lite/src/renderer.c

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C
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#include <stdio.h>
#include <stdbool.h>
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#include <assert.h>
#include <math.h>
#include "lib/stb/stb_truetype.h"
#include "renderer.h"
#define MAX_GLYPHSET 256
struct RenImage {
RenColor *pixels;
int width, height;
};
typedef struct {
RenImage *image;
stbtt_bakedchar glyphs[256];
} GlyphSet;
struct RenFont {
void *data;
stbtt_fontinfo stbfont;
GlyphSet *sets[MAX_GLYPHSET];
float size;
int height;
};
static SDL_Window *window;
static struct { int left, top, right, bottom; } clip;
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static void* check_alloc(void *ptr) {
if (!ptr) {
fprintf(stderr, "Fatal error: memory allocation failed\n");
exit(EXIT_FAILURE);
}
return ptr;
}
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static const char* utf8_to_codepoint(const char *p, unsigned *dst) {
unsigned res, n;
switch (*p & 0xf0) {
case 0xf0 : res = *p & 0x07; n = 3; break;
case 0xe0 : res = *p & 0x0f; n = 2; break;
case 0xd0 :
case 0xc0 : res = *p & 0x1f; n = 1; break;
default : res = *p; n = 0; break;
}
while (n--) {
res = (res << 6) | (*(++p) & 0x3f);
}
*dst = res;
return p + 1;
}
void ren_init(SDL_Window *win) {
assert(win);
window = win;
SDL_Surface *surf = SDL_GetWindowSurface(window);
ren_set_clip_rect( (RenRect) { 0, 0, surf->w, surf->h } );
}
void ren_update_rects(RenRect *rects, int count) {
SDL_UpdateWindowSurfaceRects(window, (SDL_Rect*) rects, count);
static bool initial_frame = true;
if (initial_frame) {
SDL_ShowWindow(window);
initial_frame = false;
}
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}
void ren_set_clip_rect(RenRect rect) {
clip.left = rect.x;
clip.top = rect.y;
clip.right = rect.x + rect.width;
clip.bottom = rect.y + rect.height;
}
void ren_get_size(int *x, int *y) {
SDL_Surface *surf = SDL_GetWindowSurface(window);
*x = surf->w;
*y = surf->h;
}
RenImage* ren_new_image(int width, int height) {
assert(width > 0 && height > 0);
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RenImage *image = malloc(sizeof(RenImage) + width * height * sizeof(RenColor));
check_alloc(image);
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image->pixels = (void*) (image + 1);
image->width = width;
image->height = height;
return image;
}
void ren_free_image(RenImage *image) {
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free(image);
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}
static GlyphSet* load_glyphset(RenFont *font, int idx) {
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GlyphSet *set = check_alloc(calloc(1, sizeof(GlyphSet)));
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/* init image */
int width = 128;
int height = 128;
retry:
set->image = ren_new_image(width, height);
/* load glyphs */
float s =
stbtt_ScaleForMappingEmToPixels(&font->stbfont, 1) /
stbtt_ScaleForPixelHeight(&font->stbfont, 1);
int res = stbtt_BakeFontBitmap(
font->data, 0, font->size * s, (void*) set->image->pixels,
width, height, idx * 256, 256, set->glyphs);
/* retry with a larger image buffer if the buffer wasn't large enough */
if (res < 0) {
width *= 2;
height *= 2;
ren_free_image(set->image);
goto retry;
}
/* adjust glyph yoffsets and xadvance */
int ascent, descent, linegap;
stbtt_GetFontVMetrics(&font->stbfont, &ascent, &descent, &linegap);
float scale = stbtt_ScaleForMappingEmToPixels(&font->stbfont, font->size);
int scaled_ascent = ascent * scale + 0.5;
for (int i = 0; i < 256; i++) {
set->glyphs[i].yoff += scaled_ascent;
set->glyphs[i].xadvance = floor(set->glyphs[i].xadvance);
}
/* convert 8bit data to 32bit */
for (int i = width * height - 1; i >= 0; i--) {
uint8_t n = *((uint8_t*) set->image->pixels + i);
set->image->pixels[i] = (RenColor) { .r = 255, .g = 255, .b = 255, .a = n };
}
return set;
}
static GlyphSet* get_glyphset(RenFont *font, int codepoint) {
int idx = (codepoint >> 8) % MAX_GLYPHSET;
if (!font->sets[idx]) {
font->sets[idx] = load_glyphset(font, idx);
}
return font->sets[idx];
}
RenFont* ren_load_font(const char *filename, float size) {
RenFont *font = NULL;
FILE *fp = NULL;
/* init font */
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font = check_alloc(calloc(1, sizeof(RenFont)));
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font->size = size;
/* load font into buffer */
fp = fopen(filename, "rb");
if (!fp) { return NULL; }
/* get size */
fseek(fp, 0, SEEK_END); int buf_size = ftell(fp); fseek(fp, 0, SEEK_SET);
/* load */
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font->data = check_alloc(malloc(buf_size));
