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[gtk/wip/exalm/consumes-motion: 1/2] dragsource: Use double coordinates for checking drag threshold


commit 15991f040303720d983b2aacbce63093d91356ab
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Fri Dec 25 22:57:48 2020 +0500

    dragsource: Use double coordinates for checking drag threshold
    
    If multiple nested widgets have drag sources on them, both using bubble
    phase, we need to reliably pick the inner one. Both of them will try to
    start dragging, and we need to make sure there are no situations where the
    outer widget starts drag earlier and cancels the inner one.
    
    Currently, this can easily happen via integer rounding: start and current
    coordinates passed into gtk_drag_check_threshold() are initially doubles
    (other than in GtkNotebook and GtkIconView), and are casted to ints. Then
    those rounded values are used to calculate deltas to compare to the drag
    threshold, losing quite a lot of precision along the way, and often
    resulting in the outer widget getting larger deltas.
    
    To avoid it, just don't round it. Introduce a variant of the function that
    operates on doubles: gtk_drag_check_threshold_double() and use it instead
    of the original everywhere.
    
    Fix coordinates in GtkEntry along the way: it was passing offsets as
    current oordinates.

 gtk/gtkcolumnview.c        |  4 ++--
 gtk/gtkdragsource.c        | 21 +++++++++++++++++++--
 gtk/gtkdragsourceprivate.h | 33 +++++++++++++++++++++++++++++++++
 gtk/gtkentry.c             |  4 ++--
 gtk/gtkgesturelongpress.c  |  4 ++--
 gtk/gtkiconview.c          | 10 +++++-----
 gtk/gtkiconviewprivate.h   |  4 ++--
 gtk/gtkimcontextwayland.c  |  9 +++++----
 gtk/gtklabel.c             |  4 ++--
 gtk/gtklistbase.c          |  4 ++--
 gtk/gtknotebook.c          | 17 ++++++++++-------
 gtk/gtkplacessidebar.c     |  4 ++--
 gtk/gtkscrolledwindow.c    |  6 +++---
 gtk/gtktext.c              |  6 ++----
 gtk/gtktextview.c          |  5 +++--
 gtk/gtktreeview.c          |  4 ++--
 gtk/gtktreeviewcolumn.c    |  4 ++--
 17 files changed, 98 insertions(+), 45 deletions(-)
---
diff --git a/gtk/gtkcolumnview.c b/gtk/gtkcolumnview.c
index f00bede003..2e835d366a 100644
--- a/gtk/gtkcolumnview.c
+++ b/gtk/gtkcolumnview.c
@@ -39,7 +39,7 @@
 #include "gtkadjustment.h"
 #include "gtkgesturedrag.h"
 #include "gtkeventcontrollermotion.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkeventcontrollerkey.h"
 #include "gtkgestureclick.h"
 
@@ -1128,7 +1128,7 @@ header_drag_update (GtkGestureDrag *gesture,
 
   if (!self->in_column_resize && !self->in_column_reorder)
     {
-      if (gtk_drag_check_threshold (GTK_WIDGET (self), 0, 0, offset_x, 0))
+      if (gtk_drag_check_threshold_double (GTK_WIDGET (self), 0, 0, offset_x, 0))
         {
           GtkColumnViewColumn *column;
           GtkWidget *header;
diff --git a/gtk/gtkdragsource.c b/gtk/gtkdragsource.c
index 98b96c7594..47f0ba179d 100644
--- a/gtk/gtkdragsource.c
+++ b/gtk/gtkdragsource.c
@@ -24,7 +24,7 @@
 
 #include "config.h"
 
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 
 #include "gtkgesturedrag.h"
 #include "gtkgesturesingleprivate.h"
@@ -292,7 +292,7 @@ gtk_drag_source_update (GtkGesture       *gesture,
 
   widget = gtk_event_controller_get_widget (GTK_EVENT_CONTROLLER (gesture));
 
