[READ-ONLY] Mirror of https://github.com/bombshell-dev/tty. Platform independent 2D layout engine for terminal applications based on Clay
feat(render): implement REP CSI Ps b
Nate Moore
(Jun 26, 2026, 11:55 PM EDT)
a24cd2bf
7f87619a
+88
-22
+88
-22
src/clayterm.c
+88
-22
src/clayterm.c
···
167
167
buf_put(&ct->out, "H", 1);
168
168
}
169
169
170
+
/* decimal digits in n (n >= 0) */
171
+
static int num_digits(int n) {
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+
int d = 1;
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+
while (n >= 10) {
174
+
n /= 10;
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+
d++;
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+
}
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+
return d;
178
+
}
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+
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+
/* glyph actually written for a cell: non-printable -> U+FFFD (see emit_ch) */
181
+
static uint32_t glyph_cp(uint32_t ch) { return iswprint(ch) ? ch : 0xfffd; }
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+
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+
/* UTF-8 byte length of a codepoint, matching buf_char's encoding */
184
+
static int cp_utf8_len(uint32_t ch) {
185
+
if (ch < 0x80)
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+
return 1;
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+
if (ch < 0x800)
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+
return 2;
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+
if (ch < 0x10000)
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+
return 3;
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+
return 4;
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+
}
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+
170
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static void emit_ch(struct Clayterm *ct, int x, int y, int row, uint32_t ch) {
171
195
if (ct->lastx != x - 1 || ct->lasty != y) {
172
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emit_cursor(ct, x, y, row);
···
174
198
ct->lastx = x;
175
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ct->lasty = y;
176
200
177
-
if (!iswprint(ch))
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-
ch = 0xfffd;
179
-
buf_char(&ct->out, ch);
201
+
buf_char(&ct->out, glyph_cp(ch));
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202
}
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203
182
204
/**
···
198
220
if (w < 1)
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221
w = 1;
200
222
201
-
if (cell_cmp(back, front)) {
202
-
/* copy to front */
203
-
*front = *back;
223
+
if (!cell_cmp(back, front)) {
224
+
x += w;
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+
continue;
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+
}
204
227
205
-
emit_attr(ct, back->fg, back->bg);
228
+
emit_attr(ct, back->fg, back->bg);
206
229
207
-
if (w > 1 && x >= ct->w - (w - 1)) {
208
-
/* wide char doesn't fit, send spaces */
209
-
for (int i = x; i < ct->w; i++)
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-
emit_ch(ct, i, y, row, ' ');
211
-
} else {
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-
emit_ch(ct, x, y, row, back->ch);
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-
/* mark trailing cells of wide char as invalid in front
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-
* so they'll diff when overwritten by narrow chars */
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-
for (int i = 1; i < w; i++) {
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-
Cell *fw = cell_at(ct, ct->front, x + i, y);
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-
fw->ch = 0xffffffff;
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-
fw->fg = 0xffffffff;
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-
fw->bg = 0xffffffff;
220
-
}
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+
if (w > 1 && x >= ct->w - (w - 1)) {
231
+
/* wide char doesn't fit, send spaces */
232
+
*front = *back;
233
+
for (int i = x; i < ct->w; i++)
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+
emit_ch(ct, i, y, row, ' ');
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+
x += w;
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+
continue;
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+
}
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+
239
+
if (w > 1) {
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+
*front = *back;
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+
emit_ch(ct, x, y, row, back->ch);
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+
/* mark trailing cells of wide char as invalid in front
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+
* so they'll diff when overwritten by narrow chars */
244
+
for (int i = 1; i < w; i++) {
245
+
Cell *fw = cell_at(ct, ct->front, x + i, y);
246
+
fw->ch = 0xffffffff;
247
+
fw->fg = 0xffffffff;
248
+
fw->bg = 0xffffffff;
221
249
}
250
+
x += w;
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+
continue;
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}
223
-
x += w;
253
+
254
+
/* width-1 cell: extend a run of identical changed cells so an
255
+
* identical horizontal span collapses to one glyph + REP (CSI b). */
256
+
int run = 1;
257
+
for (int nx = x + 1; nx < ct->w; nx++) {
258
+
Cell *nb = cell_at(ct, ct->back, nx, y);
259
+
Cell *nf = cell_at(ct, ct->front, nx, y);
260
+
int nw = wcwidth(nb->ch);
261
+
if (nw > 1)
262
+
break;
263
+
if (!cell_cmp(nb, nf))
264
+
break;
265
+
if (cell_cmp(nb, back))
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+
break;
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+
run++;
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+
}
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+
270
+
/* copy the whole run to the front buffer */
271
+
for (int i = 0; i < run; i++)
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+
*cell_at(ct, ct->front, x + i, y) = *back;
273
+
274
+
int repeats = run - 1;
275
+
int cb = cp_utf8_len(glyph_cp(back->ch));
276
+
/* inline = run*cb bytes; REP = cb + len("\x1b[") + digits + len("b").
277
+
* Only collapse when REP is strictly smaller. */
278
+
if (repeats >= 1 && run * cb > cb + 3 + num_digits(repeats)) {
279
+
emit_ch(ct, x, y, row, back->ch);
280
+
buf_str(&ct->out, "\x1b[");
281
+
buf_num(&ct->out, repeats);
282
+
buf_put(&ct->out, "b", 1);
283
+
ct->lastx = x + run - 1;
284
+
ct->lasty = y;
285
+
} else {
286
+
for (int i = 0; i < run; i++)
287
+
emit_ch(ct, x + i, y, row, back->ch);
288
+
}
289
+
x += run;
224
290
}
225
291
}
226
292
}