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• backlight doesn't work on acer 5732z tried everything I can find

  - by Dude Random21

  Ok if you can solve my problem you're really really good. I want to run ubuntu 12.04 on my acer aspire 5732z I know (from research) that these computer's have issues with the backlight on ubuntu. So I tried a couple of solutions: The "sudo lightdm restart" method. I get no change at all. The "sudo setpci -s 00:02.0 F4.B=30" method. This so far has been the most effective, I first tried it in the F1 console right away I get the screen back, problem is going back to the desktop it goes back to being black. So I tried it from a terminal window and it works as well but as soon as I unplug my external monitor the screen turns black again and doesn't come back. If I plug the monitor back in the screen stays black and the only thing I see is the mouse pointer. From here I go back into console (which I am able to see) and reboot from there. The "sudo sed -i 's/GRUB_CMDLINE_LINUX=""/GRUB_CMDLINE_LINUX="acpi_osi=Linux"/g' /etc/default/grub" method. This one I got no instant change and after reboot still no change. I'm open to pretty much any suggestions you may have.

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• Calculate travel time on road map with semaphores

  - by Ivansek

  I have a road map with intersections. At intersections there are semaphores. For each semaphore I generate a red light time and green light time which are represented with syntax [R:T1, G:T2], for example: 119 185 250 A ------- B: [R:6, G:4] ------ C: [R:5, G:5] ------ D I want to calculate a car travel time from A - D. Now I do this with this pseudo code: function get_travel_time(semaphores_configuration) { time = 0; for( i=1; i<path.length;i++) { prev_node = path[i-1]; next_node = path[i]); cost = cost_between(prev_node, next_node) time += (cost/movement_speed) // movement_speed = 50px per second light_times = get_light_times(path[i], semaphore_configurations) lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light; // Lights cycle time light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } } return time; } So for distance 119 between A and B travel time is, 119/50 = 2.38s ( exactly mesaured time is between 2.5s and 2.6s), then we add time if we came at a red light when at B. If we came at a red light is calculated with lines: lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } This pseudo code doesn't calculate exactly the same times as they are mesaured, but the calculations are very close to them. Any idea how I would calculate this?

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• Ubuntu won't load, freezes on purple screen

  - by kara

  Last time I restarted my computer, I could not get Ubuntu to load; the screen would either go black, or would hang at the purple screen indefinitely. I have had some graphics problems in the past, but had put 'nomodeset' after 'quiet splash' in the grub command line, which at least let Ubuntu load. That doesn't work now, and doesn't work if I remove it. I looked up some answers, such as this one: Purple start screen - no splash screen However, when I enter the root in recovery mode in grub, I always get errors when I run those command lines and it won't let me modify the files. Also, if I run in recovery mode and then choose 'resume normal boot', it will continue. But instead of getting a usual interface, I get a black screen that asks for my username and password. I enter these, and it tells me I'm in Ubuntu 12.04, but I'm still on a black screen with texts. It also informs me that there are updates to install. When I use the command 'sudo apt-get update', it starts to retrieve the information, but then the screen goes blank after a couple of seconds and I can't do anything anymore. Any ideas?

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• How to pass one float as four unsigned chars to shader by glVertexPointAttrib?

  - by Kog

  For each vertex I use two floats as position and four unsigned bytes as color. I want to store all of them in one table, so I tried casting those four unsigned bytes to one float, but I am unable to do that correctly... All in all, my tests came to one point: GLfloat vertices[] = { 1.0f, 0.5f, 0, 1.0f, 0, 0 }; glEnableVertexAttribArray(0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), vertices); // VER1 - draws red triangle // unsigned char colors[] = { 0xff, 0, 0, 0xff, 0xff, 0, 0, 0xff, 0xff, 0, 0, // 0xff }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors); // VER2 - draws greenish triangle (not "pure" green) // float f = 255 << 24 | 255; //Hex:0xff0000ff // float colors2[] = { f, f, f }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors2); // VER3 - draws red triangle int i = 255 << 24 | 255; //Hex:0xff0000ff int colors3[] = { i, i, i }; glEnableVertexAttribArray(1); glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), colors3); glDrawArrays(GL_TRIANGLES, 0, 3); Above code is used to draw one simple red triangle. My question is - why do versions 1 and 3 work correctly, while version 2 draws some greenish triangle? Hex values are one I read by marking variable during debug. They are equal for version 2 and 3 - so what causes the difference?

