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  • Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

    - by JonathonG
    Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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  • Software solution from the 2000's, should I attempt to patch or remake the whole thing?

    - by ShadowScripter
    I was sent out to discuss a system that a certain company is currently using and what should be done with it. The company manufactures various carton displays. This system was developed to keep track of clients, orders and prices. Lots have happened since the system was created and the system is now, as the manager described it, "locked up" and "problematic", which I translate as "not dynamic" and "unstable". Some info about the system It was developed around the year 2000 Fairly small system, 2-5 users, 6 forms, ~8 tables with average quantities of data Built on early Visual Basic, forms created with the drag and drop design. Interface is basically just a window with a menu and some forms Uses MSSQL database (SQL2005 server) to store data and ODBC driver to query, data was migrated from excel before this system, and before excel it was handled, calculated and written by hand and paper Users work in Microsoft XP environment (and up) Their main problem is that they can't adjust and calculate prices, can't add new carton types etc, correctly anymore because they can't (or rather, they don't know how to) touch the data on the server. I suggested 3 possible solutions Attempt to patch the current system Create a fresh new interface (preferably similar environment, VB.net or VB based) Bring it back to an Excel solution, considering it is such a small system There might be more options, but these are the ones I could think of. My questions are What should I recommend and why? What is or could be the pros and cons of these alternatives? Are there other (possibly better) alternatives?

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  • Getting Center and Radius of Irregural Object

    - by Moaz ELdeen
    I have drawn an asteroid object manually , and would like to get its center/radius by a specific equation. I think I can get them by calculated and hard-coded values. The code to draw the asteroid: void Asteroid::Draw() { float ratio = app::getWindowWidth()/app::getWindowHeight(); gl::pushMatrices(); gl::translate(m_Pos*ratio); gl::scale(3.5*ratio,3.5*ratio,3.5*ratio); gl::color(ci::Color(1,1,1)); gl::drawLine(Vec2f(-15,0),Vec2f(-10,-5)); gl::drawLine(Vec2f(-10,-5),Vec2f(-5,-5)); gl::drawLine(Vec2f(-5,-5),Vec2f(-5,-8)); gl::drawLine(Vec2f(-5,-8),Vec2f(5,-8)); gl::drawLine(Vec2f(5,-8),Vec2f(5,-5)); gl::drawLine(Vec2f(5,-5),Vec2f(10,-5)); gl::drawLine(Vec2f(10,-5),Vec2f(15,0)); gl::drawLine(Vec2f(15,0),Vec2f(10,5)); gl::drawLine(Vec2f(10,5),Vec2f(-10,5)); gl::drawLine(Vec2f(-10,5),Vec2f(-10,5)); gl::drawLine(Vec2f(-15,0),Vec2f(-10,5)); gl::popMatrices(); } According to the answer I have written that code to calculate the radius, is it correct or not ? cinder::Vec2f Asteroid::getCenter() { return ci::Vec2f(m_Pos.x, m_Pos.y); } double Asteroid::getRadius() { ci::Vec2f _vec = (getCenter()- Vec2f(15,5)); return _vec.length()*0.3f; }

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  • What's the best way to use requestAnimationFrame and fixed frame rates

    - by m90
    I recently got into using the HTML5-requestAnimationFrame-API a lot on animation-heavy websites, especially after seeing the Jank Busters talk. This seems to work pretty well and really improve performance in many cases. Yet one question still persists for me: When wanting to use an animation that is NOT entirely calculated (think spritesheets for example) you will have to aim for a fixed frame rate. Of course one could go back to use setInterval again, but maybe there are other ways to tackle this. The two ways I could think of using requestAnimationFrame with a fixed frame rate are: var fps = 25; //frames per second function animate(){ //actual drawing goes here setTimeout(function(){ requestAnimationFrame(animate); }, 1000 / fps) } animate(); or var fps = 25; //frames per second var lastExecution = new Date().getTime(); function animate(){ var now = new Date().getTime(); if ((now - lastExecution) > (1000 / fps)){ //do actual drawing lastExecution = new Date().getTime(); } requestAnimationFrame(animate); } animate(); Personally, I'd opt for the second option (the first one feels like cheating), yet it seems to be more buggy in certain situations. Is this approach really worth it (especially at low frame rates like 12.5)? Are there things to be improved? Is there another way to tackle this?

