path: root/src/text.cc

#include "text.h"

#include <cstddef>
#include <cstring>

#include "atlas.h"
#include "cglm/types.h"
#include "cglm/vec2.h"
#include "freetype/freetype.h"
#include "freetype/fttypes.h"
#include "geometry.h"
#include "hash.h"
#include "shaders.h"
#include "utils.h"

// Linear filtering for smooth glyph rendering, clamped UVs to prevent atlas
// bleeding
static void wayc_font_context_sampler_desc(struct sg_sampler_desc* desc) {
  wayc_notnull(desc);

  desc->min_filter = SG_FILTER_LINEAR;
  desc->mag_filter = SG_FILTER_LINEAR;
  desc->wrap_u = SG_WRAP_CLAMP_TO_EDGE;
  desc->wrap_v = SG_WRAP_CLAMP_TO_EDGE;
}

static void wayc_font_context_layout(struct sg_vertex_layout_state* layout) {
  wayc_notnull(layout);

  layout->buffers[0].stride = sizeof(text_vertex_s);

  layout->attrs[ATTR_text_in_position].format = SG_VERTEXFORMAT_FLOAT2;
  layout->attrs[ATTR_text_in_position].buffer_index = 0;
  layout->attrs[ATTR_text_in_position].offset = offsetof(text_vertex_s, pos);

  layout->attrs[ATTR_text_in_uv].format = SG_VERTEXFORMAT_FLOAT2;
  layout->attrs[ATTR_text_in_uv].buffer_index = 0;
  layout->attrs[ATTR_text_in_uv].offset = offsetof(text_vertex_s, uv);
}

// Standard alpha blending for transparent text rendering
static void wayc_font_context_color(struct sg_color_target_state* color) {
  wayc_notnull(color);

  struct sg_blend_state blend = {};
  blend.enabled = true;
  blend.src_factor_rgb = SG_BLENDFACTOR_SRC_ALPHA;
  blend.dst_factor_rgb = SG_BLENDFACTOR_ONE_MINUS_SRC_ALPHA;
  blend.src_factor_alpha = SG_BLENDFACTOR_SRC_ALPHA;
  blend.dst_factor_alpha = SG_BLENDFACTOR_ONE_MINUS_SRC_ALPHA;

  color->blend = blend;
}

static void font_context_pipeline_desc(struct sg_pipeline_desc* desc,
                                       struct sg_shader shader) {
  wayc_notnull(desc);

  struct sg_vertex_layout_state vertex_layout = {};
  wayc_font_context_layout(&vertex_layout);

  struct sg_color_target_state color = {};
  wayc_font_context_color(&color);

  desc->layout = vertex_layout;
  desc->shader = shader;
  desc->index_type = SG_INDEXTYPE_UINT16;

  desc->colors[0] = color;
  desc->color_count = 1;
}

static void wayc_text_quad(struct text_vertex_s* verts, u16* indices, u16 base,
                           const struct glyph_s* glyph, vec2 cursor) {
  f32 x0 = WAYC_X(cursor) + WAYC_X(glyph->bearing);
  f32 y0 = WAYC_Y(cursor) - WAYC_Y(glyph->bearing);
  f32 x1 = x0 + WAYC_X(glyph->size);
  f32 y1 = y0 + WAYC_Y(glyph->size);

  struct quad_s quad;
  wayc_quad_init(&quad, x0, y0, x1, y1);

  vec2 uvs[WAYC_QUAD_NVERTS] = {
      {WAYC_X(glyph->uv0), WAYC_Y(glyph->uv0)},
      {WAYC_X(glyph->uv1), WAYC_Y(glyph->uv0)},
      {WAYC_X(glyph->uv1), WAYC_Y(glyph->uv1)},
      {WAYC_X(glyph->uv0), WAYC_Y(glyph->uv1)},
  };

  for (usize j = 0; j < WAYC_QUAD_NVERTS; j++) {
    glm_vec2_copy(quad.vertices[j], verts[base + j].pos);
    glm_vec2_copy(uvs[j], verts[base + j].uv);
  }

  for (usize j = 0; j < WAYC_QUAD_NINDICES; j++)
    indices[j] = (u16)(base + quad.indices[j]);
}

enum font_context_error_e wayc_font_context_init(
    struct font_context_s* context) {
  wayc_notnull(context);
  memset(context, 0, sizeof(*context));
  bool success = false;

