DrawLines.cpp

#include "DrawLines.hpp"
#include "PathFont.hpp"
#include "ColorProgram.hpp"

#include "gl_errors.hpp"

#include <glm/gtc/type_ptr.hpp>

//All DrawLines instances share a vertex array object and vertex buffer, initialized at load time:

//n.b. declared static so they don't conflict with similarly named global variables elsewhere:
static GLuint vertex_buffer = 0;
static GLuint vertex_buffer_for_color_program = 0;

static Load< void > setup_buffers(LoadTagDefault, [](){
	//you may recognize this init code from DrawSprites.cpp:

	{ //set up vertex buffer:
		glGenBuffers(1, &vertex_buffer);
		//for now, buffer will be un-filled.
	}

	{ //vertex array mapping buffer for color_program:
		//ask OpenGL to fill vertex_buffer_for_color_program with the name of an unused vertex array object:
		glGenVertexArrays(1, &vertex_buffer_for_color_program);

		//set vertex_buffer_for_color_program as the current vertex array object:
		glBindVertexArray(vertex_buffer_for_color_program);

		//set vertex_buffer as the source of glVertexAttribPointer() commands:
		glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);

		//set up the vertex array object to describe arrays of PongMode::Vertex:
		glVertexAttribPointer(
			color_program->Position_vec4, //attribute
			3, //size
			GL_FLOAT, //type
			GL_FALSE, //normalized
			sizeof(DrawLines::Vertex), //stride
			(GLbyte *)0 + offsetof(DrawLines::Vertex, Position) //offset
		);
		glEnableVertexAttribArray(color_program->Position_vec4);
		//[Note that it is okay to bind a vec3 input to a vec4 attribute -- the w component will be filled with 1.0 automatically]

		glVertexAttribPointer(
			color_program->Color_vec4, //attribute
			4, //size
			GL_UNSIGNED_BYTE, //type
			GL_TRUE, //normalized
			sizeof(DrawLines::Vertex), //stride
			(GLbyte *)0 + offsetof(DrawLines::Vertex, Color) //offset
		);
		glEnableVertexAttribArray(color_program->Color_vec4);

		//done referring to vertex_buffer, so unbind it:
		glBindBuffer(GL_ARRAY_BUFFER, 0);

		//done setting up vertex array object, so unbind it:
		glBindVertexArray(0);
	}

	GL_ERRORS(); //PARANOIA: make sure nothing strange happened during setup
});


DrawLines::DrawLines(glm::mat4 const &world_to_clip_) : world_to_clip(world_to_clip_) {
}

void DrawLines::draw(glm::vec3 const &a, glm::vec3 const &b, glm::u8vec4 const &color) {
	attribs.emplace_back(a, color);
	attribs.emplace_back(b, color);
}

void DrawLines::draw_box(glm::mat4x3 const &mat, glm::u8vec4 const &color) {
	//draw cube as three edge sets:

	draw(mat * glm::vec4(-1.0f,-1.0f,-1.0f, 1.0f), mat * glm::vec4( 1.0f,-1.0f,-1.0f, 1.0f), color);
	draw(mat * glm::vec4(-1.0f, 1.0f,-1.0f, 1.0f), mat * glm::vec4( 1.0f, 1.0f,-1.0f, 1.0f), color);
	draw(mat * glm::vec4(-1.0f,-1.0f, 1.0f, 1.0f), mat * glm::vec4( 1.0f,-1.0f, 1.0f, 1.0f), color);
	draw(mat * glm::vec4(-1.0f, 1.0f, 1.0f, 1.0f), mat * glm::vec4( 1.0f, 1.0f, 1.0f, 1.0f), color);

