Implementing Back Color Erase (BCE).

st.c

@@ -152,7 +152,7 @@ typedef struct {
 	uchar state; /* state flags    */
 } Glyph;
 
-typedef Glyph* Line;
+typedef Glyph *Line;
 
 typedef struct {
 	Glyph attr;	 /* current char attributes */
@@ -303,7 +303,7 @@ static void strhandle(void);
 static void strparse(void);
 static void strreset(void);
 
-static void tclearregion(int, int, int, int);
+static void tclearregion(int, int, int, int, int);
 static void tcursor(int);
 static void tdeletechar(int);
 static void tdeleteline(int);
@@ -1113,7 +1113,7 @@ treset(void) {
 	term.bot = term.row - 1;
 	term.mode = MODE_WRAP;
 
-	tclearregion(0, 0, term.col-1, term.row-1);
+	tclearregion(0, 0, term.col-1, term.row-1, 0);
 	tmoveto(0, 0);
 	tcursor(CURSOR_SAVE);
 }
@@ -1157,7 +1157,7 @@ tscrolldown(int orig, int n) {
 
 	LIMIT(n, 0, term.bot-orig+1);
 
-	tclearregion(0, term.bot-n+1, term.col-1, term.bot);
+	tclearregion(0, term.bot-n+1, term.col-1, term.bot, 0);
 
 	for(i = term.bot; i >= orig+n; i--) {
 		temp = term.line[i];
@@ -1177,7 +1177,7 @@ tscrollup(int orig, int n) {
 	Line temp;
 	LIMIT(n, 0, term.bot-orig+1);
 
-	tclearregion(0, orig, term.col-1, orig+n-1);
+	tclearregion(0, orig, term.col-1, orig+n-1, 0);
 
 	for(i = orig; i <= term.bot-n; i++) {
 		 temp = term.line[i];
@@ -1305,7 +1305,7 @@ tsetchar(char *c, Glyph *attr, int x, int y) {
 }
 
 void
-tclearregion(int x1, int y1, int x2, int y2) {
+tclearregion(int x1, int y1, int x2, int y2, int bce) {
 	int x, y, temp;
 
 	if(x1 > x2)
@@ -1320,9 +1320,16 @@ tclearregion(int x1, int y1, int x2, int y2) {
 
 	for(y = y1; y <= y2; y++) {
 		term.dirty[y] = 1;
-		for(x = x1; x <= x2; x++)
+		for(x = x1; x <= x2; x++) {
+			if(bce) {
+				term.line[y][x] = term.c.attr;
+				memcpy(term.line[y][x].c, " ", 2);
+				term.line[y][x].state |= GLYPH_SET;
+			} else {
 				term.line[y][x].state = 0;
 			}
+		}
+	}
 }
 
 void
@@ -1334,13 +1341,13 @@ tdeletechar(int n) {
 	term.dirty[term.c.y] = 1;
 
 	if(src >= term.col) {
-		tclearregion(term.c.x, term.c.y, term.col-1, term.c.y);
+		tclearregion(term.c.x, term.c.y, term.col-1, term.c.y, 0);
 		return;
 	}
 
 	memmove(&term.line[term.c.y][dst], &term.line[term.c.y][src],
 			size * sizeof(Glyph));
-	tclearregion(term.col-n, term.c.y, term.col-1, term.c.y);
+	tclearregion(term.col-n, term.c.y, term.col-1, term.c.y, 0);
 }
 
 void
@@ -1352,13 +1359,13 @@ tinsertblank(int n) {
 	term.dirty[term.c.y] = 1;
 
 	if(dst >= term.col) {
-		tclearregion(term.c.x, term.c.y, term.col-1, term.c.y);
+		tclearregion(term.c.x, term.c.y, term.col-1, term.c.y, 0);
 		return;
 	}
 
 	memmove(&term.line[term.c.y][dst], &term.line[term.c.y][src],
 			size * sizeof(Glyph));
-	tclearregion(src, term.c.y, dst - 1, term.c.y);
+	tclearregion(src, term.c.y, dst - 1, term.c.y, 0);
 }
 
