Portal:HowTo Demos

This portal collects together in one place a significant number of short demonstration programs that have been posted on the Free Pascal and Lazarus Forums. Each of the demonstration programs generally provides a simple example of one particular development technique.

The Portal was the brainchild of Handoko who also provided the initial list of demonstration programs from the Forums.

Platform Portals: Android - Embedded - FreeBSD - iOS - Linux - Mac - WinCE - Windows

Topic Portals: New Users - Database Development - Game Development - Hardware and Robotics - HowTo Demos - Science and Technology - Web Development

Categories: Code - Code Snippets - Example Programs - Tutorials

Android

• OpenGL ES2 Circle. Requirement: LAMW. Drawing a circle using jCanvasES2.DrawLine instead of DrawCircle.
• OpenGL ES2 Rectangle. Requirement: LAMW. Drawing a rectangle using jCanvasES2.DrawPolyFill instead of DrawRect.
• Simple polygon animation. Requirement: LAMW. A simple animation using jCanvas.

File handling

• Binary file demo. How to show, append and delete data from a binary file.
• Text file demo. How to read and append data to a text file.
• Text File Demo #2. How to read and append data to a text file.
• Save component values to a file. Save text data easily using TStringList.SaveToFile.
• Load and show image from Resource Stream. How to add an image to a project resource and load it.
• Load a picture and show it. How to use OpenPictureDialog and LoadFromFile.
• Detect kind of file using DragAndDrop. How to detect the type of file using drag and drop.

General

• Drawing, moving, making connection between shapes. Shows TShape can be used for simple diagram drawing.
• Generating a huge text file. Demonstrates a technique for reducing program responsiveness to improve performance.
• Drag and drop shape. Drag and drop without using the built-in drag and drop feature.
• Minimize to TaskBar or Tray. A workaround to minimize to tray, not the best solution but works.
• TMyCircle Component. How to write your own component, the OOP way.
• Moving an Object by pressing a key. How to detect left/right shift key pressing.
• Pausing and Continuing an animation. How to pause and continue the animation.
• Control an Object's direction using the keyboard. How to detect user keyboard input.
• Convert Unicode to TBytes. How to use WideBytesOf and WideString functions.
• Communicate between two programs. This demo showing how to use simpleipc.
• Timer demo - How to use a TTimer control.
• Delete tags - How to delete HTML tags from text.

Graphics

• Get pixel color of an image. It may sound easy but actually it is not so easy.
• A very simple single player Pong game.
• Game Map Editor. A very basic load and edit map for game.
• Fading images using BGRABitmap. Requirement: BGRABitmap. Build your own slideshow and learn doing proportional scaling using aspect ratio of the picture.
• Center, resize image on the screen. Resize an image at the center position of the image.
• Simple animation. A very basic animation using a TTimer.
• Moving circles. How to fix an unwanted flickering effect.
• Change background color of an image. A not so accurate colorshift on an image.
• OpenGL 2D Text Using Textures. Requirement: LazOpenGLContext. How to write text in OpenGL using textures loaded from an image file.
• TCanvas Text. How to draw superscript and subscript text using TCanvas.
• Sticky Balls. Not so accurate inverse kinematics demo.
• GradientFill Rectangle. How to use GradientFill.
• Rock, Paper, Scissors. A simple game. Note for Unix/like operating systems: change the path delimiter to make the code work.
• Bullet and asteroid collision detection. How to do collision detection between a bullet and a polygonal object.
• Draw Circles Using CSMFL. Requirement: SFML/CSFML headers binding and CSFML libraries. How to use CSFML in FPC.
• Get pixel color of an image. How to load an image, show its information and the pixel color under the mouse pointer.
• Move a shape with a mouse. Move rectangles using a mouse.
• Selection Demo. A movable and resizeable selection.
• Sprite picking and moving. Hit Testing - a must learn topic for every graphics programmer.
• Dancing Balls. Balls that connect to each other.
• Screenshot capture. How to screenshot capture and crop.
• Remove image shadow. How to remove an image shadow and crop the image.
• Display image in console program. How to display an image in a console program (Windows API method).
• How to use bitmap.scanline.
• How to do offscreen rendering in Metal framework (macOS only).
• How to load a TImagelist at run time Multiplatform.

