Automatic arrangement of nodes in VisualScript/VisualShaders editors

This PR and commit adds the functionality to arrange nodes in VisualScript/VisualShader editor. The layout generated by this 
feature is compact, with minimum crossings between connections
& uniform horizontal & vertical gaps between the nodes. 

This work has been sponsored by GSoC '21.

Full list of additions/changes:
• Added arrange_nodes() method in GraphEdit module.
    • This method computes new positions for all the selected
      nodes by forming blocks and compressing them.
      The nodes are moved to these new positions. 
    • Adding this method to GraphEdit makes it available for 
      use in VisualScript/VisualShaders editors and its other
      subclasses. 
• Button with an icon has been added to call arrange_nodes() in GraphEdit. 
    • This button is inherited by VisualScript/VisualShaders editors
       to invoke the method.
• Undo/redo is functional with this method.
    • By using signals in arrange_nodes(), position changes are registered 
       in undo/redo stack of the subclass that is using the method. 
• Metadata of the method has been updated in ClassDB
• Method description has been added to class reference of GraphEdit

3 files changed, 5 insertions, 0 deletions

diff --git a/scene/resources/default_theme/default_theme.cpp b/scene/resources/default_theme/default_theme.cpp
index d0dee2b5e3..f406f3f731 100644
--- a/scene/resources/default_theme/default_theme.cpp
+++ b/scene/resources/default_theme/default_theme.cpp
@@ -953,6 +953,7 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 	theme->set_icon("more", "GraphEdit", make_icon(icon_zoom_more_png));
 	theme->set_icon("snap", "GraphEdit", make_icon(icon_snap_grid_png));
 	theme->set_icon("minimap", "GraphEdit", make_icon(icon_grid_minimap_png));
+	theme->set_icon("layout", "GraphEdit", make_icon(icon_grid_layout_png));
 	theme->set_stylebox("bg", "GraphEdit", make_stylebox(tree_bg_png, 4, 4, 4, 5));
 	theme->set_color("grid_minor", "GraphEdit", Color(1, 1, 1, 0.05));
 	theme->set_color("grid_major", "GraphEdit", Color(1, 1, 1, 0.2));
diff --git a/scene/resources/default_theme/icon_grid_layout.png b/scene/resources/default_theme/icon_grid_layout.png
new file mode 100644
