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CakePHP, CodeIgniter or Rails for multi-user Tumblr clone?

- by Jordan

I'm about to start building a tumblr clone that handles multiple users (so premade clones like Gelato won't cut it) and I'm not sure which framework I'd like to build this is. Right now, I'm only intending to build a prototype. Something I can get a dozen friends on to test the concept and grow to maybe a couple hundred users to prove the market, so I'm not worried about long term scale. My biggest concern right now is quick deployment. I'd like to get from zero to signups in as short a time as possible, with as little customization to the framework of choice as possible. I have experience with PHP, but not Ruby. However, I don't think the learning curve would be too steep so I'm not ruling out rails. I just want the framework that is most appropriate for a system like a multi-user tumblr clone so that I can build it with as little hassle, and as quickly, as possible. If anyone has experience with a similar project, or with these frameworks and can offer an insightful perspective, I'd be very appreciative. Thanks for taking the time to read. Cheers, ~Jordan Feldstein

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To Ajax or Not to Ajax a listing page

- by kaivalya

Here i am talking about product listing pages where there are multiple filters that filter the list of products appearing on the page like product types, categories price range etc. I have done such pages using both ajax and no ajax way in the past. What I like about using ajax in such page is that, when filters are selected I only update the section that contains the product list. There is no need to refresh the whole page which could end up re-loading the images on top bar, banners etc and slow down the user performance. Ajax way in my opinion becomes more compact and responsive from user experience. Down side for ajax route for me is; since filter states are not maintained in the URL I end up maintaining them on the server. This becomes complicated if I want to handle multi window scenarios and it is also costly to maintain such state on server memory for each session. Not using ajax and simply keeping all filter values on url and refreshing the page is quite simple but the luxury of refreshing only the pane that really needs to be refreshed is lost. Lately I am seeing a lot of large scale e-commerce sites that are using non-ajax approach on their listing pages and this is making me question one more time if it might be more efficient to build non-ajax listing make due to the long term maintenance ease and sacrifice a little bit from user experience. I am about to start implementing a new listing page for a product which I have the flexibility to go either way and I would appreciate your inputs.

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How to keep text inside a circle using Cairo?

- by miguelrios

I a drawing a graph using Cairo (pycairo specifically) and I need to know how can I draw text inside a circle without overlapping it, by keeping it inside the bounds of the circle. I have this simple code snippet that draws a letter "a" inside the circle: ''' Created on May 8, 2010 @author: mrios ''' import cairo, math WIDTH, HEIGHT = 1000, 1000 #surface = cairo.PDFSurface ("/Users/mrios/Desktop/exampleplaces.pdf", WIDTH, HEIGHT) surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, WIDTH, HEIGHT) ctx = cairo.Context (surface) ctx.scale (WIDTH/1.0, HEIGHT/1.0) # Normalizing the canvas ctx.rectangle(0, 0, 1, 1) # Rectangle(x0, y0, x1, y1) ctx.set_source_rgb(255,255,255) ctx.fill() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.03) ctx.stroke() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.01) ctx.set_source_rgb(255,0,255) ctx.fill() ctx.set_source_rgb(0,0,0) ctx.select_font_face("Georgia", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD) ctx.set_font_size(1.0) x_bearing, y_bearing, width, height = ctx.text_extents("a")[:4] print ctx.text_extents("a")[:4] ctx.move_to(0.5 - width / 2 - x_bearing, 0.5 - height / 2 - y_bearing) ctx.show_text("a") surface.write_to_png ("/Users/mrios/Desktop/node.png") # Output to PNG The problem is that my labels have variable amount of characters (with a limit of 20) and I need to set the size of the font dynamically. It must fit inside the circle, no matter the size of the circle nor the size of the label. Also, every label has one line of text, no spaces, no line breaks. Any suggestion?

