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LibGfx: Implement drawing dotted/dashed diagonal Lines

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The implementation simply tracks the number of pixels we have drawn so
far and draws pixels in an on-and-off pattern
This commit is contained in:
Arda Cinar 2023-01-12 14:56:23 +03:00 • committed by Jelle Raaijmakers
parent add2e2c076
commit c8d7bf5449
1 changed files with 19 additions and 5 deletions
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24
Userland/Libraries/LibGfx/Painter.cpp
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@ -2015,9 +2015,6 @@ void Painter::draw_line(IntPoint a_p1, IntPoint a_p2, Color color, int thickness
return;
}
// FIXME: Implement dotted/dashed diagonal lines.
VERIFY(style == LineStyle::Solid);
int const adx = abs(point2.x() - point1.x());
int const ady = abs(point2.y() - point1.y());
@ -2034,13 +2031,30 @@ void Painter::draw_line(IntPoint a_p1, IntPoint a_p2, Color color, int thickness
int const dy = point2.y() - point1.y();
int error = 0;
size_t number_of_pixels_drawn = 0;
auto draw_pixel_in_line = [&](int x, int y) {
bool should_draw_line = true;
if (style == LineStyle::Dotted && number_of_pixels_drawn % 2 == 1)
should_draw_line = false;
else if (style == LineStyle::Dashed && number_of_pixels_drawn % 6 >= 3)
should_draw_line = false;
if (should_draw_line)
draw_physical_pixel({ x, y }, color, thickness);
else if (!alternate_color_is_transparent)
draw_physical_pixel({ x, y }, alternate_color, thickness);
number_of_pixels_drawn++;
};
if (dx > dy) {
int const y_step = dy == 0 ? 0 : (dy > 0 ? 1 : -1);
int const delta_error = 2 * abs(dy);
int y = point1.y();
for (int x = point1.x(); x <= point2.x(); ++x) {
if (clip_rect.contains(x, y))
draw_physical_pixel({ x, y }, color, thickness);
draw_pixel_in_line(x, y);
error += delta_error;
if (error >= dx) {
y += y_step;
@ -2053,7 +2067,7 @@ void Painter::draw_line(IntPoint a_p1, IntPoint a_p2, Color color, int thickness
int x = point1.x();
for (int y = point1.y(); y <= point2.y(); ++y) {
if (clip_rect.contains(x, y))
draw_physical_pixel({ x, y }, color, thickness);
draw_pixel_in_line(x, y);
error += delta_error;
if (error >= dy) {
x += x_step;