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int _ = fread(font->data, 1, buf_size, fp); (void) _;
fclose(fp);
fp = NULL;
/* init stbfont */
int ok = stbtt_InitFont(&font->stbfont, font->data, 0);
if (!ok) { goto fail; }
/* get height and scale */
int ascent, descent, linegap;
stbtt_GetFontVMetrics(&font->stbfont, &ascent, &descent, &linegap);
float scale = stbtt_ScaleForMappingEmToPixels(&font->stbfont, size);
font->height = (ascent - descent + linegap) * scale + 0.5;
/* make tab and newline glyphs invisible */
stbtt_bakedchar *g = get_glyphset(font, '\n')->glyphs;
g['\t'].x1 = g['\t'].x0;
g['\n'].x1 = g['\n'].x0;
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return font;
fail:
if (fp) { fclose(fp); }
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if (font) { free(font->data); }
free(font);
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return NULL;
}
void ren_free_font(RenFont *font) {
for (int i = 0; i < MAX_GLYPHSET; i++) {
GlyphSet *set = font->sets[i];
if (set) {
ren_free_image(set->image);
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free(set);
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}
}
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free(font->data);
free(font);
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}
void ren_set_font_tab_width(RenFont *font, int n) {
GlyphSet *set = get_glyphset(font, '\t');
set->glyphs['\t'].xadvance = n;
}
int ren_get_font_tab_width(RenFont *font) {
GlyphSet *set = get_glyphset(font, '\t');
return set->glyphs['\t'].xadvance;
}
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int ren_get_font_width(RenFont *font, const char *text) {
int x = 0;
const char *p = text;
unsigned codepoint;
while (*p) {
p = utf8_to_codepoint(p, &codepoint);
GlyphSet *set = get_glyphset(font, codepoint);
stbtt_bakedchar *g = &set->glyphs[codepoint & 0xff];
x += g->xadvance;
}
return x;
}
int ren_get_font_height(RenFont *font) {
return font->height;
}
static inline RenColor blend_pixel(RenColor dst, RenColor src) {
int ia = 0xff - src.a;
dst.r = ((src.r * src.a) + (dst.r * ia)) >> 8;
dst.g = ((src.g * src.a) + (dst.g * ia)) >> 8;
dst.b = ((src.b * src.a) + (dst.b * ia)) >> 8;
return dst;
}
static inline RenColor blend_pixel2(RenColor dst, RenColor src, RenColor color) {
src.a = (src.a * color.a) >> 8;
int ia = 0xff - src.a;
dst.r = ((src.r * color.r * src.a) >> 16) + ((dst.r * ia) >> 8);
dst.g = ((src.g * color.g * src.a) >> 16) + ((dst.g * ia) >> 8);
dst.b = ((src.b * color.b * src.a) >> 16) + ((dst.b * ia) >> 8);
return dst;
}
#define rect_draw_loop(expr) \
for (int j = y1; j < y2; j++) { \
for (int i = x1; i < x2; i++) { \
*d = expr; \
d++; \
} \
d += dr; \
}
void ren_draw_rect(RenRect rect, RenColor color) {
if (color.a == 0) { return; }
int x1 = rect.x < clip.left ? clip.left : rect.x;
int y1 = rect.y < clip.top ? clip.top : rect.y;
int x2 = rect.x + rect.width;
int y2 = rect.y + rect.height;
x2 = x2 > clip.right ? clip.right : x2;
y2 = y2 > clip.bottom ? clip.bottom : y2;
SDL_Surface *surf = SDL_GetWindowSurface(window);
RenColor *d = (RenColor*) surf->pixels;
d += x1 + y1 * surf->w;
int dr = surf->w - (x2 - x1);
if (color.a == 0xff) {
rect_draw_loop(color);
} else {
rect_draw_loop(blend_pixel(*d, color));
}
}
void ren_draw_image(RenImage *image, RenRect *sub, int x, int y, RenColor color) {
if (color.a == 0) { return; }
/* clip */
int n;
if ((n = clip.left - x) > 0) { sub->width -= n; sub->x += n; x += n; }
if ((n = clip.top - y) > 0) { sub->height -= n; sub->y += n; y += n; }
if ((n = x + sub->width - clip.right ) > 0) { sub->width -= n; }
if ((n = y + sub->height - clip.bottom) > 0) { sub->height -= n; }
if (sub->width <= 0 || sub->height <= 0) {
return;
}
/* draw */
SDL_Surface *surf = SDL_GetWindowSurface(window);
RenColor *s = image->pixels;
RenColor *d = (RenColor*) surf->pixels;
s += sub->x + sub->y * image->width;
d += x + y * surf->w;
int sr = image->width - sub->width;
int dr = surf->w - sub->width;
for (int j = 0; j < sub->height; j++) {
for (int i = 0; i < sub->width; i++) {
*d = blend_pixel2(*d, *s, color);
d++;
s++;
}
d += dr;
s += sr;
}
}
int ren_draw_text(RenFont *font, const char *text, int x, int y, RenColor color) {
RenRect rect;
const char *p = text;
unsigned codepoint;
while (*p) {
p = utf8_to_codepoint(p, &codepoint);
GlyphSet *set = get_glyphset(font, codepoint);
stbtt_bakedchar *g = &set->glyphs[codepoint & 0xff];
rect.x = g->x0;
rect.y = g->y0;
rect.width = g->x1 - g->x0;
rect.height = g->y1 - g->y0;
ren_draw_image(set->image, &rect, x + g->xoff, y + g->yoff, color);
x += g->xadvance;
}
return x;
}