-  if (gtk_drag_check_threshold (widget, source->start_x, source->start_y, x, y))
+  if (gtk_drag_check_threshold_double (widget, source->start_x, source->start_y, x, y))
     {
       gtk_drag_source_drag_begin (source);
     }
@@ -796,3 +796,20 @@ gtk_drag_check_threshold (GtkWidget *widget,
   return (ABS (current_x - start_x) > drag_threshold ||
           ABS (current_y - start_y) > drag_threshold);
 }
+
+gboolean
+gtk_drag_check_threshold_double (GtkWidget *widget,
+                                 double     start_x,
+                                 double     start_y,
+                                 double     current_x,
+                                 double     current_y)
+{
+  int drag_threshold;
+
+  g_return_val_if_fail (GTK_IS_WIDGET (widget), FALSE);
+
+  drag_threshold = gtk_settings_get_dnd_drag_threshold (gtk_widget_get_settings (widget));
+
+  return (ABS (current_x - start_x) > drag_threshold ||
+          ABS (current_y - start_y) > drag_threshold);
+}
diff --git a/gtk/gtkdragsourceprivate.h b/gtk/gtkdragsourceprivate.h
new file mode 100644
index 0000000000..8226e3fee1
--- /dev/null
+++ b/gtk/gtkdragsourceprivate.h
@@ -0,0 +1,33 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2020 Alexander Mikhaylenko
+ *
+ * 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.
+ *
+ * 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/>.
+ */
+
+#ifndef __GTK_DRAG_SOURCE_PRIVATE_H__
+#define __GTK_DRAG_SOURCE_PRIVATE_H__
+
+#include "gtkdragsource.h"
+
+G_BEGIN_DECLS
+
+gboolean gtk_drag_check_threshold_double (GtkWidget *widget,
+                                          double     start_x,
+                                          double     start_y,
+                                          double     current_x,
+                                          double     current_y);
+
+G_END_DECLS
+
+#endif /* __GTK_DRAG_SOURCE_PRIVATE_H__ */
diff --git a/gtk/gtkentry.c b/gtk/gtkentry.c
index acb2774481..df3d62089c 100644
--- a/gtk/gtkentry.c
+++ b/gtk/gtkentry.c
@@ -66,7 +66,7 @@
 #include "gtkwindow.h"
 #include "gtknative.h"
 #include "gtkgestureclick.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdragicon.h"
 #include "gtkwidgetpaintable.h"
 
@@ -1601,7 +1601,7 @@ icon_drag_update_cb (GtkGestureDrag *gesture,
   icon_info = priv->icons[pos];
 
   if (icon_info->content != NULL &&
-      gtk_drag_check_threshold (icon_info->widget, start_x, start_y, x, y))
+      gtk_drag_check_threshold_double (icon_info->widget, 0, 0, x, y))
     {
       GdkPaintable *paintable;
       GdkSurface *surface;
diff --git a/gtk/gtkgesturelongpress.c b/gtk/gtkgesturelongpress.c
index df01077ab4..446829856e 100644
--- a/gtk/gtkgesturelongpress.c
+++ b/gtk/gtkgesturelongpress.c
@@ -37,7 +37,7 @@
 #include "gtkgesturelongpressprivate.h"
 #include "gtkgestureprivate.h"
 #include "gtkmarshalers.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkprivate.h"
 #include "gtkintl.h"
 #include "gtkmarshalers.h"
@@ -159,7 +159,7 @@ gtk_gesture_long_press_update (GtkGesture       *gesture,
   priv = gtk_gesture_long_press_get_instance_private (GTK_GESTURE_LONG_PRESS (gesture));
   gtk_gesture_get_point (gesture, sequence, &x, &y);
 
-  if (gtk_drag_check_threshold (widget, priv->initial_x, priv->initial_y, x, y))
+  if (gtk_drag_check_threshold_double (widget, priv->initial_x, priv->initial_y, x, y))
     {
       if (priv->timeout_id)
         {
diff --git a/gtk/gtkiconview.c b/gtk/gtkiconview.c
index 5d24c1f0bf..cce12cc45d 100644
--- a/gtk/gtkiconview.c
+++ b/gtk/gtkiconview.c
@@ -26,7 +26,7 @@
 #include "gtkcellrenderer.h"
 #include "gtkcellrendererpixbuf.h"
 #include "gtkcellrenderertext.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkentry.h"
 #include "gtkintl.h"
 #include "gtkmain.h"
@@ -5884,10 +5884,10 @@ gtk_icon_view_maybe_begin_drag (GtkIconView *icon_view,
   if (icon_view->priv->pressed_button < 0)
     goto out;
 
