What could be the best (as in performant, simple) way to iterate over TreeChanges in LibGit2Sharp?
If I access the .Patch property, I retrieve the full text of the changes. This is not quite enough for me... ideally I would like to be able to iterate over the diff lines, and per each line retrieve the status of the line (modified, added, deleted) and build my own output out of it.
Update:
Let's say I want to build my own diff output. What I'd like to do is to iterate over the changed lines, and during iteration I would check for the type of change (added, removed), and construct my output.
For example:
var diff = "";
foreach (LineChange line in changes) // Bogus class "LineChange"
{
if (line.Type == LineChange.TYPE_ADDED)
diff += "+";
else
diff += "-";
diff += line.Content;
diff += "\n";
}
The above is just a simple example what kind of flexibility I'm looking for. To be able to go through the changes, and run some logic along with it depending on the line change types. The Patch property is already "built", one way would be to parse it, but it seems silly that the library first builds the output, and then I parse it... I'd rather use the building ingredients directly.
I need this kind of functionality so that I can display a visual diff of changes which involves far more code and logic than the simple example I gave above.
As far as I can see, this information is not exposed by libgit2sharp, but it's provided by libgit2 in the case of blob diffs (but not for tree diffs). The relevant code is in ContentChanges.cs, specifically in the constructor and in the LineCallback() method (the code for tree diffs is in TreeChanges.cs).
Because of this, I think you have two options:
Invoke the method git_diff_blobs(), that's used internally by ContentChanges, yourself, either using reflection (it's an internal method in NativeMethods), or by copying the PInvoke signature to your project. You will most likely also need Utf8Marshaler.
Modify the code of ContentChanges, so that it fits your needs. If you do this, it might make sense to create a pull request for that change, so that others could use it too.
#svick is right. It's not exposed.
It might be useful to open an issue/feature request to further discuss this topic. Indeed, exposing a full blown line based diffgram might not fit the current "grain" of the library. However, provided you can come up with a scenario/use case that would benefit most of the users, some research may be invested in order to widen the API.
Beside this option, there might be other solutions: post-process the current produced patch against the previous version of the file
See this SO question for potential leads
Neil Fraser's "Diff Strategies" paper is also a great source of strategies and potential caveats regarding what a diff tool might aim at
DiffPlex, as a working visualization tool, might be inspirational as well
With some more work, one might even achieve something similar to the following kind of visualization (from Perforce 4 viewer)
(source: macworld.com)
Note: In order to ease this, it might be useful to expose in C# the libgit2 diffing options.
I want to cascade the SyntaxHighlighting Engine of AvalonEdit. I have 2 HighlightingDefinitions. The first one is the main syntax. The second one is a complex multiline-preprocessor-markup-language. For this reason it is too complicated to embbed the second grammar in the first one. The easier way is to render the first syntax, and change the affected line-parts (based on the second syntax) afterwards.
So I instantiated a new HighlightingColorizer with the second language and added it to the LineTransformers. But the second language colorizes the complete document and not only the lineparts with the preprocessor-directives: the non-preprocessor-code is black.
As I debugged the ColorizeLine-method of the second line transformer, the lines of the non-highlighted code (= no preprocessor code) have not been colorized, as expected. But the color of the lines are black.
So does the HighlightingColorizer reset all previous highlighting of the whole document before it starts to colorize?
Or what else could be the problem? How can I properly cascade 2 HighlightingColorizers?
The problem is that the HighlightingColorizer does not directly store a reference to the DocumentHighlighter, but instead stores it via TextView.Services. This is done to allow attaching the same colorizer to multiple editors, so that each editor gets its own DocumentHighlighter.
When you attach a second colorizer, it overwrites the IHighlighter stored in the service container; and both colorizers end up using the new highlighter.
Also, note that the 'copy to clipboard' logic in HtmlClipboard directly accesses the IHighlighter service, it does not use any colorizers. (copying text to Word preserves the syntax highlighting only, no other transformations like fold markers)
There are essentially two approaches to solve this issue:
Do not store the additional highlighter as a service. You can do this by creating your own copy of the HighlightingColorizer class, and use a field in that class instead of accessing textView.Services. This is an easy change, but additional highlighters will not be used when copying text to the clipboard.
