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/* draw.c - software rendering onto an ARGB8888 mb_buffer. */
#include "draw.h"
#include "font.h"
#include <stddef.h>
/* wl_shm ARGB8888 and Win32 layered windows both hold premultiplied alpha. */
static uint32_t premul(uint32_t argb)
{
uint32_t a = argb >> 24;
uint32_t r = (argb >> 16) & 0xff;
uint32_t g = (argb >> 8) & 0xff;
uint32_t b = argb & 0xff;
r = r * a / 255;
g = g * a / 255;
b = b * a / 255;
return (a << 24) | (r << 16) | (g << 8) | b;
}
/* Fill a logical rectangle, expanding each logical pixel to a scale*scale block
* of device pixels. Clipping is in logical space; scale=1 is the identity. */
static void fill_premul(struct mb_buffer *b, int x, int y, int w, int h,
uint32_t pm)
{
int s = b->scale;
int x1 = x + w, y1 = y + h;
if (x < 0)
x = 0;
if (y < 0)
y = 0;
if (x1 > b->w)
x1 = b->w;
if (y1 > b->h)
y1 = b->h;
int n = (x1 - x) * s;
for (int row = y; row < y1; row++) {
for (int sy = 0; sy < s; sy++) {
uint32_t *p = b->px +
(size_t)(row * s + sy) * b->stride +
(size_t)x * s;
for (int i = 0; i < n; i++)
p[i] = pm;
}
}
}
void draw_fill(struct mb_buffer *b, int x, int y, int w, int h, uint32_t argb)
{
fill_premul(b, x, y, w, h, premul(argb));
}
void draw_hline(struct mb_buffer *b, int x, int y, int len, int thick,
uint32_t argb)
{
fill_premul(b, x, y, len, thick, premul(argb));
}
void draw_vline(struct mb_buffer *b, int x, int y, int len, int thick,
uint32_t argb)
{
fill_premul(b, x, y, thick, len, premul(argb));
}
void draw_rect(struct mb_buffer *b, int x, int y, int w, int h, int thick,
uint32_t argb)
{
uint32_t pm = premul(argb);
fill_premul(b, x, y, w, thick, pm); /* top */
fill_premul(b, x, y + h - thick, w, thick, pm); /* bottom */
fill_premul(b, x, y, thick, h, pm); /* left */
fill_premul(b, x + w - thick, y, thick, h, pm); /* right */
}
int text_height(int scale)
{
return FONT_H * scale;
}
int text_width(const char *s, int scale)
{
int n = 0;
while (s[n])
n++;
if (n == 0)
return 0;
return n * (FONT_W * scale) + (n - 1) * scale; /* scale-px gaps */
}
int draw_text(struct mb_buffer *b, int x, int y, const char *s, int scale,
uint32_t fg)
{
int advance = FONT_W * scale + scale;
int w = text_width(s, scale);
uint32_t fpm = premul(fg);
int pen = x;
for (const char *c = s; *c; c++) {
const unsigned char *g = font_glyph(*c);
for (int gy = 0; gy < FONT_H; gy++) {
unsigned char bits = g[gy];
for (int gx = 0; gx < FONT_W; gx++) {
if (!(bits & (1u << gx)))
continue;
fill_premul(b, pen + gx * scale,
y + gy * scale, scale, scale, fpm);
}
}
pen += advance;
}
return w;
}
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