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  • Pixel Shader Issues :

    - by Morphex
    I have issues with a pixel shader, my issue is mostly that I get nothing draw on the screen. float4x4 MVP; // TODO: add effect parameters here. struct VertexShaderInput { float4 Position : POSITION; float4 normal : NORMAL; float2 TEXCOORD : TEXCOORD; }; struct VertexShaderOutput { float4 Position : POSITION; }; VertexShaderOutput VertexShaderFunction(VertexShaderInput input) { input.Position.w = 0; VertexShaderOutput output; output.Position = mul(input.Position, MVP); // TODO: add your vertex shader code here. return output; } float4 PixelShaderFunction(VertexShaderOutput input) : SV_TARGET { return float4(1, 0, 0, 1); } technique { pass { Profile = 11.0; VertexShader = VertexShaderFunction; PixelShader = PixelShaderFunction; } } My matrix is calculated like this : Matrix MVP = Matrix.Multiply(Matrix.Multiply(Matrix.Identity, Matrix.LookAtLH(new Vector3(-10, 10, -10), new Vector3(0), new Vector3(0, 1, -0))), Camera.Projection); VoxelEffect.Parameters["MVP"].SetValue(MVP); Visual Studio Graphics Debug shows me that my vertex shader is actually working, but not the PixelShader. I striped the Shader to the bare minimums so that I was sure the shader was correct. But why is my screen still black?

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  • TFS API Change WorkItem CreatedDate And ChangedDate To Historic Dates

