[gtk/wip/otte/bitset] listbase: Allocate rubberband according to list coords

[Benjamin Otte <otte src gnome org>]

commit 642ff1f1a43e17ce6b91e06aff319ca33222f58e
Author: Benjamin Otte <otte redhat com>
Date:   Wed Jun 24 05:02:04 2020 +0200

    listbase: Allocate rubberband according to list coords
    
    The rubberband is now handled on the list coordinate system.
    
    When starting the rubberband, we track the item under the pointer and
    follow it when it is moving.
    This may lead to the rubberband start position changing position and
    while this may be confusing, it alerts users to the fact that something
    crazy is going on.

 gtk/gtklistbase.c | 130 ++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 96 insertions(+), 34 deletions(-)
---
diff --git a/gtk/gtklistbase.c b/gtk/gtklistbase.c
index 70036eedf3..2568b0604e 100644
--- a/gtk/gtklistbase.c
+++ b/gtk/gtklistbase.c
@@ -41,24 +41,18 @@ typedef struct _RubberbandData RubberbandData;
 
 struct _RubberbandData
 {
-  GtkWidget *widget;
+  GtkWidget *widget;                            /* The rubberband widget */
+
+  GtkListItemTracker *start_tracker;            /* The item we started dragging on */
+  double              start_align_across;       /* alignment in horizontal direction */
+  double              start_align_along;        /* alignment in vertical direction */
+
   GtkBitset *active;
-  double x1, y1;
-  double x2, y2;
+  double pointer_x, pointer_y;                  /* mouse coordinates in widget space */
   gboolean modify;
   gboolean extend;
 };
 
-static void
-rubberband_data_free (gpointer data)
-{
-  RubberbandData *rdata = data;
-
-  g_clear_pointer (&rdata->widget, gtk_widget_unparent);
-  g_clear_pointer (&rdata->active, gtk_bitset_unref);
-  g_free (rdata);
-}
-
 typedef struct _GtkListBasePrivate GtkListBasePrivate;
 
 struct _GtkListBasePrivate
@@ -1387,30 +1381,82 @@ gtk_list_base_size_allocate_child (GtkListBase *self,
   gtk_widget_size_allocate (child, &child_allocation, -1);
 }
 
+static void
+gtk_list_base_widget_to_list (GtkListBase *self,
+                              double       x_widget,
+                              double       y_widget,
+                              int         *across_out,
+                              int         *along_out)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+  GtkWidget *widget = GTK_WIDGET (self);
+
+  if (gtk_widget_get_direction (widget) == GTK_TEXT_DIR_RTL)
+    x_widget = gtk_widget_get_width (widget) - x_widget;
+
+  gtk_list_base_get_adjustment_values (self, OPPOSITE_ORIENTATION (priv->orientation), across_out, NULL, 
NULL);
+  gtk_list_base_get_adjustment_values (self, priv->orientation, along_out, NULL, NULL);
+
+  if (priv->orientation == GTK_ORIENTATION_VERTICAL)
+    {
+      *across_out += x_widget;
+      *along_out += y_widget;
+    }
+  else
+    {
+      *across_out += y_widget;
+      *along_out += x_widget;
+    }
+}
+
 void
 gtk_list_base_allocate_rubberband (GtkListBase *self)
 {
   GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
-  GdkRectangle rect;
-  double x, y;
-  int min, nat;
+  GtkRequisition min_size;
+  int x1, x2, y1, y2;
+  int offset_x, offset_y;
 
   if (!priv->rubberband)
     return;
 
-  gtk_widget_measure (priv->rubberband->widget,
-                      GTK_ORIENTATION_HORIZONTAL, -1,
-                      &min, &nat, NULL, NULL);
+  if (priv->rubberband->start_tracker == NULL)
+    {
+      x1 = 0;
+      y1 = 0;
+    }
+  else
+    {
+      guint pos = gtk_list_item_tracker_get_position (priv->item_manager, priv->rubberband->start_tracker);
 
