term.ui: add dashed lines and rectangles (#6848)

vlib/term/ui/ui.v

@@ -10,7 +10,7 @@ pub:
 }
 
 pub fn (c Color) hex() string {
-	return '#${c.r.hex()}${c.g.hex()}${c.b.hex()}'
+	return '#$c.r.hex()$c.g.hex()$c.b.hex()'
 }
 
 // Synchronized Updates spec, designed to avoid tearing during renders
@@ -22,7 +22,9 @@ const (
 
 [inline]
 pub fn (mut ctx Context) write(s string) {
-	if s == '' { return }
+	if s == '' {
+		return
+	}
 	ctx.print_buf.push_many(s.str, s.len)
 }
 
@@ -103,29 +105,26 @@ pub fn (mut ctx Context) draw_text(x int, y int, s string) {
 pub fn (mut ctx Context) draw_line(x int, y int, x2 int, y2 int) {
 	min_x, min_y := if x < x2 { x } else { x2 }, if y < y2 { y } else { y2 }
 	max_x, _ := if x > x2 { x } else { x2 }, if y > y2 { y } else { y2 }
-
 	if y == y2 {
 		// Horizontal line, performance improvement
 		ctx.set_cursor_position(min_x, min_y)
 		ctx.write(strings.repeat(` `, max_x + 1 - min_x))
 		return
 	}
-
 	// Draw the various points with Bresenham's line algorithm:
 	mut x0, x1 := x, x2
 	mut y0, y1 := y, y2
-
 	sx := if x0 < x1 { 1 } else { -1 }
 	sy := if y0 < y1 { 1 } else { -1 }
 	dx := if x0 < x1 { x1 - x0 } else { x0 - x1 }
 	dy := if y0 < y1 { y0 - y1 } else { y1 - y0 } // reversed
-
 	mut err := dx + dy
-
 	for {
 		// res << Segment{ x0, y0 }
 		ctx.draw_point(x0, y0)
-		if x0 == x1 && y0 == y1 { break }
+		if x0 == x1 && y0 == y1 {
+			break
+		}
 		e2 := 2 * err
 		if e2 >= dy {
 			err += dy
@@ -138,25 +137,75 @@ pub fn (mut ctx Context) draw_line(x int, y int, x2 int, y2 int) {
 	}
 }
 
+pub fn (mut ctx Context) draw_dashed_line(x int, y int, x2 int, y2 int) {
+	// Draw the various points with Bresenham's line algorithm:
+	mut x0, x1 := x, x2
+	mut y0, y1 := y, y2
+	sx := if x0 < x1 { 1 } else { -1 }
+	sy := if y0 < y1 { 1 } else { -1 }
+	dx := if x0 < x1 { x1 - x0 } else { x0 - x1 }
+	dy := if y0 < y1 { y0 - y1 } else { y1 - y0 } // reversed
+	mut err := dx + dy
+	mut i := 0
+	for {
+		if i % 2 == 0 {
+			ctx.draw_point(x0, y0)
+		}
+		if x0 == x1 && y0 == y1 {
+			break
+		}
+		e2 := 2 * err
+		if e2 >= dy {
+			err += dy
+			x0 += sx
+		}
+		if e2 <= dx {
+			err += dx
+			y0 += sy
+		}
+		i++
+	}
+}
+
 pub fn (mut ctx Context) draw_rect(x int, y int, x2 int, y2 int) {
 	if y == y2 || x == x2 {
 		ctx.draw_line(x, y, x2, y2)
 		return
 	}
-
+	min_y, max_y := if y < y2 { y, y2 } else { y2, y }
-	min_y, max_y := if y < y2 { y } else { y2 }, if y > y2 { y } else { y2 }
-
 	for y_pos in min_y .. max_y + 1 {
 		ctx.draw_line(x, y_pos, x2, y_pos)
 	}
 }
 
+pub fn (mut ctx Context) draw_empty_dashed_rect(x int, y int, x2 int, y2 int) {
+	if y == y2 || x == x2 {
+		ctx.draw_dashed_line(x, y, x2, y2)
+		return
+	}
+
+	min_x, max_x := if x < x2 { x, x2 } else { x2, x }
+	min_y, max_y := if y < y2 { y, y2 } else { y2, y }
+
+	ctx.draw_dashed_line(min_x, min_y, max_x, min_y)
+	ctx.draw_dashed_line(min_x, min_y, min_x, max_y)
+	if (max_y - min_y) & 1 == 0 {
+		ctx.draw_dashed_line(min_x, max_y, max_x, max_y)
+	} else {
+		ctx.draw_dashed_line(min_x + 1, max_y, max_x, max_y)
+	}
+	if (max_x - min_x) & 1 == 0 {
+		ctx.draw_dashed_line(max_x, min_y, max_x, max_y)
+	} else {
+		ctx.draw_dashed_line(max_x, min_y + 1, max_x, max_y)
+	}
+}
+
 pub fn (mut ctx Context) draw_empty_rect(x int, y int, x2 int, y2 int) {
 	if y == y2 || x == x2 {
 		ctx.draw_line(x, y, x2, y2)
 		return
 	}
-
 	ctx.draw_line(x, y, x2, y)
 	ctx.draw_line(x, y2, x2, y2)
 	ctx.draw_line(x, y, x, y2)
@@ -168,3 +217,9 @@ pub fn (mut ctx Context) horizontal_separator(y int) {
 	ctx.set_cursor_position(0, y)
 	ctx.write(strings.repeat(/* `⎽` */`-`, ctx.window_width))
 }
+
+
+[inline]
+fn abs(a int) int {
+	return if a < 0 { -a } else { a }
+}