[planner: 6/32] libgnomecanvas: Restore various utility functions used by GnomeCanvasLine
- From: Mart Raudsepp <mraudsepp src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [planner: 6/32] libgnomecanvas: Restore various utility functions used by GnomeCanvasLine
- Date: Sun, 20 Jun 2021 18:13:50 +0000 (UTC)
commit 224f7c9ba56f4229ed1ff29643ee9bf011700a89
Author: Mart Raudsepp <leio gentoo org>
Date: Sun Mar 21 16:14:35 2021 +0200
libgnomecanvas: Restore various utility functions used by GnomeCanvasLine
We'll need those temporarily for GnomeCanvasLine.
This is essentially a partial revert of evolution
commit 61900647523c854d322ed6a7f79922d7e03c33a0
src/libgnomecanvas/gnome-canvas-util.c | 266 +++++++++++++++++++++++++++++++++
src/libgnomecanvas/gnome-canvas-util.h | 36 +++++
2 files changed, 302 insertions(+)
---
diff --git a/src/libgnomecanvas/gnome-canvas-util.c b/src/libgnomecanvas/gnome-canvas-util.c
index f8e33934..58697004 100644
--- a/src/libgnomecanvas/gnome-canvas-util.c
+++ b/src/libgnomecanvas/gnome-canvas-util.c
@@ -102,6 +102,272 @@ gnome_canvas_points_free (GnomeCanvasPoints *points)
}
}
+/**
+ * gnome_canvas_get_miter_points:
+ * @x1: X coordinate of the first point
+ * @y1: Y coordinate of the first point
+ * @x2: X coordinate of the second (angle) point
+ * @y2: Y coordinate of the second (angle) point
+ * @x3: X coordinate of the third point
+ * @y3: Y coordinate of the third point
+ * @width: Width of the line
+ * @mx1: The X coordinate of the first miter point is returned here.
+ * @my1: The Y coordinate of the first miter point is returned here.
+ * @mx2: The X coordinate of the second miter point is returned here.
+ * @my2: The Y coordinate of the second miter point is returned here.
+ *
+ * Given three points forming an angle, computes the coordinates of the inside
+ * and outside points of the mitered corner formed by a line of a given width at
+ * that angle.
+ *
+ * Return value: FALSE if the angle is less than 11 degrees (this is the same
+ * threshold as X uses. If this occurs, the return points are not modified.
+ * Otherwise, returns TRUE.
+ **/
+gint
+gnome_canvas_get_miter_points (gdouble x1,
+ gdouble y1,
+ gdouble x2,
+ gdouble y2,
+ gdouble x3,
+ gdouble y3,
+ gdouble width,
+ gdouble *mx1,
+ gdouble *my1,
+ gdouble *mx2,
+ gdouble *my2)
+{
+ gdouble theta1; /* angle of segment p2-p1 */
+ gdouble theta2; /* angle of segment p2-p3 */
+ gdouble theta; /* angle between line segments */
+ gdouble theta3; /* angle that bisects theta1 and theta2 and points to p1 */
+ gdouble dist; /* distance of miter points from p2 */
+ gdouble dx, dy; /* x and y offsets corresponding to dist */
+
+#define ELEVEN_DEGREES (11.0 * G_PI / 180.0)
+
+ if (y2 == y1)
+ theta1 = (x2 < x1) ? 0.0 : G_PI;
+ else if (x2 == x1)
+ theta1 = (y2 < y1) ? G_PI_2 : -G_PI_2;
+ else
+ theta1 = atan2 (y1 - y2, x1 - x2);
+
+ if (y3 == y2)
+ theta2 = (x3 > x2) ? 0 : G_PI;
+ else if (x3 == x2)
+ theta2 = (y3 > y2) ? G_PI_2 : -G_PI_2;
+ else
+ theta2 = atan2 (y3 - y2, x3 - x2);
+
+ theta = theta1 - theta2;
+
+ if (theta > G_PI)
+ theta -= 2.0 * G_PI;
+ else if (theta < -G_PI)
+ theta += 2.0 * G_PI;
+
+ if ((theta < ELEVEN_DEGREES) && (theta > -ELEVEN_DEGREES))
+ return FALSE;
+
+ dist = 0.5 * width / sin (0.5 * theta);
+ if (dist < 0.0)
+ dist = -dist;
+
+ theta3 = (theta1 + theta2) / 2.0;
+ if (sin (theta3 - (theta1 + G_PI)) < 0.0)
+ theta3 += G_PI;
+
+ dx = dist * cos (theta3);
+ dy = dist * sin (theta3);
+
+ *mx1 = x2 + dx;
+ *mx2 = x2 - dx;
+ *my1 = y2 + dy;
+ *my2 = y2 - dy;
+
+ return TRUE;
+}
+
+/**
+ * gnome_canvas_get_butt_points:
+ * @x1: X coordinate of first point in the line
+ * @y1: Y cooordinate of first point in the line
+ * @x2: X coordinate of second point (endpoint) of the line
+ * @y2: Y coordinate of second point (endpoint) of the line
+ * @width: Width of the line
+ * @project: Whether the butt points should project out by width/2 distance
+ * @bx1: X coordinate of first butt point is returned here
+ * @by1: Y coordinate of first butt point is returned here
+ * @bx2: X coordinate of second butt point is returned here
+ * @by2: Y coordinate of second butt point is returned here
+ *
+ * Computes the butt points of a line segment.
