Portal:HowTo Demos

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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.

Related topics 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.