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• SQL Source Control Contest

  - by Ajarn Mark Caldwell

  If you’re a regular reader of this blog, you know that I have written several posts about how important I think it is to protect your source code, to version it, and in particular, all the aspects I like about Red Gate’s SQL Source Control product.  But for a moment, let’s take a break from my writing and I want to hear your stories.  What nightmare situation are you in, or can you imagine, where source control for your database would save the world.  Or maybe your life is not so dramatic, but you do see a challenge that, if you just had a good tool like SQL Source Control, it would go much smoother.  What’s your pain?  You have read my writings, now tell me your story, and be in the running for a free copy of SQL Source Control from Red Gate. Yes, that’s right.  Although I am just a fan of Red Gate, they have authorized me to give out a handful of licenses to blog readers who are willing to share their story by posting a comment to this blog entry.  Simply add your comment below (be sure to include a valid email address in the box that asks for that) to be entered.  The contest starts immediately and over the next few days, the best stories will win.

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• Problem with alleg42.dll / program crashes / Allegro & Codeblocks

  - by user24152

  I'm having a serious problem with allegro. The program should display random pixels on the screen and when I build and run it I get the following error message: Below is the full code of my program: #include <stdio.h> #include <stdlib.h> #include <time.h> #include "allegro.h" #define Text_Color_Red makecol(255,0,0) int main() { int ret; int color_depth = 32; int x; int y; int red; int green; int blue; int color; //init allegro allegro_init(); //install keyboard install_keyboard(); //set color depth to 32 bits set_color_depth(color_depth); //init random seed srand(time(NULL)); //init video mode to 640 x 480 ret = set_gfx_mode(GFX_AUTODETECT_WINDOWED,640,480,0,0); if(ret !=0) { allegro_message(allegro_error); return 1; } //Display string textprintf(screen,font,0,0,10,0,Text_Color_Red,"Screen Resolution is: %dx%d -- Press ESC to quit !",SCREEN_W,SCREEN_H); //display pixels until ESC key is pressed //wait for keypress while(!key[KEY_ESC]) { //set a random location x = 10 + rand() % (SCREEN_W-20); y = 10 + rand() % (SCREEN_H-20); //set a random color red = rand() % 255; green = rand() % 255; blue = rand() % 255; color = makecol(red,green,blue); //draw the pixel putpixel(screen, x, y, color); } //quit allegro allegro_exit(); } END_OF_MAIN() Error message: AllegroPixels1.exe has encountered a problem and needs to close. We are sorry for the inconvenience. Error signature: AppName: allegropixels1.exe AppVer: 0.0.0.0 ModName: alleg42.dll ModVer: 4.2.3.0 Offset: 0006c05c I am using Windows XP inside a virtual machine under Parallels 7.0

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• Installing latest version of R-base

  - by Student

  I have been unsuccessfully trying to install the latest version (2.15.2) of r-base. Apparently, R package "Rcpp" would not install for R version 2.14.1 - the version that installs for me. I am not sure what/how/where to change my installation attempts which appear below. Please note that I am using ubuntu-12.04.1-server-i386. (1) ------------ The current installed version is R version 2.14.1 (2011-12-22) sudo apt-get install r-base Reading package lists... Done Building dependency tree Reading state information... Done r-base is already the newest version. (2) ------------ Including version information doesn't help: sudo apt-get install r-base=2.15.1-5ubuntu1 Reading package lists... Done Building dependency tree Reading state information... Done E: Version '2.15.1-5ubuntu1' for 'r-base' was not found (3) ------------- Changes based on CRAN Ubuntu instructions http://cran.r-project.org/bin/linux/ubuntu/README 3.1: Added to /etc/apt/sources.list deb http://lib.stat.cmu.edu/R/CRAN/bin/linux/ubuntu quantal/ 3.2: sudo apt-get update 3.3: sudo apt-get install r-base Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: r-base : Depends: r-base-core (= 2.15.2-1quantal2) but it is not going to be installed Depends: r-recommended (= 2.15.2-1quantal2) but it is not going to be installed Recommends: r-base-html but it is not going to be installed E: Unable to correct problems, you have held broken packages.

