From Xojo Documentation
New in 2021r3
A Button is the standard button used in desktop apps. Examples are a Default button, a Cancel button or a standard button.
To set an accelerator character, precede the character in the Caption with an ampersand. In order to show an ampersand in the Caption, use two ampersands in a row. The sets the accelerator to the "D" character:
The DesktopButton's Caption property can show a caption that uses an encoding that doesn't match the application’s region code (or while running within the IDE, the IDE's region code). For example, an English application can set a Japanese caption, as long as it first sets the button's FontName to Osaka.
If your button has a height greater than 22 pixels, on macOS it will not have the standard rounded appearance and will instead be drawn as a square button. This is a restriction of macOS.
Linux and Pi Button Height
On Linux and Pi you may find that the button height is not large enough to fit the text. This is because some themes will drastically increase the default font size for buttons causing it to exceed the size of the button. There are a couple things you can do to fix this. In the Opening event of the Button you can choose to make the button larger:
Or you can choose to make its font smaller:
The above numbers are for example. You will want to adjust them as appropriate for the theme being used.
You can also look up the best size to use based on the theme by using Declares. Refer to this example project to see how it is done: