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  • How to create closed areas (convex polygons) from set of line segments ?

    - by Marten
    The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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  • parsing ip address in php

    - by Ryan
    Hi all, I am trying to create a page that shows the user their zip code when they are on my page. (if any of you are familiar with GeoIP data, thats what I am using. ) I have a conversion that converts the users IP address into an IP number, that conversion is: ipnum = 16777216*w + 65536*x + 256*y + z where w.x.y.z are the ip sections (000.000.000.000) My question is, using $_SERVER['REMOTE_ADDR']; is there a way for me to section the users ip address and assign the section of the ip address to variables? for example: usersip = 192.168.123.5 w = 192; x = 168; y = 123; z = 5; Thanks!

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  • Ruby: wait for system command to end

    - by Ignace
    Hey all, I'm converting an xls 2 csv with a system(command) in ruby. After the conversion i'm processing this csv files. But the conversion is still going when the program wants to process the files. So at that time they are non existant. Can someone tell me if it's possible to let Ruby wait the right amount of time for the system command to finish? Right now i'm using sleep 20 but if it will take longer once, it isn't right of course... Thanks!

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  • How to generate a number in arbitrary range using random()={0..1} preserving uniformness and density?

    - by psihodelia
    Generate a random number in range [x..y] where x and y are any arbitrary floating point numbers. Use function random(), which returns a random floating point number in range [0..1] from P uniformly distributed numbers (call it "density"). Uniform distribution must be preserved and P must be scaled as well. I think, there is no easy solution for such problem. To simplify it a bit, I ask you how to generate a number in interval [-0.5 .. 0.5], then in [0 .. 2], then in [-2 .. 0], preserving uniformness and density? Thus, for [0 .. 2] it must generate a random number from P*2 uniformly distributed numbers. The obvious simple solution random() * (x - y) + y will generate not all possible numbers because of the lower density for all abs(x-y)>1.0 cases. Many possible values will be missed. Remember, that random() returns only a number from P possible numbers. Then, if you multiply such number by Q, it will give you only one of P possible values, scaled by Q, but you have to scale density P by Q as well.

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  • How to index a table with a Type 2 slowly changing dimension for optimal performance

    - by The Lazy DBA
    Suppose you have a table with a Type 2 slowly-changing dimension. Let's express this table as follows, with the following columns: * [Key] * [Value1] * ... * [ValueN] * [StartDate] * [ExpiryDate] In this example, let's suppose that [StartDate] is effectively the date in which the values for a given [Key] become known to the system. So our primary key would be composed of both [StartDate] and [Key]. When a new set of values arrives for a given [Key], we assign [ExpiryDate] to some pre-defined high surrogate value such as '12/31/9999'. We then set the existing "most recent" records for that [Key] to have an [ExpiryDate] that is equal to the [StartDate] of the new value. A simple update based on a join. So if we always wanted to get the most recent records for a given [Key], we know we could create a clustered index that is: * [ExpiryDate] ASC * [Key] ASC Although the keyspace may be very wide (say, a million keys), we can minimize the number of pages between reads by initially ordering them by [ExpiryDate]. And since we know the most recent record for a given key will always have an [ExpiryDate] of '12/31/9999', we can use that to our advantage. However... what if we want to get a point-in-time snapshot of all [Key]s at a given time? Theoretically, the entirety of the keyspace isn't all being updated at the same time. Therefore for a given point-in-time, the window between [StartDate] and [ExpiryDate] is variable, so ordering by either [StartDate] or [ExpiryDate] would never yield a result in which all the records you're looking for are contiguous. Granted, you can immediately throw out all records in which the [StartDate] is greater than your defined point-in-time. In essence, in a typical RDBMS, what indexing strategy affords the best way to minimize the number of reads to retrieve the values for all keys for a given point-in-time? I realize I can at least maximize IO by partitioning the table by [Key], however this certainly isn't ideal. Alternatively, is there a different type of slowly-changing-dimension that solves this problem in a more performant manner?

