Gambas Examples

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"Gambas Examples" is a Piga Software project to help newcomers learn the Gambas language.

These examples are largely concerned with game development.

You may use the following example codes on this page anyway you want - they are public domain.

Contents

Source Code Examples

How To Add Comments

Comments are invaluable ways to keep code organized and help other programmers. To add them to Gambas code you need to start them with an "'":

 'This is a comment.
 PUBLIC SUB Form_Open()
 'The above and bellow lines are actual code.
 END

Source(s): Source Code solutions

Hello World

To create venerable "Hello World" application add this code to the start up form's .class file:

 PUBLIC SUB Form_Open()
 
   Message("Hello World!")
 
 END

Linking Two Forms

To make one form ("FOne") link to another form ("FTwo") with a button ("BLink") add this to "FOne"'s .class file:

 PUBLIC SUB BLink_MouseDown()
 
   FTwo.Show
 
 END

To close a form, try this:

   FTwo.Close

Label Text Manipulation

To make a label ("LText") on a form ("FOne") change it's text with a click of a button ("BChange") add this to "FOne"'s .class file:

 PUBLIC SUB BLink_MouseDown()
 
   LText.text = "The Label now has different text"
 
 END

Object Picture Manipulation

Make a picture box ("PicBox") on a form as well as a button ("BChange"), and have a picture ("NewImage.png") in your project's directory.

 PUBLIC SUB BChange_MouseDown()
 
   PicBox.Picture = Picture["NewImage.png"]
 
 END

Form Colour Manipulation

To change the background colour of a form, create a button called "BChange" and add this code:

 PUBLIC SUB BChange_MouseDown()
 
   Form.BackColor = &H000000&
 
 END

This changes the from's background colour to black. This works to change any object's hexadecimal colour setting.

Common Hexadecimal Colours
  Black: &H000000&
  White: &HFFFFFF&
  Red: &HFF0000&
  Blue: &H0000FF&
  Purple: &H55007F&
  Green: &H00AA00&
  Yellow: &HFFFF00&
  Orange: &HFF5500&
  Pink: &HFF557F&
  Grey: &H787878&
  Light Blue: &H00AAFF&
  Light Green: &H55FF00&
  Light Grey: &HACACAC&

Probability Example

You can use probability to make Gambas randomly display a message box. If you add this code to a form's .class file, it will make it so that if you click a button ("BDice") it will randomly pick a message box:

 PUBLIC Dice AS Integer
 
 PUBLIC SUB BDice_Click()
 
   RANDOMIZE 
 
 Dice = Int(Rnd(0, 2))
 
 IF Dice = "1" THEN
 
   Message("You rolled a One")
 
 END IF
 
 IF Dice = "2" THEN
 
   Message("You rolled a Two")
 
 END IF
 
 END

Adding to a Numeric String

On a form ("FOne") have a label or other object ("LNumber") that has a .text variable and set it to "1" and have a button ("BAdd").

 PUBLIC SUB BAdd_MouseDown()
 
   LNumber.text = LNumber.text + "1"
 
 END

Moving an Object

On a form ("FOne") create an object (in this case a picture box: "PBPlayer") and four buttons: "BLeft", "BRight", "BUp", "BDown".

 PUBLIC SUB BLeft_MouseDown()
 
   PBPlayer.X = PBPlayer.X - "32"
 
 END
 
 PUBLIC SUB BRight_MouseDown()
 
   PBPlayer.X = PBPlayer.X + "32"
 
 END
 
 PUBLIC SUB BUp_MouseDown()
 
   PBPlayer.Y = PBPlayer.Y - "32"
 
 END
 
 PUBLIC SUB BDown_MouseDown()
 
   PBPlayer.Y = PBPlayer.Y + "32"
 
 END

Alternately, you can move an object with the keyboard's arrow keys:

PUBLIC SUB Form_Keypress()

SELECT Key.Code

 CASE Key.Left

  PBPlayer.X = PBPlayer.X - "32"

 CASE Key.Right

  PBPlayer.X = PBPlayer.X + "32"

 CASE Key.Up

  PBPlayer.Y = PBPlayer.Y - "32"

 CASE Key.Down

  PBPlayer.Y = PBPlayer.Y + "32"

END SELECT

END

Collecting an Object

Expand on Moving an Object and add another object ("PBCollectible"). Both MUST fit an even grid (32x32 or 48x48 recommended) and as such their dimensions should fit these parameters as well as their placement must be even to grid. Create a timer ("TmrCollisions") and add this code, set it to be enabled and a delay of "1".