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3x3 Sobel operator and gradient features

- by pithyless

Reading a paper, I'm having difficulty understanding the algorithm described: Given a black and white digital image of a handwriting sample, cut out a single character to analyze. Since this can be any size, the algorithm needs to take this into account (if it will be easier, we can assume the size is 2^n x 2^m). Now, the description states given this image we will convert it to a 512-bit feature (a 512-bit hash) as follows: (192 bits) computes the gradient of the image by convolving it with a 3x3 Sobel operator. The direction of the gradient at every edge is quantized to 12 directions. (192 bits) The structural feature generator takes the gradient map and looks in a neighborhood for certain combinations of gradient values. (used to compute 8 distinct features that represent lines and corners in the image) (128 bits) Concavity generator uses an 8-point star operator to find coarse concavities in 4 directions, holes, and lagrge-scale strokes. The image feature maps are normalized with a 4x4 grid. I'm for now struggling with how to take an arbitrary image, split into 16 sections, and using a 3x3 Sobel operator to come up with 12 bits for each section. (But if you have some insight into the other parts, feel free to comment :)

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Python: fetching SVG file using urllib is returning binary when I need ASCII

- by Drew Dara-Abrams

I'm using urllib (in Python) to fetch an SVG file: import urllib urllib.urlopen('http://alpha.vectors.cloudmade.com/BC9A493B41014CAABB98F0471D759707/-122.2487,37.87588,-122.265823,37.868054?styleid=1&viewport=400x231').read() which produces output of the sort: xb6\xf6\x00\xb3\xfb2\xff\xda\xc5\xf2\xc2\x14\xef\xcd\x82\x0b\xdbU\xb0\x81\xcaF\xd8\x1a\xf6\xdf[i)\xba\xcf\x80\xab\xd6\x8c\xe3l_\xe7\n\xed2,\xbdm\xa0_|\xbb\x12\xff\xb6\xf8\xda\xd9\xc3\xd9\t\xde\x9a\xf8\xae\xb3T\xa3\r`\x8a\x08!T\xfb8\x92\x95\x0c\xdd\x8b!\x02P\xea@\x98\x1c^\xc7\xda\\\xec\xe3\xe1\xbe,0\xcd\xbeZ~\x92\xb3\xfa\xdd\xfcbyu\xb8\x83\xbb\xbdS\x0f\x82\x0b\xfe\xf5_\xdawn\xff\xef_\xff\xe5\xfa\x1f?\xbf\xffoZ\x0f\x8b\xbfV\xf4\x04\x00' when I was expecting more like this: <?xml version='1.0' encoding='UTF-8'?> <svg xmlns="http://www.w3.org/2000/svg" xmlns:cm="http://cloudmade.com/" width="400" height="231"> <rect width="100%" height="100%" fill="#eae8dd" opacity="1"/> <g transform="scale(0.209849975856)"> <g transform="translate(13610569, 4561906)" flood-opacity="0.1" flood-color="grey"> <path d="M -13610027.720000000670552 -4562403.660000000149012 I guess this is an issue of binary vs. ASCII. Can anyone help me (a Python newbie) with the appropriate conversion so that I can get on with parsing and manipulating the SVG code?

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Incorrect rendering in dojox charting stacked column?

- by FokeyJoe

Hiya, I seem to be having a problem with my dojo stackedcolumn whereby the scale of some of the bars is correct for some x-axis points, but not others. Here's my code (observe the northern ireland hydro should be 70, but only shows as around 30): dojo.addOnLoad(function() { var chart1 = new dojox.charting.Chart2D("sitesbycountry"); chart1.addPlot("default", {type: "StackedColumns", gap: 10}); chart1.addPlot("horzgrid", {type: "Grid", hMajorLines: true, vMajorLines: false}); chart1.addAxis("x", {labels: [{value: 1, text: 'Northern Ireland'}, {value: 2, text: 'Wales'}, {value: 3, text: 'Scotland'}, {value: 4, text: 'England'}], minorTicks: false, microTicks: false}); chart1.addAxis("y", {vertical: true, minorTicks: false, microTicks: false}); chart1.addSeries("Hydro", [70, 53, 198, 102], {fill: "#ddddff"}); chart1.addSeries("Wind and Wave", [67, 51, 150, 245], {fill: "#FEFFBF"}); chart1.addSeries("Landfill", [1, 23, 40, 0], {fill: "#CFFFD1"}); chart1.addSeries("Other Biofuels and Wastes", [4, 3, 11, 66], {fill: "#DFD2C3"}); chart1.render(); }); Is this a behaviour of the chart that I'm not aware of? TIA FokeyJoe