index 0000000000..00a6179d5e
--- /dev/null
+++ b/scene/resources/default_theme/icon_grid_layout.png
diff --git a/scene/resources/default_theme/theme_data.h b/scene/resources/default_theme/theme_data.h
index cdb1bc527b..c26b73e059 100644
--- a/scene/resources/default_theme/theme_data.h
+++ b/scene/resources/default_theme/theme_data.h
@@ -186,6 +186,10 @@ static const unsigned char icon_grid_minimap_png[] = {
 	0x89, 0x50, 0x4e, 0x47, 0xd, 0xa, 0x1a, 0xa, 0x0, 0x0, 0x0, 0xd, 0x49, 0x48, 0x44, 0x52, 0x0, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0, 0x10, 0x8, 0x6, 0x0, 0x0, 0x0, 0x1f, 0xf3, 0xff, 0x61, 0x0, 0x0, 0x0, 0x9, 0x70, 0x48, 0x59, 0x73, 0x0, 0x0, 0xe, 0xc3, 0x0, 0x0, 0xe, 0xc3, 0x1, 0xc7, 0x6f, 0xa8, 0x64, 0x0, 0x0, 0x0, 0x19, 0x74, 0x45, 0x58, 0x74, 0x53, 0x6f, 0x66, 0x74, 0x77, 0x61, 0x72, 0x65, 0x0, 0x77, 0x77, 0x77, 0x2e, 0x69, 0x6e, 0x6b, 0x73, 0x63, 0x61, 0x70, 0x65, 0x2e, 0x6f, 0x72, 0x67, 0x9b, 0xee, 0x3c, 0x1a, 0x0, 0x0, 0x2, 0xd, 0x49, 0x44, 0x41, 0x54, 0x38, 0x8d, 0x75, 0x93, 0x31, 0x68, 0x14, 0x51, 0x10, 0x86, 0xbf, 0xd9, 0xd, 0xbb, 0xde, 0x76, 0x82, 0x21, 0xf8, 0xe0, 0xbc, 0x5d, 0x8b, 0x80, 0x69, 0x6c, 0xd2, 0x5a, 0x6a, 0x91, 0xc3, 0xd2, 0x46, 0x22, 0x8, 0x9, 0x89, 0x70, 0x85, 0x10, 0x41, 0xd, 0x24, 0x45, 0xb0, 0xb, 0x68, 0x11, 0x14, 0x24, 0x10, 0x22, 0x62, 0x21, 0x41, 0xe, 0x4b, 0x21, 0xa4, 0xb7, 0x49, 0x17, 0xb1, 0x8, 0xb9, 0xdd, 0xc7, 0x86, 0x33, 0x21, 0xe1, 0x3a, 0x8f, 0x64, 0x61, 0x6f, 0x2c, 0xbc, 0x3b, 0x36, 0xb9, 0xdc, 0xc0, 0x2b, 0xde, 0xcc, 0xfc, 0xf3, 0xff, 0xfc, 0xcc, 0x48, 0xa3, 0xd1, 0x78, 0x20, 0x22, 0x13, 0xbe, 0xef, 0xaf, 0xdf, 0xac, 0xd7, 0x1f, 0xe1, 0x38, 0xd3, 0xa8, 0x2a, 0xf0, 0x45, 0x6a, 0xb5, 0xcf, 0x5c, 0x11, 0xcd, 0x66, 0x33, 0x38, 0x3f, 0x3f, 0x9f, 0x13, 0x91, 0x7d, 0xb1, 0xd6, 0x6e, 0xaa, 0xea, 0xd3, 0xe0, 0xe8, 0xe8, 0xde, 0xe8, 0xee, 0xee, 0x37, 0xc0, 0xe9, 0xf6, 0x75, 0xf0, 0xfd, 0x9, 0x99, 0x9d, 0x6d, 0x15, 0x81, 0x59, 0x96, 0x3d, 0x3, 0x5e, 0x2, 0x63, 0x22, 0xf2, 0x69, 0xa4, 0x57, 0x1c, 0xdd, 0xdb, 0xfb, 0x5b, 0x0, 0x3, 0x38, 0x67, 0x41, 0x30, 0x11, 0xc7, 0xf1, 0x13, 0x0, 0x11, 0x71, 0xb2, 0x2c, 0x7b, 0xd8, 0xad, 0xad, 0x2, 0x6f, 0xb9, 0x0, 0x38, 0x3c, 0xfc, 0x5, 0x9c, 0xf6, 0xff, 0x22, 0x27, 0x27, 0xe3, 0xe3, 0x7f, 0xa, 0x3, 0x67, 0x45, 0xe4, 0xbb, 0xe7, 0x79, 0xb7, 0xc3, 0x30, 