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• RasterizerState set to null after calling DrawText in Nuclex

  - by ProgrammerAtWork

  I have the following code in XNA: // class members Text t1; Text t2; Text t3; // init // Debugfont is size 24 vectorfont t1 = MM.DebugFont24.Fill("hello"); t1 = MM.DebugFont24.Extrude("hello"); t2 = MM.DebugFont24.Fill("hello"); t2 = MM.DebugFont24.Extrude("hello"); t3 = MM.DebugFont24.Fill("hello"); t3 = MM.DebugFont24.Extrude("hello"); // Draw TextBatch test = new TextBatch(MM.GD); test.DrawText(t1, Color.Red); test.DrawText(t2, Color.Red); test.DrawText(t3, Color.Red); test.End(); //After the second call to the TextBatch, RasterizerState of the GraphicsDevice is set to null //But I don't get any runtime errors or any indication of that something is wrong. Is this supposed to happen? Or am I doing something wrong? I've discovered that this happened because culling was set to None when I was rendering textures

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• What’s ‘default’ for?

  - by Strenium

  Sometimes there's a need to communicate explicitly that value variable is yet to be "initialized" or in other words - we’ve never changed it from its' default value. Perhaps "initialized" is not the right word since a value type will always have some sort of value (even a nullable one) but it's just that - how do we tell? Of course an 'int' would be 0, an 'enum' would the first defined value of a given enum and so on – we sure can make this kind of check "by hand" but eventually it would get a bit messy. There's a more elegant way with a use of little-known functionality of: 'default'Let’s just say we have a simple Enum: Simple Enum namespace xxx.Common.Domain{    public enum SimpleEnum    {        White = 1,         Black = 2,         Red = 3    }}   In case below we set the value of the enum to ‘White’ which happens to be a first and therefore default value for the enum. So the snippet below will set value of the ‘isDefault’ Boolean to ‘true’. 'True' Case SimpleEnum simpleEnum = SimpleEnum.White;bool isDefault; /* btw this one is 'false' by default */ isDefault = simpleEnum == default(SimpleEnum) ? true : false; /* default value 'white' */   Here we set the value to ‘Red’ and ‘default’ will tell us whether or not this the default value for this enum type. In this case: ‘false’. 'False' Case simpleEnum = SimpleEnum.Red; /* change from default */isDefault = simpleEnum == default(SimpleEnum) ? true : false; /* value is not default any longer */ Same 'default' functionality can also be applied to DateTimes, value types and other custom types as well. Sweet ‘n Short. Happy Coding!

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• How to make backlight work on Acer 5732z?

  - by Dude Random21

  I want to run 12.04 on my Acer Aspire 5732z. I know from research that these computers have issues with the backlight on Ubuntu. So I tried a couple of solutions: The sudo lightdm restart method. I get no change at all. The sudo setpci -s 00:02.0 F4.B=30 method. This so far has been the most effective. I first tried it in the F1 console, right away I get the screen back, problem is going back to the desktop it goes back to being black. So I tried it from a terminal window and it works as well but as soon as I unplug my external monitor the screen turns black again and doesn't come back. If I plug the monitor back in the screen stays black and the only thing I see is the mouse pointer. From here I go back into console (which I am able to see) and reboot from there. The sudo sed -i 's/GRUB_CMDLINE_LINUX=""/GRUB_CMDLINE_LINUX="acpi_osi=Linux"/g /etc/default/grub method. This one I got no instant change and after reboot still no change. I'm open to pretty much any suggestions you may have.

