Mutley2003
asked on
2 shortcuts, 1 instance
I asked a variant of this question at
"A single hotkey doing wakeup and global duty"
https://www.experts-exchange.com/questions/21122673/A-single-hotkey-doing-wakeup-and-global-duty.html
and accepted the answer - that it was basically a matter of using a mutex to enforce a single instance and passing through an indication of which shortcut key was used via SendMessage.
However, I started thinking <g> and it seems to me that enforcing a single instance via a mutex is inefficient. My concern is that a second copy of the exe (MyMegaApp) is actually loaded into memory BEFORE it gets killed (after detecting the mutex).
How about this. The shortcut keys actually call a small "loader" app. It is that app which then "spawns" MyMegaApp but ONLY if needed (ie no mutex). Some sort of WinExecAndWait or is CreateProcess what I need?. We still use a SendMessage to send the arguments.. hmm, would it be better to use a more general interprocess communications approach (so I can send more stuff).
Anyone care to look at the previous answer and improve on it, given these ideas?
Thanks
"A single hotkey doing wakeup and global duty"
https://www.experts-exchange.com/questions/21122673/A-single-hotkey-doing-wakeup-and-global-duty.html
and accepted the answer - that it was basically a matter of using a mutex to enforce a single instance and passing through an indication of which shortcut key was used via SendMessage.
However, I started thinking <g> and it seems to me that enforcing a single instance via a mutex is inefficient. My concern is that a second copy of the exe (MyMegaApp) is actually loaded into memory BEFORE it gets killed (after detecting the mutex).
How about this. The shortcut keys actually call a small "loader" app. It is that app which then "spawns" MyMegaApp but ONLY if needed (ie no mutex). Some sort of WinExecAndWait or is CreateProcess what I need?. We still use a SendMessage to send the arguments.. hmm, would it be better to use a more general interprocess communications approach (so I can send more stuff).
Anyone care to look at the previous answer and improve on it, given these ideas?
Thanks
oh yea, , It is my impression that if you never call the
Application.Initialize;
Application.CreateForm(TFo
the Application and "Form" are not loaded into a Memory block, so none of the Form's class is ever given any memory for functioning
Application.Initialize;
Application.CreateForm(TFo
the Application and "Form" are not loaded into a Memory block, so none of the Form's class is ever given any memory for functioning
ASKER
hi Slick812
https://www.experts-exchange.com/questions/20623659/PostMessage-returns-wierd-string.html
does a nice job of passing string data via WM_COPYDATA, thanks.
I guess I don't understand enough about how windows loads an exe .. you say
"It is my impression that if you never call the
Application.Initialize;
Application.CreateForm(TFo
the Application and "Form" are not loaded into a Memory block, so none of the Form's class is ever given any memory for functioning"
well, there would not be any dynamic memory allocations obviously, but I would have thought that all the code and data gets loaded ... that is, an "image" of the exe.
How to test this?
https://www.experts-exchange.com/questions/20623659/PostMessage-returns-wierd-string.html
does a nice job of passing string data via WM_COPYDATA, thanks.
I guess I don't understand enough about how windows loads an exe .. you say
"It is my impression that if you never call the
Application.Initialize;
Application.CreateForm(TFo
the Application and "Form" are not loaded into a Memory block, so none of the Form's class is ever given any memory for functioning"
well, there would not be any dynamic memory allocations obviously, but I would have thought that all the code and data gets loaded ... that is, an "image" of the exe.
How to test this?
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Oh this DOES not set a Mutex if there is Not one, so you will still need to set the mutex in your MegaApp
ASKER
Slick812,
maybe I am sleepy too (or just thick<g>).. but you have shown me how to start an app if there is no mutex, cool.
If there is a mutex, then OK we send stuff to the already running instance (via WM_COPYDATA) . There is still the issue of how to "wake up" that instance. Maybe it is just something in the WM_COPYDATA event handler to make a form visible/active
maybe I am sleepy too (or just thick<g>).. but you have shown me how to start an app if there is no mutex, cool.
If there is a mutex, then OK we send stuff to the already running instance (via WM_COPYDATA) . There is still the issue of how to "wake up" that instance. Maybe it is just something in the WM_COPYDATA event handler to make a form visible/active
????
OK, I have NO IDEA what your program may or may not be doing. . .I don't know if it is minimized or hidden or whatever. So when you get the WM_COPYDATA message you can use the parameters in the TWmCopyData to indicate "Different" types of WM_COPYDATA data, if you need to do that,, , , ,
but as for your "Wake Up" the main app, , well yes, you can do code to do whatever you need if minimized or hidden or small or whatever
procedure TForm1.GetCopyData(var Msg: TWmCopyData);
var
i: Integer;
PrePc, ScanPc: PChar;
Str1: String;
begin
// add a test and then a change when you get a WM_COPYDATA message
if not Visible then Show;
if mininized then Maximize;
if IsSmall then MakeBig;
Msg.Result := 0;
if StrLen(PChar(msg.CopyDataS
begin
Msg.Result := 17;
if msg.CopyDataStruct^.dwData
begin
Str1 := PChar(msg.CopyDataStruct^.
Form1.Label3.Caption := Str1;
end
end;
end;
OK, I have NO IDEA what your program may or may not be doing. . .I don't know if it is minimized or hidden or whatever. So when you get the WM_COPYDATA message you can use the parameters in the TWmCopyData to indicate "Different" types of WM_COPYDATA data, if you need to do that,, , , ,
but as for your "Wake Up" the main app, , well yes, you can do code to do whatever you need if minimized or hidden or small or whatever
procedure TForm1.GetCopyData(var Msg: TWmCopyData);
var
i: Integer;
PrePc, ScanPc: PChar;
Str1: String;
begin
// add a test and then a change when you get a WM_COPYDATA message
if not Visible then Show;
if mininized then Maximize;
if IsSmall then MakeBig;
Msg.Result := 0;
if StrLen(PChar(msg.CopyDataS
begin
Msg.Result := 17;
if msg.CopyDataStruct^.dwData
begin
Str1 := PChar(msg.CopyDataStruct^.
Form1.Label3.Caption := Str1;
end
end;
end;
ASKER
thanks Slick812 .. I have plenty to work with now
"is actually loaded into memory BEFORE it gets killed"
and why do you have a problem with this? are you getting complaints form users about system error of running out of memory when your program loads? or some memory problems?
anyway, here is a EE question that shows a better (in my opinion) mutex for single instance PLUS it sends the first parameter to the running program! -
https://www.experts-exchange.com/questions/20623659/PostMessage-returns-wierd-string.html
if you think you need a "Small Program" to run and do the mutext thing and then launch your program, I could do an API program of 20 Kb or so to test the mutext, and then run your other program, but I can not at this point see any need for a WinExecAndWait or a CreateProcess and a wait. . . you should just use a shellexecute if there is no mutext, but it seems, like this could cause other problems, if you need one program inorder to launch another (the main) program,