text rendering chapterHEADmaster

1 files changed, 199 insertions, 0 deletions

diff --git a/text_rendering/text_rendering.c b/text_rendering/text_rendering.c
new file mode 100644
index 0000000..398b202
--- /dev/null
+++ b/text_rendering/text_rendering.c
@@ -0,0 +1,199 @@
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
+
+#include <ft2build.h>
+#include FT_FREETYPE_H
+
+#include "common.h"
+
+typedef struct {
+	U32 texture_id;
+	V2F size;
+	V2F bearing;
+	U32 advance;
+} char_t;
+
+char_t chars[128];
+static U32 vao, vbo;
+
+V2F get_text_size(const char *text, F32 scale)
+{
+	V2F size = {0};
+	for (const char *c = text; *c; c++) {
+		char_t ch = chars[(U8)*c];
+		F32 h = ch.size.y * scale;
+		if (h > size.y)
+			size.y = h;
+		size.x += (ch.advance >> 6) * scale;
+	}
+	return size;
+}
+
+void render_text(const char *text, U32 shader, V2F pos, F32 scale, V3F color)
+{
+	glUseProgram(shader);
+	shader_set_3fv(shader, "text_color", color);
+	glActiveTexture(GL_TEXTURE0);
+	glBindVertexArray(vao);
+	for (const char *c = text; *c; c++) {
+		char_t ch = chars[(U8)*c];
+		F32 x = pos.x + ch.bearing.x * scale;
+		F32 y = pos.y - (ch.size.y - ch.bearing.y) * scale;
+		F32 w = ch.size.x * scale;
+		F32 h = ch.size.y * scale;
+		F32 vertices[] = {
+			x,     y + h, 0.0f, 0.0f,
+			x,     y,     0.0f, 1.0f,
+			x + w, y,     1.0f, 1.0f,
+
+			x,     y + h, 0.0f, 0.0f,
+			x + w, y,     1.0f, 1.0f,
+			x + w, y + h, 1.0f, 0.0f,
+		};
+		glBindTexture(GL_TEXTURE_2D, ch.texture_id);
+		glBindBuffer(GL_ARRAY_BUFFER, vbo);
+		glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
+		glBindBuffer(GL_ARRAY_BUFFER, 0);
+		glDrawArrays(GL_TRIANGLES, 0, 6);
+		glBindTexture(GL_TEXTURE_2D, 0);
+		pos.x += (ch.advance >> 6) * scale;
+	}
+	glBindVertexArray(0);
+	glUseProgram(0);
+}
+
+void render_bounds(const char *text, U32 shader, V2F pos, F32 scale)
+{
+	glUseProgram(shader);
+	glBindVertexArray(vao);
+	V2F size = get_text_size(text, scale);
+	F32 x = pos.x;
+	F32 y = pos.y;
+	F32 w = size.x;
+	F32 h = size.y;
+	F32 vertices[] = {
+		x,     y + h, 0.0f, 0.0f,
+		x,     y,     0.0f, 1.0f,
+		x + w, y,     1.0f, 1.0f,
+
+		x,     y + h, 0.0f, 0.0f,
+		x + w, y,     1.0f, 1.0f,
+		x + w, y + h, 1.0f, 0.0f,
+	};
+	glBindBuffer(GL_ARRAY_BUFFER, vbo);
+	glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+	glDrawArrays(GL_TRIANGLES, 0, 6);
+	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+	glBindVertexArray(0);
+	glUseProgram(0);
+}
+
+int main(void)
+{
+	state_t state = init_state(1600, 800, 1);
+	init_glfw(&state);
+	init_gl();
+	glEnable(GL_BLEND);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+	FT_Library ft;
+	if (FT_Init_FreeType(&ft))
+		die("failed to initialize freetype");
+	FT_Face face;
+	const char *font_name = "ibmvga8x16.ttf";
+	if (FT_New_Face(ft, font_name, 0, &face))
+		die("failed to load %s", font_name);
+	FT_Set_Pixel_Sizes(face, 0, 48);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+	for (U32 c = 0; c < 128; c++) {
+		if (FT_Load_Char(face, c, FT_LOAD_RENDER))
+			die("failed to load X character");
+		U32 texture;
+		glGenTextures(1, &texture);
+		glBindTexture(GL_TEXTURE_2D, texture);
+		glTexImage2D(GL_TEXTURE_2D, 0, GL_RED,
+			     face->glyph->bitmap.width,
+			     face->glyph->bitmap.rows,
+			     0, GL_RED, GL_UNSIGNED_BYTE,
+			     face->glyph->bitmap.buffer);
+		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+		chars[c] = (char_t){
+			texture,
+		       	{face->glyph->bitmap.width, face->glyph->bitmap.rows},
+		       	{face->glyph->bitmap_left, face->glyph->bitmap_top},
+		       	face->glyph->advance.x
+		};
+
+	}
+	FT_Done_Face(face);
+	FT_Done_FreeType(ft);
+
+	U32 shader = add_shader("glyph.vert", "glyph.frag", 0);
+	MAT4 projection = ortho(0.0f, state.width, 0.0f, state.height, 0.0f, 1.0f);
+	glUseProgram(shader);
+	shader_set_mat4fv(shader, "projection", projection);
+	glUseProgram(0);
+
+	U32 bounds_shader = add_shader("bounds.vert", "bounds.frag", 0);
+	glUseProgram(bounds_shader);
+	shader_set_mat4fv(bounds_shader, "projection", projection);
+	glUseProgram(0);
+	
+	glGenVertexArrays(1, &vao);
+	glGenBuffers(1, &vbo);
+	glBindVertexArray(vao);
+	glBindBuffer(GL_ARRAY_BUFFER, vbo);
+	glBufferData(GL_ARRAY_BUFFER, sizeof(F32) * 6 * 4, 0, GL_DYNAMIC_DRAW);
+	glEnableVertexAttribArray(0);
+	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(F32), 0);
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glBindVertexArray(0);
+
+	glClearColor(0.16f, 0.16f, 0.16f, 1.0f);
+	F32 time = 0.0f;
+
+	V2F pos = {state.width / 2.0f, state.height / 2.0f};
+	V2F vel = {0.5f, 0.5f};
+
+	S32 show_bounds = 0;
+	const char *text = "foo, bar, nope";
+	F32 scale = 1.0f;
+	V2F size = get_text_size(text, scale);
+
+	while (!glfwWindowShouldClose(state.window)) {
+		handle_glfw_events(state.window, &state.input);
+		F32 dt = lock_framerate(60);
+
+		/* update */
+		F32 sin_value = 0.25f * sinf(time) + 0.75f;
+		F32 cos_value = 0.25f * cosf(time) + 0.75f;
+		V3F color = v3f(sin_value, cos_value, sin_value);
+		F32 speed = 256.0f;
+		V2F new_pos = v2f_add(pos, v2f_scalef(vel, speed * dt));
+		if (new_pos.x < 0.0f || new_pos.x + size.x > state.width)
+			vel.x = -vel.x;
+		if (new_pos.y < 0.0f || new_pos.y + size.y > state.height)
+			vel.y = -vel.y;
+		pos = new_pos;
+
+		if (key_first_press(state.input.jump))
+			show_bounds = !show_bounds;
+
+		time += dt;
+
+		/* render */
+		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+		render_text(text, shader, pos, scale, color);
+		if (show_bounds)
+			render_bounds(text, bounds_shader, pos, scale);
+
+		glfwSwapBuffers(state.window);
+	}
+
+	return 0;
+}