You know GetActiveObject just can get the COM object of the first opened application. How to get all running objects? e.g. I run two Excel applications, How to get the two Excel objects in C++ code?
There is usually only one instance of Excel as Hans says. If there is only one instance it will refuse to open the same document twice.
But there may be more than one, typically if a second has been started explicitly. In that case it may open the same file (though you will get a warning about locking).
They may or may not both appear in the Running Object Table. Use ROT viewer or something like this to determine whether that is the case:
http://social.msdn.microsoft.com/Forums/en-US/vsx/thread/ccccc9bd-f21a-4f74-a3f0-64a594fa1b16
Finally you might consider using Microsoft UI Automation:
http://msdn.microsoft.com/en-us/library/ms753388.aspx
http://msdn.microsoft.com/en-us/library/ms726294(VS.85).aspx
Related
I'm trying to make an application which to manage information about several providers.
Target system is windows and I'll be coding with c++.
The users are not expected to be handy on anything related to computers, so I want to make it as fool-proof as possible. Right now my objective is to distribute only an executable, which should store all the information they introduce in there.
Each user stores information of their own providers, so I don't need the aplication to share the data with other instances. They do upload the information into a preexisting system via csv, but I can handle that easily.
I expect them to introduce new information at least once a month, so I need to update the information embedded. Is that even possible? Making a portable exe and update its information? So far the only portable apps I've seen which allow saving some personification do so by making you drag files along with your exe.
I try to avoid SQL to avoid compatibility problems (for my own applications I use external TXTs and parse the data), but if you people tell me it's the only way, I'll use sql.
I've seen several other questions about embedding files, but it seems all of them are constants. My files need to be updatable
Thanks in advance!
Edit: Thanks everyone for your comments. I've understood that what I want is not worth the problems it'd create. I'll store the data separatedly and make an effort so my coworkers understand what's the difference between an executable and it's data (just like explaining the internet to your grandma's grandma...)
While I wouldn't go as far as to say that it's impossible, it will definitely be neither simple nor pretty nor something anyone should ever recommend doing.
The basic problem is: While your .exe is running, the .exe file is mapped into memory and cannot be modified. Now, one thing you could do is have your .exe, when it's started, create a temporary copy of itself somewhere, start that one, tell the new process where the original image is located (e.g., via commandline arguments), and then have the original exit. That temporary copy could then modify the original image. To put data into your .exe, you can either use Resources, or manually modify the PE image, e.g., using a special section created inside the image to hold your data. You can also simply append arbitrary data at the end of an .exe file without corrupting it.
However, I would like to stress again that I do not recommend actually doing stuff like that. I would simply store data in separate files. If your users are familiar with Excel, then they should be familiar with the idea that data is stored in files…
I am currently writting a .dll that uses sqlite3 to talk to a database on a windows system.
Right now, it is very simple and I have just written a test program that does inserts and selects from the database.
This issue however, is that my dll will be used by multiple programs on the same system, each writing to the same database file. This of course brings mutex issues with it.
I want to know the extent of which the sqlite3 library supports this before I go ahead and write a complicated connection pool for it. According to the doco there are things like "Shared Caches" and "No Mutex" Modes as specified by a paramater given to the sqlite3_open_v2 function: http://www.sqlite.org/c3ref/open.html
I have also hunted around for a few sqlite3 wrappers but I cannot find anything that suits my multi-access needs.
Does anyone have any experience with writing to sqlite3 db files from multiple processes that use the same .dll? Or has anyone had any luck with using their SHARED_CACHES - I seem to run into all sorts of issues.
Any help on the matter would be great, thanks!
~ Dan
As long as you're accessing the same database file through SQLite3, it should be fine. Indeed, SQLite3 is designed specifically to handle multiple processes accessing the same DB file.
SQL, as a specification, already deals with multiple accesses, and it provides controls for atomic accessing and so forth (transactions, that sort of thing). As long as you properly use those controls, you should be file.
It's multiple threads that SQLite3 has an issue with.
This seemed like a common question but after doing some searching, I wasn't really able to find my answers. There is an article on this here:
http://www.codeproject.com/KB/shell/shellextguide1.aspx
But it's for a very old version of Visual Studio. I'm using VS 2008, so the instructions and interfaces don't seem to match what I'm seeing.
I want to create a simple shell extension using C++ that creates a context menu for files with extension .GZ. When right clicking on these files, I should be able to click my context menu item and have a callback in code to do some sort of operation on that file.
Other context menu items would do things like spawn modless dialogs to accept user input before executing some action.
From what I've seen, ATL is used for this but I have never used ATL, so all of the object types and interfaces are very confusing to me. It wouldn't be so bad if I had a proper tutorial or documentation to read.
Can anyone help me out? Isn't there some sort of tutorial out there that isn't 10 years old?
I can't tell you exactly how to write a shell extension, but I will provide a number of tips. Writing a Shell Extension offers some significant advantages over the much simpler “registry-only” method:
With a Shell Extension, you can dynamically create a context menu item (or submenu) that is more relevant to the selected file(s). For example, if you are writing a Shell Extension for zip files, it is possible to create a submenu within the context menu that shows the entire contents of the zip.
You can handle multiple files simultaneously, which may be more beneficial not just for performance purposes but also so that you can work out what to do based on the selection as a whole rather than just for each file.
Some of the downfalls to Shell Extensions are:
Substantially increased complexity. Be prepared to spend a lot of effort on this to get it working. Have a home-espresso machine installed next to your computer and/or hire someone to make you coffee.
