[gimp] app: make layer picking a generic modifier of the shell.

[Jehan <jehanp src gnome org>]

commit 4c337353a034a1de779e9fc01b26192d47a0ced5
Author: Jehan <jehan girinstud io>
Date:   Sat Dec 22 19:09:34 2018 +0100

    app: make layer picking a generic modifier of the shell.
    
    Instead of having layer picking only on paint tools with alt-click, make
    it available everywhere with alt-middle click. Moving through layers is
    also a way to navigate an image, so it actually makes sense to be with
    other modifiers (panning, zooming, rotating), while making the feature
    more generic (this is definitely useful whatever the selected tool).

 app/display/gimpdisplayshell-tool-events.c | 54 +++++++++++++++++++++--
 app/display/gimpdisplayshell.h             |  2 +
 app/tools/gimppainttool.c                  | 71 +++---------------------------
 app/tools/gimppainttool.h                  |  3 --
 4 files changed, 59 insertions(+), 71 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-tool-events.c b/app/display/gimpdisplayshell-tool-events.c
index 23db94bbad..a12609e405 100644
--- a/app/display/gimpdisplayshell-tool-events.c
+++ b/app/display/gimpdisplayshell-tool-events.c
@@ -32,6 +32,7 @@
 #include "core/gimp-filter-history.h"
 #include "core/gimpcontext.h"
 #include "core/gimpimage.h"
+#include "core/gimpimage-pick-item.h"
 #include "core/gimpitem.h"
 
 #include "widgets/gimpcontrollers.h"
@@ -991,6 +992,12 @@ gimp_display_shell_canvas_tool_events (GtkWidget        *canvas,
                 return FALSE;
               }
 
+            if (gimp_display_shell_key_to_state (kevent->keyval) == GDK_MOD1_MASK)
+              /* We reset the picked layer only when hitting the Alt
+               * key.
+               */
+              shell->picked_layer = NULL;
+
             switch (kevent->keyval)
               {
               case GDK_KEY_Left:
@@ -1500,13 +1507,47 @@ gimp_display_shell_start_scrolling (GimpDisplayShell *shell,
   shell->rotating          = (state & gimp_get_extend_selection_mask ()) ? TRUE : FALSE;
   shell->rotate_drag_angle = shell->rotate_angle;
   shell->scaling           = (state & gimp_get_toggle_behavior_mask ()) ? TRUE : FALSE;
+  shell->layer_picking     = (state & GDK_MOD1_MASK) ? TRUE : FALSE;
 
   if (shell->rotating)
-    gimp_display_shell_set_override_cursor (shell,
-                                            (GimpCursorType) GDK_EXCHANGE);
+    {
+      gimp_display_shell_set_override_cursor (shell,
+                                              (GimpCursorType) GDK_EXCHANGE);
+    }
   else if (shell->scaling)
-    gimp_display_shell_set_override_cursor (shell,
-                                            (GimpCursorType) GIMP_CURSOR_ZOOM);
+    {
+      gimp_display_shell_set_override_cursor (shell,
+                                              (GimpCursorType) GIMP_CURSOR_ZOOM);
+    }
+  else if (shell->layer_picking)
+    {
+      GimpImage  *image   = gimp_display_get_image (shell->display);
+      GimpLayer  *layer;
+      GimpCoords  image_coords;
+      GimpCoords  display_coords;
+      guint32     time;
+
+      gimp_display_shell_set_override_cursor (shell,
+                                              (GimpCursorType) GIMP_CURSOR_CROSSHAIR);
+
+      gimp_display_shell_get_event_coords (shell, event,
+                                           &display_coords,
+                                           &state, &time);
+      gimp_display_shell_untransform_event_coords (shell,
+                                                   &display_coords, &image_coords,
+                                                   NULL);
+      layer = gimp_image_pick_layer (image,
+                                     (gint) image_coords.x,
+                                     (gint) image_coords.y,
+                                     shell->picked_layer);
+
+      if (layer && ! gimp_image_get_floating_selection (image))
+        {
+          if (layer != gimp_image_get_active_layer (image))
+            gimp_image_set_active_layer (image, layer);
+          shell->picked_layer = layer;
+        }
+    }
   else
     gimp_display_shell_set_override_cursor (shell,
                                             (GimpCursorType) GDK_FLEUR);
@@ -1528,6 +1569,7 @@ gimp_display_shell_stop_scrolling (GimpDisplayShell *shell,
   shell->rotating          = FALSE;
   shell->rotate_drag_angle = 0.0;
   shell->scaling           = FALSE;
+  shell->layer_picking     = FALSE;
 
