[renderer] Add a buffer print function

It handles basic cursor motion respecting \r \n \f and \t (might be a
problem for id chars), wraps at the right edge, and automatically
scrolls when the cursor tries to pass the bottom of the screen.

Clearing the buffer resets its cursor to the upper left.

include/QF/draw.h

@@ -50,6 +50,8 @@ typedef struct draw_charbuffer_s {
 	int         width;		///< width in character cells
 	int         height;		///< height in character cells
 	char       *chars;		///< width * height characters
+	int         cursx;		///< horizontal cursor position
+	int         cursy;		///< vertical cursor position
 } draw_charbuffer_t;
 
 draw_charbuffer_t *Draw_CreateBuffer (int width, int height);
@@ -57,6 +59,7 @@ void Draw_DestroyBuffer (draw_charbuffer_t *buffer);
 void Draw_ClearBuffer (draw_charbuffer_t *buffer);
 void Draw_ScrollBuffer (draw_charbuffer_t *buffer, int lines);
 void Draw_CharBuffer (int x, int y, draw_charbuffer_t *buffer);
+void Draw_PrintBuffer (draw_charbuffer_t *buffer, const char *str);
 
 extern byte *draw_chars;
 

libs/video/renderer/r_draw.c

@@ -43,6 +43,7 @@ Draw_CreateBuffer (int width, int height)
 	buffer->width = width;
 	buffer->height = height;
 	buffer->chars = (char *) (buffer + 1);
+	buffer->cursx = buffer->cursy = 0;
 	return buffer;
 }
 
@@ -56,6 +57,7 @@ VISIBLE void
 Draw_ClearBuffer (draw_charbuffer_t *buffer)
 {
 	memset (buffer->chars, ' ', buffer->height * buffer->width);
+	buffer->cursx = buffer->cursy = 0;
 }
 
 VISIBLE void
@@ -86,3 +88,51 @@ Draw_CharBuffer (int x, int y, draw_charbuffer_t *buffer)
 {
 	r_funcs->Draw_CharBuffer (x, y, buffer);
 }
+
+#define TAB 8
+
+VISIBLE void
+Draw_PrintBuffer (draw_charbuffer_t *buffer, const char *str)
+{
+	char       *dst = buffer->chars;
+	char        c;
+	int         tab;
+	dst += buffer->cursy * buffer->width + buffer->cursx;
+	while ((c = *str++)) {
+		switch (c) {
+			case '\r':
+				dst -= buffer->cursx;
+				buffer->cursx = 0;
+				break;
+			case '\n':
+				dst -= buffer->cursx;
+				buffer->cursx = 0;
+				dst += buffer->width;
+				buffer->cursy++;
+				break;
+			case '\f':
+				dst += buffer->width;
+				buffer->cursy++;
+				break;
+			case '\t':
+				tab = TAB - buffer->cursx % TAB;
+				buffer->cursx += tab;
+				dst += tab;
+				break;
+			default:
+				*dst++ = c;
+				buffer->cursx++;
+				break;
+		}
+		if (buffer->cursx >= buffer->width) {
+			buffer->cursx -= buffer->width;
+			buffer->cursy++;
+		}
+		if (buffer->cursy >= buffer->height) {
+			int         lines = buffer->cursy - buffer->height + 1;
+			Draw_ScrollBuffer (buffer, lines);
+			dst -= lines * buffer->width;
+			buffer->cursy -= lines;
+		}
+	}
+}

libs/video/renderer/r_progs.c

@@ -462,6 +462,17 @@ bi_Draw_CharBuffer (progs_t *pr, void *_res)
 	Draw_CharBuffer (x, y, cbuff->buffer);
 }
 
+static void
+bi_Draw_PrintBuffer (progs_t *pr, void *_res)
+{
+	draw_resources_t *res = _res;
+	pr_ptr_t    cbuff_handle = P_POINTER (pr, 0);
+	bi_charbuff_t *cbuff = get_charbuff (pr, res, __FUNCTION__, cbuff_handle);
+	const char *str = P_GSTRING (pr, 1);
+
+	Draw_PrintBuffer (cbuff->buffer, str);
+}
+
 static const char *
 bi_draw_get_key (const void *p, void *unused)
 {
@@ -527,6 +538,7 @@ static builtin_t builtins[] = {
 	bi(Draw_ClearBuffer,    1, p(ptr)),
 	bi(Draw_ScrollBuffer,   2, p(ptr), p(int)),
 	bi(Draw_CharBuffer,     3, p(int), p(int), p(ptr)),
+	bi(Draw_PrintBuffer,    2, p(ptr), p(string)),
 	{0}
 };