 PUBLIC SUB TmrCollisions_Timer()
 
 IF PBCollectible.x = PBPlayer.x and PBCollectible.y = PBPlayer.y THEN
 
   PBCollectible.x = "-9000"
 
   Message("You have collected this object!")
 
 END IF
 
 END

Align to Grid

This code aligns an object ("PBObject") to a given grid, (in this case 48x48). This is needed to allow collisions to work.

PBObject.x = (Round (PBObject.x/"48"))*"48"

PBObject.y = (Round (PBObject.y/"48"))*"48"

This can also be used to move an object to the grid point nearest your cursor:

PBObject.X = (Round (Mouse.x/"48"))*"48"

PBObject.y = (Round (Mouse.y/"48"))*"48"

Changing a Border

You can change a given object's borders (in this case between plain and none) by using this code.

First put this on the very top of your class file:

CONST None AS Integer = 0
CONST Plain AS Integer = 1

Then you can use this to change your object's ("PBObject") border:

PBObject.Border = "1"

Or:

PBObject.Border = "0"

Animation

Animation is a somewhat more difficult in Gambas then in some other tools. You can not make an animated image file, like say a GIF or SVG, and then just import it into a picture box or load it into a drawing area and have the animation play. Instead you must specify slide transitions and timing in code, like so:

PUBLIC SUB Constants_Timer()
 
IF Object = Picture["Animation--4.png"] THEN

Object = Picture["Animation-5.png"]

END IF


IF Object = Picture["Animation-3.png"] THEN

Object = Picture["Animation-4.png"]

END IF


IF Object = Picture["Animation-2.png"] THEN

Object = Picture["Animation-3.png"]


END IF


IF Object = Picture["Animation-1.png"] THEN

Object = Picture["Animation-2.png"]

END IF
 
END

While this is a bit complicated, it does give you more control over the animation. Especially if you adjust the timer's delay within the IF blocks. Note the descending order for the IF blocks, this ordering is vital to getting the animation running.

Using Tags

Tags are a useful object property in that they have no function in rendering it. They are used to tag in a new function. For example if you are building a strategy game you would want a building to be labelled "Not-Built" (eg, a worker needs to finish it) or "Built" (once the building is fully functional). To do this simply write this out:

Building.Tag = "Not-Built"

This can then be used as a property for this object for uses such as:

IF Building.Tag = "Not-Built" THEN

It is also useful for direction tracking, by using a tag to say "Left" or "Right" it can make it easier to adapt conditions to an object's direction by using this property to signify it.

Playing Sounds and Music

The Simple DirectMedia Layer (SDL) can be used to add sounds and music to your project. First you first must make sure it is set to use the Gambas SDL sound component. You can do this by clicking the "Project" menu, then clicking on "Properties." A window will appear showing various properties of your Gambas project. To add components, click the "Components" tab. Scroll through the list that appears until you find one called "gb.sdl.sound". Click the check-box beside the text and click the "OK" button. Now place a sound file ("AudioFile.ogg") into your project's directory. Finally, add the code below to the top of your start-up form's class file. When you start your project you should hear a sound.

 PUBLIC AudioFile AS Sound
 
 PUBLIC SUB Form_Open()
 
   AudioFile = NEW Sound("audiofile.ogg")
 
   AudioFile.Play   
 
 END

The music channel is another useful function of the Gambas sound component. Using it you not only get to play a sound, but specify how often you want it to repeat and or when to pause or stop. This is useful for ambient sounds in games just as much as it is useful for music. Sadly there can only be one user of the music channel at one time, unlike the sound channel where you can have as many sounds as you want playing. However, it should be noted that you don't have to define anything for this channel unlike the sound equivalent. To use this channel, simply input this code and add a music or ambient sound file ("Music.ogg") to your project directory.

   Music.Load("Music.ogg")
   
   Music.Play(-1)

Note that "-1" is infinite loop, to specify it to repeat five times for example simply replace it with "5".

Scrolling

Scrolling is a useful way to make your game world or GUI larger than the screen. In order to allow you to have a scene the user can scroll through you need to put your objects into a container ("World") such as a panel if you are using picture boxes, labels or buttons for your interface or game. If you are using a drawing area to render your world then you can just move the drawing area itself. Make it so the container is as large as the environment you wish the user to scroll through - don't worry if it goes beyond the form's borders as that is the effect we are looking for. Once everything is in the given container you can put in this code to allow you to scroll through it all with the container:

   PUBLIC SUB Form_Keypress()
   
   SELECT Key.Code
   
   
   CASE Key.Left
   
   World.X = World.X + "48"
   
   
   CASE Key.Right
   
   World.X = World.X - "48"
   
   
   CASE Key.Down
   
   World.Y = World.Y - "48"
   
   
   CASE Key.Up
   
   World.Y = World.Y + "48"
   
   END SELECT
   
   END

This will allow the user to scroll around the container using the keyboard but you can move it around infinitely. If you wish to make it so you can't move it beyond certain parameters you will have to add the following code to you keyboard function.