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  • nasm infinite loop with FPU

    - by Ben Ishak
    i'm trying to create a small nasm program which do this operation in floating point while(input <= 10^5) do begin input = input * 10 i = i - 1 end the equivilant program in nasm is as following section .data input: resd 1 n10: dd 0x41200000 ; 10 _start: mov eax, 200 ; eax = 200 ; extract eax -> Floating Point IEEE 754 and eax, 0x7f800000 shr eax, 23 sub eax, 127 mov dword [input], eax ; input = eax = 200 mov edx, 0x49742400 ; 10^5 ; %begin mov ecx, 0 ; i = 0 jmp alpha alpha: fld dword [input] cmp [input], edx ; input <= 10^5 jle _while jmp log2 _while: fld dword [n10] ; 10 fld dword [input] ; input fmul st0, st1 ; input * 10 fst dword [input] ; input = input dec ecx ; i = i - 1 jmp alpha the _while loop is iterating infinitely ecx / i gards always the same value = -4194304 (it is sepposed to be 0) and doesn't decrement

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  • ADC code in with atmega32

    - by Komal
    uint read_adc(uchar adc_input) { ADMUX=adc_input | (0x00 & 0xff); delay_us(10); ADCSRA|=0x40; //START THE CONVERSION while ((ADCSRA & 0x10)==0); // wait for the conversion to complete ADCSRA|=0x10; //clear the ADC flag return ADCW; } Q: Whats the meaning of "ADMUX=adc_input | (0x00 & 0xff)" ? which input channel we have selected here ?

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  • What wording in the C++ standard allows static_cast<non-void-type*>(malloc(N)); to work?

    - by ben
    As far as I understand the wording in 5.2.9 Static cast, the only time the result of a void*-to-object-pointer conversion is allowed is when the void* was a result of the inverse conversion in the first place. Throughout the standard there is a bunch of references to the representation of a pointer, and the representation of a void pointer being the same as that of a char pointer, and so on, but it never seems to explicitly say that casting an arbitrary void pointer yields a pointer to the same location in memory, with a different type, much like type-punning is undefined where not punning back to an object's actual type. So while malloc clearly returns the address of suitable memory and so on, there does not seem to be any way to actually make use of it, portably, as far as I have seen.

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  • Most "thorough" distribution of points around a circle

    - by hippietrail
    This question is intended to both abstract and focus one approach to my problem expressed at "Find the most colourful image in a collection of images". Imagine we have a set of circles, each has a number of points around its circumference. We want to find a metric that gives a higher rating to a circle with points distributed evenly around the circle. Circles with some points scattered through the full 360° are better but circles with far greater numbers of points in one area compared to a smaller number in another area are less good. The number of points is not limited. Two or more points may coincide. Coincidental points are still relevant. A circle with one point at 0° and one point at 180° is better than a circle with 100 points at 0° and 1000 points at 180°. A circle with one point every degree around the circle is very good. A circle with a point every half degree around the circle is better. In my other (colour based question) it was suggested that standard deviation would be useful but with caveat. Is this a good suggestion and does it cope with the closeness of 359° to 1°?

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  • Trouble with pointers and references in C++

    - by KingNestor
    I have a PolygonList and a Polygon type, which are std::lists of Points or lists of lists of points. class Point { public: int x, y; Point(int x1, int y1) { x = x1; y = y1; } }; typedef std::list<Point> Polygon; typedef std::list<Polygon> PolygonList; // List of all our polygons PolygonList polygonList; However, I'm confused on reference variables and pointers. For example, I would like to be able to reference the first Polygon in my polygonList, and push a new Point to it. So I attempted to set the front of the polygonList to a Polygon called currentPolygon like so: Polygon currentPolygon = polygonList.front(); currentPolygon.push_front(somePoint); and now, I can add points to currentPolygon, but these changes end up not being reflected in that same polygon in the polygonList. Is currentPolygon simply a copy of the Polygon in the front of polygonList? When I later iterate over polygonList all the points I've added to currentPolygon aren't shown. It works if I do this: polygonList.front().push_front(somePoint); Why aren't these the same and how can I create a reference to the physical front polygon rather than a copy of it?

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  • converting string to int in C++

    - by xbonez
    I am trying to convert a string I read in from a file to an int value so I can store it in an integer variable. This is what my code looks like: ifstream sin; sin.open("movie_output.txt"); string line; getline(sin,line); myMovie.setYear(atoi(line)); Over here, setYear is a mutator in the Movie class (myMovie is an object of Movie class) that looks like this: void Movie::setYear(unsigned int year) { year_ = year; } When I run the code, I get the following error: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

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  • Glitch when moving camera in OpenGL