  FT_Library ft;
  FT_Error fterr = FT_Init_FreeType(&ft);
  if (fterr) return FONT_CONTEXT_ERROR_LOAD_LIBRARY;
  wayc_defer_cond(FT_Done_FreeType(ft), success, true);

  struct sg_shader shader =
      sg_make_shader(text_shader_desc(sg_query_backend()));
  if (sg_query_shader_state(shader) != SG_RESOURCESTATE_VALID)
    return FONT_CONTEXT_ERROR_CREATE_SHADER;
  wayc_defer_cond(sg_destroy_shader(shader), success, true);

  struct sg_sampler_desc sampler_desc = {};
  wayc_font_context_sampler_desc(&sampler_desc);

  struct sg_pipeline_desc pipeline_desc = {};
  font_context_pipeline_desc(&pipeline_desc, shader);

  struct sg_sampler sampler = sg_make_sampler(&sampler_desc);
  if (sg_query_sampler_state(sampler) != SG_RESOURCESTATE_VALID)
    return FONT_CONTEXT_ERROR_CREATE_SAMPLER;

  wayc_defer_cond(sg_destroy_sampler(sampler), success, true);

  struct sg_pipeline pipeline = sg_make_pipeline(&pipeline_desc);
  if (sg_query_pipeline_state(pipeline) != SG_RESOURCESTATE_VALID)
    return FONT_CONTEXT_ERROR_CREATE_PIPELINE;

  context->ft = ft;
  context->sampler = sampler;
  context->pipeline = pipeline;

  success = true;

  return FONT_CONTEXT_ERROR_NONE;
}

void wayc_font_context_deinit(struct font_context_s* context) {
  wayc_notnull(context);

  sg_destroy_pipeline(context->pipeline);
  sg_destroy_sampler(context->sampler);
  FT_Done_FreeType(context->ft);
}

enum font_error_e wayc_font_init(struct font_s* font,
                                 struct font_context_s* context,
                                 const char* path, u32 font_size,
                                 u32 atlas_width, u32 atlas_height) {
  wayc_notnull(font);
  wayc_notnull(context);
  memset(font, 0, sizeof(*font));
  bool success = false;

  FT_Face face;
  FT_Error fterr = FT_New_Face(context->ft, path, 0, &face);
  if (fterr) return FONT_ERROR_LOAD_FACE;
  wayc_defer_cond(FT_Done_Face(face), success, true);

  fterr = FT_Set_Pixel_Sizes(face, 0, font_size);
  if (fterr) return FONT_ERROR_LOAD_FACE;

  struct atlas_s atlas;
  enum atlas_error_e aterr =
      wayc_atlas_init(&atlas, atlas_width, atlas_height, SG_PIXELFORMAT_R8);
  if (aterr) return FONT_ERROR_ATLAS_FAILED;

  font->context = context;
  font->face = face;
  font->atlas = atlas;
  wayc_hashmap_init(&font->cached);

  success = true;
  return FONT_ERROR_NONE;
}

enum font_error_e wayc_font_raster(struct font_s* font, codepoint_t codepoint,
                                   struct glyph_s* glyph) {
  wayc_notnull(font);
  wayc_notnull(glyph);

  // Return cached glyph if already rasterized to avoid redundant FreeType calls
  struct glyph_s got;
  if (wayc_hashmap_get(&font->cached, &codepoint, &got)) {
    *glyph = got;
    return FONT_ERROR_NONE;
  }

  u32 index = FT_Get_Char_Index(font->face, codepoint);
  if (index == 0) return FONT_ERROR_LOAD_GLYPH;

  FT_Error fterr = FT_Load_Glyph(font->face, index, FT_LOAD_RENDER);
  if (fterr) return FONT_ERROR_LOAD_GLYPH;

  FT_GlyphSlot slot = font->face->glyph;
  FT_Bitmap bitmap = slot->bitmap;

  vec2 bearing = {(f32)slot->bitmap_left, (f32)slot->bitmap_top};
  vec2 size = {(f32)bitmap.width, (f32)bitmap.rows};
  f32 advance = (f32)slot->advance.x / WAYC_SCALE;

  // Pack glyph bitmap into atlas texture and get UV coordinates
  vec2 uv0 = {0.0f, 0.0f};
  vec2 uv1 = {0.0f, 0.0f};

  if (bitmap.buffer != nullptr) {
    enum atlas_error_e aterr = wayc_atlas_insert(
        &font->atlas, bitmap.width, bitmap.rows, bitmap.buffer, &uv0, &uv1);
    if (aterr) return FONT_ERROR_ATLAS_FAILED;
  }

  glm_vec2_copy(uv0, got.uv0);
  glm_vec2_copy(uv1, got.uv1);
  glm_vec2_copy(size, got.size);
  glm_vec2_copy(bearing, got.bearing);
  got.advance = advance;

  wayc_hashmap_insert(&font->cached, &codepoint, &got);

