[gimp] app: add gimp_display_shell_show_image()

[Ell <ell src gnome org>]

commit 539d666ae23e35c85d11fc0e2619bcfe1bb6dcda
Author: Ell <ell_se yahoo com>
Date:   Sat Aug 10 22:00:14 2019 +0300

    app: add gimp_display_shell_show_image()
    
    ... which controls whether or not the image is rendered by the
    shell.  We'll use this to hide the image while showing its
    transform preview in the next commits.

 app/display/gimpdisplayshell-callbacks.c | 21 ++++++++++++---------
 app/display/gimpdisplayshell.c           | 16 ++++++++++++++++
 app/display/gimpdisplayshell.h           |  6 ++++++
 3 files changed, 34 insertions(+), 9 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-callbacks.c b/app/display/gimpdisplayshell-callbacks.c
index e40bc27100..31a5ae00c5 100644
--- a/app/display/gimpdisplayshell-callbacks.c
+++ b/app/display/gimpdisplayshell-callbacks.c
@@ -509,17 +509,20 @@ gimp_display_shell_canvas_draw_image (GimpDisplayShell *shell,
       gimp_display_shell_draw_checkerboard (shell, cr);
       cairo_restore (cr);
 
-      cairo_set_matrix (cr, &matrix);
-
-      for (i = 0; i < clip_rectangles->num_rectangles; i++)
+      if (shell->show_image)
         {
-          cairo_rectangle_t rect = clip_rectangles->rectangles[i];
+          cairo_set_matrix (cr, &matrix);
+
+          for (i = 0; i < clip_rectangles->num_rectangles; i++)
+            {
+              cairo_rectangle_t rect = clip_rectangles->rectangles[i];
 
-          gimp_display_shell_draw_image (shell, cr,
-                                         floor (rect.x),
-                                         floor (rect.y),
-                                         ceil (rect.width),
-                                         ceil (rect.height));
+              gimp_display_shell_draw_image (shell, cr,
+                                             floor (rect.x),
+                                             floor (rect.y),
+                                             ceil (rect.width),
+                                             ceil (rect.height));
+            }
         }
     }
 
diff --git a/app/display/gimpdisplayshell.c b/app/display/gimpdisplayshell.c
index edf197c4b3..c580fe9537 100644
--- a/app/display/gimpdisplayshell.c
+++ b/app/display/gimpdisplayshell.c
@@ -314,6 +314,8 @@ gimp_display_shell_init (GimpDisplayShell *shell)
   shell->scale_x     = 1.0;
   shell->scale_y     = 1.0;
 
+  shell->show_image  = TRUE;
+
   gimp_display_shell_items_init (shell);
 
   shell->icon_size       = 128;
@@ -1725,6 +1727,20 @@ gimp_display_shell_mask_bounds (GimpDisplayShell *shell,
   return (*width > 0) && (*height > 0);
 }
 
+void
+gimp_display_shell_set_show_image (GimpDisplayShell *shell,
+                                   gboolean          show_image)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  if (show_image != shell->show_image)
+    {
+      shell->show_image = show_image;
+
+      gimp_display_shell_expose_full (shell);
+    }
+}
+
 void
 gimp_display_shell_flush (GimpDisplayShell *shell)
 {
diff --git a/app/display/gimpdisplayshell.h b/app/display/gimpdisplayshell.h
index 00176344aa..3afbe3d164 100644
--- a/app/display/gimpdisplayshell.h
+++ b/app/display/gimpdisplayshell.h
@@ -90,6 +90,8 @@ struct _GimpDisplayShell
 
   gboolean           proximity;        /*  is a device in proximity           */
 
+  gboolean           show_image;       /*  whether to show the image          */
+
   Selection         *selection;        /*  Selection (marching ants)          */
 
   GList             *children;
@@ -302,6 +304,10 @@ gboolean          gimp_display_shell_mask_bounds   (GimpDisplayShell   *shell,
                                                     gint               *width,
                                                     gint               *height);
 
+void              gimp_display_shell_set_show_image
+                                                   (GimpDisplayShell   *shell,
+                                                    gboolean            show_image);
+
 void              gimp_display_shell_flush         (GimpDisplayShell   *shell);
 
 void              gimp_display_shell_pause         (GimpDisplayShell   *shell);