[SDL] Making a GUI system in SDL

[Iain Bethune]

An often used solution to this problem (which applies generally to all  
sorts of callbacks) is to define the callback function as

OnClickEvent(Application *data){
	 data->OnClickEvent();
}

And have it as a static method, or a function outside of a class (C- 
style), but inside the function you call the instance method on the  
supplied object.

In general(e.g. in a library), the data would be a void* and you could  
cast it down to whatever class you want to call a method on.

Cheers

- Iain


On 11 Feb 2008, at 16:39, L-28C wrote:

> Hello everyone!
>
> My system works like this:
>
> Control (base class)
>  -- GUI (control container)
>  -- Button (sample control)
>  -- ...other controls
>
> And the event system works like this (in this case we'll use mouse
> clicks): the main application calls the "OnClick()" method in the GUI
> class with the mouse pointer's position as a parameter. The GUI class
> then sees which control was clicked (based on the mouse's position),  
> and
> calls the "OnClick()" method in that control (in this case we'll use a
> button). But here's the problem; how can this control (button) class  
> let
> the main application know that it was clicked?
>
> I tried to place a function pointer called "m_pfnOnClickEvent" and let
> the main application set a function to it when it creates the  
> button...
> but C++ doesn't let you put member methods onto function pointers, and
> my program is 100% object-oriented.
>
> Any ideas? Thanks!
>
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