Move anchored menu placement strategy to Gtkmm2ext utils

So that it can be used by others.

2 files changed, 114 insertions, 0 deletions

diff --git a/libs/gtkmm2ext/gtkmm2ext/utils.h b/libs/gtkmm2ext/gtkmm2ext/utils.h
index bedaf1108e..bd09e29912 100644
--- a/libs/gtkmm2ext/gtkmm2ext/utils.h
+++ b/libs/gtkmm2ext/gtkmm2ext/utils.h
@@ -29,6 +29,7 @@
 
 #include <gtkmm/container.h>
 #include <gtkmm/filechooser.h>
+#include <gtkmm/menu.h>
 #include <gtkmm/treeview.h>
 #include <gdkmm/window.h> /* for WMDecoration */
 #include <gdkmm/pixbuf.h>
@@ -96,6 +97,11 @@ namespace Gtkmm2ext {
 								       int clip_height,
 								       Gdk::Color fg);
 
+	LIBGTKMM2EXT_API void position_menu_anchored (const Gtk::Menu* const menu,
+	                                              Gtk::Widget* const anchor,
+	                                              const std::string& selected,
+	                                              int& x, int& y, bool& push_in);
+
 	LIBGTKMM2EXT_API void set_popdown_strings (Gtk::ComboBoxText&,
 	                          const std::vector<std::string>&);
 
diff --git a/libs/gtkmm2ext/utils.cc b/libs/gtkmm2ext/utils.cc
index 0f85cd07d0..2b3a29fc0d 100644
--- a/libs/gtkmm2ext/utils.cc
+++ b/libs/gtkmm2ext/utils.cc
@@ -31,6 +31,7 @@
 #include <gtkmm/label.h>
 #include <gtkmm/comboboxtext.h>
 #include <gtkmm/tooltip.h>
+#include <gtkmm/menuitem.h>
 
 #include "gtkmm2ext/utils.h"
 #include "gtkmm2ext/persistent_tooltip.h"
@@ -309,6 +310,113 @@ Gtkmm2ext::pixbuf_from_string(const string& name, const Pango::FontDescription&
 }
 
 void
+Gtkmm2ext::position_menu_anchored (const Gtk::Menu* const menu,
+                                   Gtk::Widget* const anchor,
+                                   const std::string& selected,
+                                   int& x, int& y, bool& push_in) {
+	using namespace Gdk;
+	using namespace Gtk;
+	using namespace Gtk::Menu_Helpers;
+
+	 /* TODO: lacks support for rotated dropdown buttons */
+
+	if (!anchor->has_screen () || !anchor->get_has_window ()) {
+		return;
+	}
+
+	Rectangle monitor;
+	{
+		const int monitor_num = anchor->get_screen ()->get_monitor_at_window (
+				anchor->get_window ());
+		anchor->get_screen ()->get_monitor_geometry (
+				(monitor_num < 0) ? 0 : monitor_num, monitor);
+	}
+
+	const Requisition menu_req = menu->size_request();
+	const Rectangle allocation = anchor->get_allocation();
+
+	/* The x and y position are handled separately.
+	 *
+	 * For the x position if the direction is LTR (or RTL), then we try in order:
+	 *  a) align the left (right) of the menu with the left (right) of the button
+	 *     if there's enough room until the right (left) border of the screen;
+	 *  b) align the right (left) of the menu with the right (left) of the button
+	 *     if there's enough room until the left (right) border of the screen;
+	 *  c) align the right (left) border of the menu with the right (left) border
+	 *     of the screen if there's enough space;
+	 *  d) align the left (right) border of the menu with the left (right) border
+	 *     of the screen, with the rightmost (leftmost) part of the menu that
+	 *     overflows the screen.
+	 *     XXX We always align left regardless of the direction because if x is
+	 *     left of the current monitor, the menu popup code after us notices it
+	 *     and enforces that the menu stays in the monitor that's at the left...*/
+
+	anchor->get_window ()->get_origin (x, y);
+
+	if (anchor->get_direction() == TEXT_DIR_RTL) {
+		if (monitor.get_x() <= x + allocation.get_width() - menu_req.width) {
+			/* a) align menu right and button right */
+			x += allocation.get_width() - menu_req.width;
+		} else if (x + menu_req.width <= monitor.get_x() + monitor.get_width()) {
+			/* b) align menu left and button left: nothing to do*/
+		} else if (menu_req.width > monitor.get_width()) {
+			/* c) align menu left and screen left, guaranteed to fit */
+			x = monitor.get_x();
+		} else {
+			/* d) XXX align left or the menu might change monitors */
+			x = monitor.get_x();
+		}
+	} else { /* LTR */
+		if (x + menu_req.width <= monitor.get_x() + monitor.get_width()) {
+			/* a) align menu left and button left: nothing to do*/
+		} else if (monitor.get_x() <= x + allocation.get_width() - menu_req.width) {
+			/* b) align menu right and button right */
+			x += allocation.get_width() - menu_req.width;
+		} else if (menu_req.width > monitor.get_width()) {
+			/* c) align menu right and screen right, guaranteed to fit */
+			x = monitor.get_x() + monitor.get_width() - menu_req.width;
+		} else {
+			/* d) align left */
+			x = monitor.get_x();
+		}
+	}
+
+	/* For the y position, try in order:
+	 *  a) if there is a menu item with the same text as the button, align it
+	 *     with the button, unless that makes the menu overflow the monitor.
+	 *  b) align the top of the menu with the bottom of the button if there is
+	 *     enough room below the button;
+	 *  c) align the bottom of the menu with the top of the button if there is
+	 *     enough room above the button;
+	 *  d) align the bottom of the menu with the bottom of the monitor if there
+	 *     is enough room, but avoid moving the menu to another monitor */
+
+	const MenuList& items = menu->items ();
+	int offset = 0;
+
+	MenuList::const_iterator i = items.begin();
+	for ( ; i != items.end(); ++i) {
+		if (selected == ((std::string) i->get_label())) {
+			break;
+		}
+		offset += i->size_request().height;
+	}
+	if (i != items.end() &&
+	    y - offset >= monitor.get_y() &&
+	    y - offset + menu_req.height <= monitor.get_y() + monitor.get_height()) {
+		y -= offset;
+	} else if (y + allocation.get_height() + menu_req.height <= monitor.get_y() + monitor.get_height()) {
+		y += allocation.get_height(); /* a) */
+	} else if ((y - menu_req.height) >= monitor.get_y()) {
+		y -= menu_req.height; /* b) */
+	} else {
+		y = monitor.get_y() + max(0, monitor.get_height() - menu_req.height);
+	}
+
+	push_in = false;
+}
+
+void
 Gtkmm2ext::set_popdown_strings (Gtk::ComboBoxText& cr, const vector<string>& strings)
 {
 	vector<string>::const_iterator i;