Basic Plugin Example for C/C++

[CounterParry]

Here is a barebone example of creating a plugin for LOVR.

Inside the plugin folder create a new folder called "lovr-cppbase"

Inside the new folder create two files. The first file is "CMakeLists.txt":

project(lovr-cppbase)
cmake_minimum_required(VERSION 3.5.0)
add_library(cppbase MODULE cppbase.cpp)
set_target_properties(cppbase PROPERTIES PREFIX "")

The second file is "cppbase.cpp":

extern "C"
{
  #include "lua.h"
  #include "lauxlib.h"
  
  int one(lua_State *L) {
	  lua_pushstring(L, "one");
	  return 1;`
  }
  
  int two(lua_State *L) {
	  lua_pushstring(L, "two");
	  return 1;
  }
  
  int three(lua_State *L) {
	  lua_pushstring(L, "three");
	  return 1;
  }
  
  int four(lua_State *L) {
	  lua_pushstring(L, "four");
	  return 1;
  }
   
  int luaopen_cppbase(lua_State* L)
  {
	  const struct luaL_Reg cmds[] = {
	    	  {"one",   one},
    		  {"two",   two},
		  {"three", three},
		  {"four",  four},
		  {NULL,    NULL}
	  };
   
	  luaL_newlib(L, cmds);
	  return 1;
  }
}

Build "LOVR" and use this as the "main.lua" file:

local cppbase = require 'cppbase'
local a

function lovr.load()
	print('loaded')
end
 
function lovr.update(dt) 
  	a = cppbase.three() 
  	print('updating') 
end
 
function lovr.draw(pass)
	pass:text(a, 0, 1.7, -5)
	print('rendering')
end

[CounterParry]

Here is another example of a plugin that calls PASS:TEXT inside the cpp plugin to display HELLO WORLD.

Inside the plugin folder create a new folder called "lovr-cppbindings"

Inside the new folder create two files. The first file is "CMakeLists.txt":

project(lovr-cppbindings)
cmake_minimum_required(VERSION 3.5.0)
add_library(cppbindings MODULE cppbindings.cpp)
set_target_properties(cppbindings PROPERTIES PREFIX "")

The second file is "cppbindings.cpp":

extern "C"
{
	#include "lua.h"
	#include "lauxlib.h"
	#include "lualib.h"
}
#include <string>
 
//////////////////////////////////////////////////////////
 
void pass_text(lua_State *L, std::string text, int wrap, float halign, float valign)
{
	lua_getglobal(L, "pass_text");
	
	if (lua_isfunction(L, -1))
	{
		lua_pushstring(L, text.c_str());  // count 1
		lua_pushnumber(L, float(wrap));   // 2
		lua_pushnumber(L, float(halign)); // 3
		lua_pushnumber(L, float(valign)); // 4: this is the 4 used in the next line
		lua_pcall(L, 4, 0, 0);
	}
}
 
/////////////////////////////////////////////////////////
 
int load(lua_State *L)
{
	lua_pushstring(L, "load");
	return 1;
}
 
int update(lua_State *L)
{
	lua_pushstring(L, "update");
	return 1;
}

int draw(lua_State *L)
{
	lua_pushstring(L, "draw");
	
	pass_text(L, "Hello World.", 0, 1.7f, -5);
	
	return 1;
}
 
///////////////////////////////////////////////////////////
 
extern "C"
{
	int luaopen_cppbindings(lua_State* L)
	{
		const struct luaL_Reg cmds[] = {
		    	{"load",        load},
	    		{"update",      update},
			{"draw",        draw},
			{NULL,          NULL}
		};
		
		luaL_newlib(L, cmds);
		return 1;
	}
}

Build "LOVR" and use this as the "main.lua" file:

local cppbinding = require 'cppbindings'
local result 
local passlink 
local dtlink 
 
function pass_text(Text, Wrap, halign, valign) 
	passlink:text(Text, Wrap, halign, valign) 
end 
 
function lovr.load() 
	result = cppbinding.load() 
end 
 
function lovr.update(dt) 
	dtlink = dt 
	result = cppbinding.update() 
end 
 
function lovr.draw(pass) 
	passlink = pass 
	result = cppbinding.draw() 
end

[bjornbytes]

Nice! A small tip to make multi-line codeblocks more readable: Use three backticks (```) surrounding the piece of code:

```
code
goes
here
```

it'll look like this:

code
goes
here

You can even put a language after the first three backticks, like cpp or lua and GitHub will syntax highlight it:

-- start this codeblock with ```lua
function lovr.draw(pass)
  pass:text(a, 0, 1.7, -5)
end