tIntroducing 'smooth scrolling'. text now starts from the right and scrolls from here - skroll - scroll a text to stdout
(HTM) git clone git://z3bra.org/skroll
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---
(DIR) commit 1a40c6b37cd6aec6c0e0694d95b2bf43a7d51a96
(DIR) parent e5cfcfc2a35661baa401312bc9506fd3e3069b7d
(HTM) Author: z3bra <willy@mailoo.org>
Date: Wed, 3 Sep 2014 17:10:28 +0200
Introducing 'smooth scrolling'. text now starts from the right and scrolls from here
Diffstat:
M skroll.c | 60 +++++++++++++++++++++++++++----
1 file changed, 53 insertions(+), 7 deletions(-)
---
(DIR) diff --git a/skroll.c b/skroll.c
t@@ -26,7 +26,7 @@
static bool newline = false;/* print a new line after each step */
static bool loop = false; /* wether to loop text or not */
-static float delay = 1; /* scroll speed, in usec */
+static float delay = 0.5; /* scroll speed, in seconds */
static int number = 10; /* number of chars to be shown at the same time */
/* fills a string with spaces if it has less than <num> chars */
t@@ -52,22 +52,68 @@ void zero_fill (char **str, size_t num)
return; /* void */
}
+/*
+ * pad a string with <num> spaces, and append chars from <str> to it, until its
+ * lenght is <len>
+ */
+void zero_pad (char **pad, const char *str, size_t len, size_t num)
+{
+ /* fill the memory with zeros */
+ memset ( (*pad), 0, len );
+
+ /* pad the string with 0x20 (space char) */
+ memset ( (*pad), 0x20, num );
+
+ /* append char of the *original* string at the end of the pad */
+ strncat ( (*pad), str, len );
+
+ /* fill the stirng with spaces, in case it's too short */
+ zero_fill ( pad, len );
+
+ return; /* void */
+}
+
/* scroll <input> to stdout */
void skroll (const char *input)
{
- int offset = 0;
+ int offset, padder;
char *buf = NULL;
if ( !(buf = calloc (number, sizeof(char))) ) return;
buf[number] = 0;
+ /* main loop. will loop forever if run with -l */
do {
- for (offset=0; input[offset]; ++offset) {
- /* copy the number of char we want to the buffer */
- strncpy(buf, input + offset, number-1);
- /* fill missing chars with spaces */
- zero_fill(&buf, number);
+ offset = 0;
+ padder = number;
+
+ /* loop executed on each step, after <delay> seconds */
+ while ( input[offset] != 0 ) {
+ /*
+ * There are two different parts: padding, and filling.
+ * padding is adding spaces at the beginning to simulate text
+ * arrival from the right. filling is adding spaces at the end of
+ * the text so that the currently displayed text has always the
+ * same size, even if there is only a single char
+ */
+ if ( padder > 0 ) {
+ /*
+ * While the first letter has not reach the left edge, pad the
+ * text, decrementing padding after each step.
+ */
+ zero_pad(&buf, input, number, padder);
+ padder--;
+ } else
+ /* Once padding is finished, we start "hiding" text to the left */
+ if ( offset < number ) {
+ /* copy the number of char we want to the buffer */
+ strncpy(buf, input + offset, number-1);
+
+ /* fill missing chars with spaces */
+ zero_fill(&buf, number);
+ offset++;
+ }
/* print out the buffer ! */
printf("\r%s", buf);