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• Trouble installing gnome-shell-extensions-user-theme, dependency/PPA conflict?

  - by Drex

  I installed gnome tweak tool, and am trying to set up custom themes and whatnot. So, trying to install gnome-shell-extensions-user-theme. me@computer:~$ sudo apt-get install gnome-shell-extensions-user-theme [sudo] password for me: Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: gnome-shell-extensions-user-theme : Depends: gnome-shell-extensions-common but it is not going to be installed E: Unable to correct problems, you have held broken packages. Not going to be installed? Okay, let's see about that... me@computer:~$ sudo apt-get install gnome-shell-extensions-common Reading package lists... Done Building dependency tree Reading state information... Done gnome-shell-extensions-common is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Wait, what? Broken packages? Ruh Roh! Seems to me it might be a PPA contradiction problem or something, but I'm tired of trashing my installs. Kinda lost here. Any ideas? Output of sudo apt-get install -f drex@U110:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

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• How should I compress a file with multiple bytes that are the same with Huffman coding?

  - by Omega

  On my great quest for compressing/decompressing files with a Java implementation of Huffman coding (http://en.wikipedia.org/wiki/Huffman_coding) for a school assignment, I am now at the point of building a list of prefix codes. Such codes are used when decompressing a file. Basically, the code is made of zeroes and ones, that are used to follow a path in a Huffman tree (left or right) for, ultimately, finding a byte. In this Wikipedia image, to reach the character m the prefix code would be 0111 The idea is that when you compress the file, you will basically convert all the bytes of the file into prefix codes instead (they tend to be smaller than 8 bits, so there's some gain). So every time the character m appears in a file (which in binary is actually 1101101), it will be replaced by 0111 (if we used the tree above). Therefore, 1101101110110111011011101101 becomes 0111011101110111 in the compressed file. I'm okay with that. But what if the following happens: In the file to be compressed there exists only one unique byte, say 1101101. There are 1000 of such byte. Technically, the prefix code of such byte would be... none, because there is no path to follow, right? I mean, there is only one unique byte anyway, so the tree has just one node. Therefore, if the prefix code is none, I would not be able to write the prefix code in the compressed file, because, well, there is nothing to write. Which brings this problem: how would I compress/decompress such file if it is impossible to write a prefix code when compressing? (using Huffman coding, due to the school assignment's rules) This tutorial seems to explain a bit better about prefix codes: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html but doesn't seem to address this issue either.

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• Seek first to understand, then to be understood

  - by BuckWoody

  One of the most important (and most difficult) lessons for a technical professional to learn is to not jump to the solution. Perhaps you’ve done this, or had it happen to you. As the person you’re “listening” to is speaking, your mind is performing a B-Tree lookup on possible solutions, and when the final node of the B-Tree in your mind is reached, you blurt out the “only” solution there is to the problem, whether they are done or not. There are two issues here – both of them fatal if you don’t factor them in. First, your B-Tree may not be complete, or correct. That of course leads to an incorrect response, which blows your credibility. People will not trust you if this happens often. The second danger is that the person may modify their entire problem with a single word or phrase. I once had a client explain a detailed problem to me – and I just KNEW the answer. Then they said at the end “well, that’s what it used to do, anyway. Now it doesn’t do that anymore.” Which of course negated my entire solution – happily I had kept my mouth shut until they finished. So practice listening, rather than waiting for your turn to speak. Let the person finish, let them get the concept out, give them your full attention. They’ll appreciate the courtesy, you’ll look more intelligent, and you both may find the right answer to the problem. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Spritegroups and colorkeys

