[gnome-shell/gbsneto/viewport: 1/2] Introduce StViewport

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 4fecfee7fa23ea58b86ac6ab889a4efd7b8b8af9
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed Dec 11 12:35:05 2019 -0300

    Introduce StViewport
    
    St has the regular abstractions to handle actors that are bigger
    than their parent could handle: StScrollable, StScrollView, and
    StAdjustment.
    
    However, the only StScrollable implementation available currently
    is StBoxLayout, which forces a ClutterBoxLayout as the layout
    manager (and relies on it not being unset).
    
    Introduce StViewport, which is a minimal StScrollable implementation
    that doesn't rely on any specific layout manager, but sets a plain
    ClutterBinLayout in the absence of any.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/927

 src/st/meson.build   |   2 +
 src/st/st-viewport.c | 589 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/st/st-viewport.h |  40 ++++
 3 files changed, 631 insertions(+)
---
diff --git a/src/st/meson.build b/src/st/meson.build
index 452c30b99f..ad9209823d 100644
--- a/src/st/meson.build
+++ b/src/st/meson.build
@@ -27,6 +27,7 @@ st_headers = [
   'st-theme-context.h',
   'st-theme-node.h',
   'st-types.h',
+  'st-viewport.h',
   'st-widget.h',
   'st-widget-accessible.h'
 ]
@@ -140,6 +141,7 @@ st_sources = [
   'st-theme-node.c',
   'st-theme-node-drawing.c',
   'st-theme-node-transition.c',
+  'st-viewport.c',
   'st-widget.c'
 ]
 
diff --git a/src/st/st-viewport.c b/src/st/st-viewport.c
new file mode 100644
index 0000000000..f0526b3de7
--- /dev/null
+++ b/src/st/st-viewport.c
@@ -0,0 +1,589 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * st-scrollable-wiget.c: a scrollable actor
+ *
+ * Copyright 2009 Intel Corporation.
+ * Copyright 2009 Abderrahim Kitouni
+ * Copyright 2009, 2010 Red Hat, Inc.
+ * Copyright 2010 Florian Muellner
+ * Copyright 2019 Endless, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU Lesser General Public License,
+ * version 2.1, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Portions copied from Clutter:
+ * Clutter.
+ *
+ * An OpenGL based 'interactive canvas' library.
+ *
+ * Authored By Matthew Allum  <mallum openedhand com>
+ *
+ * Copyright (C) 2006 OpenedHand
+ * 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 of the License, or (at your option) any later version.
+ */
+
+/**
+ * SECTION:st-viewport
+ * @short_description: a scrollable container
+ *
+ * The #StViewport is a generic #StScrollable implementation.
+ *
+ */
+
+#include <stdlib.h>
+
+#include "st-viewport.h"
+
+#include "st-private.h"
+#include "st-scrollable.h"
+
+
+static void st_viewport_scrollable_interface_init (StScrollableInterface *iface);
+
+enum {
+  PROP_0,
+  PROP_HADJUST,
+  PROP_VADJUST
+};
+
+typedef struct
+{
+  ClutterLayoutManager *bin_layout;
+
+  StAdjustment *hadjustment;
+  StAdjustment *vadjustment;
+} StViewportPrivate;
+
+G_DEFINE_TYPE_WITH_CODE (StViewport, st_viewport, ST_TYPE_WIDGET,
+                         G_ADD_PRIVATE (StViewport)
+                         G_IMPLEMENT_INTERFACE (ST_TYPE_SCROLLABLE,
+                                                st_viewport_scrollable_interface_init));
+
+static void
+on_layout_manager_changed_cb (ClutterActor *actor,
+                              GParamSpec   *pspec,
+                              StViewport   *viewport)
+{
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+  ClutterLayoutManager *layout_manager =
+    clutter_actor_get_layout_manager (actor);
+
+  if (!layout_manager)
+    clutter_actor_set_layout_manager (actor, priv->bin_layout);
+}
+
+/*
+ * StScrollable Interface Implementation
+ */
+static void
+adjustment_value_notify_cb (StAdjustment *adjustment,
+                            GParamSpec   *pspec,
+                            StViewport   *viewport)
+{
+  clutter_actor_queue_relayout (CLUTTER_ACTOR (viewport));
+}
+
+static void
+scrollable_set_adjustments (StScrollable *scrollable,
+                            StAdjustment *hadjustment,
+                            StAdjustment *vadjustment)
+{
+  StViewport *viewport = ST_VIEWPORT (scrollable);
