libpayload: cbgfx: Add draw_line()

Add a function draw_line() to draw either a horizontal or vertical line
segment.

Theoretically a horizontal line can also be drawn by calling
draw_rounded_box() with dim_rel.x being the line length and dim_rel.y
being the line width. However, due to the truncation in integer division
when converting relative coordinates to absolute ones, this will
potentially produce inconsistent line widths, depending on the value of
pos_rel.y.

It is guaranteed that draw_line() will produce consistent line widths,
regardless of the position of the line. Also, when the thickness
argument is zero, this function is able to draw a line with 1-pixel
width, which is not achievable by draw_rounded_box().

BRANCH=puff
BUG=b:146399181, b:161424726
TEST=emerge-puff libpayload

Change-Id: I2d50414c4bfed343516197da9bb50791c89ba4c2
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43508
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Joel Kitching <kitching@google.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/payloads/libpayload/include/cbgfx.h b/payloads/libpayload/include/cbgfx.h
index 84e76f26d1..f2883b0c43 100644
--- a/payloads/libpayload/include/cbgfx.h
+++ b/payloads/libpayload/include/cbgfx.h
@@ -133,6 +133,22 @@ int draw_rounded_box(const struct scale *pos_rel, const struct scale *dim_rel,
 		     const struct fraction *radius);
 
 /**
+ * Draw a horizontal or vertical line segment on screen. If horizontal, pos1
+ * must be the left endpoint. If vertical, pos1 must be the top endpoint. When
+ * the specified thickness is zero (or truncated to zero), a line with 1-pixel
+ * width will be drawn.
+ *
+ * @param[in] pos1	Start position of the line relative to the canvas.
+ * @param[in] pos2	End position of the line relative to the canvas.
+ * @param[in] thickness Thickness of the line relative to the canvas.
+ * @param[in] rgb       Color of the line.
+ *
+ * @return CBGFX_* error codes
+ */
+int draw_line(const struct scale *pos1, const struct scale *pos2,
+	      const struct fraction *thickness, const struct rgb_color *rgb);
+
+/**
  * Clear the canvas
  */
 int clear_canvas(const struct rgb_color *rgb);