Computer Science Canada

Help with Erasing while dragging objects
Author:  Sceyef [ Fri Dec 12, 2014 7:24 pm ]
Post subject:  Help with Erasing while dragging objects
so like, I have never liked animating in turing.
Here's my code. It's a simple drag-an-object program. Primitive, as the object centers on your cursor and stuff, but it works.
code:

var x, y, button, a, b : int
a := 100
b := 100
var buttonpress : boolean := false
setscreen ("offscreenonly")
loop
    mousewhere (x, y, button)
    locate (1, 1)
    if x > a - 50 and x < a + 50 and y > b - 50 and y < b + 50 then
        if button = 1 then
            buttonpress := true
        else
            buttonpress := false
        end if
    end if
    if buttonpress = true then
        a := x
        b := y
    end if
    cls
    drawfillbox (a - 50, b - 50, a + 50, b + 50, red)
    View.Update
end loop


Now here's what I need: I am currently erasing the red square with CLS. Later I need to add a background. How can I do that? Try it yourself, but when I attempt to put the usual identical object with colorbg, there are.. problems..? Even If I make the object bigger. It doesn't erase properly. :/

halp
Author:  Zren [ Fri Dec 12, 2014 7:33 pm ]
Post subject:  RE:Help with Erasing while dragging objects
Draw things that appear underneath first, then draw the thing on top second.

Turing:

cls % Begin drawing a new frame
Draw.FillBox(0, 0, maxx, maxy, black) % Draw background
Draw.Oval(x, y, r, r, red) % Draw foreground
View.Update() % Done drawing the frame, show it on screen.

:


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