  - by Fristi

  I have a problem using spritegroups in pygame. In my situation I have 2 spritegroups, one for humans, one for "infected". A human is represented by a blue circle: image = pygame.Surface((32,32)) image.fill((255,255,255)) pygame.draw.circle(image,(0,0,255),(16,16),16) image = image.convert() image.set_colorkey((255,255,255)) An infected by a red one (same code, different color). I update my spritegroups as follows: self.humans.clear(self.screen, self.bg) self.humans.update(time_passed) self.humans.draw(self.screen) self.infected.clear(self.screen, self.bg) self.infected.update(time_passed) self.infected.draw(self.screen) Self.bg is defined: self.bg = pygame.Surface((SCREEN_WIDTH, SCREEN_HEIGHT)) self.bg.fill((255,255,255)) self.bg.convert() This all works, except that when a red circle overlaps with a blue one, you can see the white corners of the bounding box around the actual circle. Within a spritegroup it works, using the set_colorkey function. This does not happen with overlapping blue circles or overlapping red circles. I tried adding a colorkey to self.bg but that did not work. Same for adding a colorkey to self.screen.

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• Why does my system slow down or freeze when there is heavy disk activity?

  - by user72270

  Im a first-time user to Ubuntu-12.04 with WUBI installation. My NoteBook Information : Dell vostro 3450 : i5 2410m, 3 gb ram, intel hd3000, amd 6630m hybrid. Surfing and playing games works flawlessly, however, I'm having huge problems when installing applications and generally copying and moving files. When doing so, system is significantly slower and freezes quite often (Firefox gets bluish, sometimes even black n white). I would say that Ubuntu allocates too much resources on file transfers and installing, but even these tasks are very slow. Here is very specific example : today, i tried to move 6 GB file from win 7 installation. It was good at first, i jumped to firefox but after a while firefox started to randomly turn bluish and mouse was randomly stopping working. It was gradually worse and worse and it got to a point when firefox black n whited and mouse wasn't working at all. I raged and went for some meal, when i got back screen was black. It probably unlogged me due to inactivity, when i pushed random button to bring screen to life i had to wait few minutes to let it show me only my screen background. No log in screen, just background and working mouse. NoteBook fan was working at 100 % so I assumed that file transfer was going on and I left it to work. Nothing then changed for a full hour so I hard rebooted it. File transfer unsuccessful, It transfered hardly 2 gigs. Is this normal ? What to do in these situations ? It didn't let me load system manager and not even terminal. Thanks.

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• Drawing a TextBox in an extended Glass Frame (C# w/o WPF)

  - by Lazlo

  I am trying to draw a TextBox on the extended glass frame of my form. I won't describe this technique, it's well-known. Here's an example for those who haven't heard of it: http://www.danielmoth.com/Blog/Vista-Glass-In-C.aspx The thing is, it is complex to draw over this glass frame. Since black is considered to be the 0-alpha color, anything black disappears. There are apparently ways of countering this problem: drawing complex GDI+ shapes are not affected by this alpha-ness. For example, this code can be used to draw a Label on glass (note: GraphicsPath is used instead of DrawString in order to get around the horrible ClearType problem): public class GlassLabel : Control { public GlassLabel() { this.BackColor = Color.Black; } protected override void OnPaint(PaintEventArgs e) { GraphicsPath font = new GraphicsPath(); font.AddString( this.Text, this.Font.FontFamily, (int)this.Font.Style, this.Font.Size, Point.Empty, StringFormat.GenericDefault); e.Graphics.SmoothingMode = SmoothingMode.HighQuality; e.Graphics.FillPath(new SolidBrush(this.ForeColor), font); } } Similarly, such an approach can be used to create a container on the glass area. Note the use of the polygons instead of the rectangle - when using the rectangle, its black parts are considered as alpha. public class GlassPanel : Panel { public GlassPanel() { this.BackColor = Color.Black; } protected override void OnPaint(PaintEventArgs e) { Point[] area = new Point[] { new Point(0, 1), new Point(1, 0), new Point(this.Width - 2, 0), new Point(this.Width - 1, 1), new Point(this.Width -1, this.Height - 2), new Point(this.Width -2, this.Height-1), new Point(1, this.Height -1), new Point(0, this.Height - 2) }; Point[] inArea = new Point[] { new Point(1, 1), new Point(this.Width - 1, 1), new Point(this.Width - 1, this.Height - 1), new Point(this.Width - 1, this.Height - 1), new Point(1, this.Height - 1) }; e.Graphics.FillPolygon(new SolidBrush(Color.FromArgb(240, 240, 240)), inArea); e.Graphics.DrawPolygon(new Pen(Color.FromArgb(55, 0, 0, 0)), area); base.OnPaint(e); } } Now my problem is: How can I draw a TextBox? After lots of Googling, I came up with the following solutions: Subclassing the TextBox's OnPaint method. This is possible, although I could not get it to work properly. It should involve painting some magic things I don't know how to do yet. Making my own custom TextBox, perhaps on a TextBoxBase. If anyone has good, valid and working examples, and thinks this could be a good overall solution, please tell me. Using BufferedPaintSetAlpha. (http://msdn.microsoft.com/en-us/library/ms649805.aspx). The downsides of this method may be that the corners of the textbox might look odd, but I can live with that. If anyone knows how to implement that method properly from a Graphics object, please tell me. I personally don't, but this seems the best solution so far. Thanks!

