lite-xl/lib/font_renderer/font_renderer_alpha.h

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#pragma once
#include "agg_basics.h"
#include "agg_conv_curve.h"
#include "agg_conv_transform.h"
#include "agg_gamma_lut.h"
#include "agg_font_freetype.h"
#include "agg_pixfmt_alpha8.h"
#include "agg_rasterizer_scanline_aa.h"
#include "agg_renderer_primitives.h"
#include "agg_renderer_scanline.h"
#include "agg_rendering_buffer.h"
#include "agg_scanline_u.h"
class font_renderer_alpha
{
typedef agg::pixfmt_alpha8 pixfmt_type;
typedef agg::renderer_base<pixfmt_type> base_ren_type;
typedef agg::renderer_scanline_aa_solid<base_ren_type> renderer_solid;
typedef agg::font_engine_freetype_int32 font_engine_type;
typedef agg::font_cache_manager<font_engine_type> font_manager_type;
font_engine_type m_feng;
font_manager_type m_fman;
// Font rendering options.
bool m_hinting;
bool m_kerning;
bool m_subpixel;
bool m_prescale_x;
bool m_font_loaded;
// Pipeline to process the vectors glyph paths (curves + contour)
agg::trans_affine m_mtx;
agg::conv_curve<font_manager_type::path_adaptor_type> m_curves;
agg::conv_transform<agg::conv_curve<font_manager_type::path_adaptor_type> > m_trans;
public:
typedef agg::pixfmt_alpha8::color_type color_type;
font_renderer_alpha(bool hinting, bool kerning, bool subpixel, bool prescale_x):
m_feng(),
m_fman(m_feng),
m_hinting(hinting),
m_kerning(kerning),
m_subpixel(subpixel),
m_prescale_x(prescale_x),
m_font_loaded(false),
m_curves(m_fman.path_adaptor()),
m_trans(m_curves, m_mtx)
{ }
int get_face_height() const {
return m_feng.face_height();
}
void get_font_vmetrics(double& ascender, double& descender) {
double current_height = m_feng.height();
m_feng.height(1.0);
ascender = m_feng.ascender();
descender = m_feng.descender();
m_feng.height(current_height);
}
float scale_for_em_to_pixels(float size) {
int units_per_em = m_feng.face_units_em();
if (units_per_em > 0) {
return size / units_per_em;
}
return 0.0;
}
bool load_font(const char *font_filename) {
if(m_feng.load_font(font_filename, 0, agg::glyph_ren_outline)) {
m_font_loaded = true;
m_feng.hinting(m_hinting);
}
return m_font_loaded;
}
void set_font_height(double height) {
const double scale_x = (m_prescale_x ? 100.0 : 1.0);
m_feng.height(height);
m_feng.width(height * scale_x);
}
template<class Rasterizer, class Scanline, class RenSolid>
void draw_codepoint(Rasterizer& ras, Scanline& sl,
RenSolid& ren_solid, const color_type color,
int codepoint, double& x, double& y, const int subpixel_scale)
{
const double scale_x = (m_prescale_x ? 100.0 : 1.0);
// Coefficient to scale back the glyph to the final scale.
const double cx_inv_scale = subpixel_scale / scale_x;
// Represent the delta in x scaled by scale_x.
double x_delta = 0;
double start_x = x;
const agg::glyph_cache* glyph = m_fman.glyph(codepoint);
if(glyph)
{
if(m_kerning)
{
m_fman.add_kerning(&x_delta, &y);
}
m_fman.init_embedded_adaptors(glyph, 0, 0);
if(glyph->data_type == agg::glyph_data_outline)
{
double ty = m_hinting ? floor(y + 0.5) : y;
ras.reset();
m_mtx.reset();
m_mtx *= agg::trans_affine_scaling(cx_inv_scale, 1);
m_mtx *= agg::trans_affine_translation(start_x + cx_inv_scale * x_delta, ty);
ras.add_path(m_trans);
ren_solid.color(color);
agg::render_scanlines(ras, sl, ren_solid);
}
y += glyph->advance_y;
x += cx_inv_scale * (x_delta + glyph->advance_x);
}
}
void clear(agg::rendering_buffer& ren_buf, const color_type color) {
pixfmt_type pf(ren_buf);
base_ren_type ren_base(pf);
ren_base.clear(color);
}
void render_codepoint(agg::rendering_buffer& ren_buf,
const color_type text_color,
double& x, double& y,
int codepoint, const int subpixel_scale)
{
if (!m_font_loaded) {
return;
}
agg::scanline_u8 sl;
agg::rasterizer_scanline_aa<> ras;
ras.clip_box(0, 0, ren_buf.width(), ren_buf.height());
agg::pixfmt_alpha8 pf(ren_buf);
base_ren_type ren_base(pf);
renderer_solid ren_solid(ren_base);
draw_codepoint(ras, sl, ren_solid, text_color, codepoint, x, y, subpixel_scale);
}
};