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Table design issues - should I create separate fields or store as a blob

- by Ali

Hi guys I'm working on my web based ordering system and we would like to maintain a kind of task history for each of our orders. A hsitory in the sense that we would like to maintain a log of who did what on an order like lets say an order has been entered - we would like to know if the order was acknowledged for an example. Or lets say somebody followed up on the order - etc. Consider that there are numerous situations like this for each order would it be wise to create a schema on the lines of: Orders ID - title - description - date - is_ack - is_follow - ack_by ..... That accounts to a lot of fields - on teh other hand I could have one LongText field called 'history' and fill it with a serialised object holding all the information. However in the latter case I can't run a query to lets say retrieve all orders that have not been acknowledged and stuff like that. With time requirements woudl change and I would be required to modify it to allow for more detailed tracking and that is why I need to set up a way which would be feasible to scale upon yet I don't want to be restricted on the SQL side too much.

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Plot in GNU PLOT

- by guddi

I have to plot many lines in GNU PLOT.No problem with the X axis. The problem that I am facing is that most of the plotted lines are at yscale [0-0.05] ,few at range 60-70 and rest at 600-700. These numbers correspond to the y axis scale values. But after I plot I can see only 3 sets of lines all messed up. There is no clearity between the lines. Line at 0 and the line at 0.003 look like one single line. If I set yrange[0:0.05], the lines between this range are clearly vissible. But I want all the lines in the same graph. I have heard of breaking axis's and multi plotting..Can they be useful? how to implement them. Anyone pls help me. Below is the sript set terminal png size 1300,1200 enhanced font 'Verdana,20 set output ' output .png’ set key font 'Verdana,16' set key bottom outside set yrange[500:1000] set xtics("25k" 25000,"50k" 50000,"75k" 75000,"100k" 100000) set grid set title 'Performance Metrics' set ylabel 'Metrices' set xlabel 'FES' plot ' input ' using 1:2 title ' A' with linespoints linewidth 4, ' input ' using 1:3 title B'with linespoints linewidth 4, 'input ' using 1:4 title ' c' with linespoints linewidth 4, 'input ' using 1:5 title 'D' with linespoints linewidth 4, ' input ' using 1:6 title 'E' with linespoints linewidth 4, ' input ' using 1:7 title 'F' with linespoints linewidth 4, ' input ' using 1:8 title 'G' with linespoints linewidth 4, ' input ' using 1:9 title ' H ' with linespoints linewidth 4, ' input ' using 1:10 title ' I' Metric ' with linespoints linewidth 4 set output set terminal windows input.dat is something like this: 25 0.002 0.05 899 455 444 0.08 0.00004 900 700 0.003 This way i have other rows. I have shown only the first one

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Integration tests in Continuous Integration environment: Database and filesystem state

- by dario_ramos

I'm trying to implement automated integration tests for my application. It's a very complex monster. You could say that its database and part of the filesystem are part of its state, because it saves image files in the hard drive, and references to those in the DB. The software needs all those, in a coherent state, to work properly. Back to writing tests: To run any relevant test, I need some image files in the filesystem, and certain records filled in the database. I thought of putting all of these in a separate folder called TestEnvironmentData in the repository, and retrieving them from the Continuous Integration Server (Team City), but a colleague said the repo is quite full as it is, and that I should set up a special directory, and databases, only in the Continuous Integration server. I don't like that because the tests success depend on me manually mantaining stuff in the server, and restoring initial state before every test becomes cumbersome. What do you guys do when you need to write integration tests for an app like this? The main goal is having an automated test harness to approach a large scale refactoring. There's lots of spaghetti code and the app's current architecture is hardly unit testable, that's why I decided on integration tests first. Any alternative approach is welcome.

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QT- QImage and multi-threading problem.

