Tooltips: Improve code clarity and docs

The return type for `_make_custom_tooltip` is clarified as Control, and users
should make sure to return a visible node for proper size calculations.

Moreover in the current master branch, a PopupPanel will be added as parent
to the provided tooltip to make it a sub-window.

Clarifies documentation for `Control._make_custom_tooltip`, and shows how to
use the (until now undocumented) "TooltipPanel" and "TooltipLabel" theme types
to style tooltips.

Fixes #39677.

doc/classes/Control.xml

@@ -75,15 +75,17 @@
 			</description>
 		</method>
 		<method name="_make_custom_tooltip" qualifiers="virtual">
-			<return type="Object">
+			<return type="Control">
 			</return>
 			<argument index="0" name="for_text" type="String">
 			</argument>
 			<description>
-				Virtual method to be implemented by the user. Returns a [Control] node that should be used as a tooltip instead of the default one. Use [code]for_text[/code] parameter to determine what text the tooltip should contain (likely the contents of [member hint_tooltip]).
-				The returned node must be of type [Control] or Control-derieved. It can have child nodes of any type. It is freed when the tooltip disappears, so make sure you always provide a new instance, not e.g. a node from scene. When [code]null[/code] or non-Control node is returned, the default tooltip will be used instead.
+				Virtual method to be implemented by the user. Returns a [Control] node that should be used as a tooltip instead of the default one. The [code]for_text[/code] includes the contents of the [member hint_tooltip] property.
+				The returned node must be of type [Control] or Control-derived. It can have child nodes of any type. It is freed when the tooltip disappears, so make sure you always provide a new instance (if you want to use a pre-existing node from your scene tree, you can duplicate it and pass the duplicated instance).When [code]null[/code] or a non-Control node is returned, the default tooltip will be used instead.
+				The returned node will be added as child to a [PopupPanel], so you should only provide the contents of that panel. That [PopupPanel] can be themed using [method Theme.set_stylebox] for the type [code]"TooltipPanel"[/code] (see [member hint_tooltip] for an example).
 				[b]Note:[/b] The tooltip is shrunk to minimal size. If you want to ensure it's fully visible, you might want to set its [member rect_min_size] to some non-zero value.
-				Example of usage with custom-constructed node:
+				[b]Note:[/b] The node (and any relevant children) should be [member CanvasItem.visible] when returned, otherwise the viewport that instantiates it will not be able to calculate its minimum size reliably.
+				Example of usage with a custom-constructed node:
 				[codeblocks]
 				[gdscript]
 				func _make_custom_tooltip(for_text):
@@ -92,7 +94,7 @@
 				    return label
 				[/gdscript]
 				[csharp]
-				public override Godot.Object _MakeCustomTooltip(String forText)
+				public override Godot.Control _MakeCustomTooltip(String forText)
 				{
 				    var label = new Label();
 				    label.Text = forText;
@@ -100,18 +102,18 @@
 				}
 				[/csharp]
 				[/codeblocks]
-				Example of usage with custom scene instance:
+				Example of usage with a custom scene instance:
 				[codeblocks]
 				[gdscript]
 				func _make_custom_tooltip(for_text):
-				    var tooltip = preload("SomeTooltipScene.tscn").instance()
+				    var tooltip = preload("res://SomeTooltipScene.tscn").instance()
 				    tooltip.get_node("Label").text = for_text
 				    return tooltip
 				[/gdscript]
 				[csharp]
-				public override Godot.Object _MakeCustomTooltip(String forText)
+				public override Godot.Control _MakeCustomTooltip(String forText)
 				{
-				    Node tooltip = ResourceLoader.Load&lt;PackedScene&gt;("SomeTooltipScene.tscn").Instance();
+				    Node tooltip = ResourceLoader.Load&lt;PackedScene&gt;("res://SomeTooltipScene.tscn").Instance();
 				    tooltip.GetNode&lt;Label&gt;("Label").Text = forText;
 				    return tooltip;
 				}
@@ -993,6 +995,25 @@
 		</member>
 		<member name="hint_tooltip" type="String" setter="set_tooltip" getter="_get_tooltip" default="&quot;&quot;">
 			Changes the tooltip text. The tooltip appears when the user's mouse cursor stays idle over this control for a few moments, provided that the [member mouse_filter] property is not [constant MOUSE_FILTER_IGNORE]. You can change the time required for the tooltip to appear with [code]gui/timers/tooltip_delay_sec[/code] option in Project Settings.
+			The tooltip popup will use either a default implementation, or a custom one that you can provide by overriding [method _make_custom_tooltip]. The default tooltip includes a [PopupPanel] and [Label] whose theme properties can be customized using [Theme] methods with the [code]"TooltipPanel"[/code] and [code]"TooltipLabel"[/code] respectively. For example:
+			[codeblocks]
+			[gdscript]
+			var style_box = StyleBoxFlat.new()
+			style_box.set_bg_color(Color(1, 1, 0))
+			style_box.set_border_width_all(2)
+			# We assume here that the `theme` property has been assigned a custom Theme beforehand.
+			theme.set_stylebox("panel", "TooltipPanel", style_box)
+			theme.set_color("font_color", "TooltipLabel", Color(0, 1, 1))
+			[/gdscript]
+			[csharp]
+			var styleBox = new StyleBoxFlat();
+			styleBox.SetBgColor(new Color(1, 1, 0));
+			styleBox.SetBorderWidthAll(2);
+			// We assume here that the `Theme` property has been assigned a custom Theme beforehand.
+			Theme.SetStyleBox("panel", "TooltipPanel", styleBox);
+			Theme.SetColor("font_color", "TooltipLabel", new Color(0, 1, 1));
+			[/csharp]
+			[/codeblocks]
 		</member>
 		<member name="margin_bottom" type="float" setter="set_margin" getter="get_margin" default="0.0">
 			Distance between the node's bottom edge and its parent control, based on [member anchor_bottom].

