[Gambas-user] Gambas2 Grab in Gambas3

Discussion:

Richard Welch

2016-11-08 11:52:35 UTC

I need a simple way to copy the current image in a visible DrawingArea
to a hidden PictureBox.

The project was written in Gambas2, where a simple Grab method did the
trick, but in G3 this does something different so the converted code
does not function fully.

FMain.pbxPicture.W = FMain.drwRep.W
FMain.pbxPicture.H = FMain.drwRep.H
FMain.pbxPicture.Background = FMain.drwRep.Background
FMain.pbxPicture.Picture = FMain.drwRep.Grab()

With what do I replace the Grab method?

(The DrawingArea is painted in many different pieces of code, depending
on context, so I want to make the change which will have the smallest
impact possible on the source code)

There is a gambas-user thread started around 19 April 2012.
Is this fully relevant?
Is this the /simplest/ answer?
It would need some very tedious testing in my context.....

Fabien Bodard

2016-11-08 17:31:01 UTC

Permalink

Well... there is two answers.

First :

Use the Desktop.ScreenShot Function
(http://gambaswiki.org/wiki/comp/gb.qt4/desktop/screenshot).
But your widget must be visible on the screen... This is why it is a
SCREEN shot.

Second :

When you are drawing something in a drawingarea you use a generic
drawing function.

Exemple :

Public sub DrawingArea_Draw()

DrawARect()

End

Private Sub DrawARect()

Paint.Brush = Brush.Color(Color.Yellow)
Paint.Rectangle(10,10,Paint.Width - 20, Paint.Height - 20)
Paint.Fill

End

Public Function MakeImage(iWidth as integer, iHeight as integer) as Image

Dim hImage a new Image(iWidth, iHeight, Color.White)

Paint.Begin(hImage)
DrawARect()
Paint.End

End

With that you have only one drawing function (DrawARect) able to draw
every where ... even on a printer. This is the way used in most of the
components too

Post by Richard Welch
I need a simple way to copy the current image in a visible DrawingArea
to a hidden PictureBox.
The project was written in Gambas2, where a simple Grab method did the
trick, but in G3 this does something different so the converted code
does not function fully.
FMain.pbxPicture.W = FMain.drwRep.W
FMain.pbxPicture.H = FMain.drwRep.H
FMain.pbxPicture.Background = FMain.drwRep.Background
FMain.pbxPicture.Picture = FMain.drwRep.Grab()
With what do I replace the Grab method?
(The DrawingArea is painted in many different pieces of code, depending
on context, so I want to make the change which will have the smallest
impact possible on the source code)
There is a gambas-user thread started around 19 April 2012.
Is this fully relevant?
Is this the /simplest/ answer?
It would need some very tedious testing in my context.....
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Fabien Bodard

Richard Welch

2016-11-09 16:45:00 UTC

Permalink

Fabien, thank you for your reply.

There are snags with each of these...

First approach:

Although the DrawingArea is often fully visible on screen, sometimes it
will be too big.
I can think of a way round this but it is not very elegant!

Second approach:

The image is sometimes highly complex and can comprise hundreds of
rectangles and lines as well as text. I already do use generic
functions as you describe, with variable-driven adjustments to cope with
the differences between printing and screen display. There are many
places in the code which may build a display.

I found in G2 that there were times when the image in a DrawingArea was
not restored if it was partially covered by a window from another
application and then exposed once more. This mechanism enabled it to be
restored easily without having to rebuild it from scratch. Maybe the
DrawingArea in G3 is more robust?

Richard

Post by Fabien Bodard
Well... there is two answers.
Use the Desktop.ScreenShot Function
(http://gambaswiki.org/wiki/comp/gb.qt4/desktop/screenshot).
But your widget must be visible on the screen... This is why it is a
SCREEN shot.
When you are drawing something in a drawingarea you use a generic
drawing function.
Public sub DrawingArea_Draw()
DrawARect()
End
Private Sub DrawARect()
Paint.Brush = Brush.Color(Color.Yellow)
Paint.Rectangle(10,10,Paint.Width - 20, Paint.Height - 20)
Paint.Fill
End
Public Function MakeImage(iWidth as integer, iHeight as integer) as Image
Dim hImage a new Image(iWidth, iHeight, Color.White)
Paint.Begin(hImage)
DrawARect()
Paint.End
End
With that you have only one drawing function (DrawARect) able to draw
every where ... even on a printer. This is the way used in most of the
components too

Fabien Bodard

2016-11-09 17:53:54 UTC

Permalink

Post by Richard Welch
Fabien, thank you for your reply.
There are snags with each of these...
Although the DrawingArea is often fully visible on screen, sometimes it
will be too big.
I can think of a way round this but it is not very elegant!
The image is sometimes highly complex and can comprise hundreds of
rectangles and lines as well as text. I already do use generic
functions as you describe, with variable-driven adjustments to cope with
the differences between printing and screen display. There are many
places in the code which may build a display.
I found in G2 that there were times when the image in a DrawingArea was
not restored if it was partially covered by a window from another
application and then exposed once more. This mechanism enabled it to be
restored easily without having to rebuild it from scratch. Maybe the
DrawingArea in G3 is more robust?

And why not using cached mode ?

Post by Richard Welch
Richard

------------------------------------------------------------------------------
Developer Access Program for Intel Xeon Phi Processors
Access to Intel Xeon Phi processor-based developer platforms.
With one year of Intel Parallel Studio XE.
Training and support from Colfax.
Order your platform today. http://sdm.link/xeonphi
_______________________________________________
Gambas-user mailing list
https://lists.sourceforge.net/lists/listinfo/gambas-user

--
Fabien Bodard

Richard Welch

2016-11-11 19:16:24 UTC

Permalink

Fabien, right on the button.

Cached now seems to work for me - when the code was first written in G2
some years ago, minimising the window blanked the DrawingArea to
background and overlaying it with a window from another application
blanked the hidden part of the DrawingArea (I can't now remember if this
always happened or if it was intermittent, depending on some factor
which I never identified). Turning on cached did not help. Hence the
workaround of the use of an invisible PictureBox to backup the image,
allowing its restoration to be a neat single operation independent of
the original drawing process.

So I'm happy. What was for you, no doubt, a simple observation has
saved me a lot of hassle. Thank you.

Richard

Post by Fabien Bodard

And why not using cached mode ?

Post by Richard Welch
Richard

Fabien Bodard

2016-11-13 08:26:30 UTC

Permalink

Post by Richard Welch
Fabien, right on the button.
Cached now seems to work for me - when the code was first written in G2
some years ago, minimising the window blanked the DrawingArea to
background and overlaying it with a window from another application
blanked the hidden part of the DrawingArea (I can't now remember if this
always happened or if it was intermittent, depending on some factor
which I never identified). Turning on cached did not help. Hence the
workaround of the use of an invisible PictureBox to backup the image,
allowing its restoration to be a neat single operation independent of
the original drawing process.
So I'm happy. What was for you, no doubt, a simple observation has
saved me a lot of hassle. Thank you.
Richard

It was a pleasure

Post by Richard Welch

Post by Fabien Bodard

And why not using cached mode ?

Post by Richard Welch
Richard

--
Fabien Bodard