-  if (!gtk_drag_check_threshold (GTK_WIDGET (icon_view),
-                                 icon_view->priv->press_start_x,
-                                 icon_view->priv->press_start_y,
-                                 x, y))
+  if (!gtk_drag_check_threshold_double (GTK_WIDGET (icon_view),
+                                        icon_view->priv->press_start_x,
+                                        icon_view->priv->press_start_y,
+                                        x, y))
     goto out;
 
   model = gtk_icon_view_get_model (icon_view);
diff --git a/gtk/gtkiconviewprivate.h b/gtk/gtkiconviewprivate.h
index ef785bad04..b5fa1358d1 100644
--- a/gtk/gtkiconviewprivate.h
+++ b/gtk/gtkiconviewprivate.h
@@ -133,8 +133,8 @@ struct _GtkIconViewPrivate
   /* Drag-and-drop. */
   GdkModifierType start_button_mask;
   int pressed_button;
-  int press_start_x;
-  int press_start_y;
+  double press_start_x;
+  double press_start_y;
 
   GdkContentFormats *source_formats;
   GtkDropTargetAsync *dest;
diff --git a/gtk/gtkimcontextwayland.c b/gtk/gtkimcontextwayland.c
index ad89d83a07..77264087eb 100644
--- a/gtk/gtkimcontextwayland.c
+++ b/gtk/gtkimcontextwayland.c
@@ -21,6 +21,7 @@
 #include <string.h>
 #include <wayland-client-protocol.h>
 
+#include "gtk/gtkdragsourceprivate.h"
 #include "gtk/gtkimcontextwayland.h"
 #include "gtk/gtkintl.h"
 #include "gtk/gtkimmoduleprivate.h"
@@ -524,10 +525,10 @@ released_cb (GtkGestureClick     *gesture,
   if (global->focused &&
       n_press == 1 &&
       (hints & GTK_INPUT_HINT_INHIBIT_OSK) == 0 &&
-      !gtk_drag_check_threshold (context->widget,
-                                 context->press_x,
-                                 context->press_y,
-                                 x, y))
+      !gtk_drag_check_threshold_double (context->widget,
+                                        context->press_x,
+                                        context->press_y,
+                                        x, y))
     {
       zwp_text_input_v3_enable (global->text_input);
       g_signal_emit_by_name (global->current, "retrieve-surrounding", &result);
diff --git a/gtk/gtklabel.c b/gtk/gtklabel.c
index 19b0386c05..ab20e0bd84 100644
--- a/gtk/gtklabel.c
+++ b/gtk/gtklabel.c
@@ -54,7 +54,7 @@
 #include "gtkwindow.h"
 #include "gtkpopovermenu.h"
 #include "gtknative.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdragicon.h"
 #include "gtkcsscolorvalueprivate.h"
 
@@ -4138,7 +4138,7 @@ gtk_label_drag_gesture_update (GtkGestureDrag *gesture,
 
   if (info->in_drag)
     {
-      if (gtk_drag_check_threshold (widget, info->drag_start_x, info->drag_start_y, x, y))
+      if (gtk_drag_check_threshold_double (widget, info->drag_start_x, info->drag_start_y, x, y))
        {
           GdkDrag *drag;
           GdkSurface *surface;
diff --git a/gtk/gtklistbase.c b/gtk/gtklistbase.c
index ed4f84ad2a..6c4078a66a 100644
--- a/gtk/gtklistbase.c
+++ b/gtk/gtklistbase.c
@@ -23,7 +23,7 @@
 