Substantially increased difficulty in debugging. Ditto about coffee.
It's difficult to write a Shell Extension because they can be very hard to debug.
Shell Extensions are loaded by the explorer.exe process, and without specific configuration of Explorer, you need to force-quit the explorer.exe process so that you can install a newer version of your Shell Extension. There is a way to get Explorer to unload DLLs that it is no longer using, but you should only do this on a development machine and not on a deployment target:
In RegEdit, browse to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
Add a new DWORD key called “AlwaysUnloadDLL” and set its value to 1.
Restart explorer.
This works most of the time, but there may still be times where you need to close Explorer because the Shell Extension was not unloaded.
Keep in mind that your Shell Extension may be loaded by other applications, for example, if you right-click on a file with an applications “open file” dialog, then your Shell Extension will be loaded into that application, and not Explorer.
If your Shell Extension causes a runtime error, quite often the result will simply be that your context menu item does not show, very rarely will you be told that your Shell Extension failed to load or that it caused a runtime error.
Configuration can be hard, even with an installation, registry data needs to be created in several places, and depending where you want your context menu to show, the places in the registry may differ between different versions of Windows.
What you'll need to do:
Visual Studio offers some shortcuts to creating Shell Extensions, but basically you'll need to create a COM DLL. A Shell Extension for context menu items must implement both the IContextMenu interface and the IShellExtInit interface.
In the IShellExtInit::Initialize() method, you can obtain the selected files from the IDataObject parameter. From memory, the data is in “Drag-n-Drop” format, so you need to get an HDROP handle from the IDataObject and query the files from there (this is from memory, it may actually be different than as I described here, so proceed with caution).
Once your DLL is ready to be “installed”, you must copy it somewhere, and then run regsvr32 to make sure it is registered.
Follow this guide to know where to put registry keys.
There may be issues with 64-bit Windows, if you build a 32-bit DLL it may not load in 64-bit Explorer… so keep this in mind if you are having trouble with 64-bit Windows.
Your DLL will actually have two GUIDs associated with it. I can't remember exactly how it works, but one GUID refers to the DLL itself and the other refers to the actual Shell Extension. Make sure you use the GUID of the actual Shell Extension when creating keys in the registry where a GUID is required.
All things considered… (tl;dr)
Weigh up the costs of whether a Shell Extension is worth it. If you want to create menu items dynamically based on the selected files, then a Shell Extension may be the only way. If you want to handle all files simultaneously then you'll probably need a Shell Extension as well.
An alternative to the context menu method, could be to have a drag-n-drop target on the user's desktop or something. Explore other ways that you could have the user submit your files to your application, because a Shell Extension is often far more effort than it is worth. I found this out the hard way and I think everyone else has too.
I'm looking for a good efficient method for scanning a directory structure for changed files in Windows XP+. Something like how git does it is exactly what I'm looking for, when running a git status it displays all modified files, all new (untracked) files and deleted files very quickly which is exactly what I would like to do.
I have a basic model up and running which performs an initial scan and stores all filenames, size, dates and attributes.
On a subsequent scan it checks if the size, attributes or date have changed and marks as a changed file.
My issue now comes in detecting moved and deleted files. Is there a tried and tested method for this sort of thing? I'm struggling to come up with a good method.
I should mention that it will eventually use ReadDirectoryChangesW to monitor files and alert the user when something changes so a full scan is really a last resort after the initial scan.
Thanks,
J
EDIT: I think I may have described the problem badly. The issue I'm facing is not so much detecting the changes - I have ReadDirectoryChangesW() using IOCP on multiple threads to detected when a change happens, the issue is more what to do with the information. For example, a moved file is reported as a delete followed by a create and a rename comes in 2 parts, old name, followed by new name. So what I'm asking is how to differentiate between the delete as part of a move and an actual delete. I'm guessing buffering the changes and processing batches would be an option but feels messy.
In native code FileSystemWatcher is replaced by ReadDirectoryChangesW. Using this properly is not simple, there is a good baseline to build off here.
I have used this code in a previous job and it worked pretty well. The Win32 API itself (and FileSystemWatcher) are prone to problems that are described in the docs and also discussed in various places online, but impact of those will depending on your use cases.
EDIT: the exact change is indicated in the FILE_NOTIFY_INFORMATION structure that you get back - adds, removals, rename data including old and new name.
I voted Liviu M. up. However, another option if you don't want to use the .NET framework for some reason, would be to use the basic Win32 API call FindFirstChangeNotification.
You can use USN journaling if you are up to it, that is pretty low level (NTFS level) stuff.
Here you can find detailed information and source code included. It is written in C# but most of it is PInvoking C/C++ functions.
Is there a good way to compare the DLLs loaded between two machines running the same app. (And to replicate the process between N other machines, two at a time?)
Background: I am trying to track down a configuration/setup issue. It's the age-old, DLL-hell-type problem where an app will run on one machine but not on another.
I have eliminated our installer as an issue; it's stable but there are differences between the target systems. Different Windows flavors, MDAC versions etc.
I have tried: exporting EXE snapshots with Proc Explorer to a delimited file and using Excel to do the comparison. But this is very time-consuming and error prone. (I'm not ruling out Excel as a possibility, i just don't know enough tricks to use it to my ends.)
I'd recommend you take a look at EasyHook, using it, you can create a detour on all calls to LoadLibraryA and LoadLibraryW. This way you can monitor all files that gets loaded, and get the path to them. After that, you can compare the files in whatever way you'd like. If you need help using EasyHook, let me know, and I'll cook up an example.