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• TVirtualStringTree - resetting non-visual nodes and memory consumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paradigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• TVirtualStringTree - resetting non-visual nodes and memory comsumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paridigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• Using Effect For Fog of War

  - by Qua

  I'm trying to apply fog of war to areas on the screen not currently visible to the player. I do this by rendering the game content in one RenderTarget and the the fog of war into another, and then I merge them with an effect file that takes the color from the game RenderTarget and the alpha from the fog of war render target. The FOW RenderTarget is black where the FOW appears, and white where it doesn't. This does work, but it colors the fog of war (the unrevealed locations) white instead of the intended color of black. Before applying the effect I clear the backbuffer of the device to white. When I try to clear it to black, non of the fog of war appears at all, which I assume is a product of alpha blending with black. It works for all other colors, however - giving the resulting screen a tint of that color. How do I archieve a black fog while still being able to do alpha blending between the two render targets? The rendering code for applying the FOW: private RenderTarget2D mainTarget; private RenderTarget2D lightTarget; private void CombineRenderTargetsAndDraw() { batch.GraphicsDevice.SetRenderTarget(null); batch.GraphicsDevice.Clear(Color.White); fogOfWar.Parameters["LightsTexture"].SetValue(lightTarget); batch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend); fogOfWar.CurrentTechnique.Passes[0].Apply(); batch.Draw( mainTarget, new Rectangle(0, 0, batch.GraphicsDevice.PresentationParameters.BackBufferWidth, batch.GraphicsDevice.PresentationParameters.BackBufferHeight), Color.White ); batch.End(); } The effect file I'm using to apply the FOW: texture LightsTexture; sampler ColorSampler : register(s0); sampler LightsSampler = sampler_state{ Texture = <LightsTexture>; }; struct VertexShaderOutput { float4 Position : POSITION0; float2 TexCoord : TEXCOORD0; }; float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 { float2 tex = input.TexCoord; float4 color = tex2D(ColorSampler, tex); float4 alpha = tex2D(LightsSampler, tex); return float4(color.r, color.g, color.b, alpha.r); } technique Technique1 { pass Pass1 { PixelShader = compile ps_2_0 PixelShaderFunction(); } }

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• WPF ComboBox in Grid Issue

