Update sixdraw.

examples/sixdraw.c

@@ -26,6 +26,7 @@
 #endif  // HAVE_CONFIG_H
 
 #include <signal.h>
+#include <stdarg.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -41,6 +42,11 @@
 #  define SIXDRAW_DEFAULT_TIMEOUT_MILLIS 500
 #endif  // !SIXDRAW_DEFAULT_TIMEOUT_MILLIS
 
+#define SIXDRAW_DECRQM_SET 1
+#define SIXDRAW_DECRQM_RST 2
+#define SIXDRAW_DECTCEM    25u
+#define SIXDRAW_ALT_SCRBUF 1049u
+
 struct sixdraw_ctx {
     struct termios          termios;
     union ctlseqs_value     buffer[64];
@@ -49,6 +55,7 @@ struct sixdraw_ctx {
     struct ctlseqs_reader  *reader;
     bool                    has_termios;
     bool                    show_cursor;
+    bool                    normal_scrbuf;
     int                     in_fd;
     int                     out_fd;
     int                     timeout;
@@ -59,8 +66,13 @@ struct sixdraw_ctx {
 };
 
 static inline void
-sixdraw_print_error(struct sixdraw_ctx const *ctx, char const *msg)
+sixdraw_print_error(struct sixdraw_ctx const *ctx, char const *format, ...)
 {
+    char msg[1024];
+    va_list args;
+    va_start(args, format);
+    vsnprintf(msg, 1024, format, args);
+    va_end(args);
     dprintf(ctx->out_fd, "%s: [error] %s.\n", ctx->prog_name, msg);
 }
 
@@ -91,7 +103,17 @@ sixdraw_terminate(struct sixdraw_ctx *ctx)
     ctlseqs_matcher_free(ctx->matcher);
     ctlseqs_reader_free(ctx->reader);
 
-    // Restore original terminal modes
+    // Restore cursor status.
+    if (ctx->show_cursor) {
+        dprintf(ctx->out_fd, CTLSEQS_DECSET("%u"), SIXDRAW_DECTCEM);
+    }
+
+    // Restore normal screen buffer.
+    if (ctx->normal_scrbuf) {
+        dprintf(ctx->out_fd, CTLSEQS_DECRST("%u"), SIXDRAW_ALT_SCRBUF);
+    }
+
+    // Restore original terminal modes.
     if (ctx->has_termios) {
         tcsetattr(ctx->in_fd, TCSANOW, &ctx->termios);
     }
@@ -102,9 +124,11 @@ sixdraw_get_winsize(struct sixdraw_ctx *ctx)
 {
     struct winsize ws = { 0 };
     if (ioctl(ctx->in_fd, TIOCGWINSZ, &ws) != 0) {
+        sixdraw_print_error(ctx, "failed to get terminal window size");
         return false;
     }
     if (ws.ws_xpixel == 0 || ws.ws_ypixel == 0) {
+        sixdraw_print_error(ctx, "failed to get terminal window size (in pixels)");
         return false;
     }
     ctx->rows = ws.ws_row;
@@ -114,6 +138,26 @@ sixdraw_get_winsize(struct sixdraw_ctx *ctx)
     return true;
 }
 
+static bool
+sixdraw_decrqm(struct sixdraw_ctx *ctx, unsigned mode_id, char const *name)
+{
+    ssize_t result;
+    union ctlseqs_value *buffer = ctx->buffer;
+    dprintf(ctx->out_fd, CTLSEQS_DECRQM("%u"), mode_id);
+    do {
+        result = ctlseqs_read(ctx->reader, ctx->matcher, ctx->timeout);
+    } while (result == CTLSEQS_PARTIAL);
+    if (result != 1) {
+        sixdraw_print_error(ctx, "failed to get %s status", name);
+        return false;
+    }
+    if (buffer[0].num != mode_id || (buffer[1].num != SIXDRAW_DECRQM_SET && buffer[1].num != SIXDRAW_DECRQM_RST)) {
+        sixdraw_print_error(ctx, "%s status not recognizable", name);
+        return false;
+    }
+    return true;
+}
+
 static bool
 sixdraw_init(struct sixdraw_ctx *ctx, int argc, char **argv)
 {
@@ -219,7 +263,6 @@ sixdraw_prepare(struct sixdraw_ctx *ctx)
 
     // Get initial terminal window size.
     if (!sixdraw_get_winsize(ctx)) {
-        sixdraw_print_error(ctx, "failed to get terminal window size");
         return false;
     }
 
@@ -253,19 +296,26 @@ sixdraw_prepare(struct sixdraw_ctx *ctx)
     }
 
     // Get current cursor status.
-    dprintf(ctx->out_fd, CTLSEQS_DECRQM("25"));
-    do {
-        result = ctlseqs_read(ctx->reader, ctx->matcher, ctx->timeout);
-    } while (result == CTLSEQS_PARTIAL);
-    if (result != 1) {
-        sixdraw_print_error(ctx, "failed to get cursor status");
+    if (!sixdraw_decrqm(ctx, SIXDRAW_DECTCEM, "cursor")) {
         return false;
     }
-    if (buffer[0].num != 25 || (buffer[1].num != 1 && buffer[1].num != 2)) {
-        sixdraw_print_error(ctx, "cursor status not recognizable");
+    ctx->show_cursor = buffer[1].num == SIXDRAW_DECRQM_SET;
+
+    // Hide cursor.
+    if (ctx->show_cursor) {
+        dprintf(ctx->out_fd, CTLSEQS_DECRST("%u"), SIXDRAW_DECTCEM);
+    }
+
+    // Get current screen buffer status.
+    if (!sixdraw_decrqm(ctx, SIXDRAW_ALT_SCRBUF, "screen buffer")) {
         return false;
     }
-    ctx->show_cursor = buffer[1].num == 1;
+    ctx->normal_scrbuf = buffer[1].num == SIXDRAW_DECRQM_RST;
+
+    // Switch to alternate screen buffer.
+    if (ctx->normal_scrbuf) {
+        dprintf(ctx->out_fd, CTLSEQS_DECSET("%u"), SIXDRAW_ALT_SCRBUF);
+    }
 
     return true;
 }