Firemonkey - Message Handling

5
votes

I'm currently trying to develop a project based upon Firemonkey. I'm using Firemonkey for it's UI features as the project consists of many smaller applications, each with a 3D aspect to it. I'm currently only developing/deploying to Windows with the FMX framework, but may go cross-platform at a later date.

I've gotten around most issues I've come across by building a VCL Windows application in the background to perform a very specific action, and then building an FMX frontend. However, this is only suitable when you only want to execute the application to perform that action it's designed to do, and thus can execute the application with parameters. In one of the applications, i've come upon the need to use messages (or something similar). For example, in my FMX application, if i click "button1", i want it to send a message to the background VCL application to perform "action1", rather than execute it with parameters.

A good example could be using the VCL TMediaPlayer in the background application, with the front-end FMX application being used to display the information and provide control of play, pause, etc. Such that it essentially becomes an FMX UI with VCL ability.

I've so far been unable to find anything on how messages (e.g. in VCL, they'd be done with "SendMessage" or "PostMessage" or something similar) are handled with Firemonkey, either through the local help file, or through extensive Googling. Everything i've turned up has been related to email (presumably because of the word "Message" in most of my search terms).

Can anyone point me in the right direction on how messages would be handled with Firemonkey/FMX?

Regards, Scott Pritchard

2
delphimessage-queuedelphi-xe2firemonkey
You do know that you can use VCL and FMX in the same app process, don't you? Well, it does take some extra work, but it is technically possible, and there are third-party libraries and articles that show you how to do it. So you wouldn't need to deal with window messages directly if you could simply call your VCL button's Click() method from a FMX UI event handler (or better, isolate your shared code in its own function that both VCL an FMX can call when needed). – Remy Lebeau

2 Answers

5
votes

My understanding is that Firemonkey is not based on traditional windows, so sending window messages to Firemonkey controls is not usually an option. Although some controls do use windows (most notibly, TCommonCustomForm), so you can use the FmxHandleToHWND() function in the FMX.Platform.Win unit to extract an HWND from a TFmxHandle when needed. I have no clue how to receive and custom process window messages in FMX controls, if that is even possible.

Firemonkey under Windows has access to the Win32 API, so there should be nothing stopping you from sending window messages to other windowed controls, such as your VCL UI. Include the Winapi.Windows unit in your uses clause to access Win32 API functions, just like you would in a VCL application.

UPDATE: because FireMonkey does not expose access to messages that are sent to a Form's window, you have to manually subclass the window in order to receive messages before FireMonkey sees them. You can override the Form's CreateHandle() method, call the inherited method first to create the window, then use FmxHandleToHWND() to get the HWND that you can subclass. Be sure to also override the DestroyHandle() method to remove the subclass before then calling inherited to release the HWND.

3
votes

Currently, FireMonkey doesn't have a message handler that you can use to send and post messages.

There is a possibility of hooking things up using listeners like FireMonkey works internally, but none of it is documented.

So, instead, here's what I've done:

I created my own custom "message" class. I create instances of the class and add them to a thread-safe list from any thread I need to. On the main thread, I have a timer that checks the list and processes the "messages".