[gnome-shell] [ShellSlicer] New class to display center of child

[Colin Walters <walters src gnome org>]

commit 262f92e0be5375f7cb93bbc7516bce4c77c70ba3
Author: Colin Walters <walters verbum org>
Date:   Sat Dec 26 11:58:07 2009 -0500

    [ShellSlicer] New class to display center of child
    
    A #StBin that has 0 minimum size, and will clip its child
    in the middle.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=605491

 src/Makefile.am    |    2 +
 src/shell-slicer.c |  162 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/shell-slicer.h |   33 +++++++++++
 3 files changed, 197 insertions(+), 0 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 0b9ea5e..2c81a23 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -85,6 +85,8 @@ libgnome_shell_la_SOURCES =			\
 	shell-global.c				\
 	shell-global.h				\
 	shell-global-private.h			\
+	shell-slicer.c              \
+	shell-slicer.h              \
 	shell-stack.c				\
 	shell-stack.h				\
 	shell-tray-manager.c			\
diff --git a/src/shell-slicer.c b/src/shell-slicer.c
new file mode 100644
index 0000000..db59df8
--- /dev/null
+++ b/src/shell-slicer.c
@@ -0,0 +1,162 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/**
+ * SECTION:shell-slicer
+ * @short_description: Display only part of another actor
+ *
+ * A #StBin that has 0 minimum size, and will clip its child
+ * in the middle.
+ */
+
+#include "config.h"
+
+#include "shell-slicer.h"
+
+G_DEFINE_TYPE (ShellSlicer,
+               shell_slicer,
+               ST_TYPE_BIN);
+
+static void
+shell_slicer_get_preferred_width (ClutterActor *self,
+                                  gfloat        for_height,
+                                  gfloat       *min_width_p,
+                                  gfloat       *natural_width_p)
+{
+  ClutterActor *child = st_bin_get_child (ST_BIN (self));
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));
+
+  st_theme_node_adjust_for_height (theme_node, &for_height);
+
+  if (min_width_p)
+    *min_width_p = 0;
+
+  if (child == NULL)
+    {
+      if (natural_width_p)
+        *natural_width_p = 0;
+    }
+  else
+    {
+      clutter_actor_get_preferred_width (child, for_height,
+                                         NULL,
+                                         natural_width_p);
+    }
+
+  st_theme_node_adjust_preferred_width (theme_node, min_width_p, natural_width_p);
+}
+
+static void
+shell_slicer_get_preferred_height (ClutterActor *self,
+                                   gfloat        for_width,
+                                   gfloat       *min_height_p,
+                                   gfloat       *natural_height_p)
+{
+  ClutterActor *child = st_bin_get_child (ST_BIN (self));
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));
+
+  st_theme_node_adjust_for_width (theme_node, &for_width);
+
+  if (min_height_p)
+    *min_height_p = 0;
+
+  if (child == NULL)
+    {
+      if (natural_height_p)
+        *natural_height_p = 0;
+    }
+  else
+    {
+      clutter_actor_get_preferred_height (child, for_width,
+                                          NULL,
+                                          natural_height_p);
+    }
+
+  st_theme_node_adjust_preferred_height (theme_node, min_height_p, natural_height_p);
+}
+
+static void
+shell_slicer_allocate (ClutterActor           *self,
+                       const ClutterActorBox  *box,
+                       ClutterAllocationFlags  flags)
+{
+  ClutterActor *child;
+
