[gtk/prop-list: 6/8] columnview: Interactive column reordering

[Matthias Clasen <matthiasc src gnome org>]

commit 86a600e06a166d187901ee3c3802f5e10362bf9f
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 20 17:29:35 2019 -0500

    columnview: Interactive column reordering
    
    Allow rearranging columns by dragging, in the same
    way the treeview does.
    
    We add the "dnd" style class to the header while
    it is dragged, and we move the header of the dragged
    column to the end of its parents children, so that
    it gets drawn on top.

 gtk/gtkcolumnview.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 129 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkcolumnview.c b/gtk/gtkcolumnview.c
index 69256b146d..961a369c72 100644
--- a/gtk/gtkcolumnview.c
+++ b/gtk/gtkcolumnview.c
@@ -38,6 +38,7 @@
 #include "gtkadjustment.h"
 #include "gtkgesturedrag.h"
 #include "gtkeventcontrollermotion.h"
+#include "gtkdnd.h"
 
 /**
  * SECTION:gtkcolumnview
@@ -71,8 +72,11 @@ struct _GtkColumnView
   GtkAdjustment *hadjustment;
 
   gboolean in_column_resize;
+  gboolean in_column_reorder;
   int drag_pos;
   int drag_x;
+  int drag_offset;
+  int drag_column_x;
 };
 
 struct _GtkColumnViewClass
@@ -220,6 +224,9 @@ gtk_column_view_allocate_columns (GtkColumnView *self,
             col_size = sizes[i].natural_size;
 
           gtk_column_view_column_allocate (column, x, col_size);
+          if (self->in_column_reorder && i == self->drag_pos)
+            gtk_column_view_column_set_header_position (column, self->drag_x);
+
           x += col_size;
         }
 
@@ -558,6 +565,23 @@ gtk_column_view_in_resize_rect (GtkColumnView       *self,
   return graphene_rect_contains_point (&rect, &(graphene_point_t) { x, y});
 }
 
+static gboolean
+gtk_column_view_in_header (GtkColumnView       *self,
+                           GtkColumnViewColumn *column,
+                           double               x,
+                           double               y)
+{
+  GtkWidget *header;
+  graphene_rect_t rect;
+
+  header = gtk_column_view_column_get_header (column);
+
+  if (!gtk_widget_compute_bounds (header, self->header, &rect))
+    return FALSE;
+
+  return graphene_rect_contains_point (&rect, &(graphene_point_t) { x, y});
+}
+
 static void
 header_drag_begin (GtkGestureDrag *gesture,
                    double          start_x,
@@ -566,6 +590,8 @@ header_drag_begin (GtkGestureDrag *gesture,
 {
   int i;
 
+  self->drag_pos = -1;
+
   for (i = 0; !self->in_column_resize && i < g_list_model_get_n_items (G_LIST_MODEL (self->columns)); i++)
     {
       GtkColumnViewColumn *column = g_list_model_get_item (G_LIST_MODEL (self->columns), i);
@@ -585,6 +611,7 @@ header_drag_begin (GtkGestureDrag *gesture,
 
           gtk_column_view_column_get_allocation (column, NULL, &size);
           gtk_column_view_column_set_fixed_width (column, size);
+
           self->drag_pos = i;
           self->drag_x = start_x - size;
           self->in_column_resize = TRUE;
@@ -593,6 +620,20 @@ header_drag_begin (GtkGestureDrag *gesture,
           break;
         }
 
+      if (gtk_column_view_column_get_reorderable (column) &&
+          gtk_column_view_in_header (self, column, start_x, start_y))
+        {
+          int pos;
+
+          gtk_column_view_column_get_allocation (column, &pos, NULL);
+
+          self->drag_pos = i;
+          self->drag_offset = start_x - pos;
+
+          g_object_unref (column);
+          break;
+        }
+
       g_object_unref (column);
     }
 }
@@ -603,7 +644,49 @@ header_drag_end (GtkGestureDrag *gesture,
                  double          offset_y,
                  GtkColumnView  *self)
 {
-  self->in_column_resize = FALSE;
+  double start_x, x;
+
+  gtk_gesture_drag_get_start_point (gesture, &start_x, NULL);
+  x = start_x + offset_x;
+
+  if (self->in_column_resize)
+    {
+      self->in_column_resize = FALSE;
+    }
+  else if (self->in_column_reorder)
+    {
+      GtkColumnViewColumn *column;
+      GtkWidget *header;
+      int i;
+
+      column = g_list_model_get_item (G_LIST_MODEL (self->columns), self->drag_pos);
+      header = gtk_column_view_column_get_header (column);
+      gtk_style_context_remove_class (gtk_widget_get_style_context (header), "dnd");
+
+      for (i = 0; i < g_list_model_get_n_items (G_LIST_MODEL (self->columns)); i++)
+        {
+          GtkColumnViewColumn *col = g_list_model_get_item (G_LIST_MODEL (self->columns), i);
+
+          if (gtk_column_view_column_get_visible (col))
+            {
+              int pos, size;
+
+              gtk_column_view_column_get_allocation (col, &pos, &size);
+              if (pos <= x && x <= pos + size)
+                {
+                  gtk_column_view_insert_column (self, i, column);
+                  g_object_unref (col);
+                  break;
+                }
+            }
+
+          g_object_unref (col);
+        }
+
+      g_object_unref (column);
+
+      self->in_column_reorder = FALSE;
+    }
 }
 
 static void
@@ -617,6 +700,25 @@ update_column_resize (GtkColumnView *self,
   g_object_unref (column);
 }
 
+static void
+update_column_reorder (GtkColumnView *self,
+                       double         x)
+{
+  GtkColumnViewColumn *column;
+  int width;
+  int size;
+
+  column = g_list_model_get_item (G_LIST_MODEL (self->columns), self->drag_pos);
+  width = gtk_widget_get_allocated_width (GTK_WIDGET (self->header));
+  gtk_column_view_column_get_allocation (column, NULL, &size);
+
+  self->drag_x = CLAMP (x - self->drag_offset, 0, width - size);
+
+  gtk_widget_queue_allocate (GTK_WIDGET (self));
+  gtk_column_view_column_queue_resize (column);
+  g_object_unref (column);
+}
+
 static void
 header_drag_update (GtkGestureDrag *gesture,
                     double          offset_x,
@@ -625,11 +727,37 @@ header_drag_update (GtkGestureDrag *gesture,
 {
   double start_x, x;
 
+  if (self->drag_pos == -1)
+    return;
+
+
+  if (!self->in_column_resize && !self->in_column_reorder)
+    {
+      if (gtk_drag_check_threshold (GTK_WIDGET (self), 0, 0, offset_x, 0))
+        {
+          GtkColumnViewColumn *column;
+          GtkWidget *header;
+
+          column = g_list_model_get_item (G_LIST_MODEL (self->columns), self->drag_pos);
+          header = gtk_column_view_column_get_header (column);
+
+          gtk_widget_insert_after (header, self->header, gtk_widget_get_last_child (self->header));
+          gtk_style_context_add_class (gtk_widget_get_style_context (header), "dnd");
+
+          gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_CLAIMED);
+          self->in_column_reorder = TRUE;
+
+          g_object_unref (column);
+        }
+    }
+
   gtk_gesture_drag_get_start_point (gesture, &start_x, NULL);
   x = start_x + offset_x;
 
   if (self->in_column_resize)
     update_column_resize (self, x);
+  else if (self->in_column_reorder)
+    update_column_reorder (self, x);
 }
 
 static void