Align titles to baseline

This does the following:

* Adds a baseline argument to get_text_size (the baseline is the
distance from the top of the texture to the baseline).
* Stores the baseline in the container when calculating the title
height.
* Takes the baseline into account when calculating the config's max font
height.
* When rendering, pads the textures according to the baseline so they
line up.

include/pango.h

@@ -20,7 +20,7 @@ int escape_markup_text(const char *src, char *dest, int dest_length);
 PangoLayout *get_pango_layout(cairo_t *cairo, const char *font,
 		const char *text, double scale, bool markup);
 void get_text_size(cairo_t *cairo, const char *font, int *width, int *height,
-		double scale, bool markup, const char *fmt, ...);
+		int *baseline, double scale, bool markup, const char *fmt, ...);
 void pango_printf(cairo_t *cairo, const char *font,
 		double scale, bool markup, const char *fmt, ...);
 

include/sway/config.h

@@ -349,6 +349,7 @@ struct sway_config {
 	enum sway_container_layout default_layout;
 	char *font;
 	size_t font_height;
+	size_t font_baseline;
 	bool pango_markup;
 	size_t urgent_timeout;
 	enum sway_fowa focus_on_window_activation;

include/sway/tree/container.h

@@ -117,6 +117,7 @@ struct sway_container {
 	struct wlr_texture *title_unfocused;
 	struct wlr_texture *title_urgent;
 	size_t title_height;
+	size_t title_baseline;
 
 	struct {
 		struct wl_signal destroy;