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.

(cherry picked from commit c5d8dafec4c57d05e97bdce06b2e43bdcc6846bd)

doc/classes/Control.xml

@@ -58,25 +58,26 @@
 			</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:
+				Example of usage with a custom-constructed node:
 				[codeblock]
 				func _make_custom_tooltip(for_text):
 				    var label = Label.new()
 				    label.text = for_text
 				    return label
 				[/codeblock]
-				Example of usage with custom scene instance:
+				Example of usage with a custom scene instance:
 				[codeblock]
 				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
 				[/codeblock]
@@ -846,6 +847,15 @@
 		</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:
+			[codeblock]
+			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))
+			[/codeblock]
 		</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

@@ -2960,7 +2960,9 @@ 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

@@ -169,6 +169,11 @@ 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 PanelContainer {
 
 	GDCLASS(TooltipPanel, PanelContainer);
@@ -185,6 +190,8 @@ public:
 	TooltipLabel(){};
 };
 
+/////////////////////////////////////
+
 Viewport::GUI::GUI() {
 
 	dragging = false;
@@ -194,7 +201,7 @@ Viewport::GUI::GUI() {
 	key_focus = NULL;
 	mouse_over = NULL;
 
-	tooltip = NULL;
+	tooltip_control = NULL;
 	tooltip_popup = NULL;
 	tooltip_label = NULL;
 	subwindow_visibility_dirty = false;
@@ -1528,7 +1535,7 @@ void Viewport::_gui_sort_roots() {
 
 void Viewport::_gui_cancel_tooltip() {
 
-	gui.tooltip = NULL;
+	gui.tooltip_control = NULL;
 	gui.tooltip_timer = -1;
 	if (gui.tooltip_popup) {
 		gui.tooltip_popup->queue_delete();
@@ -1537,7 +1544,7 @@ 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;
@@ -1546,19 +1553,25 @@ String Viewport::_gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Cont
 
 		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;
 		if (p_control->is_set_as_toplevel())
 			break;
 
+		// Transform cursor pos for parent control.
+		pos = p_control->get_transform().xform(pos);
+
 		p_control = p_control->get_parent_control();
 	}
 
@@ -1567,33 +1580,39 @@ 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 = NULL;
-	String tooltip = _gui_get_tooltip(gui.tooltip, gui.tooltip->get_global_transform().xform_inv(gui.tooltip_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 = NULL;
+	String tooltip_text = _gui_get_tooltip(
+			gui.tooltip_control,
+			gui.tooltip_control->get_global_transform().xform_inv(gui.tooltip_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 = NULL;
 		gui.tooltip_label = NULL;
 	}
 
-	if (!which) {
+	if (!tooltip_owner) {
 		return;
 	}
 
-	Control *rp = which;
-
-	gui.tooltip_popup = 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 the tooltip owner.
+	gui.tooltip_popup = tooltip_owner->make_custom_tooltip(tooltip_text);
 
+	// If no custom tooltip is given, use a default implementation.
 	if (!gui.tooltip_popup) {
 		gui.tooltip_popup = memnew(TooltipPanel);
-
 		gui.tooltip_label = memnew(TooltipLabel);
 		gui.tooltip_popup->add_child(gui.tooltip_label);
 
@@ -1603,14 +1622,14 @@ void Viewport::_gui_show_tooltip() {
 		gui.tooltip_label->set_anchor_and_margin(MARGIN_TOP, Control::ANCHOR_BEGIN, ttp->get_margin(MARGIN_TOP));
 		gui.tooltip_label->set_anchor_and_margin(MARGIN_RIGHT, Control::ANCHOR_END, -ttp->get_margin(MARGIN_RIGHT));
 		gui.tooltip_label->set_anchor_and_margin(MARGIN_BOTTOM, Control::ANCHOR_END, -ttp->get_margin(MARGIN_BOTTOM));
-		gui.tooltip_label->set_text(tooltip);
+		gui.tooltip_label->set_text(tooltip_text);
 	}
 
