Xojo has many good code examples,and over my many years of programming, here are some free mini-programs that have been created to help with a concept or theory. Feel free to download and use this free material as you see fit.

Transparent Background

This example writes a string of text and makes the background transparent. Here is the link to download the Transparent Background. The size and colour of the text can be changed and code is in the Canvas2 Paint event. The text can be changed at runtime or can remain static. Them important part was to make it so that the background colour surrounding the text remained transparent. 

Validate Textfield Numerical Data

Textfield validate makes only numbers can be allowed in the textfield. If the user tries to type a letter, then the data will be ignored. This may be helpful for formatting telephone number, spreadsheet data, or preventing problems where letters may cause unintended errors. Download here: TFValidate.

Thread On/Off

Working with threads has a small need-to-know part which requires the thread to use the App.YieldToNextThread command to allow updating, otherwise the thread uses all of the time to perform work and not allow updating by any of the controls. Here is the example to be downloaded: ThreadOnOff. Start the program and press the Start Threat 1 pushbutton and the counter begins counting. Press the Kill Thread button and the thread is permanently stopped. Pressing Suspend Thread will stop the thread and keep track of where it stopped. Resume Thread 1 continues running where last suspended. Sleep thread will stop the thread from running for 1 second (1000 milliseconds) and will continue from where it left off.