If you create a new blank FMX application, the IDE will show you an empty form through the Multi-device Form Designer. The project is configured to target Win32 as the compiler target platform and the Style selector combobox is set to Windows. Our multi-platform application would be compiled for Win32 and the designer is set to preview the visual aspect of the form on the Windows platform, accordingly. If we drop a TButton instance on the form, we'll see it looking like a standard Windows button, as shown in the following screenshot:
The four platform styles provided by Embarcadero to target the four officially supported platforms (Windows, OS X/macOS, Android, and iOS) are listed in the Style selector combobox and you can select a different entry to have the Multi-device Form Designer immediately reflect the change and render your form with the new style.
In other words, the IDE (running on the Windows platform) is capable of previewing how...