A Learning Experience

I recently needed a dead simple progress bar, where I could give it a display rectangle, min, max, and a value and show me something in game, but couldn’t find anything online. I ended up writing it myself, and thought I’d share what I came up with.

My goal was to create a single file I could drop into a project to allow me to draw a progress bar. All the projects I found involved using a texture as a separate file. I knew from a previous project that you could create that texture in-memory using the Texture2D.SetData() function, and that’s what I did.

I also wanted to provide a double border so I could put the progress bar on top of any background without having its border look invisible. If you’ve ever seen closed captioning disappear because of the background color, you know what I mean. But since not everyone needs a double border, I made sure you could turn it off.

Anyways, here’s and example of what you can do with the progress bar. (download the project for this at the bottom).

So the simple way to get a progress bar into your game is this:

1. Get the source code.

2. Add ProgressBar.cs to your XNA project. Note that I wrote this in 3.0, so make sure you’re on that version or higher.

3. Create an instance of a progress bar in your game1 class;

UI.ProgressBar progressBar;

4. In your LoadContent() function, set it to a new progressBar, and provide the rectangle you want it to lie in. You can also set the minimum, maximum, and value member variables here. The defaults are 0, 100, and 0, respectively.

progressBar = new UI.ProgressBar(this, new Rectangle(10, 10, 300, 16));
progressBar.minimum = 0;
progressBar.maximum= 10000;

5. In your Update() function, update the value of your progress bar if necessary, and then call the progress bar’s Update() function, providing the gameTime (gameTime is not currently used in the progress bar code, though).

progressBar.value = character.health;
progressBar.Update(gameTime);

6. In your Draw() function, call progressBar.Draw(), specifying a spriteBatch. Make sure you’re already called SpriteBatch.Begin() before calling the progress bar Draw() function.

progressBar.Draw(spriteBatch);

And that’s it!

Now, I’ve put quite a few customizable pieces in there. They are all commented in the progress bar code, in the “public members” region.

The one I’d like to talk about is the orientation. You can specify that the progress bar be vertical or horizontal, and in which direction it fill. This is specified at creation time in the ProgressBar constructor. See the orientation member variable for more info.

Here’s a list of the public variables in there now:

float minimum – Minimum value of the progress bar. Default is 0.0f.
float maximum – Maximum value of the progress bar. Default is 100.0f.
float value – Current progress value.

Int32 borderThicknessOuter – Outer border thickness. This is drawn within the bounds of the progress bar. Default is 3.
Int32 borderThicknessInner – Inner border thickness. This is drawn within the bounds of the progress bar. Default is 2.

Color borderColorOuter – Outer border color. Default is Gray.
Color borderColorInner – Inner border color. Default is Black
Color fillColor – Color of the progress section of the bar. Default is Dark Blue.
Color backgroundColor – Color of the background (unfilled) section of the progress bar. Default is White.
Orientation orientation – Gets the orientation of this progress bar. Set at creation time.

Note that you should be careful with the border thickness values. I didn’t add any checking to make sure the border isn’t overcrowding the actual progress bar. You could theoretically have a progress bar that is all border if you set the thicknesses too big.

Ok, so here’s a sample project. Hold space bar if you want to pause.

And here’s the bare ProgressBar.cs file (zipped, of course).

In working on my code for Conway’s Game of Life, I ran into a problem with the default bitmap scaling behavior in XNA. I’m generating a bitmap that I scale to the size of the window. When this bitmap is displayed, it is shown as a blurry mess:

Removing that doggone blending is actually quite simple. You have to modify your spriteBatch.begin() call, and modify the graphics device settings immediately after, like so:

The key in the spriteBatch.Begin() call is the SpriteSortMode. Setting this value to immediate causes any changes to the graphics device to be applied immediately. And we want to make a change, as you can see in the next line of code. I’m changing the magnification filter to TextureFilter.None because I don’t want it to blue anything. After this, you draw and scale your sprites like normal. The result looks like this:

ahh… much better!

XNA doesn’t automatically show you a mouse pointer within the game window. Solving this is easy. First, you need a position for your mouse. You’ll also need a 2d texture to display as your mouse pointer. Declare this within your game class:

Be sure to initialize it to zero. For simplicity, I also generate a simple red square texture to use as the mouse pointer. I’m doing all of this in the Initialize() function. In my (very short) experience with XNA, you’d want to initialize textures in the LoadContent() function, but this is not loading from a file, so it’s safe to do it all in the Initialize() function like this:

Now, in the Update() function, update your mouse position:

And finally, in the Draw() function, draw your sprite in a spritebatch:

Grab the sample project for this here.

I thought I should talk a little about the project I’m focusing on right now. I’m still spinning up on XNA, and I was reading an article somewhere recently that mentioned Conway’s Game of Life. I was never taught about this in school for some reason. What a wonderful little thing!

Anyways, I thought it would be fun to implement Conway’s Game of Life in XNA to give myself something tangible (in the software sense… what does that really mean, anyways?) to work on. I’ve already got a basic architecture done, but I want to write down some of the guidelines I’m trying to stick to. Just basic stuff, like:

What am I trying to learn?
– I want to learn about what it will take to implement a menu system in XNA.
– I want to learn about mouse interaction with an object (the game board) on the screen.

Which Game of Life algorithm should I use?
– a few are mentioned on the wiki page, notably hashlife. Since I’m not trying to learn about Game of Life specifics, I’m going to start with brute force with two 2d arrays (one for the current interation, and one for the next). It will give me a good quick start on my goal, and also give me a good baseline if I decide to optimize the algorithm.

What operations should I allow?
– a mouse click should turn a cell on or off. Hold and drag to fill or unfill cells under the mouse pointer
– spacebar should step to the next iteration.
– enter should run through iterations at the chosen speed (we’ll need a menu for that).

What should the menu contain?
– Options
– run speed
– window size
– colors?
– I’ll leave any other nifty stuff for later.

Things that would be very interesting to implement:
– the ability to move and zoom the camera around the grid with the mouse or keyboard
– some logic to move and zoom the camera automatically, and follow the most activity in the grid. One nasty corner case for this is any gliders that come off of the high activity areas. how do i know when to ignore them?

More to come later when I have more of this implemented.