 #include "gtkadjustment.h"
 #include "gtkbitset.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdropcontrollermotion.h"
 #include "gtkgesturedrag.h"
 #include "gtkgizmoprivate.h"
@@ -1710,7 +1710,7 @@ gtk_list_base_drag_update (GtkGestureDrag *gesture,
 
   if (!priv->rubberband)
     {
-      if (!gtk_drag_check_threshold (GTK_WIDGET (self), 0, 0, offset_x, offset_y))
+      if (!gtk_drag_check_threshold_double (GTK_WIDGET (self), 0, 0, offset_x, offset_y))
         return;
       
       gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_CLAIMED);
diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index bad99cdddc..47fe9224fd 100644
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -51,7 +51,7 @@
 #include "gtkstack.h"
 #include "gtktypebuiltins.h"
 #include "gtkwidgetprivate.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkwidgetpaintable.h"
 #include "gtknative.h"
 
@@ -249,14 +249,14 @@ struct _GtkNotebook
   GList         *first_tab;             /* The first tab visible (for scrolling notebooks) */
   GList         *focus_tab;
 
-  int            drag_begin_x;
-  int            drag_begin_y;
+  double         drag_begin_x;
+  double         drag_begin_y;
   int            drag_offset_x;
   int            drag_offset_y;
   int            drag_surface_x;
   int            drag_surface_y;
-  int            mouse_x;
-  int            mouse_y;
+  double         mouse_x;
+  double         mouse_y;
   int            pressed_button;
 
   GQuark         group;
@@ -2935,8 +2935,11 @@ gtk_notebook_motion (GtkEventController *controller,
 
   if (page->reorderable &&
       (notebook->operation == DRAG_OPERATION_REORDER ||
-       gtk_drag_check_threshold (widget, notebook->drag_begin_x, notebook->drag_begin_y,
-                                 notebook->mouse_x, notebook->mouse_y)))
+       gtk_drag_check_threshold_double (widget,
+                                        notebook->drag_begin_x,
+                                        notebook->drag_begin_y,
+                                        notebook->mouse_x,
+                                        notebook->mouse_y)))
     {
       GtkNotebookPointerPosition pointer_position = get_pointer_position (notebook);
 
diff --git a/gtk/gtkplacessidebar.c b/gtk/gtkplacessidebar.c
index 41df790cc6..7c055296d3 100644
--- a/gtk/gtkplacessidebar.c
+++ b/gtk/gtkplacessidebar.c
@@ -60,7 +60,7 @@
 #include "gtkgestureclick.h"
 #include "gtkgesturedrag.h"
 #include "gtknative.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdragicon.h"
 
 /*< private >
@@ -3451,7 +3451,7 @@ on_row_dragged (GtkGestureDrag *gesture,
       return;
     }
 
-  if (gtk_drag_check_threshold (GTK_WIDGET (row), 0, 0, x, y))
+  if (gtk_drag_check_threshold_double (GTK_WIDGET (row), 0, 0, x, y))
     {
       double start_x, start_y;
       double drag_x, drag_y;
diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index d27d05c432..c780c6fc8d 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -29,7 +29,7 @@
 #include "gtkadjustment.h"
 #include "gtkadjustmentprivate.h"
 #include "gtkbuildable.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkeventcontrollermotion.h"
 #include "gtkeventcontrollerscroll.h"
 #include "gtkeventcontrollerprivate.h"
@@ -953,8 +953,8 @@ scrolled_window_drag_update_cb (GtkScrolledWindow *scrolled_window,
   GtkAdjustment *vadjustment;
   double dx, dy;
 
-  if (!gtk_drag_check_threshold (GTK_WIDGET (scrolled_window),
-                                 0, 0, offset_x, offset_y))
+  if (!gtk_drag_check_threshold_double (GTK_WIDGET (scrolled_window),
+                                        0, 0, offset_x, offset_y))
     return;
 
