Use an editor-only copy of font::set_help_string

This function shows a tooltip-like text at the bottom of the editor's screen,
for example when the paint tool is active it shows which terrains are assigned
to the left and right mouse buttons. There is similar functionality in GUI2,
for example when hovering over the title screen's buttons, which is handled via
event::MESSAGE_SHOW_TOOLTIP.

In the 1.17 branch's 3900419f92, I checked that
nothing outside the editor was calling the function. However, that analysis was
done after 1.17's refactoring of the graphics system. For 1.16 I'm not going to
repeat that analysis; the copy that's left in video.cpp is probably dead code,
but I see little reason to remove it from the stable branch.

src/editor/controller/editor_controller.cpp

@@ -1099,7 +1099,7 @@ void editor_controller::show_menu(const std::vector<config>& items_arg, int xloc
 
 void editor_controller::preferences()
 {
-	gui_->video().clear_all_help_strings();
+	gui_->clear_help_string();
 	gui2::dialogs::preferences_dialog::display();
 
 	gui_->redraw_everything();

src/editor/editor_display.cpp

@@ -17,6 +17,8 @@
 
 #include "editor/controller/editor_controller.hpp"
 #include "editor/editor_display.hpp"
+#include "floating_label.hpp"
+#include "font/sdl_ttf_compat.hpp" // for pango_line_width
 #include "lexical_cast.hpp"
 #include "overlay.hpp"
 #include "reports.hpp"
@@ -135,4 +137,40 @@ display::overlay_map& editor_display::get_overlays()
 	return controller_.get_current_map_context().get_overlays();
 }
 
+void editor_display::clear_help_string()
+{
+	font::remove_floating_label(help_handle_);
+	help_handle_ = 0;
+}
+
+void editor_display::set_help_string(const std::string& str)
+{
+	clear_help_string();
+
+	const color_t color{0, 0, 0, 0xbb};
+
+	int size = font::SIZE_LARGE;
+
+	while(size > 0) {
+		if(font::pango_line_width(str, size) > video().get_width()) {
+			size--;
+		} else {
+			break;
+		}
+	}
+
+	const int border = 5;
+
+	font::floating_label flabel(str);
+	flabel.set_font_size(size);
+	flabel.set_position(video().get_width() / 2, video().get_height());
+	flabel.set_bg_color(color);
+	flabel.set_border_size(border);
+
+	help_handle_ = font::add_floating_label(flabel);
+
+	const auto& r = font::get_floating_label_rect(help_handle_);
+	font::move_floating_label(help_handle_, 0.0, -double(r.h));
+}
+
 } //end namespace editor

src/editor/editor_display.hpp

@@ -42,6 +42,17 @@ public:
 		return controller_;
 	}
 
+	/**
+	 * Displays a help string with the given text. A 'help string' is like a tooltip,
+	 * but appears at the bottom of the screen so as to not be intrusive.
+	 *
+	 * @param str                 The text to display.
+	 */
+	void set_help_string(const std::string& str);
+
+	/** Removes the help string. */
+	void clear_help_string();
+
 protected:
 	void pre_draw() override;
 	/**
@@ -61,6 +72,10 @@ protected:
 
 	/* The controller that owns this display. */
 	editor_controller& controller_;
+
+private:
+	/** ID of the floating label that's controlled by set_help_string() / clear_help_string(). */
+	int help_handle_ = 0;
 };
 
 } //end namespace editor

src/editor/palette/editor_palettes.cpp

@@ -192,8 +192,7 @@ void editor_palette<Item>::adjust_size(const SDL_Rect& target)
 
 	set_location(target);
 	set_dirty(true);
-	gui_.video().clear_help_string(help_handle_);
-	help_handle_ = gui_.video().set_help_string(get_help_string());
+	gui_.set_help_string(get_help_string());
 }
 
 template<class Item>
@@ -203,8 +202,7 @@ void editor_palette<Item>::select_fg_item(const std::string& item_id)
 		selected_fg_item_ = item_id;
 		set_dirty();
 	}
-	gui_.video().clear_help_string(help_handle_);
-	help_handle_ = gui_.video().set_help_string(get_help_string());
+	gui_.set_help_string(get_help_string());
 }
 
 template<class Item>
@@ -214,8 +212,7 @@ void editor_palette<Item>::select_bg_item(const std::string& item_id)
 		selected_bg_item_ = item_id;
 		set_dirty();
 	}
-	gui_.video().clear_help_string(help_handle_);
-	help_handle_ = gui_.video().set_help_string(get_help_string());
+	gui_.set_help_string(get_help_string());
 }
 
 template<class Item>

src/editor/palette/editor_palettes.hpp

@@ -46,7 +46,6 @@ public:
 		, selected_bg_item_()
 		, toolkit_(toolkit)
 		, buttons_()
-		, help_handle_(-1)
 	{
 	}
 
@@ -119,9 +118,11 @@ private:
 
 	void hide(bool hidden) override {
 		widget::hide(hidden);
-		if (!hidden)
-			help_handle_ = gui_.video().set_help_string(get_help_string());
-		else gui_.video().clear_help_string(help_handle_);
+		if (!hidden) {
+			gui_.set_help_string(get_help_string());
+		} else {
+			gui_.clear_help_string();
+		}
 		for (gui::widget& w : buttons_) {
 			w.hide(hidden);
 		}
@@ -183,8 +184,6 @@ private:
 
     editor_toolkit& toolkit_;
     std::vector<gui::tristate_button> buttons_;
-
-    int help_handle_;
 };
 
 

src/editor/palette/location_palette.cpp

@@ -173,7 +173,6 @@ location_palette::location_palette(editor_display &gui, const game_config_view&
 		, button_add_()
 		, button_delete_()
 		, button_goto_()
-		, help_handle_(-1)
 		, disp_(gui)
 	{
 		for (int i = 1; i < 10; ++i) {
@@ -198,7 +197,7 @@ void location_palette::hide(bool hidden)
 {
 	widget::hide(hidden);
 
-	disp_.video().clear_help_string(help_handle_);
+	disp_.clear_help_string();
 
 	std::shared_ptr<gui::button> palette_menu_button = disp_.find_menu_button("menu-editor-terrain");
 	palette_menu_button->set_overlay("");
@@ -309,8 +308,7 @@ void location_palette::adjust_size(const SDL_Rect& target)
 
 	set_location(target);
 	set_dirty(true);
-	disp_.video().clear_help_string(help_handle_);
-	help_handle_ = disp_.video().set_help_string(get_help_string());
+	disp_.set_help_string(get_help_string());
 }
 
 void location_palette::select_item(const std::string& item_id)
@@ -319,8 +317,7 @@ void location_palette::select_item(const std::string& item_id)
 		selected_item_ = item_id;
 		set_dirty();
 	}
-	disp_.video().clear_help_string(help_handle_);
-	help_handle_ = disp_.video().set_help_string(get_help_string());
+	disp_.set_help_string(get_help_string());
 }
 
 std::size_t location_palette::num_items()

src/editor/palette/location_palette.hpp

@@ -120,7 +120,6 @@ private:
 	std::unique_ptr<location_palette_button> button_add_;
 	std::unique_ptr<location_palette_button> button_delete_;
 	std::unique_ptr<location_palette_button> button_goto_;
-    int help_handle_;
 	editor_display& disp_;
 };