+  StViewportPrivate *priv =
+    st_viewport_get_instance_private (viewport);
+
+  g_object_freeze_notify (G_OBJECT (scrollable));
+
+  if (hadjustment != priv->hadjustment)
+    {
+      if (priv->hadjustment)
+        {
+          g_signal_handlers_disconnect_by_func (priv->hadjustment,
+                                                adjustment_value_notify_cb,
+                                                scrollable);
+          g_object_unref (priv->hadjustment);
+        }
+
+      if (hadjustment)
+        {
+          g_object_ref (hadjustment);
+          g_signal_connect (hadjustment, "notify::value",
+                            G_CALLBACK (adjustment_value_notify_cb),
+                            scrollable);
+        }
+
+      priv->hadjustment = hadjustment;
+      g_object_notify (G_OBJECT (scrollable), "hadjustment");
+    }
+
+  if (vadjustment != priv->vadjustment)
+    {
+      if (priv->vadjustment)
+        {
+          g_signal_handlers_disconnect_by_func (priv->vadjustment,
+                                                adjustment_value_notify_cb,
+                                                scrollable);
+          g_object_unref (priv->vadjustment);
+        }
+
+      if (vadjustment)
+        {
+          g_object_ref (vadjustment);
+          g_signal_connect (vadjustment, "notify::value",
+                            G_CALLBACK (adjustment_value_notify_cb),
+                            scrollable);
+        }
+
+      priv->vadjustment = vadjustment;
+      g_object_notify (G_OBJECT (scrollable), "vadjustment");
+    }
+
+  g_object_thaw_notify (G_OBJECT (scrollable));
+}
+
+static void
+scrollable_get_adjustments (StScrollable  *scrollable,
+                            StAdjustment **hadjustment,
+                            StAdjustment **vadjustment)
+{
+  StViewport *viewport = ST_VIEWPORT (scrollable);
+  StViewportPrivate *priv =
+    st_viewport_get_instance_private (viewport);
+
+  if (hadjustment)
+    *hadjustment = priv->hadjustment;
+
+  if (vadjustment)
+    *vadjustment = priv->vadjustment;
+}
+
+static void
+st_viewport_scrollable_interface_init (StScrollableInterface *iface)
+{
+  iface->set_adjustments = scrollable_set_adjustments;
+  iface->get_adjustments = scrollable_get_adjustments;
+}
+
+static void
+st_viewport_get_property (GObject    *object,
+                          guint       property_id,
+                          GValue     *value,
+                          GParamSpec *pspec)
+{
+  StAdjustment *adjustment;
+
+  switch (property_id)
+    {
+    case PROP_HADJUST:
+      scrollable_get_adjustments (ST_SCROLLABLE (object), &adjustment, NULL);
+      g_value_set_object (value, adjustment);
+      break;
+
+    case PROP_VADJUST:
+      scrollable_get_adjustments (ST_SCROLLABLE (object), NULL, &adjustment);
+      g_value_set_object (value, adjustment);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+    }
+}
+
+static void
+st_viewport_set_property (GObject      *object,
+                          guint         property_id,
+                          const GValue *value,
+                          GParamSpec   *pspec)
+{
+  StViewport *viewport = ST_VIEWPORT (object);
+  StViewportPrivate *priv =
+    st_viewport_get_instance_private (viewport);
+
+  switch (property_id)
+    {
+    case PROP_HADJUST:
+      scrollable_set_adjustments (ST_SCROLLABLE (object),
+                                  g_value_get_object (value),
+                                  priv->vadjustment);
+      break;
+
+    case PROP_VADJUST:
+      scrollable_set_adjustments (ST_SCROLLABLE (object),
+                                  priv->hadjustment,
+                                  g_value_get_object (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+    }
+}
+
+static void
+st_viewport_dispose (GObject *object)
+{
+  StViewport *viewport = ST_VIEWPORT (object);
+  StViewportPrivate *priv =
+    st_viewport_get_instance_private (viewport);
+
+  g_clear_object (&priv->bin_layout);
+  g_clear_object (&priv->hadjustment);
+  g_clear_object (&priv->vadjustment);
+
+  G_OBJECT_CLASS (st_viewport_parent_class)->dispose (object);