    - by Tarun Arora
    There may be times when you need to modify the value of the fields “System.CreatedDate” and “System.ChangedDate” on a work item. Richard Hundhausen has a great blog with ample of reason why or why not you should need to set the values of these fields to historic dates. In this blog post I’ll show you, Create a PBI WorkItem linked to a Task work item by pre-setting the value of the field ‘System.ChangedDate’ to a historic date Change the value of the field ‘System.Created’ to a historic date Simulate the historic burn down of a task type work item in a sprint Explain the impact of updating values of the fields CreatedDate and ChangedDate on the Sprint burn down chart Rules of Play      1. You need to be a member of the Project Collection Service Accounts              2. You need to use ‘WorkItemStoreFlags.BypassRules’ when you instantiate the WorkItemStore service // Instanciate Work Item Store with the ByPassRules flag _wis = new WorkItemStore(_tfs, WorkItemStoreFlags.BypassRules);      3. You cannot set the ChangedDate         - Less than the changed date of previous revision         - Greater than current date Walkthrough The walkthrough contains 5 parts 00 – Required References 01 – Connect to TFS Programmatically 02 – Create a Work Item Programmatically 03 – Set the values of fields ‘System.ChangedDate’ and ‘System.CreatedDate’ to historic dates 04 – Results of our experiment Lets get started………………………………………………… 00 – Required References Microsoft.TeamFoundation.dll Microsoft.TeamFoundation.Client.dll Microsoft.TeamFoundation.Common.dll Microsoft.TeamFoundation.WorkItemTracking.Client.dll 01 – Connect to TFS Programmatically I have a in depth blog post on how to connect to TFS programmatically in case you are interested. However, the code snippet below will enable you to connect to TFS using the Team Project Picker. // Services I need access to globally private static TfsTeamProjectCollection _tfs; private static ProjectInfo _selectedTeamProject; private static WorkItemStore _wis; // Connect to TFS Using Team Project Picker public static bool ConnectToTfs() { var isSelected = false; // The user is allowed to select only one project var tfsPp = new TeamProjectPicker(TeamProjectPickerMode.SingleProject, false); tfsPp.ShowDialog(); // The TFS project collection _tfs = tfsPp.SelectedTeamProjectCollection; if (tfsPp.SelectedProjects.Any()) { // The selected Team Project _selectedTeamProject = tfsPp.SelectedProjects[0]; isSelected = true; } return isSelected; } 02 – Create a Work Item Programmatically In the below code snippet I have create a Product Backlog Item and a Task type work item and then link them together as parent and child. Note – You will have to set the ChangedDate to a historic date when you created the work item. Remember, If you try and set the ChangedDate to a value earlier than last assigned you will receive the following exception… TF26212: Team Foundation Server could not save your changes. There may be problems with the work item type definition. Try again or contact your Team Foundation Server administrator. If you notice below I have added a few seconds each time I have modified the ‘ChangedDate’ just to avoid running into the exception listed above. // Create Linked Work Items and return Ids private static List<int> CreateWorkItemsProgrammatically() { // Instantiate Work Item Store with the ByPassRules flag _wis = new WorkItemStore(_tfs, WorkItemStoreFlags.BypassRules); // List of work items to return var listOfWorkItems = new List<int>(); // Create a new Product Backlog Item var p = new WorkItem(_wis.Projects[_selectedTeamProject.Name].WorkItemTypes["Product Backlog Item"]); p.Title = "This is a new PBI"; p.Description = "Description"; p.IterationPath = string.Format("{0}\\Release 1\\Sprint 1", _selectedTeamProject.Name); p.AreaPath = _selectedTeamProject.Name; p["Effort"] = 10; // Just double checking that ByPassRules is set to true if (_wis.BypassRules) { p.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01"); } if (p.Validate().Count == 0) { p.Save(); listOfWorkItems.Add(p.Id); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in p.Validate()) { Console.WriteLine(" - '{0}' ", e); } } var t = new WorkItem(_wis.Projects[_selectedTeamProject.Name].WorkItemTypes["Task"]); t.Title = "This is a task"; t.Description = "Task Description"; t.IterationPath = string.Format("{0}\\Release 1\\Sprint 1", _selectedTeamProject.Name); t.AreaPath = _selectedTeamProject.Name; t["Remaining Work"] = 10; if (_wis.BypassRules) { t.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01"); } if (t.Validate().Count == 0) { t.Save(); listOfWorkItems.Add(t.Id); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in t.Validate()) { Console.WriteLine(" - '{0}' ", e); } } var linkTypEnd = _wis.WorkItemLinkTypes.LinkTypeEnds["Child"]; p.Links.Add(new WorkItemLink(linkTypEnd, t.Id) {ChangedDate = Convert.ToDateTime("2012-01-01").AddSeconds(20)}); if (_wis.BypassRules) { p.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01").AddSeconds(20); } if (p.Validate().Count == 0) { p.Save(); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in p.Validate()) { Console.WriteLine(" - '{0}' ", e); } } return listOfWorkItems; } 03 – Set the value of “Created Date” and Change the value of “Changed Date” to Historic Dates The CreatedDate can only be changed after a work item has been created. If you try and set the CreatedDate to a historic date at the time of creation of a work item, it will not work. // Lets do a work item effort burn down simulation by updating the ChangedDate & CreatedDate to historic Values private static void WorkItemChangeSimulation(IEnumerable<int> listOfWorkItems) { foreach (var id in listOfWorkItems) { var wi = _wis.GetWorkItem(id); switch (wi.Type.Name) { case "ProductBacklogItem": if (wi.State.ToLower() == "new") wi.State = "Approved"; // Advance the changed date by few seconds wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); // Set the CreatedDate to Changed Date wi.Fields["System.CreatedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); wi.Save(); break; case "Task": // Advance the changed date by few seconds wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); // Set the CreatedDate to Changed date wi.Fields["System.CreatedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); wi.Save(); break; } } // A mock sprint start date var sprintStart = DateTime.Today.AddDays(-5); // A mock sprint end date var sprintEnd = DateTime.Today.AddDays(5); // What is the total Sprint duration var totalSprintDuration = (sprintEnd - sprintStart).Days; // How much of the sprint have we already covered var noOfDaysIntoSprint = (DateTime.Today - sprintStart).Days; // Get the effort assigned to our tasks var totalEffortRemaining = QueryTaskTotalEfforRemaining(listOfWorkItems); // Defining how much effort to burn every day decimal dailyBurnRate = totalEffortRemaining / totalSprintDuration < 1 ? 