    - by CG
    I am writing a tile-based game engine for the iPhone and it works in general apart from the following glitch. Basically, the camera will always keep the player in the centre of the screen, and it moves to follow the player correctly and draws everything correctly when stationary. However whilst the player is moving, the tiles of the surface the player is walking on glitch as shown: Compared to the stationary (correct): Does anyone have any idea why this could be? Thanks for the responses so far. Floating point error was my first thought also and I tried slightly increasing the size of the tiles but this did not help. Changing glClearColor to red still leaves black gaps so maybe it isn't floating point error. Since the tiles in general will use different textures, I don't know if vertex arrays can be used (I always thought that the same texture had to be applied to everything in the array, correct me if I'm wrong), and I don't think VBO is available in OpenGL ES. Setting the filtering to nearest neighbour improved things but the glitch still happens every ten frames or so, and the pixelly result means that this solution is not viable anyway. The main difference between what I'm doing now and what I've done in the past is that this time I am moving the camera rather than the stationary objects in the world (i.e. the tiles, the player is still being moved). The code I'm using to move the camera is: void Camera::CentreAtPoint( GLfloat x, GLfloat y ) { glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(x - size.x / 2.0f, x + size.x / 2.0f, y + size.y / 2.0f, y - size.y / 2.0f, 0.01f, 5.0f); glMatrixMode(GL_MODELVIEW); } Is there a problem with doing things this way and if so is there a solution?

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  • use java-ffmpeg wrapper, or simply use java runtime to execute ffmpeg?

    - by user156153
    I'm pretty new to Java, need to write a program that listen to video conversion instructions and convert the video once an new instruction arrives (instructions is stored in Amazon SQS, but it's irrelevant to my question) I'm facing a choice, either use Java RunTime to exec 'ffmpeg' conversion (like from command line), or I can use a ffmpeg wrapper written inJava http://fmj-sf.net/ffmpeg-java/getting%5Fstarted.php I'd much prefer using Java Runtime to exec ffmpeg directly, and avoid using java-ffmpeg wrapper as I have to learn the library. so my question is are there any benefits using java-ffmpeg wrapper over exec ffmpeg directly using Runtime? I don't need ffmpeg to play videos, just convert videos Thanks

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  • How to write an intersects for Shapes in android

    - by Rafael T
    I have an written an Object called Shape which has a Point representing the topLeftCorner and a Dimension with represents its width and height. To get the topRightCorner I can simply add the width to the topLeftPoint.x. I use to rotate them on a certain degree around their center. The problem after the rotation is, that my intersects(Shape) method fails, because it does not honor the rotation of the Shapes. The rotation will be the same for each Shape. My current implementation looks like this inside my Shape Object: public boolean intersects(Shape s){ // functions returning a Point of shape s return intersects(s.topLeft()) || intersects(s.topRight()) || intersects(s.bottomLeft()) || intersects(s.bottomRight()) || intersects(s.leftCenter()) || intersects(s.rightCenter()) || intersects(s.center()); } public boolean intersects(Point p){ return p.x >= leftX() && p.x <= rightX() && p.y >= topY() && p.y <= bottomY(); } Basically I need functions like rotatedLeftX() or rotatedTopRight() to work properly. Also for that calculation I think it doesn't matter when the topLeft point before a rotation of ie 90 will turn into topRight... I already read this and this Question here, but do not understand it fully.

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  • You are only allowed to have a single MapView in a MapActivity

    - by ProNeticas
    I have a function that shows a map page so I can get the user to choose their current location. But if you run this function twice it crashes the App with the Single MapView in a MapActivity error (i.e. opening that settings view again). public void showMapSetterPage(View v) { Log.i(DEBUG_TAG, "Settings screen, set map center launched"); // Set which view object we fired off from set_pv(v); // Show Map Settings Screen setContentView(R.layout.set_map_center); // Initiate the center point map if (mapView == null) { mapView = (MapView) findViewById(R.id.mapview); } mapView.setLongClickable(true); mapView.setStreetView(true); mapView.setBuiltInZoomControls(false); mapView.setSatellite(false); mapController = mapView.getController(); mapController.setZoom(18); LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); Location location = lm .getLastKnownLocation(LocationManager.GPS_PROVIDER); int lat = (int) (location.getLatitude() * 1E6); int lng = (int) (location.getLongitude() * 1E6); Log.i(DEBUG_TAG, "The LAT and LONG is: " + lat + " == " + lng); point = new GeoPoint(lat, lng); // mapController.setCenter(point); mapController.animateTo(point); } So I have a button that shows this View and onClick="showMapSetterPage". But if you go back to the settings screen out of the map and click the button again I get this error: 03-06 20:55:54.091: ERROR/AndroidRuntime(28014): Caused by: java.lang.IllegalStateException: You are only allowed to have a single MapView in a MapActivity How can I delete the MapView and recreate it?

