Open Multiple Instances of an App from File Explorer - windows

Question

Short version:
On Windows, if I select several .txt files in a File Explorer and then right click on one of the selected files and choose "Open" from the popup menu, all of the selected files will be opened, each in a separate instance of Notepad.
I want the same behavior for our files/editor: select multiple output files, right click one, select Open: -> all files are opened, each in their own instance of our editor.
I have basic click-to-open working (for a single file, double click opens the file in our editor, right click and Open does the same).
Details
We have an launcher (FuBarStudioLauncher.exe) that updates then launches our editor tool (FuBarStudio.exe), which produces resource files with a custom extension (samplefile.fbr)
If you run from the command line, you can fire up the editor, opening a particular resource:
C:\path_to_my_exe\FuBarStudio.exe" -ide samplefile.fbr
I have a windows registry entry set up so that when I double click on a *.fbr resource file, or right-click and select Open from the popup menu, the launcher runs, passing the given resource through to the editor.
The relevant registry entries:
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.fbr]
#="FuBar.Place"
[HKEY_CLASSES_ROOT\.fbr\FuBar.Place]
[HKEY_CLASSES_ROOT\.fbr\FuBar.Place\ShellNew]
and
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\FuBar.Place]
#="FuBar Place"
[HKEY_CLASSES_ROOT\FuBar.Place\shell]
[HKEY_CLASSES_ROOT\FuBar.Place\shell\Open]
#="Open"
[HKEY_CLASSES_ROOT\FuBar.Place\shell\Open\command]
#="\"C:\\path_to_my_exe\\FuBarStudioLauncher.exe\" -ide \"%1\""
All of this works fine for single files.
If I select more than one .fbr file and then right click one of the selected files and select "Open", I will only open one instance of FuBar Studio.
I would like to open one Copy of FuBar Studio, one for each file.

Answer 1

So with some help I got a useful answer.
1) I read up on use of MultiSelectModel here:
https://msdn.microsoft.com/en-us/library/windows/desktop/hh127436(v=vs.85).aspx
Set my type to Document.
2) I created a batch script as an intermediary, so I could see better what was going on:
[HKEY_CLASSES_ROOT\FuBar.Place\shell\Open\command]
#="\"C:\\path_to_my_exe\\launcher.bat\" \"%1\""
Toyed around with this script, writing things to tmp files:
echo "interesting things" >> logs.txt
and using timeout to force things to pause/slow down:
timeout 10
Using "echo" and so forth I realized that whether MultiSelectModel is set to Document or Player, when I select multiple files and right click "Open", Windows is executing the business at:
HKEY_CLASSES_ROOT\FuBar.Place\shell\Open\command
once per selected file.
I could not find a way to force Windows to call the command once, passing all the files as arguments to the command.
3) By experimenting with other programs besides my own, and with the script + timeouts giving me a command shell with error spew to look at, I realized that my particular program, FuBarStudioLauncher.exe, always fails if another instance is running.
So here's what I have:
Windows is going to run one instance of <something> per input file.
<something> can't be my FuBarStudioLauncher.exe, because after one is running the next N will fail.
So I need an intermediary script that will do some kind of critical section locking:
- grab lock.
- run launcher to completion.
- release lock.
Hooray for StackOverflow:
Semaphore for CMD instances working in Parallel
Using this as input, my final product:
:lockedAppend
2>nul (
>>%~dp0launcher_script_lockfile.txt (
REM Do any amount of processing within this block.
REM All stdout will safely be appended to the queue
REM You could even call out to a subroutine, or another batch file
%~dp0FuBarStudioLauncher.exe -ide "%1"
REM The CALL below ensures that the block exits with ERRORLEVEL 0 - success
(call )
)
) || goto :lockedAppend
That did it!