[gtk/wip/otte/symbolic-paintable: 1/4] gtk: Add the GtkSymbolicPaintable interface

[Benjamin Otte <otte src gnome org>]

commit 37ca25d030bb2e35eba88d06a352486b4caaf4dc
Author: Benjamin Otte <otte redhat com>
Date:   Fri Aug 27 23:33:56 2021 +0200

    gtk: Add the GtkSymbolicPaintable interface

 gtk/gtk.h                  |   1 +
 gtk/gtksymbolicpaintable.c | 112 +++++++++++++++++++++++++++++++++++++++++++++
 gtk/gtksymbolicpaintable.h |  70 ++++++++++++++++++++++++++++
 gtk/meson.build            |   2 +
 4 files changed, 185 insertions(+)
---
diff --git a/gtk/gtk.h b/gtk/gtk.h
index 4d5dc5902d..0d4521e4ac 100644
--- a/gtk/gtk.h
+++ b/gtk/gtk.h
@@ -248,6 +248,7 @@
 #include <gtk/gtkstylecontext.h>
 #include <gtk/gtkstyleprovider.h>
 #include <gtk/gtkswitch.h>
+#include <gtk/gtksymbolicpaintable.h>
 #include <gtk/gtktext.h>
 #include <gtk/gtktextbuffer.h>
 #include <gtk/gtktextchild.h>
diff --git a/gtk/gtksymbolicpaintable.c b/gtk/gtksymbolicpaintable.c
new file mode 100644
index 0000000000..8995e6f3ae
--- /dev/null
+++ b/gtk/gtksymbolicpaintable.c
@@ -0,0 +1,112 @@
+/*
+ * Copyright © 2021 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte gnome org>
+ */
+
+#include "config.h"
+
+#include "gtksymbolicpaintable.h"
+
+/**
+ * GtkSymbolicPaintable:
+ *
+ * `GtkSymbolicPaintable` is an interface that support symbolic colors in
+ * paintables.
+ *
+ * `GdkPaintable`s implementing the interface will have the
+ * [vfunc@Gtk.SymbolicPaintableInterface.snapshot_symbolic] function called and
+ * have the colors for drawing symbolic icons passed. At least 4 colors are guaranteed
+ * to be passed every time.
+ *
+ * These 4 colors are the foreground color, and the colors to use for errors, warnings
+ * and success information in that order.
+ *
+ * More colors may be added in the future.
+ */
+
+G_DEFINE_INTERFACE (GtkSymbolicPaintable, gtk_symbolic_paintable, GDK_TYPE_PAINTABLE)
+
+static void
+gtk_symbolic_paintable_default_snapshot_symbolic (GtkSymbolicPaintable *paintable,
+                                                  GdkSnapshot          *snapshot,
+                                                  double                width,
+                                                  double                height,
+                                                  const GdkRGBA        *colors,
+                                                  gsize                 n_colors)
+{
+  gdk_paintable_snapshot (GDK_PAINTABLE (paintable), snapshot, width, height);
+}
+
+static void
+gtk_symbolic_paintable_default_init (GtkSymbolicPaintableInterface *iface)
+{
+  iface->snapshot_symbolic = gtk_symbolic_paintable_default_snapshot_symbolic;
+}
+
+/**
+ * gtk_symbolic_paintable_snapshot_symbolic
+ * @paintable: a `GtkSymbolicPaintable`
+ * @snapshot: a `GdkSnapshot` to snapshot to
+ * @width: width to snapshot in
+ * @height: height to snapshot in
+ * @colors: (array length=n_colors): a pointer to an array of colors
+ * @n_colors: The number of colors
+ *
+ * Snapshots the paintable with the given colors.
+ *
+ * If not at least 4 colors are provided, GTK will pad the array with default
+ * colors.
+ */
+void
+gtk_symbolic_paintable_snapshot_symbolic (GtkSymbolicPaintable   *paintable,
+                                          GdkSnapshot            *snapshot,
+                                          double                  width,
+                                          double                  height,
+                                          const GdkRGBA          *colors,
+                                          gsize                   n_colors)
+{
+  GtkSymbolicPaintableInterface *iface;
+
+  g_return_if_fail (GTK_IS_SYMBOLIC_PAINTABLE (paintable));
+  g_return_if_fail (snapshot != NULL);
+  g_return_if_fail (colors != NULL || n_colors == 0);
+
+  if (width <= 0.0 || height <= 0.0)
+    return;
+
+  iface = GTK_SYMBOLIC_PAINTABLE_GET_IFACE (paintable);
+
+  if (n_colors >= 4)
+    {
+      iface->snapshot_symbolic (paintable, snapshot, width, height, colors, n_colors);
+    }