Create an IHighlighter implementation that combines the HighlightedLines from multiple DocumentHighlighters. This is the approach we are using for the C# semantic highlighting in SharpDevelop 5, which works as an additional highlighter that extends the existing .xshd-based C# highlighting. However, this approach is complex (merging HighlightedLines is non-trivial given the ordering and nesting constraints on the sections), and requires an API change to the IHighlighter interface in order to deal with the OnHighlightStateChanged notification (AvalonEdit 4.x uses a derived class nested in HighlightingColorizer to get access to this callback; AvalonEdit 5.0 will use an event).
I'm writing my first ever C# application, for Windows Phone Mango. It's designed to be an extremely simple flashlight app.
Previously, it wasn't possible to access the camera's flash on Windows Phone, but in this latest version, it is. Here's the documentation about it:
http://msdn.microsoft.com/en-us/library/microsoft.devices.flashmode(v=vs.92).aspx
Unfortunately, that makes absolutely no sense to me. I have the button set up and and the if-then statements working to switch the button icon and text on click. I just can't figure out how to actually turn the flash on and off. I'd appreciate a clear example so I can finish this up.
For those of you who don't want o leave the site...That link basically says this:
public enum FlashMode
Members: On, Off, Auto, RedEyeReduction
The FlashMode enumeration is just a set of values representing valid values for FlashMode. FlashMode, however, seems to define how the flash behaves when you take a picture. "On" seems to mean that the flash will always flash. It doesn't seem to mean that the light itself is "on" in the sense of producing light continuously.
A bit of evidence in favor of this: the FlashMode documentation says that FlashMode.On means "The camera flash is enabled."
Did you see this link?
http://msdn.microsoft.com/en-us/library/hh202949(v=vs.92).aspx
If there is a variable called "cam" available to you (DISCLAIMER: I know nothing of mobile devices) you need to change the FlashMode property. So on your button click, you would do
cam.FlashMode = FlashMode.On
EDIT: After looking a bit further it appears the "cam" variable is an instance of PhotoCamera class. So this may need to be constructed in your app somehwere. This link may also be of some help in doing so.
http://msdn.microsoft.com/en-us/library/hh202956(v=vs.92).aspx
There is a great explanation at MSDN on enum so I won't try to recreate that here, but essentially a new type has been created to ease the value assignment. Rather than having to remember that (for example) 'On' is equal to 0, and 'Off' is equal to 1, you can just use FlashMode.On instead. Of course, these enums only represent values so you will still need to assign it to something.
For example I found this in a link from within the link you provided:
cam.FlashMode = FlashMode.On;
This looks like fun so Good luck!
If you are trying to make some kind of flashlight app, there is no API for the LED according to this
In C# I use the #warning and #error directives,
#warning This is dirty code...
#error Fix this before everything explodes!
This way, the compiler will let me know that I still have work to do. What technique do you use to mark code so you won't forget about it?
Mark them with // TODO, // HACK or other comment tokens that will show up in the task pane in Visual Studio.
See Using the Task List.
Todo comment as well.
We've also added a special keyword NOCHECKIN, we've added a commit-hook to our source control system (very easy to do with at least cvs or svn) where it scans all files and refuses to check in the file if it finds the text NOCHECKIN anywhere.
This is very useful if you just want to test something out and be certain that it doesn't accidentaly gets checked in (passed the watchful eyes during the diff of everything thats commited to source control).
I use a combination of //TODO: //HACK: and throw new NotImplementedException(); on my methods to denote work that was not done. Also, I add bookmarks in Visual Studio on lines that are incomplete.
//TODO: Person's name - please fix this.
This is in Java, you can then look at tasks in Eclipse which will locate all references to this tag, and can group them by person so that you can assign a TODO to someone else, or only look at your own.