   /* We may have ungrabbed the pointer when space was released while
    * mouse was down, to be able to catch a GDK_BUTTON_RELEASE event.
@@ -1563,6 +1605,10 @@ gimp_display_shell_handle_scrolling (GimpDisplayShell *shell,
                                      shell->scroll_last_x - x,
                                      shell->scroll_last_y - y);
     }
+  else if (shell->layer_picking)
+    {
+      /* Do nothing. We only pick the layer on click. */
+    }
   else
     {
       gimp_display_shell_scroll (shell,
diff --git a/app/display/gimpdisplayshell.h b/app/display/gimpdisplayshell.h
index 2435c8e9f3..a96f67aa76 100644
--- a/app/display/gimpdisplayshell.h
+++ b/app/display/gimpdisplayshell.h
@@ -208,6 +208,8 @@ struct _GimpDisplayShell
   gdouble            rotate_drag_angle;
   gboolean           scaling;
   gpointer           scroll_info;
+  gboolean           layer_picking;
+  GimpLayer         *picked_layer;
 
   GeglBuffer        *mask;
   gint               mask_offset_x;
diff --git a/app/tools/gimppainttool.c b/app/tools/gimppainttool.c
index 968cc0c90c..b303831019 100644
--- a/app/tools/gimppainttool.c
+++ b/app/tools/gimppainttool.c
@@ -32,7 +32,6 @@
 #include "core/gimpdrawable.h"
 #include "core/gimperror.h"
 #include "core/gimpimage.h"
-#include "core/gimpimage-pick-item.h"
 #include "core/gimplayer.h"
 #include "core/gimppaintinfo.h"
 #include "core/gimpprojection.h"
@@ -267,26 +266,7 @@ gimp_paint_tool_button_press (GimpTool            *tool,
   gboolean          constrain;
   GError           *error = NULL;
 
-  if (paint_tool->picking_layer)
-    {
-      GimpLayer *layer;
-
-      layer = gimp_image_pick_layer (image,
-                                     (gint) coords->x,
-                                     (gint) coords->y,
-                                     paint_tool->picked_layer);
-      if (layer)
-        {
-          if (layer != gimp_image_get_active_layer (image))
-            {
-              paint_tool->picked_layer = layer;
-              gimp_image_set_active_layer (image, layer);
-            }
-          paint_tool->picked_layer = layer;
-        }
-      return;
-    }
-  else if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
+  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
     {
       GIMP_TOOL_CLASS (parent_class)->button_press (tool, coords, time, state,
                                                     press_type, display);
@@ -385,7 +365,7 @@ gimp_paint_tool_button_release (GimpTool              *tool,
   GimpImage        *image      = gimp_display_get_image (display);
   gboolean          cancel;
 
-  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)) || paint_tool->picking_layer)
+  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
     {
       GIMP_TOOL_CLASS (parent_class)->button_release (tool, coords, time,
                                                       state, release_type,
@@ -420,7 +400,7 @@ gimp_paint_tool_motion (GimpTool         *tool,
 
   GIMP_TOOL_CLASS (parent_class)->motion (tool, coords, time, state, display);
 
-  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)) || paint_tool->picking_layer)
+  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
     return;
 
   gimp_paint_tool_paint_motion (paint_tool, coords, time);
@@ -483,15 +463,6 @@ gimp_paint_tool_modifier_key (GimpTool        *tool,
             }
         }
     }
-  if (! gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)) &&
-      ! paint_tool->draw_line)
-    {
-      paint_tool->picked_layer  = NULL;
-      if ((state & gimp_get_all_modifiers_mask ()) == GDK_MOD1_MASK)
-        paint_tool->picking_layer = TRUE;
-      else
-        paint_tool->picking_layer = FALSE;
-    }
 }
 
 static void
@@ -501,41 +472,18 @@ gimp_paint_tool_cursor_update (GimpTool         *tool,
                                GimpDisplay      *display)
 {
   GimpPaintTool      *paint_tool = GIMP_PAINT_TOOL (tool);
-  GimpToolCursorType  tool_cursor;
   GimpCursorModifier  modifier;
   GimpCursorModifier  toggle_modifier;
-  GimpToolCursorType  old_tool_cursor;
   GimpCursorModifier  old_modifier;
   GimpCursorModifier  old_toggle_modifier;
 