+}
+
+static void
+st_viewport_allocate (ClutterActor           *actor,
+                      const ClutterActorBox  *box,
+                      ClutterAllocationFlags  flags)
+{
+  StViewport *viewport = ST_VIEWPORT (actor);
+  StViewportPrivate *priv =
+    st_viewport_get_instance_private (viewport);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (actor));
+  ClutterLayoutManager *layout = clutter_actor_get_layout_manager (actor);
+  ClutterActorBox viewport_box;
+  ClutterActorBox content_box;
+  gfloat avail_width, avail_height, min_width, natural_width, min_height, natural_height;
+
+  st_theme_node_get_content_box (theme_node, box, &viewport_box);
+  clutter_actor_box_get_size (&viewport_box, &avail_width, &avail_height);
+
+  clutter_layout_manager_get_preferred_width (layout, CLUTTER_CONTAINER (actor),
+                                              avail_height,
+                                              &min_width, &natural_width);
+  clutter_layout_manager_get_preferred_height (layout, CLUTTER_CONTAINER (actor),
+                                               MAX (avail_width, min_width),
+                                               &min_height, &natural_height);
+
+  /* Because StViewport implements StScrollable, the allocation box passed here
+   * may not match the minimum sizes reported by the layout manager. When that
+   * happens, the content box needs to be adjusted to match the reported minimum
+   * sizes before being passed to clutter_layout_manager_allocate() */
+  clutter_actor_set_allocation (actor, box, flags);
+
+  content_box = viewport_box;
+  content_box.x2 += MAX (0, min_width - avail_width);
+  content_box.y2 += MAX (0, min_height - avail_height);
+
+  clutter_layout_manager_allocate (layout, CLUTTER_CONTAINER (actor),
+                                   &content_box, flags);
+
+  /* update adjustments for scrolling */
+  if (priv->vadjustment)
+    {
+      gdouble prev_value;
+
+      g_object_set (G_OBJECT (priv->vadjustment),
+                    "lower", 0.0,
+                    "upper", MAX (min_height, avail_height),
+                    "page-size", avail_height,
+                    "step-increment", avail_height / 6,
+                    "page-increment", avail_height - avail_height / 6,
+                    NULL);
+
+      prev_value = st_adjustment_get_value (priv->vadjustment);
+      st_adjustment_set_value (priv->vadjustment, prev_value);
+    }
+
+  if (priv->hadjustment)
+    {
+      gdouble prev_value;
+
+      g_object_set (G_OBJECT (priv->hadjustment),
+                    "lower", 0.0,
+                    "upper", MAX (min_width, avail_width),
+                    "page-size", avail_width,
+                    "step-increment", avail_width / 6,
+                    "page-increment", avail_width - avail_width / 6,
+                    NULL);
+
+      prev_value = st_adjustment_get_value (priv->hadjustment);
+      st_adjustment_set_value (priv->hadjustment, prev_value);
+    }
+}
+
+static void
+st_viewport_apply_transform (ClutterActor *actor,
+                             CoglMatrix   *matrix)
+{
+  StViewport *viewport = ST_VIEWPORT (actor);
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+  ClutterActorClass *parent_class =
+    CLUTTER_ACTOR_CLASS (st_viewport_parent_class);
+  gdouble x, y;
+
+  parent_class->apply_transform (actor, matrix);
+
+  if (priv->hadjustment)
+    x = st_adjustment_get_value (priv->hadjustment);
+  else
+    x = 0;
+
+  if (priv->vadjustment)
+    y = st_adjustment_get_value (priv->vadjustment);
+  else
+    y = 0;
+
+  cogl_matrix_translate (matrix, (int) -x, (int) -y, 0);
+}
+
+/* If we are translated, then we need to translate back before chaining
+ * up or the background and borders will be drawn in the wrong place */
+static void
+get_border_paint_offsets (StViewport *viewport,
+                          double     *x,
+                          double     *y)
+{
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+
+  if (priv->hadjustment)
+    *x = st_adjustment_get_value (priv->hadjustment);
+  else
+    *x = 0;
+
+  if (priv->vadjustment)
+    *y = st_adjustment_get_value (priv->vadjustment);