-  x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
-  y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+      if (gtk_list_base_get_allocation_along (self, pos, &y1, &y2) &&
+          gtk_list_base_get_allocation_across (self, pos, &x1, &x2))
+        {
+          x1 += x2 * priv->rubberband->start_align_across;
+          y1 += y2 * priv->rubberband->start_align_along;
+        }
+      else
+        {
+          x1 = 0;
+          y1 = 0;
+        }
+    }
+
+  gtk_list_base_widget_to_list (self,
+                                priv->rubberband->pointer_x, priv->rubberband->pointer_y,
+                                &x2, &y2);
+
+  gtk_widget_get_preferred_size (priv->rubberband->widget, &min_size, NULL);
 
-  rect.x = MIN (priv->rubberband->x1, priv->rubberband->x2) - x;
-  rect.y = MIN (priv->rubberband->y1, priv->rubberband->y2) - y;
-  rect.width = ABS (priv->rubberband->x1 - priv->rubberband->x2) + 1;
-  rect.height = ABS (priv->rubberband->y1 - priv->rubberband->y2) + 1;
+  gtk_list_base_get_adjustment_values (self, OPPOSITE_ORIENTATION (priv->orientation), &offset_x, NULL, 
NULL);
+  gtk_list_base_get_adjustment_values (self, priv->orientation, &offset_y, NULL, NULL);
 
-  gtk_widget_size_allocate (priv->rubberband->widget, &rect, -1);
+  gtk_list_base_size_allocate_child (self,
+                                     priv->rubberband->widget,
+                                     MIN (x1, x2) - offset_x,
+                                     MIN (y1, y2) - offset_y,
+                                     MAX (min_size.width, ABS (x1 - x2) + 1),
+                                     MAX (min_size.height, ABS (y1 - y2) + 1));
 }
 
 static void
@@ -1421,18 +1467,29 @@ gtk_list_base_start_rubberband (GtkListBase *self,
                                 gboolean     extend)
 {
   GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
-  double value_x, value_y;
+  cairo_rectangle_int_t item_area;
+  int list_x, list_y;
+  guint pos;
 
   if (priv->rubberband)
     return;
 
-  value_x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
-  value_y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+  gtk_list_base_widget_to_list (self, x, y, &list_x, &list_y);
+  if (!gtk_list_base_get_position_from_allocation (self, list_x, list_y, &pos, &item_area))
+    {
+      g_warning ("Could not start rubberbanding: No item\n");
+      return;
+    }
 
   priv->rubberband = g_new0 (RubberbandData, 1);
 
-  priv->rubberband->x1 = priv->rubberband->x2 = x + value_x;
-  priv->rubberband->y1 = priv->rubberband->y2 = y + value_y;
+  priv->rubberband->start_tracker = gtk_list_item_tracker_new (priv->item_manager);
+  gtk_list_item_tracker_set_position (priv->item_manager, priv->rubberband->start_tracker, pos, 0, 0);
+  priv->rubberband->start_align_across = (double) (list_x - item_area.x) / item_area.width;
+  priv->rubberband->start_align_along = (double) (list_y - item_area.y) / item_area.height;
+
+  priv->rubberband->pointer_x = x;
+  priv->rubberband->pointer_y = y;
 
   priv->rubberband->modify = modify;
   priv->rubberband->extend = extend;
@@ -1487,7 +1544,12 @@ gtk_list_base_stop_rubberband (GtkListBase *self)
       gtk_bitset_unref (mask);
     }
 
-  g_clear_pointer (&priv->rubberband, rubberband_data_free);
+  gtk_list_item_tracker_free (priv->item_manager, priv->rubberband->start_tracker);
+  g_clear_pointer (&priv->rubberband->widget, gtk_widget_unparent);
+  g_clear_pointer (&priv->rubberband->active, gtk_bitset_unref);
+  g_free (priv->rubberband);
+  priv->rubberband = NULL;
+
   remove_autoscroll (self);
 
   gtk_widget_queue_draw (GTK_WIDGET (self));
@@ -1503,8 +1565,8 @@ gtk_list_base_update_rubberband (GtkListBase *self,
   if (!priv->rubberband)
     return;
 
-  priv->rubberband->x2 = x + gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
-  priv->rubberband->y2 = y + gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+  priv->rubberband->pointer_x = x;
+  priv->rubberband->pointer_y = y;
 
   gtk_list_base_update_rubberband_selection (self);