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214f5a6f98
When we allocate a graphene_point_t on the stack, there's no guarantee that it will be aligned at an 8-byte boundary, which is an assumption made by gsk_pathop_encode() (which wants to use the lowest 3 bits to encode the operation). In the places where it matters, force the points on the stack and embedded in structs to be nicely aligned. By using a distinct type for this (a union with a suitable size and alignment), we ensure that the compiler will warn or error whenever we can't prove that a particular point is, in fact, suitably aligned. We can go from a `GskAlignedPoint *` to a `graphene_point_t *` (which is always valid, because the `GskAlignedPoint` is aligned) via &aligned_points[0].pt, but we cannot go back the other way (which is not always valid, because the `graphene_point_t` is not necessarily aligned nicely) without a cast. In practice, it seems that a graphene_point_t on x86_64 *is* usually placed at an 8-byte boundary, but this is not the case on 32-bit architectures or on s390x. In many cases we can avoid needing an explicit reference to the more complicated type by making use of a transparent union. There's already at least one transparent union in GSK's public API, so it's presumably portable enough to match GTK's requirements. Increasing the alignment of GskAlignedPoint also requires adjusting how a GskStandardContour is allocated and initialized. This data structure allocates extra memory to hold an array of GskAlignedPoint outside the bounds of the struct itself, and that array now needs to be aligned suitably. Previously the array started with at next byte after the flexible array of gskpathop, but the alignment of a gskpathop is only 4 bytes on 32-bit architectures, so depending on the number of gskpathop in the trailing flexible array, that pointer might be an unsuitable location to allocate a GskAlignedPoint. Resolves: https://gitlab.gnome.org/GNOME/gtk/-/issues/6395 Signed-off-by: Simon McVittie <smcv@debian.org>
99 lines
6.9 KiB
C
99 lines
6.9 KiB
C
/*
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* Copyright © 2020 Benjamin Otte
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*
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* Authors: Benjamin Otte <otte@gnome.org>
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*/
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#pragma once
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#include "gskpathprivate.h"
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#include "gskpathpoint.h"
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#include "gskpathopprivate.h"
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#include "gskboundingboxprivate.h"
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G_BEGIN_DECLS
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GskContour * gsk_standard_contour_new (GskPathFlags flags,
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const GskAlignedPoint *points,
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gsize n_points,
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const gskpathop *ops,
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gsize n_ops,
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gssize offset);
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GskContour * gsk_circle_contour_new (const graphene_point_t *center,
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float radius);
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GskContour * gsk_rect_contour_new (const graphene_rect_t *rect);
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GskContour * gsk_rounded_rect_contour_new (const GskRoundedRect *rounded_rect);
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const char * gsk_contour_get_type_name (const GskContour *self);
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void gsk_contour_copy (GskContour * dest,
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const GskContour *src);
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GskContour * gsk_contour_dup (const GskContour *src);
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GskContour * gsk_contour_reverse (const GskContour *src);
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gsize gsk_contour_get_size (const GskContour *self);
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GskPathFlags gsk_contour_get_flags (const GskContour *self);
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void gsk_contour_print (const GskContour *self,
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GString *string);
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gboolean gsk_contour_get_bounds (const GskContour *self,
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GskBoundingBox *bounds);
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gboolean gsk_contour_get_stroke_bounds (const GskContour *self,
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const GskStroke *stroke,
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GskBoundingBox *bounds);
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gboolean gsk_contour_foreach (const GskContour *self,
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GskPathForeachFunc func,
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gpointer user_data);
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int gsk_contour_get_winding (const GskContour *self,
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const graphene_point_t *point);
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gsize gsk_contour_get_n_ops (const GskContour *self);
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gboolean gsk_contour_get_closest_point (const GskContour *self,
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const graphene_point_t *point,
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float threshold,
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GskPathPoint *result,
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float *out_dist);
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void gsk_contour_get_position (const GskContour *self,
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const GskPathPoint *point,
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graphene_point_t *pos);
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void gsk_contour_get_tangent (const GskContour *self,
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const GskPathPoint *point,
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GskPathDirection direction,
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graphene_vec2_t *tangent);
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float gsk_contour_get_curvature (const GskContour *self,
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const GskPathPoint *point,
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GskPathDirection direction,
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graphene_point_t *center);
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void gsk_contour_add_segment (const GskContour *self,
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GskPathBuilder *builder,
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gboolean emit_move_to,
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const GskPathPoint *start,
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const GskPathPoint *end);
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gpointer gsk_contour_init_measure (const GskContour *self,
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float tolerance,
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float *out_length);
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void gsk_contour_free_measure (const GskContour *self,
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gpointer data);
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void gsk_contour_get_point (const GskContour *self,
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gpointer measure_data,
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float distance,
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GskPathPoint *result);
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float gsk_contour_get_distance (const GskContour *self,
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const GskPathPoint *point,
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gpointer measure_data);
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G_END_DECLS
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