[gtk/wip/otte/lottie: 20/38] pathbuilder: Add relative path commands

[Benjamin Otte <otte src gnome org>]

commit 6c32389652843e5e1e29ca1e34e0e7eb50166a36
Author: Benjamin Otte <otte redhat com>
Date:   Sat Nov 28 14:52:17 2020 +0100

    pathbuilder: Add relative path commands
    
    And gsk_path_builder_get_current_point().
    
    They will be needed by the string parser.

 docs/reference/gsk/gsk4-sections.txt |   5 ++
 gsk/gskpathbuilder.c                 | 103 +++++++++++++++++++++++++++++++++++
 gsk/gskpathbuilder.h                 |  19 +++++++
 3 files changed, 127 insertions(+)
---
diff --git a/docs/reference/gsk/gsk4-sections.txt b/docs/reference/gsk/gsk4-sections.txt
index e24292e295..8e50652f9f 100644
--- a/docs/reference/gsk/gsk4-sections.txt
+++ b/docs/reference/gsk/gsk4-sections.txt
@@ -293,12 +293,17 @@ gsk_path_builder_unref
 gsk_path_builder_to_path
 gsk_path_builder_free_to_path
 <SUBSECTION>
+gsk_path_builder_get_current_point
+<SUBSECTION>
 gsk_path_builder_add_rect
 gsk_path_builder_add_circle
 <SUBSECTION>
 gsk_path_builder_move_to
+gsk_path_builder_rel_move_to
 gsk_path_builder_line_to
+gsk_path_builder_rel_line_to
 gsk_path_builder_curve_to
+gsk_path_builder_rel_curve_to
 gsk_path_builder_close
 <SUBSECTION Private>
 GSK_TYPE_PATH_BUILDER
diff --git a/gsk/gskpathbuilder.c b/gsk/gskpathbuilder.c
index 16242a306d..4498309a1a 100644
--- a/gsk/gskpathbuilder.c
+++ b/gsk/gskpathbuilder.c
@@ -281,6 +281,25 @@ gsk_path_builder_add_contour (GskPathBuilder *builder,
   builder->contours = g_slist_prepend (builder->contours, contour);
 }
 
+/**
+ * gsk_path_builder_get_current_point:
+ * @builder: a #GskPathBuilder
+ *
+ * Gets the current point. The current point is used for relative
+ * drawing commands and updated after every operation.
+ *
+ * When @builder is created, the default current point is set to (0, 0).
+ *
+ * Returns: (transfer none) The current point
+ **/
+const graphene_point_t *
+gsk_path_builder_get_current_point (GskPathBuilder *builder)
+{
+  g_return_val_if_fail (builder != NULL, NULL);
+
+  return &builder->current_point;
+}
+
 /**
  * gsk_path_builder_add_path:
  * @builder: a #GskPathBuilder
@@ -383,6 +402,29 @@ gsk_path_builder_move_to (GskPathBuilder *builder,
   gsk_path_builder_ensure_current (builder);
 }
 
+/**
+ * gsk_path_builder_rel_move_to:
+ * @builder: a #GskPathBuilder
+ * @x: x offset
+ * @y: y offset
+ *
+ * Starts a new contour by placing the pen at @x, @y relative to the current
+ * point.
+ *
+ * This is the relative version of gsk_path_builder_move_to().
+ **/
+void
+gsk_path_builder_rel_move_to (GskPathBuilder *builder,
+                              float           x,
+                              float           y)
+{
+  g_return_if_fail (builder != NULL);
+
+  gsk_path_builder_move_to (builder,
+                            builder->current_point.x + x,
+                            builder->current_point.y + y);
+}
+
 /**
  * gsk_path_builder_line_to:
  * @builder: a #GskPathBuilder
@@ -411,6 +453,29 @@ gsk_path_builder_line_to (GskPathBuilder *builder,
                                    });
 }
 
