[READ-ONLY] Mirror of https://github.com/bombshell-dev/tty. Platform independent 2D layout engine for terminal applications based on Clay
feat(junction): resolve border junctions via per-cell direction accumulation
Nate Moore
(May 28, 2026, 12:53 AM EDT)
d415cc5c
e8c95f82
+199
-44
+172
-44
src/clayterm.c
+172
-44
src/clayterm.c
···
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}
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}
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+
/* ── Junction character lookup ────────────────────────────────────── */
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+
/* Bit layout: [1:0]=left, [3:2]=right, [5:4]=top, [7:6]=bottom style.
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+
* Style values: 0=none 1=single 2=bold 3=double.
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* Bit 8: rounded-corner hint (single-style 2-dir corner only). */
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#define _JK(l,r,t,b) \
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(((l)&3)|(((r)&3)<<2)|(((t)&3)<<4)|(((b)&3)<<6))
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+
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static const uint32_t junction_chars[512] = {
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/* ── single ─────────────────────────────────────────── */
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[_JK(1,1,0,0)] = 0x2500, /* ─ */
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[_JK(0,0,1,1)] = 0x2502, /* │ */
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[_JK(0,1,0,1)] = 0x250C, /* ┌ */
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[_JK(1,0,0,1)] = 0x2510, /* ┐ */
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[_JK(0,1,1,0)] = 0x2514, /* └ */
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[_JK(1,0,1,0)] = 0x2518, /* ┘ */
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[_JK(1,1,0,1)] = 0x252C, /* ┬ */
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[_JK(1,1,1,0)] = 0x2534, /* ┴ */
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[_JK(0,1,1,1)] = 0x251C, /* ├ */
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[_JK(1,0,1,1)] = 0x2524, /* ┤ */
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[_JK(1,1,1,1)] = 0x253C, /* ┼ */
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+
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/* ── bold ────────────────────────────────────────────── */
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[_JK(2,2,0,0)] = 0x2501, /* ━ */
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[_JK(0,0,2,2)] = 0x2503, /* ┃ */
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[_JK(0,2,0,2)] = 0x250F, /* ┏ */
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[_JK(2,0,0,2)] = 0x2513, /* ┓ */
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[_JK(0,2,2,0)] = 0x2517, /* ┗ */
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[_JK(2,0,2,0)] = 0x251B, /* ┛ */
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[_JK(2,2,0,2)] = 0x2533, /* ┳ */
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[_JK(2,2,2,0)] = 0x253B, /* ┻ */
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[_JK(0,2,2,2)] = 0x2523, /* ┣ */
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[_JK(2,0,2,2)] = 0x252B, /* ┫ */
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[_JK(2,2,2,2)] = 0x254B, /* ╋ */
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+
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/* ── double ──────────────────────────────────────────── */
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[_JK(3,3,0,0)] = 0x2550, /* ═ */
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[_JK(0,0,3,3)] = 0x2551, /* ║ */
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[_JK(0,3,0,3)] = 0x2554, /* ╔ */
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[_JK(3,0,0,3)] = 0x2557, /* ╗ */
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[_JK(0,3,3,0)] = 0x255A, /* ╚ */
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[_JK(3,0,3,0)] = 0x255D, /* ╝ */
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[_JK(3,3,0,3)] = 0x2566, /* ╦ */
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[_JK(3,3,3,0)] = 0x2569, /* ╩ */
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[_JK(0,3,3,3)] = 0x2560, /* ╠ */
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[_JK(3,0,3,3)] = 0x2563, /* ╣ */
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[_JK(3,3,3,3)] = 0x256C, /* ╬ */
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/* ── single+double mixed corners ─────────────────────── */
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[_JK(0,3,0,1)] = 0x2552, /* ╒ right=dbl bot=sgl */
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[_JK(0,1,0,3)] = 0x2553, /* ╓ right=sgl bot=dbl */
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[_JK(3,0,0,1)] = 0x2555, /* ╕ left=dbl bot=sgl */
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[_JK(1,0,0,3)] = 0x2556, /* ╖ left=sgl bot=dbl */
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[_JK(0,3,1,0)] = 0x2558, /* ╘ right=dbl top=sgl */
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[_JK(0,1,3,0)] = 0x2559, /* ╙ right=sgl top=dbl */
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[_JK(3,0,1,0)] = 0x255B, /* ╛ left=dbl top=sgl */
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[_JK(1,0,3,0)] = 0x255C, /* ╜ left=sgl top=dbl */
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/* mixed T-junctions */
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[_JK(0,3,1,1)] = 0x255E, /* ╞ right=dbl v=sgl */
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[_JK(0,1,3,3)] = 0x255F, /* ╟ right=sgl v=dbl */
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[_JK(3,0,1,1)] = 0x2561, /* ╡ left=dbl v=sgl */
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[_JK(1,0,3,3)] = 0x2562, /* ╢ left=sgl v=dbl */
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[_JK(3,3,0,1)] = 0x2564, /* ╤ h=dbl bot=sgl */
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[_JK(1,1,0,3)] = 0x2565, /* ╥ h=sgl bot=dbl */
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[_JK(3,3,1,0)] = 0x2567, /* ╧ h=dbl top=sgl */
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[_JK(1,1,3,0)] = 0x2568, /* ╨ h=sgl top=dbl */
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/* mixed cross */
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[_JK(3,3,1,1)] = 0x256A, /* ╪ h=dbl v=sgl */
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[_JK(1,1,3,3)] = 0x256B, /* ╫ h=sgl v=dbl */
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/* ── rounded single corners (bit 8 set) ──────────────── */
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[_JK(0,1,0,1)|0x100] = 0x256D, /* ╭ */
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[_JK(1,0,0,1)|0x100] = 0x256E, /* ╮ */
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[_JK(0,1,1,0)|0x100] = 0x2570, /* ╰ */
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[_JK(1,0,1,0)|0x100] = 0x256F, /* ╯ */
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};
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static void mark_junction(struct Clayterm *ct, int x, int y,
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uint16_t bits, uint32_t fg) {
