EnumDisplayDevices... What I'm doing wrong?

BlitzMax Forums/BlitzMax Programming/EnumDisplayDevices... What I'm doing wrong?

SLotman

(Posted 2011) [#1]

Title is self explanatory... what I'm doing wrong in the code below?

Extern "Win32"
	Function EnumDisplayDevices:Int (Unused:Int, iDevNum:Int, display:Byte Ptr, flags:Int)"Win32"= "EnumDisplayDevicesA@16"
EndExtern


Type DISPLAY_DEVICE
  Field cb:Int
  Field DeviceName:Byte[32] 'Byte Ptr[32]
  Field DeviceString:Byte[128] 'Byte Ptr[128]
  Field StateFlags: Int
  Field DeviceID:Byte[128] 'Byte Ptr[128]
  Field DeviceKey:Byte[128] 'Byte Ptr[128]
End Type

Local dd:DISPLAY_DEVICE = New DISPLAY_DEVICE
dd.cb = SizeOf(dd.cb) + SizeOf(dd.DeviceName) + SizeOf(dd.DeviceString) + SizeOf(dd.StateFlags) + SizeOf(dd.DeviceID) + SizeOf(dd.DeviceKey)

Print dd.cb

Print "--------------------------"
Print "Retrieving devices info..."
Print "--------------------------"

Local i:Int=0
Local done:Int=False

While Not done
   If EnumDisplayDevices(0, i, Varptr(dd), 0) Then
	   Print "Display " + i + " info:"
	   Print "Device ID:" + String.FromCString(dd.DeviceID)
   Else
 	   Print "Finished looking for display adapters"
	   done=True
   End If
   i:+1
Wend
Print "done!"

I ran this code, and the program just ends, no error, no anything! Not even the "done!" is printed!

I have no idea what is wrong with it :(

Last edited 2011

Last edited 2011

Last edited 2011

Brucey

(Posted 2011) [#2]

Well, to begin with, a TCHAR[32] is not the same as a Byte Ptr[32]...

You'll probably find it easier to either write some C glue, or a TBank...

SLotman

(Posted 2011) [#3]

Edit: Updated the code, but it still doesn't work...

...but the same code on VB works. I really have no clue how to fix this :/

Also I don't get it why sizeof(type) returns a complete bogus value - I had to get sizeOf each type element to get it's size correctly.

Ahhh... using Banks was the (ugly) solution:

Extern "Win32"
	Function EnumDisplayDevices:Int (Unused:Int, iDevNum:Int, display:Byte Ptr, flags:Int)"Win32"= "EnumDisplayDevicesA@16"
EndExtern


Type DISPLAY_DEVICE
  Field cb:Int
  Field DeviceName:Byte[32] 'Byte Ptr[32]
  Field DeviceString:Byte[128] 'Byte Ptr[128]
  Field StateFlags: Int
  Field DeviceID:Byte[128] 'Byte Ptr[128]
  Field DeviceKey:Byte[128] 'Byte Ptr[128]
End Type

Local dd:DISPLAY_DEVICE = New DISPLAY_DEVICE
dd.cb = SizeOf(dd.cb) + SizeOf(dd.DeviceName) + SizeOf(dd.DeviceString) + SizeOf(dd.StateFlags) + SizeOf(dd.DeviceID) + SizeOf(dd.DeviceKey)

Print "--------------------------"
Print "Retrieving devices info..."
Print "--------------------------"

Local i:Int=0
Local done:Int=False

Local b:TBank=CreateBank(424)
'MemCopy(b.buf(), dd, dd.cb)
PokeInt b, 0, dd.cb

While Not done
   If EnumDisplayDevices(0, i, b.buf(), 0) Then
      'MemCopy(dd, b.buf(), dd.cb)

	   Print "Display " + i + " info:"

	   Local str:String = ""
	   For Local f:Int=0 To 31
	      str = str + Chr(PeekByte(b,4+f))
	   Next
	   Print "Device Name:" + str

	   str = ""
	   For f=0 To 31
	      str = str + Chr(PeekByte(b,36+f))
	   Next
	   Print "Device String:" + str
   Else
 	   Print "Finished looking for display adapters"
	   done=True
   End If
   i:+1
Wend
b = Null
Print "done!"

Last edited 2011

Floyd

(Posted 2011) [#4]

Also I don't get it why sizeof(type) returns a complete bogus value

It returns the correct value. There are six fields, each of which is four bytes ( integer or pointer ).

In C you just get a block of memory with names like DevideID giving offsets into the block. That's why Brucey suggested using C, or a bank and handle the offsets yourself.

Last edited 2011

Czar Flavius

(Posted 2011) [#5]

Byte is 1 byte and Byte Ptr is 4 bytes.

Brucey

(Posted 2011) [#6]

VB <> BlitzMax

Arrays in BlitzMax are not like arrays in C/C++. And Types too are not like structs...

sizeof 4+32+128+4+128+128 = .... ?

Despite what Floyd says, the six fields are not all 4 bytes, since the TCHAR fields are inlined character arrays of the struct, not pointers.

If you don't want to use a TBank, do a straight memory allocation, but you'll have to remember to free it yourself...

Local dd:Byte Ptr = MemAlloc(4+32+128+4+128+128)

Int Ptr(dd)[0] = 4+32+128+4+128+128

.. call your function, passing in dd, not Var Ptr dd....
EnumDisplayDevices(0, i, dd, 0)

.. then..

Print "Device Name:" + String.FromCString(dd + 4)

etc...

Try not to over-complicate things :-)

SLotman

(Posted 2011) [#7]

Ah! That look so much better! Didn't know bmax had Malloc! :)

Brucey

(Posted 2011) [#8]

Well, TBank hides all that away, and manages the deallocation of the memory for you. Otherwise you need to remember to MemFrree() your Byte Ptr....