1 : totalEffortRemaining / totalSprintDuration; // we have just created one task var totalNoOfTasks = 1; var simulation = sprintStart; var currentDate = DateTime.Today.Date; // Carry on till effort has been burned down from sprint start to today while (simulation.Date != currentDate.Date) { var dailyBurnRate1 = dailyBurnRate; // A fixed amount needs to be burned down each day while (dailyBurnRate1 > 0) { // burn down bit by bit from all unfinished task type work items foreach (var id in listOfWorkItems) { var wi = _wis.GetWorkItem(id); var isDirty = false; // Set the status to in progress if (wi.State.ToLower() == "to do") { wi.State = "In Progress"; isDirty = true; } // Ensure that there is enough effort remaining in tasks to burn down the daily burn rate if (QueryTaskTotalEfforRemaining(listOfWorkItems) > dailyBurnRate1) { // If there is less than 1 unit of effort left in the task, burn it all if (Convert.ToDecimal(wi["Remaining Work"]) <= 1) { wi["Remaining Work"] = 0; dailyBurnRate1 = dailyBurnRate1 - Convert.ToDecimal(wi["Remaining Work"]); isDirty = true; } else { // How much to burn from each task? var toBurn = (dailyBurnRate / totalNoOfTasks) < 1 ? 1 : (dailyBurnRate / totalNoOfTasks); // Check that the task has enough effort to allow burnForTask effort if (Convert.ToDecimal(wi["Remaining Work"]) >= toBurn) { wi["Remaining Work"] = Convert.ToDecimal(wi["Remaining Work"]) - toBurn; dailyBurnRate1 = dailyBurnRate1 - toBurn; isDirty = true; } else { wi["Remaining Work"] = 0; dailyBurnRate1 = dailyBurnRate1 - Convert.ToDecimal(wi["Remaining Work"]); isDirty = true; } } } else { dailyBurnRate1 = 0; } if (isDirty) { if (Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).Date == simulation.Date) { wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(20); } else { wi.Fields["System.ChangedDate"].Value = simulation.AddSeconds(20); } wi.Save(); } } } // Increase date by 1 to perform daily burn down by day simulation = Convert.ToDateTime(simulation).AddDays(1); } } // Get the Total effort remaining in the current sprint private static decimal QueryTaskTotalEfforRemaining(List<int> listOfWorkItems) { var unfinishedWorkInCurrentSprint = _wis.GetQueryDefinition( new Guid(QueryAndGuid.FirstOrDefault(c => c.Key == "Unfinished Work").Value)); var parameters = new Dictionary<string, object> { { "project", _selectedTeamProject.Name } }; var q = new Query(_wis, unfinishedWorkInCurrentSprint.QueryText, parameters); var results = q.RunLinkQuery(); var wis = new List<WorkItem>(); foreach (var result in results) { var _wi = _wis.GetWorkItem(result.TargetId); if (_wi.Type.Name == "Task" && listOfWorkItems.Contains(_wi.Id)) wis.Add(_wi); } return wis.Sum(r => Convert.ToDecimal(r["Remaining Work"])); }   04 – The Results If you are still reading, the results are beautiful! Image 1 – Create work item with Changed Date pre-set to historic date Image 2 – Set the CreatedDate to historic date (Same as the ChangedDate) Image 3 – Simulate of effort burn down on a task via the TFS API   Image 4 – The history of changes on the Task. So, essentially this task has burned 1 hour per day Sprint Burn Down Chart – What’s not possible? The Sprint burn down chart is calculated from the System.AuthorizedDate and not the System.ChangedDate/System.CreatedDate. So, though you can change the System.ChangedDate and System.CreatedDate to historic dates you will not be able to synthesize the sprint burn down chart. Image 1 – By changing the Created Date and Changed Date to ‘18/Oct/2012’ you would have expected the burn down to have been impacted, but it won’t be, because the sprint burn down chart uses the value of field ‘System.AuthorizedDate’ to calculate the unfinished work points. The AsOf queries that are used to calculate the unfinished work points use the value of the field ‘System.AuthorizedDate’. Image 2 – Using the above code I burned down 1 hour effort per day over 5 days from the task work item, I would have expected the sprint burn down to show a constant burn down, instead the burn down shows the effort exhausted on the 24th itself. Simply because the burn down is calculated using the ‘System.AuthorizedDate’. Now you would ask… “Can I change the value of the field System.AuthorizedDate to a historic date” Unfortunately that’s not possible! You will run into the exception ValidationException –  “TF26194: The value for field ‘Authorized Date’ cannot be changed.” Conclusion - You need to be a member of the Project Collection Service account group in order to set the fields ‘System.ChangedDate’ and ‘System.CreatedDate’ to historic dates - You need to instantiate the WorkItemStore using the flag ByPassValidation - The System.ChangedDate needs to be set to a historic date at the time of work item creation. You cannot reset the ChangedDate to a date earlier than the existing ChangedDate and you cannot reset the ChangedDate to a date greater than the current date time. - The System.CreatedDate can only be reset after a work item has been created. You cannot set the CreatedDate at the time of work item creation. The CreatedDate cannot be greater than the current date. You can however reset the CreatedDate to a date earlier than the existing value. - You will not be able to synthesize the Sprint burn down chart by changing the value of System.ChangedDate and System.CreatedDate to historic dates, since the burn down chart uses AsOf queries to calculate the unfinished work points which internally uses the System.AuthorizedDate and NOT the System.ChangedDate & System.CreatedDate - System.AuthorizedDate cannot be set to a historic date using the TFS API Read other posts on using the TFS API here… Enjoy!