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if (x < 0 || x >= ct->w || y < 0 || y >= ct->h)
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return;
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if (ct->clipping) {
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if (x < ct->clipx || x >= ct->clipx + ct->clipw)
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return;
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if (y < ct->clipy || y >= ct->clipy + ct->cliph)
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return;
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}
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ct->junctions[y * ct->w + x] |= bits;
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cell_at(ct, ct->back, x, y)->fg = fg;
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}
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static void render_border(struct Clayterm *ct, int x0, int y0, int x1, int y1,
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Clay_BorderRenderData *b) {
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uint32_t fg = color(b->color);
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uint32_t bg = ATTR_DEFAULT;
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int top = b->width.top > 0;
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int bot = b->width.bottom > 0;
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int left = b->width.left > 0;
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int right = b->width.right > 0;
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int top = b->width.top > 0;
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int bot = b->width.bottom > 0;
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int left = b->width.left > 0;
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int right = b->width.right > 0;
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uint8_t style = (uint8_t)b->width.betweenChildren;
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uint32_t h_char, v_char, tl, tr, bl, br;
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switch (style) {
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case 1: /* double */
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tl = 0x2554; tr = 0x2557; bl = 0x255a; br = 0x255d;
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h_char = 0x2550; v_char = 0x2551;
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break;
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case 2: /* bold */
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tl = 0x250f; tr = 0x2513; bl = 0x2517; br = 0x251b;
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h_char = 0x2501; v_char = 0x2503;
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break;
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default: /* single — corners rounded when cornerRadius > 0 */
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tl = b->cornerRadius.topLeft > 0 ? 0x256d : 0x250c;
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tr = b->cornerRadius.topRight > 0 ? 0x256e : 0x2510;
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bl = b->cornerRadius.bottomLeft > 0 ? 0x2570 : 0x2514;
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br = b->cornerRadius.bottomRight > 0 ? 0x256f : 0x2518;
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h_char = 0x2500; v_char = 0x2502;
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break;
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/* map border style (0=single,1=double,2=bold) → junction style (1=single,3=double,2=bold) */
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static const uint8_t smap[] = {1, 3, 2};
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uint8_t js = style < 3 ? smap[style] : 1;
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int rounded = (style == 0) &&
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(b->cornerRadius.topLeft > 0 || b->cornerRadius.topRight > 0 ||
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b->cornerRadius.bottomLeft > 0 || b->cornerRadius.bottomRight > 0);
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#define JL(s) ((uint16_t)((s)&3))
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#define JR(s) ((uint16_t)(((s)&3)<<2))
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#define JT(s) ((uint16_t)(((s)&3)<<4))
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#define JB(s) ((uint16_t)(((s)&3)<<6))
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#define JROUND ((uint16_t)0x100)
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/* corners */
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if (top && left) {
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uint16_t r = (rounded && b->cornerRadius.topLeft > 0) ? JROUND : 0;
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mark_junction(ct, x0, y0, JR(js)|JB(js)|r, fg);
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}
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if (top && right) {
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uint16_t r = (rounded && b->cornerRadius.topRight > 0) ? JROUND : 0;
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mark_junction(ct, x1-1, y0, JL(js)|JB(js)|r, fg);
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}
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if (bot && left) {
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uint16_t r = (rounded && b->cornerRadius.bottomLeft > 0) ? JROUND : 0;
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mark_junction(ct, x0, y1-1, JR(js)|JT(js)|r, fg);
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}
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if (bot && right) {
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uint16_t r = (rounded && b->cornerRadius.bottomRight > 0) ? JROUND : 0;
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mark_junction(ct, x1-1, y1-1, JL(js)|JT(js)|r, fg);
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}
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if (top && left)
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setcell(ct, x0, y0, tl, fg, bg);
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if (top && right)
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setcell(ct, x1 - 1, y0, tr, fg, bg);
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if (bot && left)
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setcell(ct, x0, y1 - 1, bl, fg, bg);
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if (bot && right)
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setcell(ct, x1 - 1, y1 - 1, br, fg, bg);
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/* horizontal edges — trim endpoint bits when no corner caps the edge */
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if (top) {
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for (int x = x0 + left; x < x1 - right; x++) {
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uint16_t hb = JL(js)|JR(js);
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if (!left && x == x0) hb = (uint16_t)(hb & ~JL(js));
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if (!right && x == x1 - 1) hb = (uint16_t)(hb & ~JR(js));