 void
@@ -1542,8 +1549,10 @@ tsetmode(bool priv, bool set, int *args, int narg) {
 			case 47:
 			case 1047: {
 				alt = IS_SET(MODE_ALTSCREEN);
-				if(alt)
-					tclearregion(0, 0, term.col-1, term.row-1);
+				if(alt) {
+					tclearregion(0, 0, term.col-1,
+							term.row-1, 0);
+				}
 				if(set ^ alt)		/* set is always 1 or 0 */
 					tswapscreen();
 				if(*args != 1049)
@@ -1662,17 +1671,19 @@ csihandle(void) {
 		sel.bx = -1;
 		switch(csiescseq.arg[0]) {
 		case 0: /* below */
-			tclearregion(term.c.x, term.c.y, term.col-1, term.c.y);
-			if(term.c.y < term.row-1)
-				tclearregion(0, term.c.y+1, term.col-1, term.row-1);
+			tclearregion(term.c.x, term.c.y, term.col-1, term.c.y, 1);
+			if(term.c.y < term.row-1) {
+				tclearregion(0, term.c.y+1, term.col-1,
+						term.row-1, 1);
+			}
 			break;
 		case 1: /* above */
 			if(term.c.y > 1)
-				tclearregion(0, 0, term.col-1, term.c.y-1);
-			tclearregion(0, term.c.y, term.c.x, term.c.y);
+				tclearregion(0, 0, term.col-1, term.c.y-1, 1);
+			tclearregion(0, term.c.y, term.c.x, term.c.y, 1);
 			break;
 		case 2: /* all */
-			tclearregion(0, 0, term.col-1, term.row-1);
+			tclearregion(0, 0, term.col-1, term.row-1, 1);
 			break;
 		default:
 			goto unknown;
@@ -1681,13 +1692,14 @@ csihandle(void) {
 	case 'K': /* EL -- Clear line */
 		switch(csiescseq.arg[0]) {
 		case 0: /* right */
-			tclearregion(term.c.x, term.c.y, term.col-1, term.c.y);
+			tclearregion(term.c.x, term.c.y, term.col-1,
+					term.c.y, 1);
 			break;
 		case 1: /* left */
-			tclearregion(0, term.c.y, term.c.x, term.c.y);
+			tclearregion(0, term.c.y, term.c.x, term.c.y, 1);
 			break;
 		case 2: /* all */
-			tclearregion(0, term.c.y, term.col-1, term.c.y);
+			tclearregion(0, term.c.y, term.col-1, term.c.y, 1);
 			break;
 		}
 		break;
@@ -1712,7 +1724,8 @@ csihandle(void) {
 		break;
 	case 'X': /* ECH -- Erase <n> char */
 		DEFAULT(csiescseq.arg[0], 1);
-		tclearregion(term.c.x, term.c.y, term.c.x + csiescseq.arg[0], term.c.y);
+		tclearregion(term.c.x, term.c.y, term.c.x + csiescseq.arg[0],
+				term.c.y, 0);
 		break;
 	case 'P': /* DCH -- Delete <n> char */
 		DEFAULT(csiescseq.arg[0], 1);
@@ -2505,6 +2518,7 @@ xinit(void) {
 		xw.fy = 0;
 	}
 
+	/* Events */
 	attrs.background_pixel = dc.col[defaultbg].pixel;
 	attrs.border_pixel = dc.col[defaultbg].pixel;
 	attrs.bit_gravity = NorthWestGravity;
@@ -2898,6 +2912,7 @@ drawregion(int x1, int y1, int x2, int y2) {
 					ox = x;
 					base = new;
 				}
+
 				sl = utf8size(new.c);
 				memcpy(buf+ib, new.c, sl);
 				ib += sl;

st.info

@@ -3,7 +3,7 @@
 st| simpleterm,
 	acsc=``aaffggiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
 	am,
-#	bce,
+	bce,
 	bel=^G,
 #	blink=\E[5m,
 	bold=\E[1m,