If I've got to drop everything in the middle of a change, then
#error finish this
If it's something I should do later, it goes into my bug tracker (which is used for all tasks).
'To do' comments are great in theory, but not so good in practice, at least in my experience. If you are going to be pulled away for long enough to need them, then they tend to get forgotten.
I favor Jon T's general strategy, but I usually do it by just plain breaking the code temporarily - I often insert a deliberately undefined method reference and let the compiler remind me about what I need to get back to:
PutTheUpdateCodeHere();
An approach that I've really liked is "Hack Bombing", as demonstrated by Oren Eini here.
try
{
//do stuff
return true;
}
catch // no idea how to prevent an exception here at the moment, this make it work for now...
{
if (DateTime.Today > new DateTime(2007, 2, 7))
throw new InvalidOperationException("fix me already!! no catching exceptions like this!");
return false;
}
Add a test in a disabled state. They show up in all the build reports.
If that doesn't work, I file a bug.
In particular, I haven't seen TODO comments ever decrease in quantity in any meaningful way. If I didn't have time to do it when I wrote the comment, I don't know why I'd have time later.
//TODO: Finish this
If you use VS you can setup your own Task Tags under Tools>Options>Environment>Task List
gvim highlights both "// XXX" and "// TODO" in yellow, which amazed me the first time I marked some code that way to remind myself to come back to it.
I'm a C++ programmer, but I imagine my technique could be easily implemented in C# or any other language for that matter:
I have a ToDo(msg) macro that expands into constructing a static object at local scope whose constructor outputs a log message. That way, the first time I execute unfinished code, I get a reminder in my log output that tells me that I can defer the task no longer.
It looks like this:
class ToDo_helper
{
public:
ToDo_helper(const std::string& msg, const char* file, int line)
{
std::string header(79, '*');
Log(LOG_WARNING) << header << '\n'
<< " TO DO:\n"
<< " Task: " << msg << '\n'
<< " File: " << file << '\n'
<< " Line: " << line << '\n'
<< header;
}
};
#define TODO_HELPER_2(X, file, line) \
static Error::ToDo_helper tdh##line(X, file, line)
#define TODO_HELPER_1(X, file, line) TODO_HELPER_2(X, file, line)
#define ToDo(X) TODO_HELPER_1(X, __FILE__, __LINE__)
... and you use it like this:
void some_unfinished_business() {
ToDo("Take care of unfinished business");
}
It's not a perfect world, and we don't always have infinite time to refactor or ponder the code.
I sometimes put //REVIEW in the code if it's something I want to come back to later. i.e. code is working, but perhaps not convinced it's the best way.
// REVIEW - RP - Is this the best way to achieve x? Could we use algorithm y?
Same goes for //REFACTOR
// REFACTOR - should pull this method up and remove near-dupe code in XYZ.cs
I use // TODO: or // HACK: as a reminder that something is unfinished with a note explaining why.
I often (read 'rarely') go back and finish those things due to time constraints.
However, when I'm looking over the code I have a record of what was left uncompleted and more importantly WHY.
One more comment I use often at the end of the day or week:
// START HERE CHRIS
^^^^^^^^^^^^^^^^^^^^
Tells me where I left off so I can minimize my bootstrap time on Monday morning.
// TODO: <explanation>
if it's something that I haven't gotten around to implementing, and don't want to forget.
// FIXME: <explanation>
if it's something that I don't think works right, and want to come back later or have other eyes look at it.
Never thought of the #error/#warning options. Those could come in handy too.
I use //FIXME: xxx for broken code, and //CHGME: xxx for code that needs attention but works (perhaps only in a limited context).
Todo Comment.
These are the three different ways I have found helpful to flag something that needs to be addressed.
Place a comment flag next to the code that needs to be looked at. Most compilers can recognize common flags and display them in an organized fashion. Usually your IDE has a watch window specifically designed for these flags. The most common comment flag is: //TODO This how you would use it:
//TODO: Fix this before it is released. This causes an access violation because it is using memory that isn't created yet.
