Using character callback

support
1

wayasam wrote on Saturday, September 21, 2013:

Hello! I haven’t been able to find any examples on how to implement a character callback function, so I am here to ask for review about my implementation. I want to store all the printable characters in a std::wstring if the player has opened the chat window. This is how I implemented the function, but it seems kind of stupid to me:

http://pastebin.com/zhUcmsS5

Can you guys tell me a better way to do this?

2

dougbinks wrote on Sunday, September 22, 2013:

Copying the code you linked to below to make this easier to follow:

void Text_Callback(GLFWwindow* window,unsigned int character)
{
	if(this_shared->is_chatting)
	{
		wchar_t* input = new wchar_t[1];
		input[0]=character;
		std::wstring ws(input);
		this_shared->game_logic->chat_buffer->insert(this_shared->game_logic->chat_cursor_pos,input);
		delete [] input;
	}
}

This can indeed be simplified. There isn’t a constructor for wstring which takes a single character, so you need to append as follows:

void Text_Callback(GLFWwindow* window,unsigned int character)
{
	if(this_shared->is_chatting)
	{
		std::wstring ws;
		ws += character;
		this_shared->game_logic->chat_buffer->insert(this_shared->game_logic->chat_cursor_pos,input);
	}
}

Note that your original code has a buffer overrun issue as the array ‘input’ does not have a null terminator. You need to have it one longer than the characters inside with a 0 at the end. Additionally you don’t need to ‘new’ a small array, you can declare it on the stack as: ‘wchar_t input[2];’, and that way you don’t have to delete it.

3

dougbinks wrote on Sunday, September 22, 2013:

Also worth noting you could simplify things by having a function for chat buffer which takes a single character as input.

4

wayasam wrote on Sunday, September 22, 2013:

Thanks for your reply.

Yes there were a lot of unwanted memory garbage inserted to my string, beacuse of the lack of null terminator.

I used pastebin, because I was not able to find a clear example of how to insert code on the ‘Formatting Help’ page. Can you clarify this to me?

5

dougbinks wrote on Sunday, September 22, 2013:

To format for code I put a line of six ‘~’ characters before and after the code, with empty lines before and after the block. So:

[empty line]
[line of six ~]

[Code… as many lines as you want]
[line of six ~]
[empty line]