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  • UITextView adding text to new line

    - by Subro
    I would like to add new lines of text to my UITextView for my iPhone app. Basically my textview starts with a single line, and as app advances, new lines are added. However I can add only to the end or beginning of the existing text. How can I make such an entry into a new line. Can I manually send \n to the textview.text at a calculated range/location. E.g. of what I mean. line 1: This is first line of text. This is second line 2: line of text. --- I want: line 1: This is first line of text. line 2: This is second line of text. Thanks!

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  • Anyone had any experience with *.pcap manipulation libs?

    - by zxcvbnm
    I'm using the SharpPcap + PacketDotNet libraries to process some .pcap files and came across a bug in the way the timestamps are calculated. Take this Timeval property, which is something along these lines: PosixTimeval Timeval { DateTime Date; ulong Seconds; ulong MicroSeconds; } The problem is as follows: Suppose you have a trace open in Wireshark with one of the packets with a timestamp of "0.002". Once you open it within one of your programs, it retrieves the packet and its Timeval is setup such that Seconds = 0 and MicroSeconds = 002 = 2. This is done under the hood, so there is no way to avoid it as far as I can tell. My question is if that problem is common to other libraries (and maybe all of them?) who manipulate the pcap file format, which I think are built around the same collection of c/c++ functions, or if this is a problem only with the ones I'm using.

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  • Laplacian of Gaussian: how does it work? (opencv)

    - by maximus
    Does anybody know how does it work and how to do it using opencv? Laplacian can be calculated using opencv, but the result is not what I expected. I mean I expect the image to be approximately constant contrast at background regions, but it is black, and edges are white. There are a lot of noise also, even after gauss filter. I filter image using gaussian filter and then apply laplace. I think what I want is done by a different way.

