Copy/Paste property paths/values in inspector.

Resolves godotengine/godot-proposals#106.

Adds the following property menu options with default bindings:

- Copy Property (ctrl+c)
- Paste Property (ctrl+v)
- Copy Property Path (ctrl+shift+c)

If you hover over a property label in the inspector dock, you can copy
either the property value or the property path to the system clipboard
using the shortcuts above This is especially useful for the
`AnimationTree`, where code might reference properties like
"parameters/state/aim/move/blend_position".

One issue is that if you click a property, then click on the node you
currently have selected in the node tree, then press ctrl+shift+c, it
will still copy the selected property path rather than the node path. If
you click on a different node in the nodetree, however, ctrl+shift+c
will return to copying the nodepath.

The property value copy/paste was implemented by @KoBeWi at #39398 and
merged into this PR due to their similarity.

editor/editor_inspector.cpp

@@ -31,11 +31,13 @@
 #include "editor_inspector.h"
 
 #include "array_property_edit.h"
+#include "core/os/keyboard.h"
 #include "dictionary_property_edit.h"
 #include "editor/doc_tools.h"
 #include "editor_feature_profile.h"
 #include "editor_node.h"
 #include "editor_scale.h"
+#include "editor_settings.h"
 #include "multi_node_edit.h"
 #include "scene/resources/packed_scene.h"
 
@@ -782,6 +784,30 @@ void EditorProperty::gui_input(const Ref<InputEvent> &p_event) {
 			update();
 			emit_signal(SNAME("property_checked"), property, checked);
 		}
+	} else if (mb.is_valid() && mb->is_pressed() && mb->get_button_index() == MOUSE_BUTTON_RIGHT) {
+		_ensure_popup();
+		menu->set_position(get_screen_position() + get_local_mouse_position());
+		menu->set_size(Vector2(1, 1));
+		menu->popup();
+		select();
+		return;
+	}
+}
+
+void EditorProperty::unhandled_key_input(const Ref<InputEvent> &p_event) {
+	if (!selected) {
+		return;
+	}
+
+	if (ED_IS_SHORTCUT("property_editor/copy_property", p_event)) {
+		menu_option(MENU_COPY_PROPERTY);
+		accept_event();
+	} else if (ED_IS_SHORTCUT("property_editor/paste_property", p_event) && !is_read_only()) {
+		menu_option(MENU_PASTE_PROPERTY);
+		accept_event();
+	} else if (ED_IS_SHORTCUT("property_editor/copy_property_path", p_event)) {
+		menu_option(MENU_COPY_PROPERTY_PATH);
+		accept_event();
 	}
 }
 
@@ -895,6 +921,20 @@ String EditorProperty::get_tooltip_text() const {
 	return tooltip_text;
 }
 
+void EditorProperty::menu_option(int p_option) {
+	switch (p_option) {
+		case MENU_COPY_PROPERTY: {
+			EditorNode::get_singleton()->get_inspector()->set_property_clipboard(object->get(property));
+		} break;
+		case MENU_PASTE_PROPERTY: {
+			emit_changed(property, EditorNode::get_singleton()->get_inspector()->get_property_clipboard());
+		} break;
+		case MENU_COPY_PROPERTY_PATH: {
+			DisplayServer::get_singleton()->clipboard_set(property);
+		} break;
+	}
+}
+
 void EditorProperty::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_label", "text"), &EditorProperty::set_label);
 	ClassDB::bind_method(D_METHOD("get_label"), &EditorProperty::get_label);
@@ -971,6 +1011,21 @@ EditorProperty::EditorProperty() {
 	label_reference = nullptr;
 	bottom_editor = nullptr;
 	delete_hover = false;
+	menu = nullptr;
+	set_process_unhandled_key_input(true);
+}
+
+void EditorProperty::_ensure_popup() {
+	if (menu) {
+		return;
+	}
+	menu = memnew(PopupMenu);
+	menu->add_shortcut(ED_GET_SHORTCUT("property_editor/copy_property"), MENU_COPY_PROPERTY);
+	menu->add_shortcut(ED_GET_SHORTCUT("property_editor/paste_property"), MENU_PASTE_PROPERTY);
+	menu->add_shortcut(ED_GET_SHORTCUT("property_editor/copy_property_path"), MENU_COPY_PROPERTY_PATH);
+	menu->connect("id_pressed", callable_mp(this, &EditorProperty::menu_option));
+	menu->set_item_disabled(MENU_PASTE_PROPERTY, is_read_only());
+	add_child(menu);
 }
 