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  • Optimizing this "Boundarize" method for Numerics in Ruby

    - by mstksg
    I'm extending Numerics with a method I call "Boundarize" for lack of better name; I'm sure there are actually real names for this. But its basic purpose is to reset a given point to be within a boundary. That is, "wrapping" a point around the boundary; if the area is betweeon 0 and 100, if the point goes to -1, -1.boundarize(0,100) = 99 (going one too far to the negative "wraps" the point around to one from the max). 102.boundarize(0,100) = 2 It's a very simple function to implement; when the number is below the minimum, simply add (max-min) until it's in the boundary. If the number is above the maximum, simply subtract (max-min) until it's in the boundary. One thing I also need to account for is that, there are cases where I don't want to include the minimum in the range, and cases where I don't want to include the maximum in the range. This is specified as an argument. However, I fear that my current implementation is horribly, terribly, grossly inefficient. And because every time something moves on the screen, it has to re-run this, this is one of the bottlenecks of my application. Anyone have any ideas? module Boundarizer def boundarize min=0,max=1,allow_min=true,allow_max=false raise "Improper boundaries #{min}/#{max}" if min >= max new_num = self if allow_min while new_num < min new_num += (max-min) end else while new_num <= min new_num += (max-min) end end if allow_max while new_num > max new_num -= (max-min) end else while new_num >= max new_num -= (max-min) end end return new_num end end class Numeric include Boundarizer end

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  • jQuery slideDown + CSS Floats

    - by danilo
    I'm using a HTML Table with several rows. Every second row - containing details about the preceding row - is hidden using CSS. When clicking the first row, the second row gets showed using jQuery show(). This is quite nice, but I would prefer the slideDown-Effect. The problem is, inside the details row, there are two floating DIVs, one floating on the left, and one on the right. Now if i slideDown the previously hidden row, the contained DIVs behave strange and "jump around". See this animated gif to understand what I mean: http://ich-wars-nicht.ch/tmp/lunapic_127365879362365_.gif The markup: <tr class="row-vm"> <td>...</td> ... </tr> <tr class="row-details"> <td colspan="8"> <div class="vmdetail-left"> ... </div> <div class="vmdetail-right"> ... </div> </td> </tr> The CSS: .table-vmlist tr.row-details { display: none; } div.vmdetail-left { float: left; width: 50%; } div.vmdetail-right { float: right; width: 50%; } And the jQuery code: if ($(this).next().css('display') == 'none') { // Show details //$(this).next().show(); $(this).next().slideDown(); } else { // Hide details //$(this).next().hide(); $(this).next().slideUp(); } Is there a way to fix this behavior, and to implement a nice slideDown-effect?

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  • Errors in Decimal Calcs within def clean method?

    - by allanhenderson
    I'm attempting a few simple calculations in a def clean method following validation (basically spitting out a euro conversion of retrieved uk product price on the fly). I keep getting a TypeError. Full error reads: Cannot convert {'product': , 'invoice': , 'order_discount': Decimal("0.00"), 'order_price': {...}, 'order_adjust': None, 'order_value': None, 'DELETE': False, 'id': 92, 'quantity': 8} to Decimal so I guess django is passing through the entire cleaned_data form to Decimal method. Not sure where I'm going wrong - the code I'm working with is: def clean_order_price(self): cleaned_data = self.cleaned_data data = self.data order_price = cleaned_data.get("order_price") if not order_price: try: existing_price = ProductCostPrice.objects.get(supplier=data['supplier'], product_id=cleaned_data['product'], is_latest=True) except ProductCostPrice.DoesNotExist: existing_price = None if not existing_price: raise forms.ValidationError('No match found, please enter new price') else: if data['invoice_type'] == 1: return existing_price.cost_price_gross elif data['invoice_type'] == 2: exchange = EuroExchangeRate.objects.latest('exchange_date') calc = exchange.exchange_rate * float(existing_price.cost_price_gross) calc = Decimal(str(calc)) return calc return cleaned_data If the invoice is of type 2 (a euro invoice) then the system should grab the latest exchange rate and apply that to the matching UK pound price pulled through to get euro result. Should performing a decimal conversion be a problem within def clean method? Thanks

