[gimp/gimp-2-10] app: replace using the "draw" signal by "expose-event" on GTK+2.

[Jehan <jehanp src gnome org>]

commit 6be014fc599d47b3ce3211a00b383c7ad9bf81f6
Author: Jehan <jehan girinstud io>
Date:   Fri Oct 22 23:08:07 2021 +0200

    app: replace using the "draw" signal by "expose-event" on GTK+2.
    
    Not sure why but adding a handler to the "expose-event" signal of
    GimpDisplayShell (similarly to how we do it in master branch on "draw")
    just didn't work. But it works on the already existing signal handling
    on the canvas instead (which actually is not a bad deal, as we also
    remove the coordinates translation so maybe we should test this on
    `master` too).
    
    Note: why we are backporting all this logics to gimp-2-10 is because
    changes in macOS BigSur broke the selection's marching ants the same way
    they broke on Wayland and it was confirmed this fix worked for BigSur as
    well, at least on the dev builds.
    It is unnecessary to backport for Wayland (because GIMP 2.10 is based on
    GTK2 which anyway works only through XWayland, hence doesn't have the
    issue), we do it only for macOS BigSur (and further). Well at least the
    fix will hopefully work on the stable branch, because I cannot test
    myself.
    
    See issue #5952.

 app/display/gimpdisplayshell-callbacks.c |  1 +
 app/display/gimpdisplayshell-selection.c |  6 ------
 app/display/gimpdisplayshell.c           | 17 -----------------
 3 files changed, 1 insertion(+), 23 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-callbacks.c b/app/display/gimpdisplayshell-callbacks.c
index 9b65529b3c..2b621ac5bf 100644
--- a/app/display/gimpdisplayshell-callbacks.c
+++ b/app/display/gimpdisplayshell-callbacks.c
@@ -593,6 +593,7 @@ gimp_display_shell_canvas_draw_image (GimpDisplayShell *shell,
   gimp_canvas_item_draw (shell->unrotated_item, cr);
 
   /* restart (and recalculate) the selection boundaries */
+  gimp_display_shell_selection_draw (shell, cr);
   gimp_display_shell_selection_restart (shell);
 }
 
diff --git a/app/display/gimpdisplayshell-selection.c b/app/display/gimpdisplayshell-selection.c
index 85526619ca..3cfacd3a30 100644
--- a/app/display/gimpdisplayshell-selection.c
+++ b/app/display/gimpdisplayshell-selection.c
@@ -412,12 +412,6 @@ selection_generate_segs (Selection *selection)
                          &selection->n_segs_in, &selection->n_segs_out,
                          0, 0, 0, 0);
 
-  if (selection->n_segs_in || selection->n_segs_out)
-    gtk_widget_translate_coordinates (GTK_WIDGET (selection->shell->canvas),
-                                      GTK_WIDGET (selection->shell),
-                                      0, 0,
-                                      &canvas_offset_x, &canvas_offset_y);
-
   if (selection->n_segs_in)
     {
       selection->segs_in = g_new (GimpSegment, selection->n_segs_in);
diff --git a/app/display/gimpdisplayshell.c b/app/display/gimpdisplayshell.c
index 5cc8369dec..9603e4fae4 100644
--- a/app/display/gimpdisplayshell.c
+++ b/app/display/gimpdisplayshell.c
@@ -151,8 +151,6 @@ static void      gimp_display_shell_unmap          (GtkWidget        *widget);
 static void      gimp_display_shell_screen_changed (GtkWidget        *widget,
                                                     GdkScreen        *previous);
 static gboolean  gimp_display_shell_popup_menu     (GtkWidget        *widget);
-static gboolean  gimp_display_shell_draw           (GtkWidget        *widget,
-                                                    cairo_t          *cr);
 
 static void      gimp_display_shell_real_scaled    (GimpDisplayShell *shell);
 static void      gimp_display_shell_real_scrolled  (GimpDisplayShell *shell);
@@ -257,7 +255,6 @@ gimp_display_shell_class_init (GimpDisplayShellClass *klass)
   widget_class->unmap              = gimp_display_shell_unmap;
   widget_class->screen_changed     = gimp_display_shell_screen_changed;
   widget_class->popup_menu         = gimp_display_shell_popup_menu;
-  widget_class->draw               = gimp_display_shell_draw;
 
   klass->scaled                    = gimp_display_shell_real_scaled;
   klass->scrolled                  = gimp_display_shell_real_scrolled;
@@ -1056,20 +1053,6 @@ gimp_display_shell_popup_menu (GtkWidget *widget)
   return TRUE;
 }
 
-static gboolean
-gimp_display_shell_draw (GtkWidget *widget,
-                         cairo_t   *cr)
-{
-  GtkWidgetClass   *widget_class = g_type_class_peek_parent (parent_class);
-  GimpDisplayShell *shell        = GIMP_DISPLAY_SHELL (widget);
-  gboolean          stop_handlers;
-
-  stop_handlers = widget_class->draw (widget, cr);
-  gimp_display_shell_selection_draw (shell, cr);
-
-  return stop_handlers;
-}
-
 static void
 gimp_display_shell_real_scaled (GimpDisplayShell *shell)
 {