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  • Social Game Mechanics in Django

    - by oliland
    I want users to receive 'points' for completing various tasks in my application - ranging from tasks such as tagging objects to making friends. I havn't yet found a Django application that simplifies this. At the moment I'm thinking that the best way to accumulate points is that each user action creates the equivalent of a "stream item", and the points are calculated through counting the value of each action published to their stream. Obviously social game mechanics is a huge area with a lot of research going on at the moment. But from a development perspective what's the easiest way to get started? Am I on the wrong track or are there better / simpler ways?

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  • Vertically split variable-sized div using CSS

    - by Martijn
    I'm trying to divide an auto-scaling div into two vertically using two other div's. What I have so far: <div id='wrapper'> <div id='left'>some stuff</div> <div id='right'>more stuff</div> </div> with #frame { position: static; width: 1000px; height: auto; /* more positioning stuff */ } #left { position: absolute; width: 200px; height: 100%; } #right { position: static; margin-left: 200px; } This seems to work OK, except if the contents of #right are higher than those of #left. In this case, part of the contents of left are invisible. How can I make sure that the height of the left div is also taken into account when the needed height of #wrapper is calculated?

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  • YUI Menu rendering below "fold" on first open

    - by Flash84x
    I have a YUI menu on the bottom navigation of the screen which creates a large white space beneath it where the action list would be rendered if visible... On the first click the menu will render in that white space which requires the user to scroll to see it... on the second click however it will draw upward (ideally) so that the user does not have to scroll to see the menu... the second click also kills that block of white space... i found adding a style of display:none to the div kills the white space... but then YUI doesn't set the display to block, which from what I understood it should... so I wrote another method that would do that manually... but the same behavior happens, the menu first renders below the fold requiring the user to scroll.... 2nd time its works fine... some reason the top/left positions are not being calculated properly on the first click and i cannot seem to figure out why

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  • Core Text's CTFramesetterSuggestFrameSizeWithConstraints() returns incorrect size everytime

    - by nsapplication
    According to the docs, CTFramesetterSuggestFrameSizeWithConstraints () "determines the frame size needed for a string range". Unfortunately the size returned by this function is never accurate. Here is what I am doing: NSAttributedString *string = [[[NSAttributedString alloc] initWithString:@"lorem ipsum" attributes:nil] autorelease]; CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef) string); CGSize textSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0,0), NULL, CGSizeMake(rect.size.width, CGFLOAT_MAX), NULL); The returned size always has the correct width calculated, however the height is always slightly shorter than what is expected. Is this the correct way to use this method? Is there any other way to layout Core Text? Seems I am not the only one to run into problems with this method. See https://devforums.apple.com/message/181450.

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  • Sumproduct using Django's aggregation

    - by Matthew Rankin
    Question Is it possible using Django's aggregation capabilities to calculate a sumproduct? Background I am modeling an invoice, which can contain multiple items. The many-to-many relationship between the Invoice and Item models is handled through the InvoiceItem intermediary table. The total amount of the invoice—amount_invoiced—is calculated by summing the product of unit_price and quantity for each item on a given invoice. Below is the code that I'm currently using to accomplish this, but I was wondering if there is a better way to handle this using Django's aggregation capabilities. Current Code class Item(models.Model): item_num = models.SlugField(unique=True) description = models.CharField(blank=True, max_length=100) class InvoiceItem(models.Model): item = models.ForeignKey(Item) invoice = models.ForeignKey('Invoice') unit_price = models.DecimalField(max_digits=10, decimal_places=2) quantity = models.DecimalField(max_digits=10, decimal_places=4) class Invoice(models.Model): invoice_num = models.SlugField(max_length=25) invoice_items = models.ManyToManyField(Item,through='InvoiceItem') def _get_amount_invoiced(self): invoice_items = self.invoiceitem_set.all() amount_invoiced = 0 for invoice_item in invoice_items: amount_invoiced += (invoice_item.unit_price * invoice_item.quantity) return amount_invoiced amount_invoiced = property(_get_amount_invoiced)