Networking

• Game Client and Server. The basics for building a client and server program.
• FTP Connect. Requirement: Synapse (can be installed using OPM). How to connect to a FTP server.
• HTML to Text. Requirement: fasthtmlparser. Extract data from a web page.
• Synapse TCP/IP client and server. Requirement: Synapse.
• Retrieve https web page. Cross-platform. No openssl DLLs/libraries need to be deployed. No third party components required.
• Simple webserver. Multi-threaded, cross-platform. No third party components required.
• File download - How to resume a file download.
• Obtain Redirected URL - How to obtain the redirected URL using TFPHTTPClient.
• Upload file - How to send a file to a web server using TFPHTTPClient.
• CAPTCHA implementation - How to implement a CAPTCHA.
• Retrieve https web page. Cross-platform. No openssl DLLs/libraries need to be deployed. No third party components required.

Retrieving system information

• System Information - Cross-platform unit to retrieve system information (CPU, memory, swap, operating system version etc).

User Interface

• Make your UI look interesting by adding some simple transition effects.
• Searchable StringGrid. Requirement: DBFLaz. Load data from a dbf, show it on a TStringGrid, search and highlight the cells. See here and here.
• Popup with ListBox. A custom popup form with a list box.
• Frameless popup. An alternative to ShowMessage.
• Drag a Button to a Panel. How to do drag and drop.
• Checkbox in a StringGrid. TStringGrid can show a checkbox instead of text.
• Darken a Form. Requirement: BGRAControls. How to darken a form.
• Darkening a Form. Requirement: BGRAControls. How to darken the Main Form when a modal window is shown.
• Open a Form beside the current Form. Programmatically open and close a form beside the current form.
• Scaling a Form. How to scale a form by using TForm.ScaleBy. Unfortunately it does not work correctly on Linux.
• Vertical Menu. How to make a vertical menu using TPanel and TScrollBox.
• Colorful Panels. How to use TControl.Align.
• Button with animation. How to show a TBitButton with animation images.
• Small icon in a TEdit. How to put an icon in a TEdit.
• StringGrid Cell Validation. Automatically set focus on the cell if it contains incorrect input.
• ListBox Work as Tabs For StringGrid. How to add items to a ListBox and StringGrid at runtime.
• Vertical Menu. A TVerticalMenu component.
• Color Fade ProgressBar. Requirement: BGRAControls. How to use TBGRAFlashProgressBar.
• Color Fade ProgressBar. How to color fade a progress bar without using a third party component.
• Task bar icon progress bar - Windows only.
• Progress in Status Bar - Cross-platform.
• ShowMessage in Console Mode. Requirement: LCL needed to be in the project’s required packages. How to use ShowMessage in a console mode program.
• Save & Restore StringGrid. How to save/load a grid’s content.
• StringGrid With Autosum Column. How to create a column that can auto calculate the row sum.
• Activate button with keypress. How to activate a button with a keypress.
• Detect user's language. How to detect the user's language (multi-platform method).
• Adding CHM Help. A demo project to call a CHM help file from three buttons as context-sensitive help (press F1), or from a help menu.
• GUI program that allocates a console whenever it needs one and frees it when it no longer needs it (Windows only).
• CHM Help Demo for an application.
• Speedbutton demonstration of using four arrow speedbuttons for moving an object. Shows how to handle speedbutton glyph states.
• Runtime forms How to create a form at runtime.
• TAchart example displaying the time on the X axis.
• How to hide application window on startup.
• How to use a Global HotKey to show a form (Windows only).
• How to resume a download.

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From the Free Pascal wiki, page "Portal:HowTo Demos", as it stood on 2022-03-27 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.