-	rp->add_child(gui.tooltip_popup);
+	tooltip_owner->add_child(gui.tooltip_popup);
 	gui.tooltip_popup->force_parent_owned();
 	gui.tooltip_popup->set_as_toplevel(true);
-	if (gui.tooltip) // Avoids crash when rapidly switching controls.
-		gui.tooltip_popup->set_scale(gui.tooltip->get_global_transform().get_scale());
+	if (gui.tooltip_control) // Avoids crash when rapidly switching controls.
+		gui.tooltip_popup->set_scale(gui.tooltip_control->get_global_transform().get_scale());
 
 	Point2 tooltip_offset = ProjectSettings::get_singleton()->get("display/mouse_cursor/tooltip_position_offset");
 	Rect2 r(gui.tooltip_pos + tooltip_offset, gui.tooltip_popup->get_minimum_size());
@@ -1860,7 +1879,7 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 
 		gui.key_event_accepted = false;
 
-		Control *over = nullptr;
+		Control *over = NULL;
 
 		Point2 mpos = mb->get_position();
 		if (mb->is_pressed()) {
@@ -2002,8 +2021,6 @@ 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) {
@@ -2242,8 +2259,8 @@ 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();
@@ -2260,14 +2277,12 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 
 			if (can_tooltip && !is_tooltip_shown) {
 
-				gui.tooltip = over;
-				gui.tooltip_pos = mpos; //(parent_xform * get_transform()).affine_inverse().xform(pos);
+				gui.tooltip_control = over;
+				gui.tooltip_pos = mpos;
 				gui.tooltip_timer = gui.tooltip_delay;
 			}
 		}
 
-		//pos = gui.focus_inv_xform.xform(pos);
-
 		mm->set_position(pos);
 
 		Control::CursorShape cursor_shape = Control::CURSOR_ARROW;
@@ -2633,21 +2648,11 @@ void Viewport::_gui_hid_control(Control *p_control) {
 		_drop_mouse_focus();
 	}
 
-	/* ???
-	if (data.window==p_control) {
-		window->drag_data=Variant();
-		if (window->drag_preview) {
-			memdelete( window->drag_preview);
-			window->drag_preview=NULL;
-		}
-	}
-	*/
-
 	if (gui.key_focus == p_control)
 		_gui_remove_focus();
 	if (gui.mouse_over == p_control)
 		gui.mouse_over = NULL;
-	if (gui.tooltip == p_control)
+	if (gui.tooltip_control == p_control)
 		_gui_cancel_tooltip();
 }
 
@@ -2664,8 +2669,8 @@ void Viewport::_gui_remove_control(Control *p_control) {
 		gui.key_focus = NULL;
 	if (gui.mouse_over == p_control)
 		gui.mouse_over = NULL;
-	if (gui.tooltip == p_control)
-		gui.tooltip = NULL;
+	if (gui.tooltip_control == p_control)
+		gui.tooltip_control = NULL;
 	if (gui.tooltip_popup == p_control) {
 		_gui_cancel_tooltip();
 	}
@@ -3448,14 +3453,13 @@ Viewport::Viewport() {
 	disable_3d = false;
 	keep_3d_linear = 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::REAL, "gui/timers/tooltip_delay_sec", PROPERTY_HINT_RANGE, "0,5,0.01,or_greater")); // No negative numbers
 
-	gui.tooltip = NULL;
+	gui.tooltip_control = NULL;
 	gui.tooltip_label = NULL;
 	gui.drag_preview = NULL;
 	gui.drag_attempted = false;

scene/main/viewport.h

@@ -299,7 +299,7 @@ private:
 		int mouse_focus_mask;
 		Control *key_focus;
 		Control *mouse_over;
-		Control *tooltip;
+		Control *tooltip_control;
 		Control *tooltip_popup;
 		Label *tooltip_label;
 		Point2 tooltip_pos;
@@ -360,7 +360,7 @@ private:
 	void _gui_remove_root_control(List<Control *>::Element *RI);
 	void _gui_remove_subwindow_control(List<Control *>::Element *SI);
 
-	String _gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_which = NULL);
+	String _gui_get_tooltip(Control *p_control, const Vector2 &p_pos, Control **r_tooltip_owner = NULL);
 	void _gui_cancel_tooltip();
 	void _gui_show_tooltip();