  - by Nathan

  I am trying to put a series of comboboxes in a grid and then I bind them to a list. For some reason unknown to me when I click the open button on the combobox nothing happens. If I move a comobobox outside the grid it opens just fine. Can someone please tell me what I am doing wrong here. It has to be something stupid because I've used comoboxes before just fine. Here is my xaml: <Grid> <Grid.RowDefinitions> <RowDefinition Height="*" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <GroupBox Header="Download Critera" Margin="70,30" Name="groupBox1" Grid.RowSpan="2"> <Grid Height="Auto" Name="grid1" Width="Auto" Margin="0" IsHitTestVisible="False"> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition Width="*" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <TextBlock Grid.Row="1" Margin="10,5,5,5" Name="textBlock1" Text="A:" Foreground="Black" VerticalAlignment="Center" FontSize="14" FontWeight="Bold" /> <TextBlock Grid.Row="2" Margin="10,5,5,5" Name="textBlock2" Text="B:" Foreground="Black" VerticalAlignment="Center" FontWeight="Bold" /> <TextBlock Grid.Row="3" Margin="10,5,5,5" Name="textBlock3" Text="C:" Foreground="Black" VerticalAlignment="Center" FontWeight="Bold" /> <TextBlock Grid.Row="4" Margin="10,5,5,5" Name="textBlock4" Foreground="Black" Text="D:" VerticalAlignment="Center" FontWeight="Bold" /> <TextBlock Grid.Row="5" Margin="10,5,5,5" Name="textBlock5" Text="E:" Foreground="Black" TextAlignment="Left" VerticalAlignment="Center" FontWeight="Bold" /> <ComboBox x:Name="cb1" Grid.Column="1" Grid.Row="1" Margin="5" MaxDropDownHeight="100" ItemsSource="{Binding Projects}"/> <ComboBox x:Name="cb2" Grid.Column="1" Grid.Row="2" Margin="5" MaxDropDownHeight="100" ItemsSource="{Binding Projects}"/> <ComboBox x:Name="cb3" Grid.Column="1" Grid.Row="3" Margin="5" MaxDropDownHeight="100" ItemsSource="{Binding Projects}"/> <ComboBox x:Name="cb4" Grid.Column="1" Grid.Row="4" Margin="5" MaxDropDownHeight="100" ItemsSource="{Binding Projects}"/> <ComboBox x:Name="cb5" Grid.Column="1" Grid.Row="5" Margin="5" MaxDropDownHeight="100" ItemsSource="{Binding Projects}"/> </Grid> </GroupBox> </Grid>

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• What's the best way to do base36 arithmetic in perl?

  - by DVK

  What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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• How to group items by date range in XSLT?

  - by glenatron

  I have a bunch of data that looks a little like this: <item> <colour>Red</colour> <date_created>2009-10-10 12:01:55</date_created> <date_sold>2009-10-20 22:32:12</date_sold> </item> <item> <colour>Blue</colour> <date_created>2009-11-01 13:21:00</date_created> <date_sold>2009-11-21 12:32:12</date_sold> </item> <item> <colour>Blue</colour> <date_created>2009-10-29 21:23:02</date_created> <date_sold>2009-10-20 02:02:22</date_sold> </item> <item> <colour>Red</colour> <date_created>2009-11-02 09:11:51</date_created> <date_sold>2009-11-20 09:15:53</date_sold> </item> <item> <colour>Red</colour> <date_created>2009-10-18 11:00:55</date_created> <date_sold>2009-10-20 11:12:22</date_sold> </item> Now what I would like to be able to do is to run that through an XSLT stylesheet such that I get ouput looking like this: Colour | In stock 1 week | In stock 2 weeks | In stock 3 weeks Red | 1 | 3 | 2 Blue | 0 | 2 | 1 Currently I have a stylesheet that uses basic muenchian grouping to show that 30% of stock was Red and 70% blue, but I can't see a way to find the number of nodes withing a given date range. Is there a way to use keys to select a range? Do I need to create some kind of intermediate data node? Is there a different route that shows I'm barking up the wrong tree with both those suggestions? Is this even possible with XSLT or do I need to find a way to change the data source?

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• How to generate and encode (for use in GA), random, strict, binary rooted trees with N leaves?