scene/gui/control.cpp

@@ -2738,7 +2738,9 @@ void Control::_bind_methods() {
 
 	BIND_VMETHOD(MethodInfo(Variant::BOOL, "can_drop_data", PropertyInfo(Variant::VECTOR2, "position"), PropertyInfo(Variant::NIL, "data")));
 	BIND_VMETHOD(MethodInfo("drop_data", PropertyInfo(Variant::VECTOR2, "position"), PropertyInfo(Variant::NIL, "data")));
-	BIND_VMETHOD(MethodInfo(Variant::OBJECT, "_make_custom_tooltip", PropertyInfo(Variant::STRING, "for_text")));
+	BIND_VMETHOD(MethodInfo(
+			PropertyInfo(Variant::OBJECT, "control", PROPERTY_HINT_RESOURCE_TYPE, "Control"),
+			"_make_custom_tooltip", PropertyInfo(Variant::STRING, "for_text")));
 	BIND_VMETHOD(MethodInfo(Variant::BOOL, "_clips_input"));
 
 	ADD_GROUP("Anchor", "anchor_");

scene/main/viewport.cpp

@@ -161,6 +161,11 @@ ViewportTexture::~ViewportTexture() {
 
 /////////////////////////////////////
 
+// Aliases used to provide custom styles to tooltips in the default
+// theme and editor theme.
+// TooltipPanel is also used for custom tooltips, while TooltipLabel
+// is only relevant for default tooltips.
+
 class TooltipPanel : public PopupPanel {
 	GDCLASS(TooltipPanel, PopupPanel);
 
@@ -175,6 +180,8 @@ public:
 	TooltipLabel() {}
 };
 
+/////////////////////////////////////
+
 Viewport::GUI::GUI() {
 	embed_subwindows_hint = false;
 	embedding_subwindows = false;
@@ -188,7 +195,7 @@ Viewport::GUI::GUI() {
 	mouse_over = nullptr;
 	drag_mouse_over = nullptr;
 
