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Run only one instance of your application: Difference between revisions
Run only one instance of your application (view source)
Revision as of 15:30, 27 September 2021
, 27 September 2021Updated "createmutex succeeded" test to test for NULL not ERROR_INVALID_HANDLE as per Frank Cheng's recommendation see https://support.dataaccess.com/Forums/showthread.php?67791-Limiting-Dataflex-Instances-to-1-per-Laptop&p=368346#post368346
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(Updated "createmutex succeeded" test to test for NULL not ERROR_INVALID_HANDLE as per Frank Cheng's recommendation see https://support.dataaccess.com/Forums/showthread.php?67791-Limiting-Dataflex-Instances-to-1-per-Laptop&p=368346#post368346) |
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# Using mutexes | # Using mutexes | ||
# Using FindWindow WinAPI | # Using FindWindow WinAPI | ||
# Using Atoms | |||
=== Using mutexes === | === Using mutexes === | ||
| Line 11: | Line 12: | ||
In the SRC file within the panel object put this piece of code: | In the SRC file within the panel object put this piece of code: | ||
< | <source lang="dataflex"> | ||
Procedure Exit_Application | Procedure Exit_Application | ||
integer iVoid | integer iVoid | ||
| Line 18: | Line 19: | ||
Forward Send Exit_Application | Forward Send Exit_Application | ||
End_Procedure | End_Procedure | ||
</ | </source> | ||
And in a package that gets hit on startup: | And in a package that gets hit on startup: | ||
< | <source lang="dataflex"> | ||
// Constants | // Constants | ||
Define ERROR_INVALID_HANDLE for 6 // taken from error.h of VS7 | Define ERROR_INVALID_HANDLE for 6 // taken from error.h of VS7 | ||
Define ERROR_ALREADY_EXISTS for 183 | Define ERROR_ALREADY_EXISTS for 183 | ||
Handle ghMuteX | |||
Handle ghMuteX | |||
// external functions | // external functions | ||
#IFNDEF Get_CreateMuteX | #IFNDEF Get_CreateMuteX | ||
| Line 31: | Line 35: | ||
#IFNDEF Get_CloseHandle | #IFNDEF Get_CloseHandle | ||
External_Function CloseHandle "CloseHandle" Kernel32.dll Integer i1 Returns Integer | External_Function CloseHandle "CloseHandle" Kernel32.dll Integer i1 Returns Integer | ||
#ENDIF | #ENDIF | ||
// function to create a mutex | // function to create a mutex | ||
Procedure Create_MuteX_Object | Procedure Create_MuteX_Object | ||
| Line 38: | Line 43: | ||
Move "Unique String For My Application" To sID | Move "Unique String For My Application" To sID | ||
Move (CreateMuteX(0,1,AddressOf(sID))) To ghMuteX | Move (CreateMuteX(0,1,AddressOf(sID))) To ghMuteX | ||
If (ghMuteX <> | If (ghMuteX <> 0) Begin | ||
Move (GetLastError()) To iErr | Move (GetLastError()) To iErr | ||
If (iErr = ERROR_ALREADY_EXISTS) Begin // program is already | If (iErr = ERROR_ALREADY_EXISTS) Begin // program is already | ||
| Line 51: | Line 56: | ||
End | End | ||
Else Send None // rare error; object could not be created | Else Send None // rare error; object could not be created | ||
End_Procedure // Create_MuteX_Object | End_Procedure // Create_MuteX_Object | ||
// create the mutex | // create the mutex | ||
Send Create_MuteX_Object | Send Create_MuteX_Object | ||
</ | </source> | ||
Dave Robinson says - | |||
A warning: We found CodeJock skinning broke this, though YMMV. | |||
=== Using FindWindow WinAPI === | === Using FindWindow WinAPI === | ||
| Line 61: | Line 70: | ||
Usage in SRC: | Usage in SRC: | ||
< | <source lang="dataflex"> | ||
Use myPanel,pkg | Use myPanel,pkg | ||
Object Main is a myPanel | Object Main is a myPanel | ||
</ | </source> | ||
Source myPanel.pkg | Source myPanel.pkg | ||
< | <source lang="dataflex"> | ||
//////////////////////////////////////////// | //////////////////////////////////////////// | ||
// | // | ||
| Line 104: | Line 113: | ||
End_Procedure // End_Construct_Object | End_Procedure // End_Construct_Object | ||
End_class | End_class | ||
</ | </source> | ||
The FindWindow technique is also discussed in the book [http://starzen.com/products/books-and-magazines/mastering-visual-dataflex/ Mastering Visual DataFlex] from Starzen. | |||
Dave Robinson says: | |||
The FindWindow method depends on the Title in the program taskbar being known and consistent. | |||
[[Category: Tutorials]] | [[Category: Tutorials]] | ||