- by umanga

Greetings all, Please refer to image at : http://i48.tinypic.com/316qb78.jpg We are developing an application to extract cell edges from MRC images from electron microscope. MRC file format stores volumetric pixel data (http://en.wikipedia.org/wiki/Voxel) and we simply use 3D char array(char***) to load and store data (gray scale values) from a MRC file. As shown in the image,there are 3 viewers to display XY,YZ and ZX planes respectively. Scrollbars on the top of the viewers use to change the image slice along an axis. Here is the steps we do when user changes the scrollbar position. 1) get the new scrollbar value.(this is the selected slice) 2) for the relavant plane (YZ,XY or ZX), generate (char* slice;) array for the selected slice by reading 3D char array (char***) 3) Create a new QImage* (Format_RGB888) and set pixel values by reading 'slice' (using img-setPixel(x,y,c);) 4) This new QImage* is painted in the paintEvent() method. We are going to execute "edge-detection" process in a seperate thread since it is an intensive process.During this process we need to draw detected curve (set of pixels) on top of above QImage*.(as a layer).This means we need to call drawPoint() methods outside the QT thread. Is it the best wayto use QImage for this case? What is the best way to execute QT drawing methods from another thread? thanks in advance,

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Setting UIImage dimensions on UITableViewCell image

- by bbrown

I've got a standard UITableViewCell where I'm using the text and image properties to display a favicon.ico and a label. For the most part, this works really well since UIImage supports the ICO format. However, some sites (like Amazon.com say) have favicon.icos that make use of the ICO format's ability to store multiple sizes in the same file. Amazon stores four different sizes, all the way up to 48x48. This results in most images being 16x16 except for a few that come in at 32x32 or 48x48 and make everything look terrible. I have searched here, the official forum, the documentation, and elsewhere without success. I have tried everything that I could think of to constrain the image size. The only thing that worked was an undocumented method, which I'm not about to use. This is my first app and my first experience with Cocoa (came from C#). In case I wasn't clear in what I'm looking for, ideally the advice would center around setting the dimensions of the UIImage so that the 48x48 version would scale down to 16x16 or a method to tell UIImage to use the 16x16 version present in the ICO file. I don't necessarily need code: just a suggestion of an approach would do me fine. Does anyone have any suggestions? (I asked in the official forum as well because I've sunk more than a day into this already. If a solution is posted there, I'll put it here as well.)

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Method for finding memory leak in large Java heap dumps

- by Rickard von Essen

I have to find a memory leak in a Java application. I have some experience with this but would like advice on a methodology/strategy for this. Any reference and advice is welcome. About our situation: Heap dumps are larger than 1 GB We have heap dumps from 5 occasions. We don't have any test case to provoke this. It only happens in the (massive) system test environment after at least a weeks usage. The system is built on a internally developed legacy framework with so many design flaws that they are impossible to count them all. Nobody understands the framework in depth. It has been transfered to one guy in India who barely keeps up with answering e-mails. We have done snapshot heap dumps over time and concluded that there is not a single component increasing over time. It is everything that grows slowly. The above points us in the direction that it is the frameworks homegrown ORM system that increases its usage without limits. (This system maps objects to files?! So not really a ORM) Question: What is the methodology that helped you succeed with hunting down leaks in a enterprise scale application?

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Starting out NLP - Python + large data set

- by pencilNero

Hi, I've been wanting to learn python and do some NLP, so have finally gotten round to starting. Downloaded the english wikipedia mirror for a nice chunky dataset to start on, and have been playing around a bit, at this stage just getting some of it into a sqlite db (havent worked with dbs in the past unfort). But I'm guessing sqlite is not the way to go for a full blown nlp project(/experiment :) - what would be the sort of things I should look at ? HBase (.. and hadoop) seem interesting, i guess i could run then im java, prototype in python and maybe migrate the really slow bits to java... alternatively just run Mysql.. but the dataset is 12gb, i wonder if that will be a problem? Also looked at lucene, but not sure how (other than breaking the wiki articles into chunks) i'd get that to work.. What comes to mind for a really flexible NLP platform (i dont really know at this stage WHAT i want to do.. just want to learn large scale lang analysis tbh) ? Many thanks.