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mark_junction(ct, x, y0, hb, fg);
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}
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}
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if (bot) {
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for (int x = x0 + left; x < x1 - right; x++) {
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uint16_t hb = JL(js)|JR(js);
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if (!left && x == x0) hb = (uint16_t)(hb & ~JL(js));
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if (!right && x == x1 - 1) hb = (uint16_t)(hb & ~JR(js));
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mark_junction(ct, x, y1-1, hb, fg);
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}
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}
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/* horizontal edges */
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if (top)
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for (int x = x0 + left; x < x1 - right; x++)
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setcell(ct, x, y0, h_char, fg, bg);
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if (bot)
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for (int x = x0 + left; x < x1 - right; x++)
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setcell(ct, x, y1 - 1, h_char, fg, bg);
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/* vertical edges — trim endpoint bits when no corner caps the edge */
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if (left) {
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for (int y = y0 + top; y < y1 - bot; y++) {
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uint16_t vb = JT(js)|JB(js);
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if (!top && y == y0) vb = (uint16_t)(vb & ~JT(js));
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if (!bot && y == y1 - 1) vb = (uint16_t)(vb & ~JB(js));
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mark_junction(ct, x0, y, vb, fg);
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}
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}
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if (right) {
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for (int y = y0 + top; y < y1 - bot; y++) {
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uint16_t vb = JT(js)|JB(js);
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if (!top && y == y0) vb = (uint16_t)(vb & ~JT(js));
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if (!bot && y == y1 - 1) vb = (uint16_t)(vb & ~JB(js));
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mark_junction(ct, x1-1, y, vb, fg);
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}
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}
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/* vertical edges */
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if (left)
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for (int y = y0 + top; y < y1 - bot; y++)
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setcell(ct, x0, y, v_char, fg, bg);
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if (right)
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for (int y = y0 + top; y < y1 - bot; y++)
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setcell(ct, x1 - 1, y, v_char, fg, bg);
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#undef JL
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#undef JR
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#undef JT
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#undef JB
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#undef JROUND
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}
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/* ── Command buffer helpers ───────────────────────────────────────── */
···
617
736
ct->lastx = ct->lasty = -1;
618
737
619
738
cells_fill(ct->back, ct->w, ct->h, ' ', ATTR_DEFAULT, ATTR_DEFAULT);
739
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memset(ct->junctions, 0, (size_t)(ct->w * ct->h) * sizeof(uint16_t));
620
740
621
741
/* walk Clay render commands into back buffer */
622
742
for (int32_t j = 0; j < cmds.length; j++) {
···
650
770
default:
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771
break;
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772
}
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}
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/* junction resolution: write correct Unicode glyph for each accumulated cell */
776
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for (int j = 0; j < ct->w * ct->h; j++) {
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uint16_t bits = ct->junctions[j];
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if (!bits) continue;
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uint32_t ch = junction_chars[bits & 0x1ff];
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if (ch) ct->back[j].ch = ch;
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781
}
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655
783
if (mode == 1) {
+27
test/term.test.ts
+27
test/term.test.ts
···
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160
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛`.trim());
161
161
});
162
162
163
+
it("renders T-junction where inner separator meets outer border (single)", () => {
164
+
let out = print(
165
+
decode(
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+
term.render([
167
+
open("root", {
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layout: { width: grow(), height: grow(), direction: "ltr" },
169
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border: { color: rgba(255, 255, 255), left: 1, right: 1, top: 1, bottom: 1 },
170
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}),
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open("left", {
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layout: { width: fixed(10), height: grow() },
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border: { color: rgba(255, 255, 255), right: 1 },
174
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}),
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close(),
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open("right", { layout: { width: grow(), height: grow() } }),
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close(),
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close(),
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]).output,
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),
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+
40,
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+
10,
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);
184
+
185
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expect(out).toContain("┬");
186
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expect(out).toContain("┴");
187
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expect(out).toMatch(/^┌─+┬/m);
188
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});
189
+
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describe("line mode", () => {
164
191
let box = (msg: string) => [
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open("root", {