I have a customer with an application which makes heavy use of GDI calls for graphics rendering, and with a desire to migrate this application to OSX. Unfortunately, in this case, OSX has no GDI to call upon, and so the low level drawing functions must be replaced.

In the video, I demonstrate how to use FMX to perform simple drawing operations, similar to those that would have been done with the VCL TCanvas or GDI. As per request, these routines are placed into a separate unit as procedural code, though you could translate it to a more object-oriented approach if you’d prefer that.

[* Note *] This form of rendering is not the fastest performing. It will compare approximately to GDI rendering, however, it would not be sufficient for high-speed graphics as might be required for games applications. For those purposes, please see my posts on building a sprite engine.

Here we go…

And the source code can be downloaded here

Note!: In this video, and attached source code, I perform drawing operations outside of the OnPaint() event handler. This works on Windows because the DirectX context is persistent, however, under all other platforms rendering is done using OpenGL which encapsulates rendering operations between Begin…End calls. These calls prepare the OpenGL state machine for updates, and so you can’t render outside of them. Despite this error on my part, I believe this demonstration still illustrates the point I was trying to make with it.