+  else
+    *y = 0;
+}
+
+
+static void
+st_viewport_paint (ClutterActor        *actor,
+                   ClutterPaintContext *paint_context)
+{
+  StViewport *viewport = ST_VIEWPORT (actor);
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (actor));
+  gdouble x, y;
+  ClutterActorBox allocation_box;
+  ClutterActorBox content_box;
+  ClutterActor *child;
+  CoglFramebuffer *fb = clutter_paint_context_get_framebuffer (paint_context);
+
+  get_border_paint_offsets (viewport, &x, &y);
+  if (x != 0 || y != 0)
+    {
+      cogl_framebuffer_push_matrix (fb);
+      cogl_framebuffer_translate (fb, (int)x, (int)y, 0);
+    }
+
+  st_widget_paint_background (ST_WIDGET (actor), paint_context);
+
+  if (x != 0 || y != 0)
+    cogl_framebuffer_pop_matrix (fb);
+
+  if (clutter_actor_get_n_children (actor) == 0)
+    return;
+
+  clutter_actor_get_allocation_box (actor, &allocation_box);
+  st_theme_node_get_content_box (theme_node, &allocation_box, &content_box);
+
+  content_box.x1 += x;
+  content_box.y1 += y;
+  content_box.x2 += x;
+  content_box.y2 += y;
+
+  /* The content area forms the viewport into the scrolled contents, while
+   * the borders and background stay in place; after drawing the borders and
+   * background, we clip to the content area */
+  if (priv->hadjustment || priv->vadjustment)
+    cogl_framebuffer_push_rectangle_clip (fb,
+                                          (int)content_box.x1,
+                                          (int)content_box.y1,
+                                          (int)content_box.x2,
+                                          (int)content_box.y2);
+
+  for (child = clutter_actor_get_first_child (actor);
+       child != NULL;
+       child = clutter_actor_get_next_sibling (child))
+    clutter_actor_paint (child, paint_context);
+
+  if (priv->hadjustment || priv->vadjustment)
+    cogl_framebuffer_pop_clip (fb);
+}
+
+static void
+st_viewport_pick (ClutterActor       *actor,
+                  ClutterPickContext *pick_context)
+{
+  StViewport *viewport = ST_VIEWPORT (actor);
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (actor));
+  gdouble x, y;
+  ClutterActorBox allocation_box;
+  ClutterActorBox content_box;
+  ClutterActor *child;
+  CoglFramebuffer *fb = clutter_pick_context_get_framebuffer (pick_context);
+
+  get_border_paint_offsets (viewport, &x, &y);
+  if (x != 0 || y != 0)
+    {
+      cogl_framebuffer_push_matrix (fb);
+      cogl_framebuffer_translate (fb, (int)x, (int)y, 0);
+    }
+
+  CLUTTER_ACTOR_CLASS (st_viewport_parent_class)->pick (actor, pick_context);
+
+  if (x != 0 || y != 0)
+    {
+      cogl_framebuffer_pop_matrix (fb);
+    }
+
+  if (clutter_actor_get_n_children (actor) == 0)
+    return;
+
+  clutter_actor_get_allocation_box (actor, &allocation_box);
+  st_theme_node_get_content_box (theme_node, &allocation_box, &content_box);
+
+  content_box.x1 += x;
+  content_box.y1 += y;
+  content_box.x2 += x;
+  content_box.y2 += y;
+
+  if (priv->hadjustment || priv->vadjustment)
+    cogl_framebuffer_push_rectangle_clip (fb,
+                                          (int)content_box.x1,
+                                          (int)content_box.y1,
+                                          (int)content_box.x2,
+                                          (int)content_box.y2);
+
+  for (child = clutter_actor_get_first_child (actor);
+       child != NULL;
+       child = clutter_actor_get_next_sibling (child))
+    clutter_actor_pick (child, pick_context);
+
+  if (priv->hadjustment || priv->vadjustment)
+    cogl_framebuffer_pop_clip (fb);
+}
+
+static gboolean
+st_viewport_get_paint_volume (ClutterActor       *actor,
+                              ClutterPaintVolume *volume)
+{
+  StViewport *viewport = ST_VIEWPORT (actor);
+  StViewportPrivate *priv = st_viewport_get_instance_private (viewport);
+  gdouble x, y, lower, upper;
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (actor));
+  ClutterActorBox allocation_box;
+  ClutterActorBox content_box;
+  graphene_point3d_t origin;
+
+  /* Setting the paint volume does not make sense when we don't have any allocation */