One way to flag something that needs to be addressed before release would be to create a useless variable. Most compilers will warn you if you have a variable that isn't used. Here is how you could use this technique:
int This_Is_An_Access_Violation = 0;
IDE Bookmarks. Most products will come with a way to place a bookmark in your code for future reference. This is a good idea, except that it can only be seen by you. When you share your code most IDE's won't share your bookmarks. You can check the help file system of your IDE to see how to use it's bookmarking features.
I also use TODO: comments. I understand the criticism that they rarely actually get fixed, and that they'd be better off reported as bugs. However, I think that misses a couple points:
I use them most during heavy development, when I'm constantly refactoring and redesigning things. So I'm looking at them all the time. In situations like that, most of them actually do get addressed. Plus it's easy to do a search for TODO: to make sure I didn't miss anything.
It can be very helpful for people reading your code, to know the spots that you think were poorly written or hacked together. If I'm reading unfamiliar code, I tend to look for organizational patterns, naming conventions, consistent logic, etc.. If that consistency had to be violated one or two times for expediency, I'd rather see a note to that effect. That way I don't waste time trying to find logic where there is none.
If it's some long term technical debt, you can comment like:
// TODO: This code loan causes an annual interest rate of 7.5% developer/hour. Upfront fee as stated by the current implementation. This contract is subject of prior authorization from the DCB (Developer's Code Bank), and tariff may change without warning.
... err. I guess a TODO will do it, as long as you don't simply ignore them.
This is my list of temporary comment tags I use:
//+TODO Usual meaning.
//+H Where I was working last time.
//+T Temporary/test code.
//+B Bug.
//+P Performance issue.
To indicate different priorities, e.g.: //+B vs //+B+++
Advantages:
Easy to search-in/remove-from the code (look for //+).
Easy to filter on a priority basis, e.g.: search for //+B to find all bugs, search for //+B+++ to only get high priority ones.
Can be used with C++, C#, Java, ...
Why the //+ notation? Because the + symbol looks like a little t, for temporary.
Note: this is not a Standard recommendation, just a personal one.
As most programmers seem to do here, I use TODO comments. Additionally, I use Eclipse's task interface Mylyn. When a task is active, Mylyn remembers all resources I have opened. This way I can track
where in a file I have to do something (and what),
in which files I have to do it, and
to what task they are related.
Besides keying off the "TODO:" comment, many IDE's also key off the "TASK:" comment. Some IDE's even let you configure your own special identifier.
It is probably not a good idea to sprinkle your code base with uninformative TODOs, especially if you have multiple contributors over time. This can be quite confusing to the newcomers. However, what seems to me to work well in practice is to state the author and when the TODO was written, with a header (50 characters max) and a longer body.
Whatever you pack into the TODO comments, I'd recommend to be systematic in how you track them. For example, there is a service that examines the TODO comments in your repository based on git blame (http://www.tickgit.com).
I developed my own command-line tool to enforce the consistent style of the TODO comments using ideas from the answers here (https://github.com/mristin/opinionated-csharp-todos). It was fairly easy to integrate it into the continuous integration so that the task list is re-generated on every push to the master.
It also makes sense to have the task list separate from your IDE for situations when you discuss the TODOs in a meeting with other people, when you want to share it by email etc.
I got this error when trying to update an image.
It was a cross-thread update, but I used .Invoke(), so that shouldn't be the problem, should it.
(Answering my own question, for others, and for future reference)
I think (not yet entirely sure) that this is because InvokeRequired will always return false if the control has not yet been loaded/shown. I have done a workaround which seems to work for the moment, which is to simple reference the handle of the associated control in its creator, like so:
var x = this.Handle;
(See http://ikriv.com:8765/en/prog/info/dotnet/MysteriousHang.html - down? cached version)
(Related question: Boiler plate code replacement - is there anything bad about this code?)
If the handle doesn't yet exist, you can force it by subclassing the control and calling CreateHandle; however, the bigger question is: why are you doing things with a form that hasn't been loaded? Personally I'd only start such an operation after Load.