[Gambas-user] DRAWEREA

[Benoît Minisini]

> hello,
> I'm new and I have a question.
> I would like to draw some points in defferent colors in a drawarea.
> But my program dosn't work. (see source) There is nothing to see. (no
> points)
> Can somebody help me?
>
> Source:
>   DrawingArea1.Clear
>   DrawingArea1.Show
>   DrawingArea1.Visible = TRUE
>   DrawingArea1.Foreground = Color.Black
>   DrawingArea1.Background = Color.White
>   DrawingArea1.Refresh
>   Draw.Begin(DrawingArea1)
>     Draw.Transparent = FALSE
>     Draw.ForeColor = Color.Black
>     Draw.Foreground = Color.Black
>     Draw.BackColor = Color.White
>     Draw.Background = Color.White
>     Draw.FillStyle = 1
>     f = &HFF00
>     FOR x = 10 TO 50 STEP 1
>       Draw.ForeColor = f
>       Draw Foreground = f
>       FOR y = 10 TO 50 STEP 1
>         Draw.Point(x, y)
>       NEXT
>       f = f + 4
>     NEXT
>   Draw.End
>   DrawingArea1.Refresh

A DrawingArea has two possible behaviours:

1) When its Cached property is set to False (the default).

Then you must draw inside the DrawingArea Draw event handler. This event will 
be raised each time X11 tells your application that the drawing area has to be 
redrawn. You don't have to call Draw.Begin() and Draw.End() inside the event 
handler, this is done automatically.

In that case, drawing outside of the Draw event handler is useless.

2) When its Cached property is set to True.

Then drawing on the DrawingArea is done inside a internal bitmap buffer. Then 
you can draw when you want, and the internal bitmap buffer will be used to 
refresh the DrawingArea contents as needed.

Regards,

-- 
Benoît