-	tooltip = nullptr;
+	tooltip_control = nullptr;
 	tooltip_popup = nullptr;
 	tooltip_label = nullptr;
 }
@@ -1465,7 +1472,7 @@ void Viewport::_gui_sort_roots() {
 }
 
 void Viewport::_gui_cancel_tooltip() {
-	gui.tooltip = nullptr;
+	gui.tooltip_control = nullptr;
 	gui.tooltip_timer = -1;
 	if (gui.tooltip_popup) {
 		gui.tooltip_popup->queue_delete();
@@ -1474,21 +1481,23 @@ void Viewport::_gui_cancel_tooltip() {
 	}
 }
 
-String Viewport::_gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_which) {
+String Viewport::_gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_tooltip_owner) {
 	Vector2 pos = p_pos;
 	String tooltip;
 
 	while (p_control) {
 		tooltip = p_control->get_tooltip(pos);
 
-		if (r_which) {
-			*r_which = p_control;
+		if (r_tooltip_owner) {
+			*r_tooltip_owner = p_control;
 		}
 
-		if (tooltip != String()) {
+		// If we found a tooltip, we stop here.
+		if (!tooltip.empty()) {
 			break;
 		}
-		pos = p_control->get_transform().xform(pos);
+
+		// Otherwise, we check parent controls unless some conditions prevent it.
 
 		if (p_control->data.mouse_filter == Control::MOUSE_FILTER_STOP) {
 			break;
@@ -1497,6 +1506,9 @@ String Viewport::_gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Cont
 			break;
 		}
 
+		// Transform cursor pos for parent control.
+		pos = p_control->get_transform().xform(pos);
+
 		p_control = p_control->get_parent_control();
 	}
 
@@ -1504,34 +1516,40 @@ String Viewport::_gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Cont
 }
 
 void Viewport::_gui_show_tooltip() {
-	if (!gui.tooltip) {
+	if (!gui.tooltip_control) {
 		return;
 	}
 
-	Control *which = nullptr;
-	String tooltip = _gui_get_tooltip(gui.tooltip, gui.tooltip->get_global_transform().xform_inv(gui.last_mouse_pos), &which);
-	tooltip = tooltip.strip_edges();
-	if (tooltip.length() == 0) {
-		return; // bye
+	// Get the Control under cursor and the relevant tooltip text, if any.
+	Control *tooltip_owner = nullptr;
+	String tooltip_text = _gui_get_tooltip(
+			gui.tooltip_control,
+			gui.tooltip_control->get_global_transform().xform_inv(gui.last_mouse_pos),
+			&tooltip_owner);
+	tooltip_text.strip_edges();
+	if (tooltip_text.empty()) {
+		return; // Nothing to show.
 	}
 
+	// Remove previous popup if we change something.
 	if (gui.tooltip_popup) {
 		memdelete(gui.tooltip_popup);
 		gui.tooltip_popup = nullptr;
 		gui.tooltip_label = nullptr;
 	}
 
-	if (!which) {
+	if (!tooltip_owner) {
 		return;
 	}
 
-	Control *rp = which;
-
-	Control *base_tooltip = which->make_custom_tooltip(tooltip);
+	// Controls can implement `make_custom_tooltip` to provide their own tooltip.
+	// This should be a Control node which will be added as child to a TooltipPanel.
+	Control *base_tooltip = tooltip_owner->make_custom_tooltip(tooltip_text);
 
+	// If no custom tooltip is given, use a default implementation.
 	if (!base_tooltip) {
 		gui.tooltip_label = memnew(TooltipLabel);
-		gui.tooltip_label->set_text(tooltip);
+		gui.tooltip_label->set_text(tooltip_text);
 		base_tooltip = gui.tooltip_label;
 	}
 
@@ -1545,10 +1563,7 @@ void Viewport::_gui_show_tooltip() {
 
 	gui.tooltip_popup = panel;
 
-	rp->add_child(gui.tooltip_popup);
-
-	//if (gui.tooltip) // Avoids crash when rapidly switching controls.
-	//	gui.tooltip_popup->set_scale(gui.tooltip->get_global_transform().get_scale());
+	tooltip_owner->add_child(gui.tooltip_popup);
 
