I am new to Gambas and I am struggling with the drawing features.

I have created a DrawingArea ( DA1) in FMain, and I am trying to draw to ot with this code.


Public Sub button1_Click()
  Button1.visible = False
  Message("a parrot of course. Not dead yet")
   PictureBox1.Picture = Picture["barefoot_2.png"]
   Wait 3.0
  Message("could be dead now")

   PictureBox1.Picture = Picture["bird2.png"]
   Draw.begin(DA1)
   Draw.LineWidth = 2
   Draw.ForeColor = Color.Red
   Draw.Line(10, 10, 100, 100)
   Draw.End
  Wait 3.0
  Quit
  End

However I keep getting this message

Cannot paint outside of draw event handler

what am I doing wrong?

thanks, Colin McMurchie

Hi colinmc

Gambas is telling you that you need to draw in event DA1_Draw() which you then call from the button with the Refresh() method

 

Thankyou GianLuigi,

I know see a line, and no error messages.

Colin 

Just FYI:

"The Draw class is deprecated since Gambas 3.4. It is now emulated through the Paint class."

Draw — Gambas Documentation
/comp/gb.qt4/paint - Gambas Documentation

I moved from Draw to Paint a while ago and it took me some 'head scratching' to do the transition.

I wrote this subroutine to make painting grids on drawing areas easier - I'm still using this in some simple games I am making.

InScale is generally around 34
InClear = True
InDRa is the DrawingArea                         


Which if 510 X 510 ( 15 X InScale ) you 'should' get a 10 X 10 grid of width & height of 34

This is an example of the grid drawn by the sub in a game called 'Blocks'









End

Thanks Technopeasant and Quincunxian for your comments.

I am now happily painting lines on a drawingarea.

I do have a further issue with persistancy however.  I have a demo which shows four lines in the form of a diagoonal cross. Each line is triggered by a button click.

You will see that for each new line I have to repaint the previous lines. Is there an easier way to preserve these lines between clicks? Then I will not have to redraw them. I have looked at save/restore and cache but so far without success.

Thanks, Colin

Here is the code (next time I will use a proper code box).

' Gambas class file

badgo As Integer = 0

 Public Sub DA1_Draw()

Paint.begin(DA1)
   Paint.Brush = Paint.Color(Color.Red)
   Paint.LineWidth = 5
    Select badgo
      Case 1
        Paint.Moveto(10, 10)
        Paint.LineTo(100, 100)
      Case 2
        Paint.Moveto(10, 10)
        Paint.LineTo(100, 100)
        Paint.Moveto(190, 10)
        Paint.LineTo(100, 100)
      Case 3
        Paint.Moveto(10, 10)
        Paint.LineTo(100, 100)
        Paint.Moveto(190, 10)
        Paint.LineTo(100, 100)
        Paint.Moveto(190, 190)
        Paint.LineTo(100, 100)
      Case 4
        Paint.Moveto(10, 10)
        Paint.LineTo(100, 100)
        Paint.Moveto(190, 10)
        Paint.LineTo(100, 100)
        Paint.Moveto(190, 190)
        Paint.LineTo(100, 100)
        Paint.Moveto(10, 190)
        Paint.LineTo(100, 100)
    End Select
      Paint.Stroke(True)
  Paint.End
 End


Public Sub button1_Click()
  badgo += 1
If badgo > 4 Then
badgo = 0
DA1.Clear()
Endif
DA1.Refresh()
End


Public Sub Form_Open()
End

and here is the form

# Gambas Form File 3.0

{ Form Form
  MoveScaled(0,0,29,39)
  Background = &HFFFFDF
  Text = ("Getting Cross Now")
  { Button1 Button
    MoveScaled(6,31,16,4)
    Background = &HFFC71F
    Text = ("press me")
  }
  { DA1 DrawingArea
    MoveScaled(3,3,23,24)
    Background = &HFFC71F
    Border = Border.Plain
  }
}


 

You could do something similar:


 

Thankyou Gianluigi,

I have tried your suggestion, but I still need to re-draw each line on each button click.

I think I am looking for a method that preserves the Drawarea image as something akin to a picture, which I can then paint on following a click, and in turn preseve that.

I suspect that may not be possible in the end, but that is not a big issue, as I am only experimenting out of curiousity.

Thanks again for your thoughts.

What you want can be done.
See gambas wiki: Paint on Gambas wiki
"Paint can draw on the following targets:
    Picture.
    Image.
    DrawingArea.
    Printer.
    SvgImage."

So in short:
You you can draw on the DrawingArea, next save it and load it as picture, next draw on the picture as an example. More options possible, this is just what came to my mind.
I created a screenshot application and to include a mousepointer I capture the screen and based on mouse x and Y position, I draw a pointer onto the just captured screenshot, before saving it as a picture, using Paint.
It's and awesome and powerfull tool.
 

Hello,

thanks to the help I have received I now have a working demo of bit-by-bit drawing, so to speak. There are still some rough edges, especially around file handling, but I have learned a lot, which is saying something at my age.

Having now satisfied my curiousness over this, I now have to find a useful application for it!

 

Hi colinmc

The files in the project are read-only and are used to copy them to other folders (e.g., User.Home &/Application.Name). Temporary files can be saved in Temp (Temp — Gambas Documentation) and are automatically deleted when the program closes.
If you want to display the code, put it between the "code" and "/code" tags into square brackets.

 

Thank you.