Vertex shader source code:
	#version 150
	in vec2 xy;
	in vec3 stw;
	out vec3 atlas;
	void main(void) {
		gl_Position = vec4(xy, 0, 1);
		atlas = stw;
	}

Geometry shader source code:
	#version 150
	layout (points) in;
	layout (triangle_strip, max_vertices = 4) out;
	in vec3 atlas[1];
	out vec2 texCoord;
	uniform mat4 matrix;
	uniform float lineHeight;
	void main(void) {
		gl_Position = matrix * vec4(gl_in[0].gl_Position.x + atlas[0].z, gl_in[0].gl_Position.y, 0, 1);
		texCoord = vec2(atlas[0].x+atlas[0].z, atlas[0].y + lineHeight);
		EmitVertex();

		gl_Position = matrix * vec4(gl_in[0].gl_Position.x + atlas[0].z, gl_in[0].gl_Position.y + lineHeight, 0, 1);
		texCoord = vec2(atlas[0].x+atlas[0].z, atlas[0].y);
		EmitVertex();

		gl_Position = matrix * vec4(gl_in[0].gl_Position.x, gl_in[0].gl_Position.y, 0, 1);
		texCoord = vec2(atlas[0].x, atlas[0].y + lineHeight);
		EmitVertex();

		gl_Position = matrix * vec4(gl_in[0].gl_Position.x, gl_in[0].gl_Position.y + lineHeight, 0, 1);
		texCoord = vec2(atlas[0].x, atlas[0].y);
		EmitVertex();

		EndPrimitive();
	}

Fragment shader source code:
	#version 150
	in vec2 texCoord;
	uniform sampler2D tex;
	uniform float opacity;
	out vec4 fragColor;
	void main(void) {
		float alpha = opacity * texelFetch(tex, ivec2(texCoord), 0).r;
		fragColor = vec4(0,0,0,alpha);
	}