Virtual Graphic - Memory Demand?

[Gary Beene]

I assumed that using Graphic Set Virtual 8000,4000 would create a hidden bitmap of about 32MB - increasing the memory footprint of the app.

But in this example, Task Manager shows no increase in memory requirements at all when going Virtual.

'Compilable Example:
#Compile Exe
#Dim All
%Unicode = 1
#Include "Win32API.inc"

Enum Equates Singular
   IDC_ButtonA  = 500
   IDC_ButtonB
   IDC_Graphic
End Enum

Global hDlg As Dword

Function PBMain() As Long
   Dialog New Pixels, 0, "Fixed",300,300,300,200, %WS_OverlappedWindow To hDlg
   Control Add Graphic, hDlg, %IDC_Graphic, "", 0,0,300,200
   Graphic Attach hDlg, %IDC_Graphic
   Control Add Button, hDlg, %IDC_ButtonA,"Virtual", 50,10,100,20
   Control Add Button, hDlg, %IDC_ButtonB,"Fixed", 50,50,100,20
   Dialog Show Modal hDlg Call DlgProc
End Function

CallBack Function DlgProc() As Long
   Select Case Cb.Msg
      Case %WM_Command
         Select Case Cb.Ctl
            Case %IDC_ButtonA : Graphic Set Virtual 8000,4000 : Dialog Set Text hDlg, "Virtual"
            Case %IDC_ButtonB : Graphic Set Fixed : Dialog Set Text hDlg, "Fixed"
         End Select
   End Select
End Function

But, if I add a small BMP to the Graphic Virtual control, the app does seem to grow by the size of the BMP.

Bob apparently does something more than a very large bitmap ... not sure of the details.

[Borje Hagsten]

Yeah, since we don't know, we can only guess that Graphic Set Virtual equals SetScrollInfo, nothing more. What we do know is that a Graphic control is a simple Static (Label) control.. and from there on it becomes a guessing game. A memDC "canvas" is probably created (CreateCompatibleDC + CreateCompatibleBitmap) at some point and BitBlt'd och StretchBlt'd under WM_CTLCOLORSTATIC.. or a subclassed Static control's WM_PAINT or WM_ERASE.

[Borje Hagsten]

But reading the manual after guessing a reply, I see it says "When executed, a new virtual bitmap of the specified height and width is created." So, sorry - I got nothing..

[Paul Dixon]

The graphic is stored by the system, not by your program.
The memory use DOES increase if you look at overall memory rather than just the memory used by your program.
Make the virtual graphic bigger 20000x20000 and it becomes more obvious.

[Tim Lakinir]

Hi , this is pretty interesting
Can someone provide a working usage of this Virtual graphics technique ?
maybe draw a virtual bitmap and display it later?

[Gary Beene]

Howdy, Dave!

"... stored by the system."

Nice sleuthing! But, how can that be? I wasn't aware that memory requested my app has the option of being in-process memory or not? Can I do that intentionally ... ask for memory that doesn't increase my app's footprint?

[Stuart McLachlan]

Looks like it may be using a memory mapped file based on what Procexp shows

You can do the same yourself in any application by creating a MMF.

[Paul Dixon]

Gary,
" But, how can that be?"
It can be because the graphics processor handles the graphics for display, not the CPU.
The graphics processor might have its own memory or it might share the system memory but it's outside of the memory your program can access.

It's not an option that you can choose. It's just how graphics work.
When you use something like GRAPHIC SET BITS, your accessible bitmap in your application's memory is copied to the device memory for display.
That device memory is outside of your application's memory space. It's the display adapter which needs the memory, not your application.

Here's what my laptop says about the memory for my display.
It has access to 4059MB of system memory plus 128MB of dedicated graphics memory.

[Michael Mattias]

Don't use Task Manager for this ... use code at appropriate points in your program. Be sure to put inside a ...

#IF %SHOW_MEMORY_USAGE
       memory call
#ENDIF

. code block so you can quickly skip for production version of your code.

LINKS ===> :

Add Process Memory Usage Report to any program 1-12-04
Discussion, results: http://www.powerbasic.com/support/pb...ad.php?t=20645


Oops those are the old ref lets see if we can find the current ones..

Found 'Em.....

Here's the report code from the Source Code Forum (thank you, "Search")

https://forum.powerbasic.com/forum/u...to-any-program

Discussion and results
https://forum.powerbasic.com/forum/u...y-info?t=20645


MCM

[Michael Mattias]

I just re-read that "discussion and results" thread which I started in 2004... a lot of the same kinds of issues from... oh, call it last week!