+ **/
+void
+gnome_canvas_get_butt_points (gdouble x1, gdouble y1, gdouble x2, gdouble y2,
+ gdouble width, gint project,
+ gdouble *bx1, gdouble *by1, gdouble *bx2, gdouble *by2)
+{
+ gdouble length;
+ gdouble dx, dy;
+
+ width *= 0.5;
+ dx = x2 - x1;
+ dy = y2 - y1;
+ length = sqrt (dx * dx + dy * dy);
+
+ if (length < GNOME_CANVAS_EPSILON) {
+ *bx1 = *bx2 = x2;
+ *by1 = *by2 = y2;
+ } else {
+ dx = -width * (y2 - y1) / length;
+ dy = width * (x2 - x1) / length;
+
+ *bx1 = x2 + dx;
+ *bx2 = x2 - dx;
+ *by1 = y2 + dy;
+ *by2 = y2 - dy;
+
+ if (project) {
+ *bx1 += dy;
+ *bx2 += dy;
+ *by1 -= dx;
+ *by2 -= dx;
+ }
+ }
+}
+
+/**
+ * gnome_canvas_polygon_to_point:
+ * @poly: Vertices of the polygon. X coordinates are in the even indices, and Y
+ * coordinates are in the odd indices
+ * @num_points: Number of points in the polygon
+ * @x: X coordinate of the point
+ * @y: Y coordinate of the point
+ *
+ * Computes the distance between a point and a polygon.
+ *
+ * Return value: The distance from the point to the polygon, or zero if the
+ * point is inside the polygon.
+ **/
+gdouble
+gnome_canvas_polygon_to_point (gdouble *poly, gint num_points, gdouble x, gdouble y)
+{
+ gdouble best;
+ gint intersections;
+ gint i;
+ gdouble *p;
+ gdouble dx, dy;
+
+ /* Iterate through all the edges in the polygon, updating best and
+ * intersections.
+ *
+ * When computing intersections, include left X coordinate of line
+ * within its range, but not Y coordinate. Otherwise if the point
+ * lies exactly below a vertex we'll count it as two intersections. */
+
+ best = 1.0e36;
+ intersections = 0;
+
+ for (i = num_points, p = poly; i > 1; i--, p += 2) {
+ gdouble px, py, dist;
+
+ /* Compute the point on the current edge closest to the
+ * point and update the intersection count. This must be
+ * done separately for vertical edges, horizontal edges,
+ * and others. */
+
+ if (p[2] == p[0]) {
+ /* Vertical edge */
+
+ px = p[0];
+
+ if (p[1] >= p[3]) {
+ py = MIN (p[1], y);
+ py = MAX (py, p[3]);
+ } else {
+ py = MIN (p[3], y);
+ py = MAX (py, p[1]);
+ }
+ } else if (p[3] == p[1]) {
+ /* Horizontal edge */
+
+ py = p[1];
+
+ if (p[0] >= p[2]) {
+ px = MIN (p[0], x);
+ px = MAX (px, p[2]);
+
+ if ((y < py) && (x < p[0]) && (x >= p[2]))
+ intersections++;
+ } else {
+ px = MIN (p[2], x);
+ px = MAX (px, p[0]);
+
+ if ((y < py) && (x < p[2]) && (x >= p[0]))
+ intersections++;
+ }
+ } else {
+ gdouble m1, b1, m2, b2;
+ gint lower;
+
+ /* Diagonal edge. Convert the edge to a line equation (y = m1*x + b1), then
+ * compute a line perpendicular to this edge but passing through the point,
+ * (y = m2*x + b2).
