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LibGfx: Fix glyph render to create implied points in start/end of path

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Implied point = point created by two subsequent "off curve" points.

Fixes following issues in function that builds glyph path from points:
- If first point is "off curve" it was wrongly treated as "on curve"
  which caused wrong first point position in the path.
- If both first and last points in the path are "off curve" implied
  point was not created between them which caused wrong path shape in
  the end of the path.
This commit is contained in:
Aliaksandr Kalenik 2023-05-26 00:53:05 +03:00 • committed by Andreas Kling
parent 6a886e4aac
commit 6891676fce
1 changed files with 50 additions and 69 deletions
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119
Userland/Libraries/LibGfx/Font/OpenType/Glyf.cpp
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@ -272,82 +272,63 @@ void Glyf::Glyph::rasterize_impl(Gfx::PathRasterizer& rasterizer, Gfx::AffineTra
Gfx::Path path; Gfx::Path path;
PointIterator point_iterator(m_slice, num_points, flags_offset, x_offset, y_offset, transform); PointIterator point_iterator(m_slice, num_points, flags_offset, x_offset, y_offset, transform);
int last_contour_end = -1; u32 current_point_index = 0;
i32 contour_index = 0; for (u16 contour_index = 0; contour_index < m_num_contours; contour_index++) {
u32 contour_size = 0; u32 current_contour_last_point_index = be_u16(m_slice.offset_pointer(contour_index * 2));
Optional<Gfx::FloatPoint> contour_start = {}; Optional<Gfx::FloatPoint> start_off_curve_point;
Optional<Gfx::FloatPoint> last_offcurve_point = {}; Optional<Gfx::FloatPoint> start_on_curve_point;
Optional<Gfx::FloatPoint> unprocessed_off_curve_point;
while (current_point_index <= current_contour_last_point_index) {
auto current_point = point_iterator.next();
current_point_index++;
if (!current_point.has_value())
break;
// Render glyph if (current_point->on_curve) {
while (true) { if (!start_on_curve_point.has_value()) {
if (!contour_start.has_value()) { start_on_curve_point = current_point->point;
if (contour_index >= m_num_contours) { path.move_to(current_point->point);
break;
} }
int current_contour_end = be_u16(m_slice.offset_pointer(contour_index++ * 2));
contour_size = current_contour_end - last_contour_end; if (unprocessed_off_curve_point.has_value()) {
last_contour_end = current_contour_end; path.quadratic_bezier_curve_to(unprocessed_off_curve_point.value(), current_point->point);
auto opt_item = point_iterator.next(); unprocessed_off_curve_point = {};
VERIFY(opt_item.has_value());
contour_start = opt_item.value().point;
path.move_to(contour_start.value());
contour_size--;
} else if (!last_offcurve_point.has_value()) {
if (contour_size > 0) {
auto opt_item = point_iterator.next();
// FIXME: Should we draw a line to the first point here?
if (!opt_item.has_value()) {
break;
}
auto item = opt_item.value();
contour_size--;
if (item.on_curve) {
path.line_to(item.point);
} else if (contour_size > 0) {
auto opt_next_item = point_iterator.next();
// FIXME: Should we draw a quadratic bezier to the first point here?
if (!opt_next_item.has_value()) {
break;
}
auto next_item = opt_next_item.value();
contour_size--;
if (next_item.on_curve) {
path.quadratic_bezier_curve_to(item.point, next_item.point);
} else { } else {
auto mid_point = (item.point + next_item.point) * 0.5f; path.line_to(current_point->point);
path.quadratic_bezier_curve_to(item.point, mid_point);
last_offcurve_point = next_item.point;
} }
} else { } else {
path.quadratic_bezier_curve_to(item.point, contour_start.value()); if (!start_on_curve_point.has_value() && !start_off_curve_point.has_value()) {
contour_start = {}; // If "off curve" point comes first it needs to be saved to use while closing the path
start_off_curve_point = current_point->point;
} }
if (unprocessed_off_curve_point.has_value()) {
// Two subsequent "off curve" points create implied "on-curve" point lying between them
auto implied_point = (unprocessed_off_curve_point.value() + current_point->point) * 0.5f;
if (!start_on_curve_point.has_value()) {
start_on_curve_point = implied_point;
path.move_to(implied_point);
}
path.quadratic_bezier_curve_to(unprocessed_off_curve_point.value(), implied_point);
}
unprocessed_off_curve_point = current_point->point;
}
}
if (start_off_curve_point.has_value()) {
// Close the path creating "implied" point if both first and last points were "off curve"
if (unprocessed_off_curve_point.has_value()) {
auto implied_point = (start_off_curve_point.value() + unprocessed_off_curve_point.value()) * 0.5f;
path.quadratic_bezier_curve_to(unprocessed_off_curve_point.value(), implied_point);
}
// Add bezier curve from new "implied point" to first "on curve" point in the path
path.quadratic_bezier_curve_to(start_off_curve_point.value(), start_on_curve_point.value());
} else if (unprocessed_off_curve_point.has_value()) {
// Add bezier curve to first "on curve" point using last "off curve" point
path.quadratic_bezier_curve_to(unprocessed_off_curve_point.value(), start_on_curve_point.value());
} else { } else {
path.line_to(contour_start.value()); path.line_to(start_on_curve_point.value());
contour_start = {};
}
} else {
auto point0 = last_offcurve_point.value();
last_offcurve_point = {};
if (contour_size > 0) {
auto opt_item = point_iterator.next();
// FIXME: Should we draw a quadratic bezier to the first point here?
if (!opt_item.has_value()) {
break;
}
auto item = opt_item.value();
contour_size--;
if (item.on_curve) {
path.quadratic_bezier_curve_to(point0, item.point);
} else {
auto mid_point = (point0 + item.point) * 0.5f;
path.quadratic_bezier_curve_to(point0, mid_point);
last_offcurve_point = item.point;
}
} else {
path.quadratic_bezier_curve_to(point0, contour_start.value());
contour_start = {};
}
} }
} }