If you are adding lines really quickly to a TMemo you may run into this problem where it will cause an error or crash.
Head over and check out a blog post that shows how to patch FMX.Platform.Android to keep this from happening.
If you need to draw a Bezier curve there is a forum post up that explains you can use the CurveTo function to achieve this.
Head over and read the full forum thread for drawing a bezier curve with Firemonkey.
If you use TListView and you don’t care for the functionality where when you click the blank space under all items it selects the last item in the list then this fix is for you. You make this change in the FMX.ListView unit.
Head over and check out the blog post which features a code change to change this behavior.
There are a few ways to resize an image with Delphi Firemonkey but there is a forum thread over on Embarcadero where two different options are suggested. One option is to use CreateThumbnail and the second is to use DrawBitmap().
Head over and check out the forum thread about creating a thumbnail with Firemonkey.