Why does timeGetDevCaps fail?

[joeu2004]

Why does timeGetDevCaps fail in the VBA sub below?

And when it fails, why does it return TIMERR_NOCANDO instead of
TIMERR_STATUS? (Or so it seems.)

(I suspect the latter is simply a defect either in the documentation
or in the library implementation. Other related functions do return
TIMERR_NOCANDO.)

According to "man pages" and header files that I found in Google
searches, timeGetDevCaps and related identifiers are defined as
follows.

MMRESULT timeGetDevCaps( LPTIMECAPS ptc, UINT cbtc )

Parameters:
ptc: Pointer to a TIMECAPS structure.
cbtc: Size, in bytes, of the TIMECAPS structure.

Return Values
Returns TIMERR_NOERROR if successful or TIMERR_STRUCT if it fails
to return the timer device capabilities.

Requirements and Library:
Same as timeGetTime et al, which seem to work just fine.

Related declarations:
alias UINT MMRESULT
struct TIMECAPS { UINT wPeriodMin; UINT wPeriodMax; }
alias TIMECAPS* PTIMECAPS, LPTIMECAPS
const TIMERR_BASE=96
const TIMERR_NOERROR=0
const TIMERR_NOCANDO=(TIMERR_BASE+1) // 97
const TIMERR_STRUCT=(TIMERR_BASE+33) // 129

Of course, I cannot say for sure whether those related declarations --
especially the TIMERR constant -- apply to my system. But I assume
they do. I am using MSWin XP Pro (32-bit), Excel 2003 with VB 6.3.

On the off-chance that the DLL integer is different from the VBA
integer -- unlikely, I know, but I am used to ILP32 archtectures where
int and long (and pointer) are 32-bit -- I tried calling
timeGetDevCaps with cbtc set to 8 instead of 4. Not surprisingly, I
get run-time error 49 (bad DLL calling convention).

My VBA code....

Type TIMECAPS
min As Integer
max As Integer
End Type

Public Declare Function timeGetDevCaps Lib "winmm" (ByRef tcaps As
TIMECAPS, ByVal sz As Integer) As Integer
Public Declare Function timeBeginPeriod Lib "winmm" (ByVal msec As
Integer) As Integer
Public Declare Function timeEndPeriod Lib "winmm" (ByVal msec As
Integer) As Integer
Public Declare Function timeGetTime Lib "winmm" () As Long
Public Declare Sub Sleep Lib "kernel32" (ByVal msec As Long)

Private Sub testWinmm()
Dim tc As TIMECAPS
Dim x As Integer
Dim st As Long, et As Long, dt As Long

'*****ERROR: timeGetDevCaps does not return 0
tc.min = -123: tc.max = -456
x = timeGetDevCaps(tc, 4)
Debug.Print "timeGetDevCaps="; x; _
" min="; IIf(tc.min = -123, "UNCHANGED ", tc.min); _
" max="; IIf(tc.max = -456, "UNCHANGED", tc.max)

'Everything else works (i.e. does not return error status)
x = timeBeginPeriod(1)
Debug.Print "timeBeginPeriod="; x

x = timeEndPeriod(1)
Debug.Print "timeEndPeriod="; x

st = timeGetTime()
Call Sleep(1000)
et = timeGetTime()
dt = et - st
Debug.Print "st="; st; " et="; et; " dt="; dt
End Sub

 

[joeu2004]

joeu2004;269503 Wrote:
[....]

On the off-chance that the DLL integer is different from the VBA
integer -- unlikely, I know, but I am used to ILP32 archtectures where
int and long (and pointer) are 32-bit -- I tried calling
timeGetDevCaps with cbtc set to 8 instead of 4. Not surprisingly, I
get run-time error 49 (bad DLL calling convention).

[....]
The biggest change was changing from Integer (16 bit) to Long (32 bit).

So my intuition was right after all(!). I made the mistake of
changing only cbtc. In hindsight, that was foolish of me. If that
had worked, I would have clobbered memory. Klunk!

Unless you are working with Windows 3.1 or know for certain a
value can be an Integer in the API declaration, use Long types.

Thanks for the tip. It should not be hard for me to remember ;-).


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