+  if (!clutter_actor_has_allocation (actor))
+    return FALSE;
+
+  /* When have an adjustment we are clipped to the content box, so base
+   * our paint volume on that. */
+  if (priv->hadjustment || priv->vadjustment)
+    {
+      gdouble width, height;
+
+      clutter_actor_get_allocation_box (actor, &allocation_box);
+      st_theme_node_get_content_box (theme_node, &allocation_box, &content_box);
+      origin.x = content_box.x1 - allocation_box.x1;
+      origin.y = content_box.y1 - allocation_box.y2;
+      origin.z = 0.f;
+
+      if (priv->hadjustment)
+        {
+          g_object_get (priv->hadjustment,
+                        "lower", &lower,
+                        "upper", &upper,
+                        NULL);
+          width = upper - lower;
+        }
+      else
+        {
+          width = content_box.x2 - content_box.x1;
+        }
+
+      if (priv->vadjustment)
+        {
+          g_object_get (priv->vadjustment,
+                        "lower", &lower,
+                        "upper", &upper,
+                        NULL);
+          height = upper - lower;
+        }
+      else
+        {
+          height = content_box.y2 - content_box.y1;
+        }
+
+      clutter_paint_volume_set_width (volume, width);
+      clutter_paint_volume_set_height (volume, height);
+    }
+  else if (!CLUTTER_ACTOR_CLASS (st_viewport_parent_class)->get_paint_volume (actor, volume))
+    return FALSE;
+
+  /* When scrolled, st_viewport_apply_transform() includes the scroll offset
+   * and affects paint volumes. This is right for our children, but our paint volume
+   * is determined by our allocation and borders and doesn't scroll, so we need
+   * to reverse-compensate here, the same as we do when painting.
+   */
+  get_border_paint_offsets (viewport, &x, &y);
+  if (x != 0 || y != 0)
+    {
+      clutter_paint_volume_get_origin (volume, &origin);
+      origin.x += x;
+      origin.y += y;
+      clutter_paint_volume_set_origin (volume, &origin);
+    }
+
+  return TRUE;
+}
+
+static void
+st_viewport_class_init (StViewportClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);
+
+  object_class->get_property = st_viewport_get_property;
+  object_class->set_property = st_viewport_set_property;
+  object_class->dispose = st_viewport_dispose;
+
+  actor_class->allocate = st_viewport_allocate;
+  actor_class->apply_transform = st_viewport_apply_transform;
+
+  actor_class->paint = st_viewport_paint;
+  actor_class->get_paint_volume = st_viewport_get_paint_volume;
+  actor_class->pick = st_viewport_pick;
+
+  /* StScrollable properties */
+  g_object_class_override_property (object_class,
+                                    PROP_HADJUST,
+                                    "hadjustment");
+
+  g_object_class_override_property (object_class,
+                                    PROP_VADJUST,
+                                    "vadjustment");
+
+}
+
+static void
+st_viewport_init (StViewport *self)
+{
+  StViewportPrivate *priv = st_viewport_get_instance_private (self);
+
+  priv->bin_layout = g_object_new (CLUTTER_TYPE_BIN_LAYOUT, NULL);
+
+  g_signal_connect (self, "notify::layout-manager",
+                    G_CALLBACK (on_layout_manager_changed_cb),
+                    self);
+}
diff --git a/src/st/st-viewport.h b/src/st/st-viewport.h
new file mode 100644
index 0000000000..8f0b16b45e
--- /dev/null
+++ b/src/st/st-viewport.h
@@ -0,0 +1,40 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * st-viewport.h: viewport actor
+ *
+ * Copyright 2009 Intel Corporation.
+ * Copyright 2009, 2010 Red Hat, Inc.
+ * Copyright 2019 Endless, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU Lesser General Public License,
+ * version 2.1, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if !defined(ST_H_INSIDE) && !defined(ST_COMPILATION)
+#error "Only <st/st.h> can be included directly.h"
+#endif
+
+#pragma once
+
+#include <st/st-widget.h>
+
+G_BEGIN_DECLS
+
+#define ST_TYPE_VIEWPORT (st_viewport_get_type())
+G_DECLARE_DERIVABLE_TYPE (StViewport, st_viewport, ST, VIEWPORT, StWidget)
+
+struct _StViewportClass
+{
+  StWidgetClass parent_class;
+};
+
+G_END_DECLS