Note: you will have to find, based on your own container, where the * Last Point Before Going Too Far * is. The "<" or ">" portions of the IFs are there in case it is not properly aligned to grid as it prevents the user from going too far past the end-points They are not strictly necessary. You can ensure that it is placed to grid yourself in the IDE or by using the align to grid code mentioned earlier.

   CASE Key.Left
   
   IF World.X = "0" OR World.X < "0" THEN
   
   ELSE
   
   World.X = World.X + "48"
   
   END IF
   
   
   CASE Key.Right
   
   IF World.X = "* Last Point Before Going Too Far *" OR World.X > "* Last Point Before Going Too Far *" THEN
   
   ELSE
   
   World.X = World.X - "48"
   
   END IF
   
   
   CASE Key.Down
   
   IF World.Y = "* Last Point Before Going Too Far *" OR World.Y > "* Last Point Before Going Too Far *" THEN
   
   ELSE
   
   World.Y = World.Y - "48"
   
   END IF
   
   
   CASE Key.Up
   
   IF World.Y = "0" OR World.Y < "0" THEN
   
   ELSE
   
   World.Y = World.Y + "48"
   
   END IF

To see this technique in action you can download the Lamp Refugee technical demo.

Gambas Project Examples

Gambler

Gambler Screenshot
Enlarge
Gambler Screenshot

Gambler is a probability example built with Gambas 2.7.0, and tested on Fedora 9 GNU/Linux. It allows you to gamble with virtual money (represented by a variable) using probability to simulate the throw of a die. Aspiring Gambas programmers should find this example useful in learning how to use probability and variable manipulation. The example is released Free Software under version three of the GNU General Public License.

Walk About

Walk About Screenshot
Enlarge
Walk About Screenshot

Walk About is a movement example built with Gambas 2.7.0, and tested on Fedora 9 GNU/Linux. It allows you to move a player (represented by picture box) around, as well as being blocked by walls. Aspiring Gambas programmers should find this example useful in learning how to use coordinates for object movement and control. The example is released Free Software under version three of the GNU General Public License.

String Fun

String Fun is a command line example built with Gambas 2.7.0, and tested on Fedora 9 GNU/Linux. It allows you to manipulate Strings to create a humorous paragraph. Aspiring Gambas programmers should find this example useful in learning how to manipulate strings and create simple command line programs. The example is released Free Software under version three of the GNU General Public License.

Mouse Movement

PPC Screenshot
Enlarge
PPC Screenshot

A tech demo created for the Gambas Genie engine project tested in Fedora 8 GNU/Linux. It shows you how to make a selectable object, and how to make it so you can drop a movement point with your mouse which the object will move too. The example is released Free Software under version three of the GNU General Public License.

Piga's Pumpkin Carving

PTDH Screenshot
Enlarge
PTDH Screenshot

Although not exactly a technical demo, it is still a fairly small program, though expanded notably in its next two versions. It will teach you the basics about using drawing areas, which support a wide variety of graphics features, including transparency! With version 2.0's inclusion of the "Creepy Jukebox" it is also a good guide to using the music channel and it also features global variables. The example is Free Software under the GNU General Public License version 3 though the music is under the Creative Commons Attribution 3.0 Unported license (not share-alike/copyleft license meaning it can be license changed).

Gambas Arcade Engine

Similar to Carving the games using this engine are somewhat larger then a code demo but still highly instructive and small enough to be easily examined. Studying them will teach you the basics of using drawing areas but more along the lines of a game instead of a graphics program. It will show you how to define game objects, render them and manipulate them in real time, use them in cut-scenes, as well as game logic functions such as collisions, score, projectiles, artificial intelligence, gravity and more! In addition each game comes with score board code which will teach you how to save and load information from text files. The article on the engine provides more complete technical information.

DONKEY.GB
Enlarge
DONKEY.GB

DONKEY.GB

Donkey (DONKEY.GB) is a modern free software GNU/Linux remake of the classic BASIC computer game Donkey. Written in Gambas it is based on the original by Bill Gates and Neil Konzen that was created to demonstrate the power of GW-BASIC for the original IBM PC. It was also ported to QBasic and a first-person version was later made for Visual Basic .Net. As an example it helps show basic collisions, computer-controlled movement patterns, keyboard control, treadmill-type scrolling and the basics of a Gambas "picture box"-type graphics engine.


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