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  • pchart pie chart legend and graph not correlating

    - by madphp
    Hi, I have ten values in the dataset, numbers 1 - 10 and corresponding values. Some of the values are coming back as zero, so they are not added to the chart, BUT, the legend is still listing 1 - 10. Because theres values missing in the chart, the colour coding is knocked off. ie Item 1, has a value of zero, its passed over in the chart, the colour in the legend is red, Item 2, has a value of 4, the percentage is calculated, and the chart gives it the colour red which is the colour for item 1 in the legend. Hope that makes sense. How can I print the legend just for the values that are displayed in the chart? --Mark

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  • [RESTful] Calculation with RESTful web service with MySQL database : )

    - by Dobby
    Dears, I am now making some RESTful web service with MySQL database. I used NetBeans to create the resources of RESTful service with MySQL, and now I can now using GET and POST/PUT to list and add/modify data entities in the MySQL server. Currently, I wish to make some calculations right after a client makes the POST activities, then the posted data with calculated results will be inserted into the MySQL database. I am very new to this, I guess I need to add some functions and call them to calculate but I don't know where and how to do that : ( Could any one help me on this issue? Thanks a lot in advance! : ) Best! Dobby

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  • C#: Cached Property: Easier way?

    - by Peterdk
    I have a object with properties that are expensive to compute, so they are only calculated on first access and then cached. private List<Note> notes; public List<Note> Notes { get { if (this.notes == null) { this.notes = CalcNotes(); } return this.notes; } } I wonder, is there a better way to do this? Is it somehow possible to create a Cached Property or something like that in C#?

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  • CGBitmapContextCreate: unsupported parameter combination

    - by tarmes
    I'm getting this error when creating a bitmap context: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 24 bits/pixel; 3-component color space; kCGImageAlphaNone; 7936 bytes/row. Here's the code (note that the context is based on the parameters of an existing CGImage: context = CGBitmapContextCreate(NULL, (int)pi.bufferSizeRequired.width, (int)pi.bufferSizeRequired.height, CGImageGetBitsPerComponent(imageRef), 0, CGImageGetColorSpace(imageRef), CGImageGetBitmapInfo(imageRef)); Width is 2626, height is 3981. I've leaving bytesPerRow at zero so that it gets calculated automatically for me, and it's chosen 7936 of its own accord. So, where on Earth is the inconsistency? It's driving me nuts.

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  • Resizing screenshots/screen captures for inclusion in Beamer

    - by Stephen
    Sorry, this may or may not be a programming question directly, but I am trying to resize screenshots with Imagemagick and Gimp to include in a Beamer presentation, but it comes out even blurrier than the resizing done by LaTeX. For instance, in Beamer I might have a command to rescale the image \includegraphics[width=.5\textwidth]{fig.png}. Using something like \begin{frame} \message{width = \the\textwidth} \message{height = \the\textheight} \end{frame} I have gotten the \textwidth and \textheight parameters in points (345.69548, 261.92444). So I have a script (in Python) that sends a system call to Imagemagick: 'convert %s -resize %.6f@ resized_%s' % (f,a,f) where a is calculated as \textwidth*\textheight*0.5**2. When I then go back into my Beamer presentation and include the resized figure, \includegraphics{resized_fig.png}, the size looks approximately correct but it's super-blurry. I also tried resizing in Gimp (using the GUI) but no luck either... help? Thanks...