 ////////////////////////////////////////////////
@@ -2615,6 +2670,14 @@ void EditorInspector::set_restrict_to_basic_settings(bool p_restrict) {
 	update_tree();
 }
 
+void EditorInspector::set_property_clipboard(const Variant &p_value) {
+	property_clipboard = p_value;
+}
+
+Variant EditorInspector::get_property_clipboard() const {
+	return property_clipboard;
+}
+
 void EditorInspector::_bind_methods() {
 	ClassDB::bind_method("_edit_request_change", &EditorInspector::_edit_request_change);
 
@@ -2657,6 +2720,7 @@ EditorInspector::EditorInspector() {
 	property_focusable = -1;
 	sub_inspector = false;
 	deletable_properties = false;
+	property_clipboard = Variant();
 
 	get_v_scrollbar()->connect("value_changed", callable_mp(this, &EditorInspector::_vscroll_changed));
 	update_scroll_request = -1;
@@ -2666,4 +2730,8 @@ EditorInspector::EditorInspector() {
 		//used when class is created by the docgen to dump default values of everything bindable, editorsettings may not be created
 		refresh_countdown = 0.33;
 	}
+
+	ED_SHORTCUT("property_editor/copy_property", TTR("Copy Property"), KEY_MASK_CMD | KEY_C);
+	ED_SHORTCUT("property_editor/paste_property", TTR("Paste Property"), KEY_MASK_CMD | KEY_V);
+	ED_SHORTCUT("property_editor/copy_property_path", TTR("Copy Property Path"), KEY_MASK_CMD | KEY_MASK_SHIFT | KEY_C);
 }

editor/editor_inspector.h

@@ -51,6 +51,13 @@ public:
 class EditorProperty : public Container {
 	GDCLASS(EditorProperty, Container);
 
+public:
+	enum MenuItems {
+		MENU_COPY_PROPERTY,
+		MENU_PASTE_PROPERTY,
+		MENU_COPY_PROPERTY_PATH,
+	};
+
 private:
 	String label;
 	int text_size;
@@ -84,6 +91,7 @@ private:
 	bool use_folding;
 	bool draw_top_bg;
 
+	void _ensure_popup();
 	bool _is_property_different(const Variant &p_current, const Variant &p_orig);
 	bool _get_instantiated_node_original_property(const StringName &p_prop, Variant &value);
 	void _focusable_focused(int p_index);
@@ -97,6 +105,7 @@ private:
 	Vector<Control *> focusables;
 	Control *label_reference;
 	Control *bottom_editor;
+	PopupMenu *menu;
 
 	mutable String tooltip_text;
 
@@ -108,6 +117,7 @@ protected:
 	static void _bind_methods();
 
 	virtual void gui_input(const Ref<InputEvent> &p_event) override;
+	virtual void unhandled_key_input(const Ref<InputEvent> &p_event) override;
 
 public:
 	void emit_changed(const StringName &p_property, const Variant &p_value, const StringName &p_field = StringName(), bool p_changing = false);
@@ -175,6 +185,8 @@ public:
 
 	bool can_revert_to_default() const { return can_revert; }
 
+	void menu_option(int p_option);
+
 	EditorProperty();
 };
 
@@ -321,6 +333,7 @@ class EditorInspector : public ScrollContainer {
 
 	String property_prefix; //used for sectioned inspector
 	String object_class;
+	Variant property_clipboard;
 
 	bool restrict_to_basic = false;
 
@@ -412,6 +425,8 @@ public:
 	void set_use_deletable_properties(bool p_enabled);
 
 	void set_restrict_to_basic_settings(bool p_restrict);
+	void set_property_clipboard(const Variant &p_value);
+	Variant get_property_clipboard() const;
 
 	EditorInspector();
 };