	draw(mat * glm::vec4(-1.0f,-1.0f,-1.0f, 1.0f), mat * glm::vec4(-1.0f, 1.0f,-1.0f, 1.0f), color);
	draw(mat * glm::vec4( 1.0f,-1.0f,-1.0f, 1.0f), mat * glm::vec4( 1.0f, 1.0f,-1.0f, 1.0f), color);
	draw(mat * glm::vec4(-1.0f,-1.0f, 1.0f, 1.0f), mat * glm::vec4(-1.0f, 1.0f, 1.0f, 1.0f), color);
	draw(mat * glm::vec4( 1.0f,-1.0f, 1.0f, 1.0f), mat * glm::vec4( 1.0f, 1.0f, 1.0f, 1.0f), color);
	
	draw(mat * glm::vec4(-1.0f,-1.0f,-1.0f, 1.0f), mat * glm::vec4(-1.0f,-1.0f, 1.0f, 1.0f), color);
	draw(mat * glm::vec4( 1.0f,-1.0f,-1.0f, 1.0f), mat * glm::vec4( 1.0f,-1.0f, 1.0f, 1.0f), color);
	draw(mat * glm::vec4(-1.0f, 1.0f,-1.0f, 1.0f), mat * glm::vec4(-1.0f, 1.0f, 1.0f, 1.0f), color);
	draw(mat * glm::vec4( 1.0f, 1.0f,-1.0f, 1.0f), mat * glm::vec4( 1.0f, 1.0f, 1.0f, 1.0f), color);
}

void DrawLines::draw_text(std::string const &text, glm::vec3 const &anchor_in, glm::vec3 const &x, glm::vec3 const &y, glm::u8vec4 const &color, glm::vec3 *anchor_out) {

	glm::vec3 anchor = anchor_in;

	uint32_t start = 0;
	while (start < text.size()) {
		uint32_t end = start;
		uint32_t glyph = -1U;
		while (end < text.size()) {
			end += 1;
			auto f = PathFont::font.glyph_map.find(text.substr(start, end-start));
			if (f == PathFont::font.glyph_map.end()) {
				end -= 1;
				break;
			}
			glyph = f->second;
		}
		if (glyph == -1U) {
			assert(start == end);
			end += 1;
			//missing! draw a tofu:
			for (const auto &pt : {
				glm::vec2(0.1f, 0.1f), glm::vec2(0.6f, 0.1f),
				glm::vec2(0.6f, 0.1f), glm::vec2(0.6f, 0.9f),
				glm::vec2(0.9f, 0.6f), glm::vec2(0.1f, 0.9f),
				glm::vec2(0.1f, 0.9f), glm::vec2(0.1f, 0.1f)
			}) {
				attribs.emplace_back(anchor + pt.x * x + pt.y * y, color);
			}
			anchor += x * 0.6f;
		} else {
			for (uint32_t c = PathFont::font.glyph_coord_starts[glyph]; c + 1 < PathFont::font.glyph_coord_starts[glyph+1]; c += 2) {
				attribs.emplace_back(anchor + x * PathFont::font.coords[c] + y * PathFont::font.coords[c+1], color);
			}
			anchor += x * PathFont::font.glyph_widths[glyph];
		}
		start = end;
	}

	if (anchor_out) *anchor_out = anchor;
}

DrawLines::~DrawLines() {
	if (attribs.empty()) return;

	//based on DrawSprites.cpp :

	//upload vertices to vertex_buffer:
	glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer); //set vertex_buffer as current
	glBufferData(GL_ARRAY_BUFFER, attribs.size() * sizeof(attribs[0]), attribs.data(), GL_STREAM_DRAW); //upload attribs array
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	//set color_program as current program:
	glUseProgram(color_program->program);

	//upload OBJECT_TO_CLIP to the proper uniform location:
	glUniformMatrix4fv(color_program->OBJECT_TO_CLIP_mat4, 1, GL_FALSE, glm::value_ptr(world_to_clip));

	//use the mapping vertex_buffer_for_color_program to fetch vertex data:
	glBindVertexArray(vertex_buffer_for_color_program);

	//run the OpenGL pipeline:
	glDrawArrays(GL_LINES, 0, GLsizei(attribs.size()));

	//reset vertex array to none:
	glBindVertexArray(0);

	//reset current program to none:
	glUseProgram(0);
}