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Is there any special tool for interactive GUI development

- by niko

Hi, Currently I am preparing exercises about networks and mobile communications for students. I was thinking about creating an interactive user-interface which enables the user to drag&drop predefined elements and then implement a logic based upon element distances etc. An example would be to place two base stations (a predefined element with several properties), set the scale in the interface and then check the signal interferrence in the environment (user-interface). The first part might be too abstract whereas the example might be too specific, but I was wondering whether there already exists any friendly framework or language which enables developers to create interactive interfaces (for teaching/learning purpouses) in short ammount of time. Usually I write applications for PC environment in .NET but in this case it would take too much time to create a specific interface for every exercise. I would appreciate if anyone could suggest any way to create interactive user-interface in short ammount of time. Are there any special programming languages or development tools for this kind of applications or are there any useful frameworks for .NET, Java or any other language to speed up the development of user-interfaces? Thank you!

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SQL Server 2005 database design - many-to-many relationships with hierarchy

- by Remnant

Note I have completely re-written my original post to better explain the issue I am trying to understand. I have tried to generalise the problem as much as possible. Also, my thanks to the original people who responded. Hopefully this post makes things a little clearer. Context In short, I am struggling to understand the best way to design a small scale database to handle (what I perceive to be) multiple many-to-many relationships. Imagine the following scenario for a company organisational structure: Textile Division Marketing Division | | ---------------------- ---------------------- | | | | HR Dept Finance Dept HR Dept Finance Dept | | | | ---------- ---------- ---------- --------- | | | | | | | | Payroll Hiring Audit Tax Payroll Hiring Audit Accounts | | | | | | | | Emps Emps Emps Emps Emps Emps Emps Emps NB: Emps denotes a list of employess that work in that area When I first started with this issue I made four separate tables: Divisions - Textile, Marketing (PK = DivisionID) Departments - HR, Finance (PK = DeptID) Functions - Payroll, Hiring, Audit, Tax, Accounts (PK = FunctionID) Employees - List of all Employees (PK = EmployeeID) The problem as I see it is that there are multiple many-to-many relationships i.e. many departments have many divisions and many functions have many departments. Question Giving the database structure above, suppose I wanted to do the following: Get all employees who work in the Payroll function of the Marketing Division To do this I need to be able to differentiate between the two Payroll departments but I am not sure how this can be done? I understand that I could build a 'Link / Junction' table between Departments and Functions so that I can retrieve which Functions are in which Departments. However, I would still need to differentiate the Division they belong to. Research Effort As you can see I am an abecedarian when it comes to database deisgn. I have spent the last two days resaerching this issue, traversing nested set models, adjacency models, reading that this issue is known not to be NP complete etc. I am sure there is a simple solution?

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Character Encoding: â??

- by akaphenom

I am trying to piece together the mysterious string of characters â?? I am seeing quite a bit of in our database - I am fairly sure this is a result of conversion between character encodings, but I am not completely positive. The users are able to enter text (or cut and paste) into a Ext-Js rich text editor. The data is posted to a severlet which persists it to the database, and when I view it in the database i see those strange characters... is there any way to decode these back to their original meaning, if I was able to discover the correct encoding - or is there a loss of bits or bytes that has occured through the conversion process? Users are cutting and pasting from multiple versions of MS Word and PDF. Does the encoding follow where the user copied from? Thank you website is UTF-8 We are using ms sql server 2005; SELECT serverproperty('Collation') -- Server default collation. Latin1_General_CI_AS SELECT databasepropertyex('xxxx', 'Collation') -- Database default SQL_Latin1_General_CP1_CI_AS and the column: Column_name Type Computed Length Prec Scale Nullable TrimTrailingBlanks FixedLenNullInSource Collation text varchar no -1 yes no yes SQL_Latin1_General_CP1_CI_AS The non-Unicode equivalents of the nchar, nvarchar, and ntext data types in SQL Server 2000 are listed below. When Unicode data is inserted into one of these non-Unicode data type columns through a command string (otherwise known as a "language event"), SQL Server converts the data to the data type using the code page associated with the collation of the column. When a character cannot be represented on a code page, it is replaced by a question mark (?), indicating the data has been lost. Appearance of unexpected characters or question marks in your data indicates your data has been converted from Unicode to non-Unicode at some layer, and this conversion resulted in lost characters. So this may be the root cause of the problem... and not an easy one to solve on our end.