+/**
+ * gsk_path_builder_line_to:
+ * @builder: a #GskPathBuilder
+ * @x: x offset
+ * @y: y offset
+ *
+ * Draws a line from the current point to a point offset to it by @x, @y
+ * and makes it the new current point.
+ *
+ * This is the relative version of gsk_path_builder_line_to().
+ **/
+void
+gsk_path_builder_rel_line_to (GskPathBuilder *builder,
+                              float           x,
+                              float           y)
+{
+  g_return_if_fail (builder != NULL);
+
+  gsk_path_builder_line_to (builder,
+                            builder->current_point.x + x,
+                            builder->current_point.y + y);
+}
+
 /**
  * gsk_path_builder_curve_to:
  * @builder: a #GskPathBuilder
@@ -424,6 +489,8 @@ gsk_path_builder_line_to (GskPathBuilder *builder,
  * Adds a [cubic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
  * from the current point to @x3, @y3 with @x1, @y1 and @x2, @y2 as the control
  * points.
+ *
+ * After this, @x3, @y3 will be the new current point.
  **/
 void
 gsk_path_builder_curve_to (GskPathBuilder *builder,
@@ -446,6 +513,42 @@ gsk_path_builder_curve_to (GskPathBuilder *builder,
                                    });
 }
 
+/**
+ * gsk_path_builder_rel_curve_to:
+ * @builder: a #GskPathBuilder
+ * @x1: x offset of first control point
+ * @y1: y offset of first control point
+ * @x2: x offset of second control point
+ * @y2: y offset of second control point
+ * @x3: x offset of the end of the curve
+ * @y3: y offset of the end of the curve
+ *
+ * Adds a [cubic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
+ * from the current point to @x3, @y3 with @x1, @y1 and @x2, @y2 as the control
+ * points. All coordinates are given relative to the current point.
+ *
+ * This is the relative version of gsk_path_builder_curve_to().
+ **/
+void
+gsk_path_builder_rel_curve_to (GskPathBuilder *builder,
+                               float           x1,
+                               float           y1,
+                               float           x2,
+                               float           y2,
+                               float           x3,
+                               float           y3)
+{
+  g_return_if_fail (builder != NULL);
+
+  gsk_path_builder_curve_to (builder,
+                             builder->current_point.x + x1,
+                             builder->current_point.y + y1,
+                             builder->current_point.x + x2,
+                             builder->current_point.y + y2,
+                             builder->current_point.x + x3,
+                             builder->current_point.y + y3);
+}
+
 /**
  * gsk_path_builder_close:
  * @builder: a #GskPathBuilder
diff --git a/gsk/gskpathbuilder.h b/gsk/gskpathbuilder.h
index 2bc7a3933d..4868ccf25e 100644
--- a/gsk/gskpathbuilder.h
+++ b/gsk/gskpathbuilder.h
@@ -45,6 +45,9 @@ GskPath *               gsk_path_builder_free_to_path           (GskPathBuilder
 GDK_AVAILABLE_IN_ALL
 GskPath *               gsk_path_builder_to_path                (GskPathBuilder         *builder) 
G_GNUC_WARN_UNUSED_RESULT;
 
+GDK_AVAILABLE_IN_ALL
+const graphene_point_t *gsk_path_builder_get_current_point      (GskPathBuilder         *builder);
+
 GDK_AVAILABLE_IN_ALL
 void                    gsk_path_builder_add_path               (GskPathBuilder         *builder,
                                                                  GskPath                *path);
@@ -61,10 +64,18 @@ void                    gsk_path_builder_move_to                (GskPathBuilder
                                                                  float                   x,
                                                                  float                   y);
 GDK_AVAILABLE_IN_ALL
+void                    gsk_path_builder_rel_move_to            (GskPathBuilder         *builder,
+                                                                 float                   x,
+                                                                 float                   y);
+GDK_AVAILABLE_IN_ALL
 void                    gsk_path_builder_line_to                (GskPathBuilder         *builder,
                                                                  float                   x,
                                                                  float                   y);
 GDK_AVAILABLE_IN_ALL
+void                    gsk_path_builder_rel_line_to            (GskPathBuilder         *builder,
+                                                                 float                   x,
+                                                                 float                   y);
+GDK_AVAILABLE_IN_ALL
 void                    gsk_path_builder_curve_to               (GskPathBuilder         *builder,
                                                                  float                   x1,
                                                                  float                   y1,
@@ -73,6 +84,14 @@ void                    gsk_path_builder_curve_to               (GskPathBuilder
                                                                  float                   x3,
                                                                  float                   y3);
 GDK_AVAILABLE_IN_ALL
+void                    gsk_path_builder_rel_curve_to           (GskPathBuilder         *builder,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2,
+                                                                 float                   x3,
+                                                                 float                   y3);
+GDK_AVAILABLE_IN_ALL
 void                    gsk_path_builder_close                  (GskPathBuilder         *builder);
 
 G_END_DECLS