 	Point2 tooltip_offset = ProjectSettings::get_singleton()->get("display/mouse_cursor/tooltip_position_offset");
 	Rect2 r(gui.tooltip_pos + tooltip_offset, gui.tooltip_popup->get_contents_minimum_size());
@@ -1897,8 +1912,6 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 			}
 
 			_gui_cancel_tooltip();
-			//gui.tooltip_popup->hide();
-
 		} else {
 			if (gui.drag_data.get_type() != Variant::NIL && mb->get_button_index() == BUTTON_LEFT) {
 				if (gui.drag_mouse_over) {
@@ -2052,8 +2065,8 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 				bool is_tooltip_shown = false;
 
 				if (gui.tooltip_popup) {
-					if (can_tooltip && gui.tooltip) {
-						String tooltip = _gui_get_tooltip(over, gui.tooltip->get_global_transform().xform_inv(mpos));
+					if (can_tooltip && gui.tooltip_control) {
+						String tooltip = _gui_get_tooltip(over, gui.tooltip_control->get_global_transform().xform_inv(mpos));
 
 						if (tooltip.length() == 0) {
 							_gui_cancel_tooltip();
@@ -2078,14 +2091,12 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 				}
 
 				if (can_tooltip && !is_tooltip_shown) {
-					gui.tooltip = over;
-					gui.tooltip_pos = over->get_screen_transform().xform(pos); //(parent_xform * get_transform()).affine_inverse().xform(pos);
+					gui.tooltip_control = over;
+					gui.tooltip_pos = over->get_screen_transform().xform(pos);
 					gui.tooltip_timer = gui.tooltip_delay;
 				}
 			}
 
-			//pos = gui.focus_inv_xform.xform(pos);
-
 			mm->set_position(pos);
 
 			Control::CursorShape cursor_shape = Control::CURSOR_ARROW;
@@ -2436,7 +2447,7 @@ void Viewport::_gui_hide_control(Control *p_control) {
 	if (gui.drag_mouse_over == p_control) {
 		gui.drag_mouse_over = nullptr;
 	}
-	if (gui.tooltip == p_control) {
+	if (gui.tooltip_control == p_control) {
 		_gui_cancel_tooltip();
 	}
 }
@@ -2459,8 +2470,8 @@ void Viewport::_gui_remove_control(Control *p_control) {
 	if (gui.drag_mouse_over == p_control) {
 		gui.drag_mouse_over = nullptr;
 	}
-	if (gui.tooltip == p_control) {
-		gui.tooltip = nullptr;
+	if (gui.tooltip_control == p_control) {
+		gui.tooltip_control = nullptr;
 	}
 }
 
@@ -3579,14 +3590,13 @@ Viewport::Viewport() {
 
 	disable_input = false;
 
-	//window tooltip
+	// Window tooltip.
 	gui.tooltip_timer = -1;
 
-	//gui.tooltip_timer->force_parent_owned();
 	gui.tooltip_delay = GLOBAL_DEF("gui/timers/tooltip_delay_sec", 0.5);
 	ProjectSettings::get_singleton()->set_custom_property_info("gui/timers/tooltip_delay_sec", PropertyInfo(Variant::FLOAT, "gui/timers/tooltip_delay_sec", PROPERTY_HINT_RANGE, "0,5,0.01,or_greater")); // No negative numbers
 
-	gui.tooltip = nullptr;
+	gui.tooltip_control = nullptr;
 	gui.tooltip_label = nullptr;
 	gui.drag_preview = nullptr;
 	gui.drag_attempted = false;

scene/main/viewport.h

@@ -323,7 +323,7 @@ private:
 		Control *mouse_over;
 		Control *drag_mouse_over;
 		Vector2 drag_mouse_over_pos;
-		Control *tooltip;
+		Control *tooltip_control;
 		Window *tooltip_popup;
 		Label *tooltip_label;
 		Point2 tooltip_pos;
@@ -382,7 +382,7 @@ private:
 
 	void _gui_remove_root_control(List<Control *>::Element *RI);
 
-	String _gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_which = nullptr);
+	String _gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_tooltip_owner = nullptr);
 	void _gui_cancel_tooltip();
 	void _gui_show_tooltip();