  *glyph = got;
  return FONT_ERROR_NONE;
}

void wayc_font_deinit(struct font_s* font) {
  wayc_notnull(font);

  wayc_hashmap_deinit(&font->cached);
  wayc_atlas_deinit(&font->atlas);
  FT_Done_Face(font->face);
}

bool wayc_text_mesh_init(struct text_mesh_s* mesh, const char* text,
                         usize text_len, struct font_s* font, vec2 position) {
  wayc_notnull(mesh);
  wayc_notnull(text);
  wayc_notnull(font);
  memset(mesh, 0, sizeof(*mesh));

  bool success = false;

  usize nverts = text_len * WAYC_QUAD_NVERTS;
  usize nindices = text_len * WAYC_QUAD_NINDICES;

  usize bytes_verts = nverts * sizeof(struct text_vertex_s);
  usize bytes_indices = nindices * sizeof(u16);

  struct text_vertex_s* verts = (struct text_vertex_s*)mi_malloc(bytes_verts);
  wayc_defer_cond(mi_free(verts), success, true);

  u16* indices = (u16*)mi_malloc(bytes_indices);
  wayc_defer_cond(mi_free(indices), success, true);

  // Build quads for each character, advancing cursor by glyph width
  vec2 cursor;
  glm_vec2_copy(position, cursor);
  for (usize i = 0; i < text_len; i++) {
    codepoint_t codepoint = (codepoint_t)text[i];  // TODO: handle UTF-8

    struct glyph_s glyph;
    enum font_error_e err = wayc_font_raster(font, codepoint, &glyph);
    if (err != FONT_ERROR_NONE) return false;

    u16 base = (u16)(i * WAYC_QUAD_NVERTS);
    wayc_text_quad(verts, &indices[i * WAYC_QUAD_NINDICES], base, &glyph,
                   cursor);
    WAYC_X(cursor) += glyph.advance;
  }

  mesh->vertices = verts;
  mesh->vertex_count = nverts;
  mesh->indices = indices;
  mesh->index_count = nindices;

  success = true;
  return true;
}

void wayc_text_mesh_deinit(struct text_mesh_s* mesh) {
  wayc_notnull(mesh);

  if (mesh->vertices == nullptr || mesh->indices == nullptr) return;

  mi_free(mesh->vertices);
  mi_free(mesh->indices);

  mesh->vertices = nullptr;
  mesh->indices = nullptr;
}

static inline void wayc_text_buf_desc(struct sg_buffer_desc* vbo,
                                      struct sg_buffer_desc* ebo) {
  wayc_notnull(vbo);
  wayc_notnull(ebo);

  struct sg_buffer_usage usage = {};
  usage.vertex_buffer = true;
  usage.dynamic_update = false;
  usage.stream_update = true;
  usage.immutable = false;

  vbo->usage = usage;
  usage.vertex_buffer = false;
  usage.index_buffer = true;
  ebo->usage = usage;
}

bool wayc_text_group_init(struct text_group_s* group, struct font_s* font,
                          usize glyph_capacity) {
  wayc_notnull(group);
  wayc_notnull(font);
  memset(group, 0, sizeof(*group));

  bool success = false;

  usize nverts = glyph_capacity * WAYC_QUAD_NVERTS;
  usize nindices = glyph_capacity * WAYC_QUAD_NINDICES;

  usize verts_bytes = nverts * sizeof(struct text_vertex_s);
  usize indices_bytes = nindices * sizeof(u16);

  struct sg_buffer_desc vbo_desc = {};
  struct sg_buffer_desc ebo_desc = {};
  wayc_text_buf_desc(&vbo_desc, &ebo_desc);

  vbo_desc.size = verts_bytes;
  ebo_desc.size = indices_bytes;

  struct sg_buffer vbuf = sg_make_buffer(&vbo_desc);
  if (sg_query_buffer_state(vbuf) != SG_RESOURCESTATE_VALID) return false;
  wayc_defer_cond(sg_destroy_buffer(vbuf), success, true);

  struct sg_buffer ebuf = sg_make_buffer(&ebo_desc);
  if (sg_query_buffer_state(ebuf) != SG_RESOURCESTATE_VALID) return false;
  wayc_defer_cond(sg_destroy_buffer(ebuf), success, true);

  group->vbuf = vbuf;
  group->ebuf = ebuf;
  group->glyph_capacity = glyph_capacity;
  group->font = font;

  success = true;
  return success;
}

void wayc_text_group_begin(struct text_group_s* group) {
  wayc_notnull(group);

  group->index_count = 0;
  group->glyph_count = 0;
}

void wayc_text_group_end(struct text_group_s* group,
                         struct font_context_s* context) {
  wayc_notnull(group);
  wayc_notnull(context);
}

void wayc_text_group_deinit(struct text_group_s* group) {
  wayc_notnull(group);

  sg_destroy_buffer(group->vbuf);
  sg_destroy_buffer(group->ebuf);
}