+  /* Chain up directly to ClutterActor to set actor->allocation.  We explicitly skip our parent class
+   * StBin here because we want to override the allocate function. */
+  CLUTTER_ACTOR_CLASS (g_type_class_peek (clutter_actor_get_type ()))->allocate (self, box, flags);
+
+  child = st_bin_get_child (ST_BIN (self));
+  if (child)
+    clutter_actor_allocate_preferred_size (child, flags);
+}
+
+static void
+shell_slicer_paint_child (ShellSlicer *self)
+{
+  ClutterActor *child;
+  ClutterActorBox self_box;
+  ClutterActorBox child_box;
+  float width, height, child_width, child_height;
+  double x_align, y_align;
+
+  child = st_bin_get_child (ST_BIN (self));
+
+  if (!child)
+    return;
+
+  _st_bin_get_align_factors (ST_BIN (self), &x_align, &y_align);
+
+  clutter_actor_get_allocation_box (CLUTTER_ACTOR (self), &self_box);
+  clutter_actor_get_allocation_box (child, &child_box);
+
+  width = self_box.x2 - self_box.x1;
+  height = self_box.y2 - self_box.y1;
+  child_width = child_box.x2 - child_box.x1;
+  child_height = child_box.y2 - child_box.y1;
+
+  cogl_push_matrix ();
+
+  cogl_clip_push (0, 0, width, height);
+  cogl_translate ((int)(0.5 + x_align * (width - child_width)),
+                  (int)(0.5 + y_align * (height - child_height)),
+                  0);
+
+  clutter_actor_paint (child);
+
+  cogl_clip_pop ();
+
+  cogl_pop_matrix ();
+}
+
+static void
+shell_slicer_paint (ClutterActor *self)
+{
+  /* StWidget paints CSS elements */
+  CLUTTER_ACTOR_CLASS (g_type_class_peek (st_widget_get_type ()))->paint (self);
+
+  shell_slicer_paint_child (SHELL_SLICER (self));
+}
+
+static void
+shell_slicer_pick (ClutterActor       *self,
+                   const ClutterColor *pick_color)
+{
+  shell_slicer_paint_child (SHELL_SLICER (self));
+}
+
+static void
+shell_slicer_class_init (ShellSlicerClass *klass)
+{
+  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);
+
+  actor_class->get_preferred_width = shell_slicer_get_preferred_width;
+  actor_class->get_preferred_height = shell_slicer_get_preferred_height;
+  actor_class->allocate = shell_slicer_allocate;
+  actor_class->paint = shell_slicer_paint;
+  actor_class->pick = shell_slicer_pick;
+}
+
+static void
+shell_slicer_init (ShellSlicer *actor)
+{
+}
diff --git a/src/shell-slicer.h b/src/shell-slicer.h
new file mode 100644
index 0000000..29c44bb
--- /dev/null
+++ b/src/shell-slicer.h
@@ -0,0 +1,33 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+#ifndef __SHELL_SLICER_H__
+#define __SHELL_SLICER_H__
+
+#include "st/st.h"
+
+#define SHELL_TYPE_SLICER                 (shell_slicer_get_type ())
+#define SHELL_SLICER(obj)                 (G_TYPE_CHECK_INSTANCE_CAST ((obj), SHELL_TYPE_SLICER, ShellSlicer))
+#define SHELL_SLICER_CLASS(klass)         (G_TYPE_CHECK_CLASS_CAST ((klass), SHELL_TYPE_SLICER, ShellSlicerClass))
+#define SHELL_IS_SLICER(obj)              (G_TYPE_CHECK_INSTANCE_TYPE ((obj), SHELL_TYPE_SLICER))
+#define SHELL_IS_SLICER_CLASS(klass)      (G_TYPE_CHECK_CLASS_TYPE ((klass), SHELL_TYPE_SLICER))
+#define SHELL_SLICER_GET_CLASS(obj)       (G_TYPE_INSTANCE_GET_CLASS ((obj), SHELL_TYPE_SLICER, ShellSlicerClass))
+
+typedef struct _ShellSlicer        ShellSlicer;
+typedef struct _ShellSlicerClass   ShellSlicerClass;
+
+typedef struct _ShellSlicerPrivate ShellSlicerPrivate;
+
+struct _ShellSlicer
+{
+    StBin parent;
+
+    ShellSlicerPrivate *priv;
+};
+
+struct _ShellSlicerClass
+{
+    StBinClass parent_class;
+};
+
+GType shell_slicer_get_type (void) G_GNUC_CONST;
+
+#endif /* __SHELL_SLICER_H__ */