0x7c, 0xd7, 0x67, 0xe9, 0xe3, 0x67, 0x66, 0x5c, 0x60, 0x1, 0x50, 0x40, 0x51, 0x7d, 0x71, 0x6b, 0x72, 0xf2, 0x20, 0x8a, 0xa2, 0xf9, 0x28, 0x8a, 0xe6, 0x1, 0x3a, 0x9d, 0xce, 0x4f, 0x63, 0x4c, 0x3b, 0x4d, 0xd3, 0xd2, 0xc0, 0x80, 0x3c, 0xcf, 0xf, 0x92, 0xa9, 0xa9, 0x31, 0x60, 0x5, 0x58, 0x91, 0x5a, 0xed, 0xc7, 0x15, 0xfe, 0x95, 0xac, 0xb5, 0xcf, 0xf3, 0x3c, 0x3f, 0xe8, 0x25, 0x46, 0xa, 0xc5, 0xd, 0x11, 0x59, 0xb3, 0xd5, 0xea, 0x1b, 0xa0, 0x95, 0x54, 0xab, 0x5b, 0x97, 0xd1, 0x22, 0xb2, 0xa6, 0xaa, 0x6d, 0x60, 0xd, 0x58, 0xba, 0xa0, 0x20, 0xc, 0xc3, 0x65, 0xd7, 0x75, 0x23, 0xe0, 0x2e, 0xb0, 0x1, 0x5c, 0xbf, 0xf4, 0x0, 0xbe, 0xba, 0xae, 0x1b, 0x85, 0x61, 0xb8, 0x3c, 0xa0, 0x20, 0x4d, 0xd3, 0x52, 0xb9, 0x5c, 0x6e, 0xc5, 0x71, 0xbc, 0x23, 0x22, 0xd3, 0x61, 0x18, 0xde, 0x2f, 0xb2, 0x27, 0x49, 0xa2, 0xaa, 0xba, 0x53, 0x2e, 0x97, 0x5b, 0x69, 0x9a, 0x96, 0xf2, 0x3c, 0x1f, 0xf0, 0xc0, 0x5a, 0x6b, 0x5f, 0x1, 0x25, 0x86, 0x84, 0xe3, 0x38, 0x9e, 0xb5, 0x76, 0x2e, 0xcf, 0xf3, 0xfd, 0x1, 0x5, 0x22, 0xb2, 0xa1, 0xaa, 0x4b, 0x22, 0x72, 0xad, 0xcb, 0x38, 0xe0, 0x81, 0xaa, 0x7e, 0x0, 0xce, 0x44, 0xe4, 0xbd, 0xaa, 0xbe, 0xbe, 0xa0, 0xa0, 0x52, 0xa9, 0x2c, 0x7a, 0x9e, 0x17, 0x1, 0x3d, 0xe0, 0x55, 0x1e, 0x6c, 0x79, 0x9e, 0x17, 0x55, 0x2a, 0x95, 0xc5, 0x1, 0x5, 0xcd, 0x66, 0x33, 0x30, 0xc6, 0x9c, 0xc6, 0x71, 0xbc, 0x2d, 0x22, 0x8f, 0x87, 0x78, 0xb0, 0x6d, 0x8c, 0x39, 0xed, 0xae, 0x74, 0xdf, 0x83, 0x3a, 0x70, 0x9c, 0x65, 0x59, 0x23, 0x49, 0x92, 0x5, 0x11, 0x9, 0x86, 0x79, 0x20, 0x22, 0x41, 0x92, 0x24, 0xb, 0x59, 0x96, 0x35, 0x80, 0x63, 0xa0, 0x2e, 0x3d, 0xf6, 0xc2, 0x91, 0xdc, 0x0, 0x5c, 0x55, 0x5d, 0xbf, 0x4, 0x9e, 0x3, 0x72, 0xfe, 0xaf, 0xfb, 0xaa, 0xe7, 0x79, 0x1f, 0x8d, 0x31, 0x6d, 0x29, 0x36, 0xf5, 0xce, 0x14, 0xb8, 0x33, 0x44, 0xc4, 0x6f, 0xdf, 0xf7, 0xd7, 0x8d, 0x31, 0xed, 0x5e, 0xe2, 0x1f, 0xb, 0x5c, 0xe2, 0xcb, 0xd, 0x9b, 0x69, 0xcb, 0x0, 0x0, 0x0, 0x0, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82
 };
 
+static const unsigned char icon_grid_layout_png[] = {