+ */
+
+ m1 = (p[3] - p[1]) / (p[2] - p[0]);
+ b1 = p[1] - m1 * p[0];
+
+ m2 = -1.0 / m1;
+ b2 = y - m2 * x;
+
+ px = (b2 - b1) / (m1 - m2);
+ py = m1 * px + b1;
+
+ if (p[0] > p[2]) {
+ if (px > p[0]) {
+ px = p[0];
+ py = p[1];
+ } else if (px < p[2]) {
+ px = p[2];
+ py = p[3];
+ }
+ } else {
+ if (px > p[2]) {
+ px = p[2];
+ py = p[3];
+ } else if (px < p[0]) {
+ px = p[0];
+ py = p[1];
+ }
+ }
+
+ lower = (m1 * x + b1) > y;
+
+ if (lower && (x >= MIN (p[0], p[2])) && (x < MAX (p[0], p[2])))
+ intersections++;
+ }
+
+ /* Compute the distance to the closest point, and see if that is the best so far */
+
+ dx = x - px;
+ dy = y - py;
+ dist = sqrt (dx * dx + dy * dy);
+ if (dist < best)
+ best = dist;
+ }
+
+ /* We've processed all the points. If the number of
+ * intersections is odd, the point is inside the polygon. */
+
+ if (intersections & 0x1)
+ return 0.0;
+ else
+ return best;
+}
+
/* Here are some helper functions for aa rendering: */
/**
diff --git a/src/libgnomecanvas/gnome-canvas-util.h b/src/libgnomecanvas/gnome-canvas-util.h
index ed491048..22d36efd 100644
--- a/src/libgnomecanvas/gnome-canvas-util.h
+++ b/src/libgnomecanvas/gnome-canvas-util.h
@@ -56,6 +56,42 @@ GnomeCanvasPoints *gnome_canvas_points_ref (GnomeCanvasPoints *points);
/* Decrease ref count and free structure if it has reached zero */
void gnome_canvas_points_free (GnomeCanvasPoints *points);
+/* Given three points forming an angle, compute the coordinates of the inside and outside points of
+ * the mitered corner formed by a line of a given width at that angle.
+ *
+ * If the angle is less than 11 degrees, then FALSE is returned and the return points are not
+ * modified. Otherwise, TRUE is returned.
+ */
+gint gnome_canvas_get_miter_points (gdouble x1, gdouble y1, gdouble x2, gdouble y2, gdouble x3, gdouble y3,
+ gdouble width,
+ gdouble *mx1, gdouble *my1, gdouble *mx2, gdouble *my2);
+
+/* Compute the butt points of a line segment. If project is FALSE, then the results are as follows:
+ *
+ * -------------------* (bx1, by1)
+ * |
+ * (x1, y1) *------------------* (x2, y2)
+ * |
+ * -------------------* (bx2, by2)
+ *
+ * that is, the line is not projected beyond (x2, y2). If project is TRUE, then the results are as
+ * follows:
+ *
+ * -------------------* (bx1, by1)
+ * (x2, y2) |
+ * (x1, y1) *-------------* |
+ * |
+ * -------------------* (bx2, by2)
+ */
+void gnome_canvas_get_butt_points (gdouble x1, gdouble y1, gdouble x2, gdouble y2,
+ gdouble width, gint project,
+ gdouble *bx1, gdouble *by1, gdouble *bx2, gdouble *by2);
+
+/* Calculate the distance from a polygon to a point. The polygon's X coordinates are in the even
+ * indices of the poly array, and the Y coordinates are in the odd indices.
+ */
+gdouble gnome_canvas_polygon_to_point (gdouble *poly, gint num_points, gdouble x, gdouble y);
+
/* Sets the svp to the new value, requesting repaint on what's changed. This
* function takes responsibility for freeing new_svp. This routine also adds the
* svp's bbox to the item's.
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