+  else
+    {
+      /* Taken from GTK3, no idea where it got those from */
+      GdkRGBA fg_default = { 0.7450980392156863, 0.7450980392156863, 0.7450980392156863, 1.0 };
+      GdkRGBA error_default = { 0.796887159533074, 0, 0, 1.0 };
+      GdkRGBA warning_default = {0.9570458533607996, 0.47266346227206835, 0.2421911955443656, 1.0 };
+      GdkRGBA success_default = { 0.3046921492332342,0.6015716792553597, 0.023437857633325704, 1.0 };
+
+      iface->snapshot_symbolic (paintable, snapshot, width, height, (GdkRGBA[4]) {
+                                  n_colors > 0 ? colors[0] : fg_default,
+                                  n_colors > 1 ? colors[1] : error_default,
+                                  n_colors > 2 ? colors[2] : warning_default,
+                                  success_default,
+                                }, 4);
+    }
+}
diff --git a/gtk/gtksymbolicpaintable.h b/gtk/gtksymbolicpaintable.h
new file mode 100644
index 0000000000..66b984973b
--- /dev/null
+++ b/gtk/gtksymbolicpaintable.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright © 2021 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte gnome org>
+ */
+
+#ifndef __GTK_SYMBOLIC_PAINTABLE_H__
+#define __GTK_SYMBOLIC_PAINTABLE_H__
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#include <gtk/gtktypes.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_SYMBOLIC_PAINTABLE       (gtk_symbolic_paintable_get_type ())
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_INTERFACE (GtkSymbolicPaintable, gtk_symbolic_paintable, GTK, SYMBOLIC_PAINTABLE, GListModel)
+
+/**
+ * GtkSymbolicPaintableInterface:
+ * @snapshot_symbolic: Snapshot the paintable using the given colors. 
+ *   See `GtkSymbolicPaintable::snapshot_symbolic()` for details.
+ *   If this function is not implemented, [vfunc@Gdk.PaintableInterface.snaphsot]
+ *   will be called.
+ *
+ * The list of virtual functions for the `GtkSymbolicPaintable` interface.
+ * No function must be implemented, default implementations exist for each one.
+ */
+struct _GtkSymbolicPaintableInterface
+{
+  /*< private >*/
+  GTypeInterface g_iface;
+
+  /*< public >*/
+  void                  (* snapshot_symbolic)                           (GtkSymbolicPaintable   *paintable,
+                                                                         GdkSnapshot            *snapshot,
+                                                                         double                  width,
+                                                                         double                  height,
+                                                                         const GdkRGBA          *colors,
+                                                                         gsize                   n_colors);
+};
+
+GDK_AVAILABLE_IN_4_6
+void                    gtk_symbolic_paintable_snapshot_symbolic        (GtkSymbolicPaintable   *paintable,
+                                                                         GdkSnapshot            *snapshot,
+                                                                         double                  width,
+                                                                         double                  height,
+                                                                         const GdkRGBA          *colors,
+                                                                         gsize                   n_colors);
+
+G_END_DECLS
+
+#endif /* __GTK_SYMBOLIC_PAINTABLE_H__ */
diff --git a/gtk/meson.build b/gtk/meson.build
index bfb5105fe5..a4cdfabecc 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -391,6 +391,7 @@ gtk_public_sources = files([
   'gtkstylecontext.c',
   'gtkstyleprovider.c',
   'gtkswitch.c',
+  'gtksymbolicpaintable.c',
   'gtktestatcontext.c',
   'gtktestutils.c',
   'gtktext.c',
@@ -663,6 +664,7 @@ gtk_public_headers = files([
   'gtkstylecontext.h',
   'gtkstyleprovider.h',
   'gtkswitch.h',
+  'gtksymbolicpaintable.h',
   'gtktestatcontext.h',
   'gtktestutils.h',
   'gtktext.h',