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Resizing image algorithm in python

- by hippocampus

So, I'm learning my self python by this tutorial and I'm stuck with exercise number 13 which says: Write a function to uniformly shrink or enlarge an image. Your function should take an image along with a scaling factor. To shrink the image the scale factor should be between 0 and 1 to enlarge the image the scaling factor should be greater than 1. This is not meant as a question about PIL, but to ask which algorithm to use so I can code it myself. I've found some similar questions like this, but I dunno how to translate this into python. Any help would be appreciated. I've come to this: import image win = image.ImageWin() img = image.Image("cy.png") factor = 2 W = img.getWidth() H = img.getHeight() newW = int(W*factor) newH = int(H*factor) newImage = image.EmptyImage(newW, newH) for col in range(newW): for row in range(newH): p = img.getPixel(col,row) newImage.setPixel(col*factor,row*factor,p) newImage.draw(win) win.exitonclick() I should do this in a function, but this doesn't matter right now. Arguments for function would be (image, factor). You can try it on OP tutorial in ActiveCode. It makes a stretched image with empty columns :.

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How to Create Deterministic Guids

- by desigeek

In our application we are creating Xml files with an attribute that has a Guid value. This value needed to be consistent between file upgrades. So even if everything else in the file changes, the guid value for the attribute should remain the same. One obvious solution was to create a static dictionary with the filename and the Guids to be used for them. Then whenever we generate the file, we look up the dictionary for the filename and use the corresponding guid. But this is not feasible coz we might scale to 100's of files and didnt want to maintain big list of guids. So another approach was to make the Guid the same based on the path of the file. Since our file paths and application directory structure are unique, the Guid should be unique for that path. So each time we run an upgrade, the file gets the same guid based on its path. I found one cool way to generate such 'Deterministic Guids' (Thanks Elton Stoneman). It basically does this: private Guid GetDeterministicGuid(string input) { //use MD5 hash to get a 16-byte hash of the string: MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider(); byte[] inputBytes = Encoding.Default.GetBytes(input); byte[] hashBytes = provider.ComputeHash(inputBytes); //generate a guid from the hash: Guid hashGuid = new Guid(hashBytes); return hashGuid; } So given a string, the Guid will always be the same. Are there any other approaches or recommended ways to doing this? What are the pros or cons of that method?

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How to pass PHP variable as FlashVars via SWFObject

- by Matt

I am trying to take a PHP variable and pass it along to Flash via Flash vars. My end goal is to pass a string formatted as XML to Flash, but because I'm struggling I've stripped everything down to the basics. I'm just trying to pass a simple PHP string variable to Flash via FlashVars with SWFObject but something isn't right. The page won't load when I try to pass the variable inside of php tags, but it will load if I just pass a hard coded string. The basic structure of my page is that I have some PHP declared at the top like so: PHP <?php $test = "WTF"; ?> Some HTML (excluded here for simplicity sake) and then the JavaScript SWFObject Embed within my HTML: <script type="text/javascript" src="js/swfobject2.js"></script> <script type="text/javascript"> // <![CDATA[ var swfURL = "swfs/Init-Flash-PHP.swf"; var flashvars = {}; flashvars.theXML = <?php print $test ?>; var params = {}; //params.menu = "false"; params.scale = "showAll"; params.bgcolor = "#000000"; params.salign = "TL"; //params.wmode = "transparent"; params.allowFullScreen = "true"; params.allowScriptAccess = "always"; var attributes = {}; attributes.id = "container"; attributes.name = "container"; swfobject.embedSWF(swfURL, "container", '100%', '100%', "9.0.246", "elements/swfs/expressinstall.swf", flashvars, params, attributes); // ]]> </script> And the bare essentials of the ActionScript 3 Code: _paramObj = LoaderInfo(stage.loaderInfo).parameters; theText_txt.text = _paramObj['theXML']; How do I pass a PHP variable using SWFObject and FlashVars? Thanks.