+	0x89, 0x50, 0x4e, 0x47, 0xd, 0xa, 0x1a, 0xa, 0x0, 0x0, 0x0, 0xd, 0x49, 0x48, 0x44, 0x52, 0x0, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0, 0x10, 0x8, 0x6, 0x0, 0x0, 0x0, 0x1f, 0xf3, 0xff, 0x61, 0x0, 0x0, 0x0, 0x9, 0x70, 0x48, 0x59, 0x73, 0x0, 0x0, 0xe, 0xc3, 0x0, 0x0, 0xe, 0xc3, 0x1, 0xc7, 0x6f, 0xa8, 0x64, 0x0, 0x0, 0x0, 0x19, 0x74, 0x45, 0x58, 0x74, 0x53, 0x6f, 0x66, 0x74, 0x77, 0x61, 0x72, 0x65, 0x0, 0x77, 0x77, 0x77, 0x2e, 0x69, 0x6e, 0x6b, 0x73, 0x63, 0x61, 0x70, 0x65, 0x2e, 0x6f, 0x72, 0x67, 0x9b, 0xee, 0x3c, 0x1a, 0x0, 0x0, 0x2, 0xd, 0x49, 0x44, 0x41, 0x54, 0x38, 0x8d, 0x75, 0x93, 0x31, 0x68, 0x14, 0x51, 0x10, 0x86, 0xbf, 0xd9, 0xd, 0xbb, 0xde, 0x76, 0x82, 0x21, 0xf8, 0xe0, 0xbc, 0x5d, 0x8b, 0x80, 0x69, 0x6c, 0xd2, 0x5a, 0x6a, 0x91, 0xc3, 0xd2, 0x46, 0x22, 0x8, 0x9, 0x89, 0x70, 0x85, 0x10, 0x41, 0xd, 0x24, 0x45, 0xb0, 0xb, 0x68, 0x11, 0x14, 0x24, 0x10, 0x22, 0x62, 0x21, 0x41, 0xe, 0x4b, 0x21, 0xa4, 0xb7, 0x49, 0x17, 0xb1, 0x8, 0xb9, 0xdd, 0xc7, 0x86, 0x33, 0x21, 0xe1, 0x3a, 0x8f, 0x64, 0x61, 0x6f, 0x2c, 0xbc, 0x3b, 0x36, 0xb9, 0xdc, 0xc0, 0x2b, 0xde, 0xcc, 0xfc, 0xf3, 0xff, 0xfc, 0xcc, 0x48, 0xa3, 0xd1, 0x78, 0x20, 0x22, 0x13, 0xbe, 0xef, 0xaf, 0xdf, 0xac, 0xd7, 0x1f, 0xe1, 0x38, 0xd3, 0xa8, 0x2a, 0xf0, 0x45, 0x6a, 0xb5, 0xcf, 0x5c, 0x11, 0xcd, 0x66, 0x33, 0x38, 0x3f, 0x3f, 0x9f, 0x13, 0x91, 0x7d, 0xb1, 0xd6, 0x6e, 0xaa, 0xea, 0xd3, 0xe0, 0xe8, 0xe8, 0xde, 0xe8, 0xee, 0xee, 0x37, 0xc0, 0xe9, 0xf6, 0x75, 0xf0, 0xfd, 0x9, 0x99, 0x9d, 0x6d, 0x15, 0x81, 0x59, 0x96, 0x3d, 0x3, 0x5e, 0x2, 0x63, 0x22, 0xf2, 0x69, 0xa4, 0x57, 0x1c, 0xdd, 0xdb, 0xfb, 0x5b, 0x0, 0x3, 0x38, 0x67, 0x41, 0x30, 0x11, 0xc7, 0xf1, 0x13, 0x0, 0x11, 0x71, 0xb2, 0x2c, 0x7b, 0xd8, 0xad, 0xad, 0x2, 0x6f, 0xb9, 0x0, 0x38, 0x3c, 0xfc, 0x5, 0x9c, 0xf6, 0xff, 0x22, 0x27, 0x27, 0xe3, 0xe3, 0x7f, 0xa, 0x3, 0x67, 0x45, 0xe4, 0xbb, 0xe7, 0x79, 0xb7, 0xc3, 0x30, 0x7c, 0xd7, 0x67, 0xe9, 0xe3, 0x67, 0x66, 0x5c, 0x60, 0x1, 0x50, 0x40, 0x51, 0x7d, 0x71, 0x6b, 0x72, 0xf2, 0x20, 0x8a, 0xa2, 0xf9, 0x28, 0x8a, 0xe6, 0x1, 0x3a, 0x9d, 0xce, 0x4f, 0x63, 0x4c, 0x3b, 0x4d, 0xd3, 0xd2, 0xc0, 0x80, 0x3c, 0xcf, 0xf, 0x92, 0xa9, 0xa9, 0x31, 0x60, 0x5, 0x58, 0x91, 0x5a, 0xed, 0xc7, 0x15, 0xfe, 0x95, 0xac, 0xb5, 0xcf, 0xf3, 0x3c, 0x3f, 0xe8, 0x25, 0x46, 0xa, 0xc5, 0xd, 0x11, 0x59, 0xb3, 0xd5, 0xea, 0x1b, 0xa0, 0x95, 0x54, 0xab, 0x5b, 0x97, 0xd1, 0x22, 0xb2, 0xa6, 0xaa, 0x6d, 0x60, 0xd, 0x58, 0xba, 0xa0, 0x20, 0xc, 0xc3, 0x65, 0xd7, 0x75, 0x23, 0xe0, 0x2e, 0xb0, 0x1, 0x5c, 0xbf, 0xf4, 0x0, 0xbe, 0xba, 0xae, 0x1b, 0x85, 0x61, 0xb8, 0x3c, 0xa0, 0x20, 