Component Editor (FMX)
You can set IconFontsImageList properties using the classic Delphi Object inspector, in combination with the collection editor and the Structure editor, but it's most simple to use the advanced Image Editor supplied: double-click to the component to open the component editor as you can do with any Delphi component.
In this figure you can see the new advanced component editor for FMX version of IconFontsImageList:
At the top-left of the editor you can set the properties of your IconFontsImageList instance: the Size property is used only if you don't use the AutoResizeBitmap option, and the Width and Height property is useful only if you have font-icons with different sizes of width and height (like weathericons-regular-webfont.ttf present in Demo/Font folder).
AutoResizeBitmap option give to any components that required a bitmap of the Icon Font to get a perfect resized bitmap of the requested dimensions.
A big advantage when you use the component editor is that the Source and the Destination collections of the ImageList are always syncronized, one-by-one, so you can easily build your collection of icons, simply Adding/Insering or Deleting the icons in the editor.
At the center of the editor you can see a preview of the icons in the collection. Selecting an icon you can see the properties of the selected Source item and change it. When you change the IconName of a Source Icon also the Destination Icon acquire the same name.
You can also specify a different Font or Color on every single icon, so you can use different Fonts to build your icons.
Setting FontColor property at main level (ImageList) apply to all Icons present, but if you specifiy a specific color at Icon level (different from "none") the color of this Icon is preserved!
Using the bottom panel named "IconBuilder" you can simply build icons from a range of values (in Hexadecimal) as you can see in the figure.