This is a somewhat simple process once the code "saves" the newly drawn boxes somehow. I think a good way to do this is to create a PyGame sprite object for each new box, and keep them in a sprite Group.
At the end of a "mouse drag" operation, we have a start-position - the mouse-xy of the MOUSEBUTTONDOWN event, and the end-position is the mouse-xy of the MOUSEBUTTONUP event. With a bit of fiddling to handle negative-ranges, we calculate a PyGame rectangle object (Rect), using it as the basis for a BoxSprite:
class BoxSprite( pygame.sprite.Sprite ):
""" Rectangular, coloured box-sprite """
def __init__( self, drag_rect ):
super().__init__()
self.image = pygame.Surface( ( drag_rect.width, drag_rect.height ) )
self.rect = drag_rect.copy()
self.image.fill( GREEN )
Looking at the BoxSprite, it's really not much more than a coloured Surface, sized and positioned over the original drag_rect.
Once we have a Sprite to hold the box, PyGame has the super-useful Sprite Group class. This can be used to hold all the BoxSprites, and provides easy drawing, membership and collision functions.
So now the code can "remember" every box, how can we determine if the user clicked on one? An easy way to do this is to test if the click mouse-position is inside any of the group members. A simple approach would be to iterate through every sprite in the group, checking each sprite's Rect. Or if we can somehow treat the mouse-click as a sprite-object, we can use the existing Sprite Group's "Sprite Vs Sprite-Group" collision-test function. This operation returns a handy list of collided sprites from the group. Nice.
Once you have this list, how you treat them is up to you. In the example below I implemented a drag-existing sprite, so clicking on an existing Box "grabs" it until the mouse button is released.
import pygame
# window sizing
WIDTH = 500
HEIGHT = 500
MAX_FPS = 60
BLACK = ( 0, 0, 0)
RED = (255, 0, 0)
GREEN = ( 20, 200, 20)
YELLOW= ( 255,255, 0)
pygame.init()
window = pygame.display.set_mode( ( WIDTH, HEIGHT ) )
pygame.display.set_caption( "Box Dragging Demo" )
###
### This is a sprite we use to hold each rectangular box the User creates.
### Once the user completes an on-screen draw operation, the box gets stored in
### an instance of a BoxSprite
###
class BoxSprite( pygame.sprite.Sprite ):
""" Rectangular, coloured box-sprite """
def __init__( self, drag_rect ):
super().__init__()
self.image = pygame.Surface( ( drag_rect.width, drag_rect.height ) )
self.rect = drag_rect.copy()
self.image.fill( GREEN )
def moveBy( self, dx, dy ):
""" Reposition the sprite """
self.rect.x += dx
self.rect.y += dy
def setColour( self, c ):
self.image.fill( c )
###
### Sprite Groups have no function to test collision against a point
### So this object holds a position as a "dummy" 1x1 sprite, which
### can be used efficiently in collision functions.
###
class CollidePoint( pygame.sprite.Sprite ):
""" Simple single-point Sprite for easy collisions """
def __init__( self, point=(-1,-1) ):
super().__init__()
self.image = None # this never gets drawn
self.rect = pygame.Rect( point, (1,1) )
def moveTo( self, point ):
""" Reposition the point """
self.rect.topleft = point
# Sprite Group to hold all the user-created sprites
user_boxes_group = pygame.sprite.Group() # initially empty
rect_start = ( -1, -1 ) # start position of drawn rectangle
drag_start = ( -1, -1 ) # start position of a mouse-drag
mouse_click = CollidePoint() # create a sprite around the mouse-click for easier collisions
clicked_boxes = [] # the list of sprites being clicked and/or dragged
clock = pygame.time.Clock() # used to govern the max MAX_FPS
### MAIN
exiting = False
while not exiting:
# Handle events
mouse_pos = pygame.mouse.get_pos()
for event in pygame.event.get():
if ( event.type == pygame.QUIT ):
exiting = True
elif ( event.type == pygame.MOUSEBUTTONDOWN ):
# MouseButton-down signals beginning a drag or a draw
# Did the user click on an existing sprite?
mouse_click.moveTo( mouse_pos )
clicked_boxes = pygame.sprite.spritecollide( mouse_click, user_boxes_group, False ) # get the list of boxes clicked (if any)
# was anything clicked?
if ( len( clicked_boxes ) > 0 ):
drag_start = mouse_pos # yes, begin a drag operation
for box in clicked_boxes:
box.setColour( YELLOW )
else:
# Nothing clicked, not already drawing, start new rectangle-draw
rect_start = pygame.mouse.get_pos()
elif ( event.type == pygame.MOUSEBUTTONUP ):
# MouseButton-up signals both drag is complete, and draw is complete
# Was the user dragging any sprites?
if ( len( clicked_boxes ) > 0 ):
# drag is over, drop anything we were dragging
for box in clicked_boxes:
box.setColour( GREEN )
drag_start = ( -1, -1 )
clicked_boxes = []
# Was the user drawing a rectangle?
elif ( rect_start != ( -1, -1 ) ):
# Rects are always defined from a top-left point
# So swap the points if the user dragged up
if ( rect_start > mouse_pos ):
swapper = ( mouse_pos[0], mouse_pos[1] )
mouse_pos = rect_start
rect_start = swapper
# create a new sprite from the drag
new_width = abs( mouse_pos[0] - rect_start[0] )
new_height = abs( mouse_pos[1] - rect_start[1] )
if ( new_width > 0 and new_height > 0 ):
new_sprite = BoxSprite( pygame.Rect( rect_start, ( new_width, new_height ) ) )
user_boxes_group.add( new_sprite )
rect_start = ( -1, -1 ) # done drawing
elif ( event.type == pygame.MOUSEMOTION ):
# The mouse is moving, so move anything we're dragging along with it
# Note that we're moving the boxes bit-by-bit, not a start->final move
if ( len( clicked_boxes ) > 0 ):
x_delta = mouse_pos[0] - drag_start[0]
y_delta = mouse_pos[1] - drag_start[1]
for box in clicked_boxes:
box.moveBy( x_delta, y_delta )
drag_start = mouse_pos
# Handle keys
keys = pygame.key.get_pressed()
if ( keys[pygame.K_ESCAPE] ):
exiting = True
# paint the window
window.fill( BLACK ) # paint background
user_boxes_group.draw( window ) # paint the sprites
# If we're already dragging a box, paint a target-rectangle
if ( rect_start != ( -1, -1 ) ):
# Use a lines instead of a Rect, so we don't have to handle width/height co-ordinate position issues
box = [ rect_start, ( mouse_pos[0], rect_start[1] ), mouse_pos, ( rect_start[0], mouse_pos[1] ) ]
pygame.draw.lines( window, RED, True, box, 1 )
pygame.display.flip()
clock.tick( MAX_FPS )
pygame.quit()
