave the pointer on the image before the removed one,
       otherwise don't disturb the pointer.
    """
    global cur_imgno
    if cur_imgno == -1:
        move_pointer = False
    elif not img:
        img = current_image()
        move_pointer = True
    elif img == current_image():
        move_pointer = True
    else:
        move_pointer = False
    index = img_list.index(img)
    img_list.remove(img)
    if move_pointer and index > 0:
        cur_imgno = index - 1





[docs]
def pop_image(imgno=None, advance=False):
    """Remove the indicated image from the list and return it.
       If img is None, remove the current image.
       If deleting the current image, leave the pointer on the image
       before the removed one unless advance is True;
       if popping any other image, don't move the pointer.
    """
    global cur_imgno
    if imgno is None:
        imgno = current_imageno()
        move_pointer = True
    elif imgno == cur_imgno:
        move_pointer = True
    else:
        move_pointer = False
    ret = img_list.pop(imgno)
    if move_pointer:
        if ((advance and imgno > len(img_list) - 1)
            or (imgno > 0 and not advance)):
            cur_imgno = imgno - 1
    return ret