From 96d17772f92a50796df4b4b7be1b25d4a5fa25d9 Mon Sep 17 00:00:00 2001
From: CismonX <admin@cismon.net>
Date: Mon, 11 Jan 2021 04:58:39 +0800
Subject: [PATCH] Update sixdraw.

---
 examples/sixdraw.c | 64 +++++++++++++++++++++++-----------------------
 1 file changed, 32 insertions(+), 32 deletions(-)

diff --git a/examples/sixdraw.c b/examples/sixdraw.c
index d429d1e..663d90e 100644
--- a/examples/sixdraw.c
+++ b/examples/sixdraw.c
@@ -56,6 +56,8 @@
 
 #define SIXEL_SEQ_HEAD CTLSEQS_DCS "0;1q\"1;1;"
 
+static char sixel_seq[2048] = SIXEL_SEQ_HEAD;
+
 struct sixdraw_ctx {
     struct termios          termios;
     union ctlseqs_value     result[64];
@@ -70,9 +72,13 @@ struct sixdraw_ctx {
     int                     in_fd;
     int                     out_fd;
     int                     timeout;
+    unsigned                rows;
+    unsigned                canvas_width;
+    unsigned                canvas_height;
     unsigned                ch_width;
     unsigned                ch_height;
     unsigned                line_color;
+    unsigned                sixel_init_size;
 };
 
 static inline void
@@ -128,8 +134,11 @@ get_winsize(struct sixdraw_ctx *ctx)
         print_error(ctx, "failed to get terminal window size (in pixels)");
         return false;
     }
+    ctx->rows = ws.ws_row;
     ctx->ch_width = ws.ws_xpixel / ws.ws_col;
     ctx->ch_height = ws.ws_ypixel / ws.ws_row;
+    ctx->canvas_width = ws.ws_xpixel - ctx->ch_width;
+    ctx->canvas_height = ws.ws_ypixel - ctx->ch_height * 3;
     return true;
 }
 
@@ -153,51 +162,32 @@ decrqm(struct sixdraw_ctx *ctx, unsigned mode, char const *name)
     return true;
 }
 
-static inline void
-get_sixel_color(unsigned rgb888, unsigned *red, unsigned *green, unsigned *blue)
-{
-    *red   = ((rgb888 >> 16) & 0xFF) * 100 / 0xFF;
-    *green = ((rgb888 >> 8)  & 0xFF) * 100 / 0xFF;
-    *blue  = ((rgb888 >> 0)  & 0xFF) * 100 / 0xFF;
-}
-
-static inline char *
-get_sixel_buffer()
-{
-    static char sixel_seq_buffer[2048] = SIXEL_SEQ_HEAD;
-    return sixel_seq_buffer;
-}
-
 static void
 print_sixel_dot(struct sixdraw_ctx *ctx, unsigned x, unsigned y)
 {
-    char *sixel_seq = get_sixel_buffer();
-    size_t seq_len = sizeof(SIXEL_SEQ_HEAD) - 1;
-    seq_len += sprintf(sixel_seq + seq_len, "%d;%d", ctx->ch_width, ctx->ch_height);
-    
-    // Select color.
-    unsigned red, green, blue;
-    get_sixel_color(ctx->line_color, &red, &green, &blue);
-    seq_len += sprintf(sixel_seq + seq_len, "#0;2;%d;%d;%d#0", red, green, blue);
+    if (x >= ctx->canvas_width || y >= ctx->canvas_height) {
+        return;
+    }
 
     // Move cursor.
     unsigned row = y / ctx->ch_height + 1;
     unsigned col = x / ctx->ch_width + 1;
     dprintf(ctx->out_fd, CTLSEQS_CUP("%d", "%d"), row, col);
 
-    // Draw dot.
+    // Build sixel sequence.
     row = y % ctx->ch_height;
     col = x % ctx->ch_width;
-    seq_len += sprintf(sixel_seq + seq_len, "%.*s", row / 6, "------------------------");
-    seq_len += sprintf(sixel_seq + seq_len, "!%u?%c" CTLSEQS_ST, col, (1 << row % 6) + 0x3F);
+    unsigned seq_size = ctx->sixel_init_size;
+    seq_size += sprintf(sixel_seq + seq_size, "%.*s!%u?%c" CTLSEQS_ST,
+        row / 6, "------------------------", col, (1 << row % 6) + 0x3F);
 
     // Output sixel sequence.
-    do {
-        ssize_t nbytes = write(ctx->out_fd, sixel_seq, seq_len);
-        if (nbytes > 0) {
-            seq_len -= nbytes;
+    for (ssize_t nbytes; seq_size > 0; seq_size -= nbytes) {
+        nbytes = write(ctx->out_fd, sixel_seq, seq_size);
+        if (nbytes < 0) {
+            break;
         }
-    } while (seq_len > 0);
+    }
 }
 
 static bool
@@ -364,17 +354,27 @@ prepare(struct sixdraw_ctx *ctx)
         dprintf(ctx->out_fd, CTLSEQS_DECSET("%d"), SGR_MOUSE_PIXELMODE);
     }
 
+    // Build the immutable part of sixel sequence.
+    ctx->sixel_init_size = sizeof(SIXEL_SEQ_HEAD) - 1;
+    ctx->sixel_init_size += sprintf(sixel_seq + ctx->sixel_init_size, "%u;%u#0;2;%d;%d;%d#0",
+        ctx->ch_width, ctx->ch_height, ((ctx->line_color >> 16) & 0xFF) * 100 / 0xFF,
+        ((ctx->line_color >> 8) & 0xFF) * 100 / 0xFF, ((ctx->line_color >> 0) & 0xFF) * 100 / 0xFF);
+
     return true;
 }
 
 static bool
 draw(struct sixdraw_ctx *ctx)
 {
+    dprintf(ctx->out_fd, CTLSEQS_CUP("%d", "1") "Canvas size: %ux%u. Line color: #%06X.",
+        ctx->rows - 1, ctx->canvas_width, ctx->canvas_height, ctx->line_color);
+    dprintf(ctx->out_fd, CTLSEQS_CUP("%d", "1") "Usage: Draw with mouse. Press Ctrl+C to exit.", ctx->rows);
+
     union ctlseqs_value *result = ctx->result;
     while (true) {
         switch (ctlseqs_read(ctx->reader, ctx->matcher, -1)) {
             case 2:  // CTLSEQS_RESP_SGR_MOUSE
-                print_sixel_dot(ctx, result[1].num, result[2].num);
+                print_sixel_dot(ctx, result[1].num - 1, result[2].num - 1);
                 break;
             case CTLSEQS_NOSEQ:
                 // Press Ctrl+C to exit.