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Product Catalog Schema design

- by FlySwat

I'm building a proof of concept schema for a product catalog to possibly replace a very aging and crufty one we use. In our business, we sell both physical materials and services (one time and reoccurring charges). The current catalog schema has each distinct category broken out into individual tables, while this is nicely normalized and performs well, it is fairly difficult to extend. Adding a new attribute to a particular product involves changing the table schema and backpopulating old data. An idea I've been toying with has been something along the line of a base set of entity tables in 3rd normal form, these will contain the facts that are common among ALL products. Then, I'd like to build an Attribute-Entity-Value schema that allows each entity type to be extended in a flexible way using just data and no schema changes. Finally, I'd like to denormalize this data model into materialized views for each individual entity type. This views are what the application would access. We also have many tables that contain business rules and compatibility rules. These would join against the base entity tables instead of the views. My big concerns here are: Performance - Attribute-Entity-Value schemas are flexible, but typically perform poorly, should I be concerned? More Performance - Denormalizing using materialized views may have some risks, I'm not positive on this yet. Complexity - While this schema is flexible and maintainable using just data, I worry that the complexity of the design might make future schema changes difficult. For those who have designed product catalogs for large scale enterprises, am I going down the totally wrong path? Is there any good best practice schema design reading available for product catalogs?

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Pros & Cons of Google App Engine

- by Rishi

Pros & Cons of Google App Engine [An Updated List 21st Aug 09] Help me Compile a List of all the Advantages & Disadvantages of Building an Application on the Google App Engine Pros: 1) No Need to buy Servers or Server Space (no maintenance). 2) Makes solving the problem of scaling much easier. Cons: 1) Locked into Google App Engine ?? 2)Developers have read-only access to the filesystem on App Engine. 3)App Engine can only execute code called from an HTTP request (except for scheduled background tasks). 4)Users may upload arbitrary Python modules, but only if they are pure-Python; C and Pyrex modules are not supported. 5)App Engine limits the maximum rows returned from an entity get to 1000 rows per Datastore call. 6)Java applications may only use a subset (The JRE Class White List) of the classes from the JRE standard edition. 7)Java applications cannot create new threads. Known Issues!! http://code.google.com/p/googleappengine/issues/list Hard limits Apps per developer - 10 Time per request - 30 sec Files per app - 3,000 HTTP response size - 10 MB Datastore item size - 1 MB Application code size - 150 MB Pro or Con? App Engine's infrastructure removes many of the system administration and development challenges of building applications to scale to millions of hits. Google handles deploying code to a cluster, monitoring, failover, and launching application instances as necessary. While other services let users install and configure nearly any *NIX compatible software, App Engine requires developers to use Python or Java as the programming language and a limited set of APIs. Current APIs allow storing and retrieving data from a BigTable non-relational database; making HTTP requests; sending e-mail; manipulating images; and caching. Most existing Web applications can't run on App Engine without modification, because they require a relational database.

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How to get image's coordinate on JPanel

- by Jessy

This question is related to my previous question http://stackoverflow.com/questions/2376027/how-to-generate-cartesian-coordinate-x-y-from-gridbaglayout I have successfully get the coordinate of each pictures, however when I checked the coordinate through (System.out.println) and the placement of the images on the screen, it seems to be wrong. e.g. if on the screen it was obvious that the x point of the first picture is on cell 2 which is on coordinate of 20, but the program shows x=1. Here is part of the code: public Grid (){ setPreferredSize(new Dimension(600,600)); .... setLayout(new GridBagLayout()); GridBagConstraints gc = new GridBagConstraints(); gc.weightx = 1d; gc.weighty = 1d; gc.insets = new Insets(0, 0, 0, 0);//top, left, bottom, and right gc.fill = GridBagConstraints.BOTH; JLabel[][] label = new JLabel[ROWS][COLS]; Random rand = new Random(); // fill the panel with labels for (int i=0;i<IMAGES;i++){ ImageIcon icon = createImageIcon("myPics.jpg"); int r, c; do{ //pick random cell which is empty r = (int)Math.floor(Math.random() * ROWS); c = (int)Math.floor(Math.random() * COLS); } while (label[r][c]!=null); //randomly scale the images int x = rand.nextInt(50)+30; int y = rand.nextInt(50)+30; Image image = icon.getImage().getScaledInstance(x,y, Image.SCALE_SMOOTH); icon.setImage(image); JLabel lbl = new JLabel(icon); // Instantiate GUI components gc.gridx = r; gc.gridy = c; add(lbl, gc); //add(component, constraintObj); label[r][c] = lbl; } I checked the coordinate through this code: Component[] components = getComponents(); for (Component component : components) { System.out.println(component.getBounds()); }