0x4d, 0xd3, 0x52, 0xb9, 0x5c, 0x6e, 0xc5, 0x71, 0xbc, 0x23, 0x22, 0xd3, 0x61, 0x18, 0xde, 0x2f, 0xb2, 0x27, 0x49, 0xa2, 0xaa, 0xba, 0x53, 0x2e, 0x97, 0x5b, 0x69, 0x9a, 0x96, 0xf2, 0x3c, 0x1f, 0xf0, 0xc0, 0x5a, 0x6b, 0x5f, 0x1, 0x25, 0x86, 0x84, 0xe3, 0x38, 0x9e, 0xb5, 0x76, 0x2e, 0xcf, 0xf3, 0xfd, 0x1, 0x5, 0x22, 0xb2, 0xa1, 0xaa, 0x4b, 0x22, 0x72, 0xad, 0xcb, 0x38, 0xe0, 0x81, 0xaa, 0x7e, 0x0, 0xce, 0x44, 0xe4, 0xbd, 0xaa, 0xbe, 0xbe, 0xa0, 0xa0, 0x52, 0xa9, 0x2c, 0x7a, 0x9e, 0x17, 0x1, 0x3d, 0xe0, 0x55, 0x1e, 0x6c, 0x79, 0x9e, 0x17, 0x55, 0x2a, 0x95, 0xc5, 0x1, 0x5, 0xcd, 0x66, 0x33, 0x30, 0xc6, 0x9c, 0xc6, 0x71, 0xbc, 0x2d, 0x22, 0x8f, 0x87, 0x78, 0xb0, 0x6d, 0x8c, 0x39, 0xed, 0xae, 0x74, 0xdf, 0x83, 0x3a, 0x70, 0x9c, 0x65, 0x59, 0x23, 0x49, 0x92, 0x5, 0x11, 0x9, 0x86, 0x79, 0x20, 0x22, 0x41, 0x92, 0x24, 0xb, 0x59, 0x96, 0x35, 0x80, 0x63, 0xa0, 0x2e, 0x3d, 0xf6, 0xc2, 0x91, 0xdc, 0x0, 0x5c, 0x55, 0x5d, 0xbf, 0x4, 0x9e, 0x3, 0x72, 0xfe, 0xaf, 0xfb, 0xaa, 0xe7, 0x79, 0x1f, 0x8d, 0x31, 0x6d, 0x29, 0x36, 0xf5, 0xce, 0x14, 0xb8, 0x33, 0x44, 0xc4, 0x6f, 0xdf, 0xf7, 0xd7, 0x8d, 0x31, 0xed, 0x5e, 0xe2, 0x1f, 0xb, 0x5c, 0xe2, 0xcb, 0xd, 0x9b, 0x69, 0xcb, 0x0, 0x0, 0x0, 0x0, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82
+};
+
 static const unsigned char icon_parent_folder_png[] = {
 	0x89, 0x50, 0x4e, 0x47, 0xd, 0xa, 0x1a, 0xa, 0x0, 0x0, 0x0, 0xd, 0x49, 0x48, 0x44, 0x52, 0x0, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0, 0x10, 0x8, 0x4, 0x0, 0x0, 0x0, 0xb5, 0xfa, 0x37, 0xea, 0x0, 0x0, 0x0, 0x68, 0x49, 0x44, 0x41, 0x54, 0x78, 0xda, 0x63, 0xa0, 0x33, 0xb8, 0x27, 0xfe, 0xe0, 0xfc, 0x83, 0x73, 0xf7, 0xc4, 0x71, 0x48, 0xdf, 0x11, 0x7b, 0x78, 0xe9, 0xc1, 0x3f, 0x20, 0xbc, 0xfe, 0x40, 0x12, 0x8f, 0x34, 0x4c, 0x9, 0xa6, 0xe1, 0x57, 0x80, 0x12, 0x17, 0x81, 0xf8, 0x2f, 0x58, 0xe1, 0x15, 0x34, 0x8b, 0x1e, 0x9c, 0x5, 0xa, 0x5e, 0xb8, 0x23, 0x6, 0x52, 0x70, 0x5b, 0x14, 0xac, 0xf0, 0xc, 0xaa, 0x82, 0x7d, 0xf, 0x8e, 0xde, 0x14, 0xf9, 0xcf, 0x8, 0x52, 0xc0, 0xc0, 0x70, 0x5b, 0xf4, 0xe1, 0xc9, 0x7, 0x47, 0xb1, 0xb8, 0x3, 0xaa, 0x0, 0xa, 0x48, 0x52, 0x80, 0xb0, 0xea, 0xc8, 0xc3, 0x83, 0xc, 0x83, 0xe, 0x0, 0x0, 0xb8, 0x27, 0x55, 0x4c, 0xbe, 0xc0, 0xd2, 0xac, 0x0, 0x0, 0x0, 0x0, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82
 };