   gtk_scrolled_window_invalidate_overshoot (scrolled_window);
diff --git a/gtk/gtktext.c b/gtk/gtktext.c
index c39e007d61..6d10722e6b 100644
--- a/gtk/gtktext.c
+++ b/gtk/gtktext.c
@@ -29,7 +29,7 @@
 #include "gtkbutton.h"
 #include "gtkdebug.h"
 #include "gtkdragicon.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdroptarget.h"
 #include "gtkeditable.h"
 #include "gtkemojichooser.h"
@@ -2941,9 +2941,7 @@ gtk_text_drag_gesture_update (GtkGestureDrag *gesture,
   if (priv->in_drag)
     {
       if (gtk_text_get_display_mode (self) == DISPLAY_NORMAL &&
-          gtk_drag_check_threshold (widget,
-                                    priv->drag_start_x, priv->drag_start_y,
-                                    x, y))
+          gtk_drag_check_threshold_double (widget, 0, 0, offset_x, offset_y))
         {
           int *ranges;
           int n_ranges;
diff --git a/gtk/gtktextview.c b/gtk/gtktextview.c
index 5a4ad33e2a..765d67aea6 100644
--- a/gtk/gtktextview.c
+++ b/gtk/gtktextview.c
@@ -32,6 +32,7 @@
 #include "gtkadjustmentprivate.h"
 #include "gtkcsscolorvalueprivate.h"
 #include "gtkdebug.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdropcontrollermotion.h"
 #include "gtkintl.h"
 #include "gtkmain.h"
@@ -7232,7 +7233,7 @@ gtk_text_view_drag_gesture_update (GtkGestureDrag *gesture,
       /* If no data is attached, the initial press happened within the current
        * text selection, check for drag and drop to be initiated.
        */
-      if (gtk_drag_check_threshold (GTK_WIDGET (text_view), start_x, start_y, x, y))
+      if (gtk_drag_check_threshold_double (GTK_WIDGET (text_view), 0, 0, offset_x, offset_y))
         {
           if (!is_touchscreen)
             {
@@ -7366,7 +7367,7 @@ gtk_text_view_drag_gesture_end (GtkGestureDrag *gesture,
     gdk_device_get_source (device) == GDK_SOURCE_TOUCHSCREEN;
 
   if ((is_touchscreen || clicked_in_selection) &&
-      !gtk_drag_check_threshold (GTK_WIDGET (text_view), start_x, start_y, x, y))
+      !gtk_drag_check_threshold_double (GTK_WIDGET (text_view), 0, 0, offset_x, offset_y))
     {
       GtkTextIter iter;
 
diff --git a/gtk/gtktreeview.c b/gtk/gtktreeview.c
index 82d5fd97d8..39292db8ae 100644
--- a/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@ -29,7 +29,7 @@
 #include "gtkcssnumbervalueprivate.h"
 #include "gtkcsscolorvalueprivate.h"
 #include "gtkcssstylepropertyprivate.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkdragicon.h"
 #include "gtkdroptargetasync.h"
 #include "gtkentryprivate.h"
@@ -7046,7 +7046,7 @@ gtk_tree_view_maybe_begin_dragging_row (GtkTreeView *tree_view)
   gtk_gesture_drag_get_offset (GTK_GESTURE_DRAG (priv->drag_gesture),
                                &offset_x, &offset_y);
 
-  if (!gtk_drag_check_threshold (widget, 0, 0, offset_x, offset_y))
+  if (!gtk_drag_check_threshold_double (widget, 0, 0, offset_x, offset_y))
     goto out;
 
   model = gtk_tree_view_get_model (tree_view);
diff --git a/gtk/gtktreeviewcolumn.c b/gtk/gtktreeviewcolumn.c
index e321bed4b6..638c9707da 100644
--- a/gtk/gtktreeviewcolumn.c
+++ b/gtk/gtktreeviewcolumn.c
@@ -24,7 +24,7 @@
 #include "gtkcellareabox.h"
 #include "gtkcellareacontext.h"
 #include "gtkcelllayout.h"
-#include "gtkdragsource.h"
+#include "gtkdragsourceprivate.h"
 #include "gtkframe.h"
 #include "gtkimage.h"
 #include "gtkintl.h"
@@ -1076,7 +1076,7 @@ column_button_drag_update (GtkGestureDrag    *gesture,
 {
   GtkTreeViewColumnPrivate *priv = column->priv;
 
-  if (gtk_drag_check_threshold (priv->button, 0, 0, offset_x, offset_y))
+  if (gtk_drag_check_threshold_double (priv->button, 0, 0, offset_x, offset_y))
     {
       gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_CLAIMED);
       _gtk_tree_view_column_start_drag (GTK_TREE_VIEW (priv->tree_view), column,
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