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Flex: How to resize DisplayObject to fit panel in Flex application

- by ohm

I am trying to attach some of my actionscript class, inherited from Sprite, to my Flex application by attaching it to a UIComponent, then add UIComponent to a panel. However, the size of my Sprite class appears to be larger than the panel. So, I try to resize it using DisplayObject.scale property, but I need to know the size of my container. Since I try to make my code reusable, I figure that I should let my Sprite class handle the resize by getting it via its parent property (let's say, I can resize it by set this.scaleX = this.parent.Width/this.width or something like this) However, my Sprite class's parent, which is the UIComponent, has width/height of 0. So, my question is: 1) Is there any better way to resize DisplayObject class to fit its container when attached to Flex object? 2) If you know, why my UIComponent's size remain 0 and my DisplayObject still appears at its full size? Here's my code, using Flash Builder 4: private var loader:Loader = new Loader(); private function testLoader():void { var urlRequest:URLRequest = new URLRequest("http://localhost/welcome.png"); loader.load(urlRequest); loader.contentLoaderInfo.addEventListener(Event.COMPLETE,onLoaderLoadComplete); } private function onLoaderLoadComplete(e:Event):void { loader.contentLoaderInfo.removeEventListener(Event.COMPLETE,onLoaderLoadComplete); var ui : UIComponent = new UIComponent(); ui.addChild(loader); panelTest.addElement(ui); trace("ui.width = " + ui.width); trace("ui.height = " + ui.height); trace("loader.width = " + loader.width); trace("loader.height = " + loader.height); trace("panelTest.width = " + panelTest.width); trace("panelTest.height = " + panelTest.height); } And this is the result when run: ui.width = 0 ui.height = 0 loader.width = 571 loader.height = 411 panelTest.width = 480 panelTest.height = 320

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How should I implement reverse AJAX in a Django application?

- by Carson Myers

How should I implement reverse AJAX when building a chat application in Django? I've looked at Django-Orbited, and from my understanding, this puts a comet server in front of the HTTP server. This seems fine if I'm just running the Django development server, but how does this work when I start running the application from mod_wsgi? How does having the orbited server handling every request scale? Is this the correct approach? I've looked at another approach (long polling) that seems like it would work, although I'm not sure what all would be involved. Would the client request a page that would live in its own thread, so as not to block the rest of the application? Would it even block? Wouldn't the script requested by the client have to continuously poll for information? Which of the approaches is more proper? Which is more portable, scalable, sane, etc? Are there other good approaches to this (aside from the client polling for messages) that I have overlooked?

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best way to pick a random subset from a collection?

- by Tom

I have a set of objects in a Vector from which I'd like to select a random subset (e.g. 100 items coming back; pick 5 randomly). In my first (very hasty) pass I did an extremely simple and perhaps overly clever solution: Vector itemsVector = getItems(); Collections.shuffle(itemsVector); itemsVector.setSize(5); While this has the advantage of being nice and simple, I suspect it's not going to scale very well, i.e. Collections.shuffle() must be O(n) at least. My less clever alternative is Vector itemsVector = getItems(); Random rand = new Random(System.currentTimeMillis()); // would make this static to the class List subsetList = new ArrayList(5); for (int i = 0; i < 5; i++) { // be sure to use Vector.remove() or you may get the same item twice subsetList.add(itemsVector.remove(rand.nextInt(itemsVector.size()))); } Any suggestions on better ways to draw out a random subset from a Collection?

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