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  • Quaddratic Bezier Curve: Calculate Tangent

    - by stefan.at.wpf
    Hello, I have have a quadratic bezier curve and I want to calculate the slope of the tangent in a given point. For example, let it be the middlepoint of the quadratic bezier curve, therefore t=0.5 (please see the link below for a picture of this). I've calculated the first derivation of the formula for the quadratic bezier curve, however I get 400 as value for the slope, though it should be 0. Maybe I'm using the first derivation in a wrong way? I know I could also calculate the tangents using trigonometric functions, however I'd like to do it using the first derivation, shouldn't this be possible? Thanks for any hint! For clarification / please note: I'm interested in a general way to get the slope in a arbitrary given point on a quadratic bezier curve, not only to get the tangent in the start- and end point. A picture of my problem including the text above: http://cid-0432ee4cfe9c26a0.skydrive.live.com/self.aspx/%c3%96ffentlich/Quadratic%20Bezier%20Curve.pdf Thank you very much for any hint!

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  • Loose Coupling vs. Information Hiding and Ease of Change

    - by cretzel
    I'm just reading Code Complete by Steve McConell and I'm thinking of an Example he gives in a section about loose coupling. It's about the interface of a method that calculates the number of holidays for an employee, which is calculated from the entry date of the employee and her sales. The author suggests a to have entry date and sales as the parameters of the method instead of an instance of the employee: int holidays(Date entryDate, Number sales) instead of int holidays(Employee emp) The argument is that this decouples the client of the method because it does not need to know anything about the Employee class. Two things came to my mind: Providing all the parameters that are needed for the calculation breaks encapsulation. It shows the internals of the method on how it computes the result. It's harder to change, e.g. when someone decides that also the age of the employee should be included in the calculation. One would have to change the signature. What's your opinion?

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  • C# ASPNET MVC - How do you use ModelState.IsValid in a jquery/ajax postback?

    - by JK
    From what I've seen ModelState.IsValid is only calculated by the MVC frame work on a full postback, is that true? I have a jquery postback like so: var url = "/path/to/controller/myaction"; var id = $("#Id").val(); var somedata = $("#somedata").val(); // repeated for every textbox $.post(url, { id: id, somedata: somedata }, function (data) { // etc }); And the controller action looks like: public JsonResult MyAction(MyModel modelInstance) { if (ModelState.IsValid) { // ... ModelState.IsValid is always true, even when there is invalid data } } But this does not seem to trigger ModelState.IsValid. For example if somedata is 5 characters long, but the DataAnnotation says [StringLength(3)] - in this case ModelStae.IsValid is still true, because it hasn't been triggered. Is there something special I need to do when making a jquery/ajax post instead of a full post? Thanks!

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  • C# - using decimal in switch impossible?

    - by phobia
    Hi, I'm justing starting out learning C# and I've become stuck at something very basic. For my first "app" I thought I'd go for something simple, so I decided for a BMI calculator. The BMI is calculated into a decimal type which I'm now trying to use in a switch statement, but aparently decimal can't be used in a switch? What would be the C# solution for this: decimal bmi = calculate_bmi(h, w); switch (bmi) { case < 18.5: bmi_description = "underweight."; break; case > 25: bmi_description = "overweight"; case > 30: bmi_description = "very overweight"; case > 40: bmi_description = "extreme overweight"; break; } Thanks in advance :)

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  • UITableView details as a subview

    - by Leonardo
    Hi all, I have a UITableView in iPhone with enough cell to make it scrollable. I would like to have a subview display whenever I click on a cell, rather than using the navigation controller behaviour. The problem is that I cannot calculate the CGRect exactly to have the subview always centered in page, because the CGRect is calculated from top of table, and if I scroll table and click cell, the subview will be added out of screen. The solution could be easy, but I don't know if it's possible: identify the portion of the current viewable area of the UITableView and obtain in some way the frame and therefore origin and size, then build a subview based on such coordinates. Do you think it's possible without writing not too much code ? thanks Leonardo

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  • Printing an NSDocument

    - by Brian Postow
    I'm trying to print a document. The document is an array of NSImageReps, or a single NSPDFImageRep, which has multiple pages. I'm having trouble figuring out how to use the NSPrintOperation class to print this. The NSPrintOperation seems to need an NSView to print. Do I need to manually add each image into the view at a calculated position and then let it do the pagination? that seems like it isn't in the spirit of Cocoa... is there some technique that I'm missing?

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