[nautilus/wip/antoniof/gtk4-preparation-step-event-controllers: 4/22] list-view: Stop chaining up to ::button_press_event()

[António Fernandes <antoniof src gnome org>]

commit b89f56dbc5d956bd41f76c10066e67bd1bb43c8f
Author: António Fernandes <antoniof gnome org>
Date:   Thu Aug 12 00:53:58 2021 +0100

    list-view: Stop chaining up to ::button_press_event()
    
    Event signals are gone in GTK4.
    
    We rely on the chain-up for two cases:
        - holding Shift while clicking
        - clicking an unselected row (without holding Ctrl)
    
    The later can be easily emulated in our side. For the former, we can
    fall through and let GtkTreeView's default handler do everything.
    
    Side effects of this change:
        - secondary click while holding down Shift:
             BEFORE: opens context menu without changing selection, even
                     when clicking outside selection;
             AFTER:  range-select without opening the context menu.
        - click on expander while holding down Ctrl:
             BEFORE: adds row to selection and expands tree simultaneously;
             AFTER:  expands tree without changing selection.
    
    Both are exotic corner cases without an obvious expected behavior and
    the behavior before this change is unexpected and inconsistent. So,
    the side effects are neutral at worst. Not worth keeping the chain-up.

 src/nautilus-list-view.c | 78 ++++++++++++++----------------------------------
 1 file changed, 23 insertions(+), 55 deletions(-)
---
diff --git a/src/nautilus-list-view.c b/src/nautilus-list-view.c
index 7731f407c..655315745 100644
--- a/src/nautilus-list-view.c
+++ b/src/nautilus-list-view.c
@@ -470,13 +470,12 @@ on_tree_view_multi_press_gesture_pressed (GtkGestureMultiPress *gesture,
     g_autoptr (GtkTreePath) path = NULL;
     GtkTreeViewColumn *column;
     GtkTreeSelection *selection;
-    GtkWidgetClass *tree_view_class;
     guint button;
     gint bin_x;
     gint bin_y;
     GdkEventSequence *sequence;
     const GdkEvent *event;
-    gboolean call_parent, on_expander, show_expanders;
+    gboolean on_expander, show_expanders;
     gboolean is_simple_click, path_selected;
     NautilusFile *file;
     gboolean on_star;
@@ -484,7 +483,6 @@ on_tree_view_multi_press_gesture_pressed (GtkGestureMultiPress *gesture,
     view = NAUTILUS_LIST_VIEW (callback_data);
     widget = gtk_event_controller_get_widget (GTK_EVENT_CONTROLLER (gesture));
     tree_view = GTK_TREE_VIEW (widget);
-    tree_view_class = GTK_WIDGET_GET_CLASS (tree_view);
     selection = gtk_tree_view_get_selection (tree_view);
     button = gtk_gesture_single_get_current_button (GTK_GESTURE_SINGLE (gesture));
 
@@ -541,7 +539,6 @@ on_tree_view_multi_press_gesture_pressed (GtkGestureMultiPress *gesture,
         return;
     }
 
-    call_parent = TRUE;
     on_expander = FALSE;
     path_selected = gtk_tree_selection_path_is_selected (selection, path);
     show_expanders = g_settings_get_boolean (nautilus_list_view_preferences,
@@ -625,34 +622,33 @@ on_tree_view_multi_press_gesture_pressed (GtkGestureMultiPress *gesture,
 
         gdk_event_get_state (event, &state);
 
-        if (path_selected)
+        /* We cannot easily match the expected behavior of Shift+click, so we
+         * must fall back to GtkTreeView's default event handling.
+         *
+         * If Shift and Ctrl are held simultateously, GtkTreeView ignores Shift,
+         * so we implement a more useful behavior ourselves.
+         */
+        if ((state & GDK_SHIFT_MASK) != 0 && (state & GDK_CONTROL_MASK) == 0)
         {
-            if ((state & GDK_SHIFT_MASK) == 0)
-            {
-                /* We're going to filter out some situations where
-                 * we can't let the default code run because all
-                 * but one row would be would be deselected. We don't
-                 * want that; we want the right click menu or single
-                 * click to apply to everything that's currently selected.
-                 */
-                call_parent = FALSE;
-            }
+            return;
         }
-        else
+
+        /* Let GtkTreeView handle tree expanding/collapsing. */
+        if (is_simple_click && on_expander)
+        {
+            return;
+        }
+
+        /* As we don't let GtkTreeView default event handling go through, so we
+         * must grab the focus ourselves. */
+        gtk_widget_grab_focus (widget);
+
+        if (!path_selected)
         {
             if ((state & GDK_CONTROL_MASK) != 0)
             {
-                /* If CTRL is pressed, we don't allow the parent
-                 * class to handle it, since GtkTreeView doesn't
-                 * do it as intended currently.
-                 */
-                call_parent = FALSE;
                 if ((state & GDK_SHIFT_MASK) != 0)
                 {
-                    /* This is the CTRL+SHIFT selection mode which
-                     * we handleourselves, as the parent class would
-                     * otherwise do an unexpected selection.
-                     */
                     gtk_tree_view_get_cursor (tree_view, &cursor, NULL);
                     if (cursor != NULL)
                     {
@@ -679,41 +675,13 @@ on_tree_view_multi_press_gesture_pressed (GtkGestureMultiPress *gesture,
                 }
                 g_list_free_full (selected_rows, (GDestroyNotify) gtk_tree_path_free);
             }
-
-            if (button == GDK_BUTTON_SECONDARY &&
-                on_expander &&
-                !button_event_modifies_selection (event))
+            else
             {
-                /* If the right click happened on an expander, we should
-                 * fully change the selection on that row solely.
-                 */
                 gtk_tree_view_set_cursor (tree_view, path, NULL, FALSE);
             }
         }
 
-        if (is_simple_click && on_expander)
-        {
-            /* Need to let the event propagate down, since propagating up
-             * by chaining up to button_press_event() doesn’t expand the
-             * expander.
-             */
-            return;
-        }
-
-        /* Needed to select an item before popping up a menu. */
-        if (call_parent)
-        {
-            g_signal_handlers_block_by_func (tree_view, row_activated_callback, view);
-            /* GTK+ 4 TODO: replace with event(), at the very least. */
-            tree_view_class->button_press_event (widget, (GdkEventButton *) event);
-            g_signal_handlers_unblock_by_func (tree_view, row_activated_callback, view);
-        }
-        else if (path_selected)
-        {
-            gtk_widget_grab_focus (widget);
-        }
-
-        if (is_simple_click && !on_expander)
+        if (is_simple_click)
         {
             view->details->drag_started = FALSE;
             view->details->drag_button = button;