  - by Peter Simon

  First, I am an engineer, not a computer scientist, so I apologize in advance for any misuse of nomenclature and general ignorance of CS background. Here is the motivational background for my question: I am contemplating writing a genetic algorithm optimizer to aid in designing a power divider network (also called a beam forming network, or BFN for short). The BFN is intended to distribute power to each of N radiating elements in an array of antennas. The fraction of the total input power to be delivered to each radiating element has been specified. Topologically speaking, a BFN is a strictly binary, rooted tree. Each of the (N-1) interior nodes of the tree represents the input port of an unequal, binary power splitter. The N leaves of the tree are the power divider outputs. Given a particular power divider topology, one is still free to map the power divider outputs to the array inputs in an arbitrary order. There are N! such permutations of the outputs. There are several considerations in choosing the desired ordering: 1) The power ratio for each binary coupler should be within a specified range of values. 2) The ordering should be chosen to simplify the mechanical routing of the transmission lines connecting the power divider. The number of ouputs N of the BFN may range from, say, 6 to 22. I have already written a genetic algorithm optimizer that, given a particular BFN topology and desired array input power distribution, will search through the N! permutations of the BFN outputs to generate a design with compliant power ratios and good mechanical routing. I would now like to generalize my program to automatically generate and search through the space of possible BFN topologies. As I understand it, for N outputs (leaves of the binary tree), there are $C_{N-1}$ different topologies that can be constructed, where $C_N$ is the Catalan number. I would like to know how to encode an arbitrary tree having N leaves in a way that is consistent with a chromosomal description for use in a genetic algorithm. Also associated with this is the need to generate random instances for filling the initial population, and to implement crossover and mutations operators for this type of chromosome. Any suggestions will be welcome. Please minimize the amount of CS lingo in your reply, since I am not likely to be acquainted with it. Thanks in advance, Peter

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• Idiomatic use of auto_ptr to transfer ownership to a container

  - by heycam

  I'm refreshing my C++ knowledge after not having used it in anger for a number of years. In writing some code to implement some data structure for practice, I wanted to make sure that my code was exception safe. So I've tried to use std::auto_ptrs in what I think is an appropriate way. Simplifying somewhat, this is what I have: class Tree { public: ~Tree() { /* delete all Node*s in the tree */ } void insert(const string& to_insert); ... private: struct Node { ... vector<Node*> m_children; }; Node* m_root; }; template<T> void push_back(vector<T*>& v, auto_ptr<T> x) { v.push_back(x.get()); x.release(); } void Tree::insert(const string& to_insert) { Node* n = ...; // find where to insert the new node ... push_back(n->m_children, auto_ptr<Node>(new Node(to_insert)); ... } So I'm wrapping the function that would put the pointer into the container, vector::push_back, and relying on the by-value auto_ptr argument to ensure that the Node* is deleted if the vector resize fails. Is this an idiomatic use of auto_ptr to save a bit of boilerplate in my Tree::insert? Any improvements you can suggest? Otherwise I'd have to have something like: Node* n = ...; // find where to insert the new node auto_ptr<Node> new_node(new Node(to_insert)); n->m_children.push_back(new_node.get()); new_node.release(); which kind of clutters up what would have been a single line of code if I wasn't worrying about exception safety and a memory leak. (Actually I was wondering if I could post my whole code sample (about 300 lines) and ask people to critique it for idiomatic C++ usage in general, but I'm not sure whether that kind of question is appropriate on stackoverflow.)

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• jQuery UI problem: why do the elements go flying around the screen?

  - by George Edison

  Yes, I know the title sounds a little suspicious. I will try to explain this the best I can... The code below is supposed to have the blue div slide down beside the red div. The first time you hit the Show the div button, it works. Also, the Hide the div works. Then when I click to show the div again, it appears to the right of where it is supposed to be! Why is this?!? Note: You can find a live example of the code here <html> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>Demo</title> <style type='text/css'> #red { background-color: red; width: 200px; height: 150px; position: absolute; } #blue { background-color: blue; width: 150px; height: 200px; position: absolute; display: none; } #tester_1 { top: 300px; left: 300px; position: absolute; } #tester_2 { top: 350px; left: 300px; position: absolute; } </style> </head> <script type="text/javascript" src="jquery.js"></script> <script type='text/javascript'> function Show() { $('#blue').position({ of: $('#red'), my: 'left top', at: 'right top'}).slideDown(); } function Hide() { $('#blue').hide(); } </script> <body> <div id='red'></div> <div id='blue'></div> <button id='tester_1' onclick='Show()'>Show the <kbd>div</kbd></button> <button id='tester_2' onclick='Hide()'>Hide the <kbd>div</kbd></button> </body> </html>

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