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  • overloading "<<" with a struct (no class) cout style

    - by monkeyking
    I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

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  • How to use anonymous types with Netflix OData API

    - by obautista
    If I create this collection: IEnumerable<_TITLE> _titles = null; How can I set the result set from Netflix in this expression: _titles = from t in Titles where t.Id == "ApUFq" select new {t, t.Cast} I am getting: Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable<_Title'. An explicit conversion exists (are you missing a cast?) I understand it's because I am using an anonymous type. _TITLE is a custom complex object I create that exposes a subset of Netflix properties. If I add "_TITLE" in front the of the "new" it says that my object does not implement IENUMBERABLE. If then _TITLE implements IENUMBERABLE, it says _TITLE does not contain a definition for ADD and still getting conversion error. Basically, I want to set the _TITLE properties with the data returned from Netflix. I have defined _TITLE to contain the fields I need, plus a collection of PERSON (for Cast).

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  • Get File Size of Modified Image Before Writing to Disk

    - by Otaku
    I'm doing a conversion from .jpg to .png in System.Drawing and one thing that I've found is that this conversion tends to make the resulting converted .png much larger than the .jpg original. Sometimes more than 10x larger after converting to .png. Given that seems to always be the case (unless you know of a way around this), is there any way to determine the file size of that .png before it is saved to disk? For example, maybe write it to a stream first and then get that stream size? How would I go about doing this?

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  • Problems with starting an activity in onStart

    - by Fizz
    Hello everyone. I'm trying to start a floating activity from onStart to retrieve some info from the user right when the initial activity begins. I have the following: @Override public void onStart(){ super.onStart(); callProfileDialog(); } And callProfileDialog() is just: private void callProfileDialog(){ Intent i = new Intent(this, com.utility.ProfileDialog.class); startActivityForResult(i, PROFDIALOG); } ProfileDialog.class returns a String from an input box. If the result returned is RESULT_CANCELED then I restart the activity. The problem I'm having is that when the program starts, the screen is just black. If I hit the Back button a RESULT_CANCELED is returned then the initial activity shows as well as the floating activity (since it recalled itself when it got a RESULT_CANCELED). Why can't I get the activities show by calling ProfileDialog.class from onStart()? I got the same result when I called it at the end of onCreate() which is way I switch over to use onStart(). Thanks for the help.

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  • Making a video with opencv and ffmpeg. How to find the right color format?

    - by luc
    I have a webcam video recorder program built with python, opencv and ffmpeg It works ok except that the color of the video is more blue than the reality. The problem seems to come from color format of images. It seems that OpenCv is giving BGR images and ffmpeg+libx264 is expecting YUV420p. I've read that YUV420p correspond to YCbCr. opencv has no conversion from BGR to YCbCr. It only has a conversion to YCrCb. I have made some searchs and tried different alternatives to try converting opencv image to something that could be ok for ffmpeg+libx264. None is working. At this point, I am a bit lost and I would appreciate any pointer that could help me to fix this color issue.

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  • Click at specified client area

    - by VixinG
    Click doesn't work - I don't know why and can't find a solution :( ie. Click(150,215) should move mouse to the client area and click there. [DllImport("user32.dll")] private static extern bool ScreenToClient(IntPtr hWnd, ref Point lpPoint); [DllImport("user32", SetLastError = true)] private static extern int SetCursorPos(int x, int y); static void MouseMove(int x, int y) { Point p = new Point(x * -1, y * -1); ScreenToClient(hWnd, ref p); p = new Point(p.X * -1, p.Y * -1); SetCursorPos(p.X, p.Y); } static void Click(int x, int y) { MouseMove(x, y); SendMessage(hWnd, WM_LBUTTONDOWN, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); SendMessage(hWnd, WM_LBUTTONUP, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); } Edit: Of course I can use mouse_event for that, but I would like to see a solution for SendMessage()... [DllImport("user32.dll")] static extern void mouse_event(int dwFlags, int dx, int dy, int dwData, int dwExtraInfo); const int LEFTDOWN = 0x00000002; const int LEFTUP = 0x00000004; static void Click(int x, int y) { MouseMove(x, y); mouse_event((int)(LEFTDOWN), 0, 0, 0, 0); mouse_event((int)(LEFTUP), 0, 0, 0, 0); }

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