lua Add scrollable stack traceback WIP

lua currently splashes a stack traceback on error
for deep tracebacks and especially on devices with smaller screens
this leaves out a lot of vital information

in the past I have resorted to splitting the traceback string or
even saving the return to a file

This patch provides a scrollable buffer with rudimentary text reflow
to allow you to read the whole traceback string

Upon traceback if you press nothing the screen will display for 5 seconds
If you press OK or CANCEL it will quit immediately
PREV/NEXT scrolls the list on button press timeout is disabled

lua now provides rb.splash_scroller(timeout, str)

example script provided too

Change-Id: Idbc8ce0c514196f0fae48c43aeaea8b60d6da1a5

apps/plugins/lua/rockaux.c

@@ -41,6 +41,122 @@ char *strerror(int errnum)
     return NULL;
 }
 
+/* splash string and allow user to scroll around
+ * provides rudimentary text reflow
+ * timeout is disabled on user interaction
+ * returns the action that caused quit
+ * [ACTION_NONE, ACTION_STD_CANCEL, ACTION_STD_OK]
+ * !ACTION_NONE (only on initial timeout)!
+ * TIMEOUT can be TIMEOUT_BLOCK or time in ticks
+*/
+int splash_scroller(int timeout, const char* str)
+{
+    int w, ch_w, ch_h;
+    rb->lcd_getstringsize("W", &ch_w, &ch_h);
+
+    const int max_w = LCD_WIDTH - (ch_w * 2);
+    const int max_lines = LCD_HEIGHT / ch_h - 1;
+    const int wrap_thresh = (LCD_WIDTH / 3);
+    const char *ch;
+    char *brk;
+
+    const int max_ch = (LCD_WIDTH / ch_w - 1) * 2;
+    char line[max_ch + 2]; /* display buffer */
+    const char break_chars[] = "@#$%^&*+-{}[]()/\\|<>:;.,? _\n\r\t";
+
+    int linepos, curline, linesdisp, realline, chars_next_break;
+    int action = ACTION_NONE;
+    int firstline = 0;
+    int cycles = 2; /* get action timeout returns immediately on first call */
+
+    while (cycles > 0)
+    {
+        /* walk whole buffer every refresh, only display relevant portion */
+        rb->lcd_clear_display();
+        curline = 0;
+        linepos = 0;
+        linesdisp = 0;
+        ch = str;
+        for (; *ch && linepos < max_ch; ch++)
+        {
+            if (ch[0] == '\t')
+            {
+                line[linepos++] = ' ';
+                line[linepos] = ' ';
+            }
+            else if (ch[0] == '\b' && timeout > 0)
+            {
+                line[linepos] = ' ';
+                rb->beep_play(1000, HZ, 1000);
+            }
+            else if (ch[0] < ' ') /* Dont copy control characters */
+                line[linepos] = (linepos == 0) ? '\0' : ' ';
+            else
+                line[linepos] = ch[0];
+
+            line[linepos + 1] = '\0'; /* terminate to check text extent */
+            rb->lcd_getstringsize(line, &w, NULL);
+
+            /* try to not split in middle of words */
+            if (w + wrap_thresh >= max_w && strpbrk (&line[linepos], break_chars))
+            {
+                brk = strpbrk(ch+1, break_chars);
+                chars_next_break = (brk - ch);
+                if (chars_next_break < 2 || w + (ch_w * chars_next_break) > max_w)
+                {
+                    if (!isprint(line[linepos]))
+                    {
+                        line[linepos] = '\0';
+                        ch--; /* back-up we want it on the next line */
+                    }
+                    w += max_w;
+                }
+            }
+
+            if (w > max_w ||
+               (ch[0] >= '\n' && iscntrl(ch[0])) ||
+                ch[1] == '\0')
+            {
+                realline = curline - firstline;
+                if (realline >= 0 && realline < max_lines)
+                {
+                    rb->lcd_putsxy(0, realline * ch_h, line);
+                    linesdisp++;
+                }
+                linepos = 0;
+                curline++;
+                continue;
+            }
+            linepos++;
+        }
+
+        rb->lcd_update();
+
+        action = rb->get_action(CONTEXT_STD, timeout);
+        switch(action)
+        {
+            case ACTION_STD_OK:
+            case ACTION_STD_CANCEL:
+                cycles--;
+            /* Fall Through */
+            case ACTION_NONE:
+                cycles--;
+                break;
+            case ACTION_STD_PREV:
+                timeout = TIMEOUT_BLOCK; /* disable timeout */
+                if(firstline > 0)
+                    firstline--;
+                break;
+            case ACTION_STD_NEXT:
+                timeout = TIMEOUT_BLOCK; /* disable timeout */
+                if (linesdisp == max_lines)
+                    firstline++;
+                break;
+        }
+    }
+    return action;
+}
+
 long rb_pow(long x, long n)
 {
     long pow = 1;