-  tool_cursor     = tool->control->tool_cursor;
   modifier        = tool->control->cursor_modifier;
   toggle_modifier = tool->control->toggle_cursor_modifier;
 
-  old_tool_cursor     = tool_cursor;
   old_modifier        = modifier;
   old_toggle_modifier = toggle_modifier;
 
-  if (paint_tool->picking_layer)
-    {
-      GimpImage *image = gimp_display_get_image (display);
-      GimpLayer *layer;
-
-      layer = gimp_image_pick_layer (image,
-                                     (gint) coords->x,
-                                     (gint) coords->y,
-                                     paint_tool->picked_layer);
-
-      modifier = GIMP_CURSOR_MODIFIER_NONE;
-      if (gimp_image_get_floating_selection (image))
-        modifier = GIMP_CURSOR_MODIFIER_BAD;
-      else if (layer && layer != gimp_image_get_active_layer (image))
-        modifier = GIMP_CURSOR_MODIFIER_SELECT;
-
-      gimp_tool_control_set_tool_cursor (tool->control, GIMP_TOOL_CURSOR_HAND);
-      gimp_tool_control_set_cursor_modifier (tool->control, modifier);
-    }
-  else if (! gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
+  if (! gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
     {
       GimpImage    *image    = gimp_display_get_image (display);
       GimpDrawable *drawable = gimp_image_get_active_drawable (image);
@@ -571,8 +519,6 @@ gimp_paint_tool_cursor_update (GimpTool         *tool,
   /*  reset old stuff here so we are not interfering with the modifiers
    *  set by our subclasses
    */
-  gimp_tool_control_set_tool_cursor            (tool->control,
-                                                old_tool_cursor);
   gimp_tool_control_set_cursor_modifier        (tool->control,
                                                 old_modifier);
   gimp_tool_control_set_toggle_cursor_modifier (tool->control,
@@ -594,8 +540,7 @@ gimp_paint_tool_oper_update (GimpTool         *tool,
   GimpImage        *image         = gimp_display_get_image (display);
   GimpDrawable     *drawable      = gimp_image_get_active_drawable (image);
 
-  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)) ||
-      paint_tool->picking_layer)
+  if (gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (tool)))
     {
       GIMP_TOOL_CLASS (parent_class)->oper_update (tool, coords, state,
                                                    proximity, display);
@@ -712,11 +657,9 @@ gimp_paint_tool_oper_update (GimpTool         *tool,
 static void
 gimp_paint_tool_draw (GimpDrawTool *draw_tool)
 {
-  GimpPaintTool *paint_tool = GIMP_PAINT_TOOL (draw_tool);
-
-  if (! gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (draw_tool)) &&
-      ! paint_tool->picking_layer)
+  if (! gimp_color_tool_is_enabled (GIMP_COLOR_TOOL (draw_tool)))
     {
+      GimpPaintTool  *paint_tool = GIMP_PAINT_TOOL (draw_tool);
       GimpPaintCore  *core       = paint_tool->core;
       GimpImage      *image      = gimp_display_get_image (draw_tool->display);
       GimpDrawable   *drawable   = gimp_image_get_active_drawable (image);
diff --git a/app/tools/gimppainttool.h b/app/tools/gimppainttool.h
index f927807009..387239e7f4 100644
--- a/app/tools/gimppainttool.h
+++ b/app/tools/gimppainttool.h
@@ -44,9 +44,6 @@ struct _GimpPaintTool
   gboolean       pick_colors;  /*  pick color if ctrl is pressed   */
   gboolean       draw_line;
 
-  gboolean       picking_layer; /*  pick layer in progress (alt pressed)  */
-  GimpLayer     *picked_layer;
-
   gboolean       show_cursor;
   gboolean       draw_brush;
   gboolean       draw_fallback;