xwm: Deal with title in a smarter way when there isn't enough space

The title in X11 windows and Wayland application using Weston toy
toolkit were placing the title in a very naive fashion. It was
only try to center the string in the title bar. This patch:

 * Makes sure the title isn't renderer underneath buttons;
 * Move the title to the left if the titlebar isn't large enough;
 * Clip the end of the title if needed.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

shared/cairo-util.c

@@ -454,13 +454,14 @@ theme_destroy(struct theme *t)
 void
 theme_render_frame(struct theme *t,
 		   cairo_t *cr, int width, int height,
-		   const char *title, struct wl_list *buttons,
+		   const char *title, cairo_rectangle_int_t *title_rect,
-		   uint32_t flags)
+		   struct wl_list *buttons, uint32_t flags)
 {
 	cairo_text_extents_t extents;
 	cairo_font_extents_t font_extents;
 	cairo_surface_t *source;
 	int x, y, margin, top_margin;
+	int text_width, text_height;
 
 	cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
 	cairo_set_source_rgba(cr, 0, 0, 0, 0);
@@ -491,11 +492,10 @@ theme_render_frame(struct theme *t,
 		    t->width, top_margin);
 
 	if (title || !wl_list_empty(buttons)) {
-		cairo_rectangle (cr, margin + t->width, margin,
-				 width - (margin + t->width) * 2,
-				 t->titlebar_height - t->width);
-		cairo_clip(cr);
 
+		cairo_rectangle (cr, title_rect->x, title_rect->y,
+				 title_rect->width, title_rect->height);
+		cairo_clip(cr);
 		cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
 		cairo_select_font_face(cr, "sans",
 				       CAIRO_FONT_SLANT_NORMAL,
@@ -503,11 +503,15 @@ theme_render_frame(struct theme *t,
 		cairo_set_font_size(cr, 14);
 		cairo_text_extents(cr, title, &extents);
 		cairo_font_extents (cr, &font_extents);
-		x = (width - extents.width) / 2;
+		text_width = extents.width;
-		y = margin +
+		text_height = font_extents.descent - font_extents.ascent;
-			(t->titlebar_height -
+
-			 font_extents.ascent - font_extents.descent) / 2 +
+		x = (width - text_width) / 2;
-			font_extents.ascent;
+		y = margin + (t->titlebar_height - text_height) / 2;
+		if (x < title_rect->x)
+			x = title_rect->x;
+		else if (x + text_width > (title_rect->x + title_rect->width))
+			x = (title_rect->x + title_rect->width) - text_width;
 
 		if (flags & THEME_FRAME_ACTIVE) {
 			cairo_move_to(cr, x + 1, y  + 1);

shared/cairo-util.h

@@ -75,8 +75,8 @@ theme_set_background_source(struct theme *t, cairo_t *cr, uint32_t flags);
 void
 theme_render_frame(struct theme *t,
 		   cairo_t *cr, int width, int height,
-		   const char *title, struct wl_list *buttons,
+		   const char *title, cairo_rectangle_int_t *title_rect,
-		   uint32_t flags);
+		   struct wl_list *buttons, uint32_t flags);
 
 enum theme_location {
 	THEME_LOCATION_INTERIOR = 0,

shared/frame.c

@@ -98,6 +98,8 @@ struct frame {
 	int opaque_margin;
 	int geometry_dirty;
 
+	cairo_rectangle_int_t title_rect;
+
 	uint32_t status;
 
 	struct wl_list buttons;
@@ -532,6 +534,11 @@ frame_refresh_geometry(struct frame *frame)
 		}
 	}
 
+	frame->title_rect.x = x_l;
+	frame->title_rect.y = y;
+	frame->title_rect.width = x_r - x_l;
+	frame->title_rect.height = titlebar_height;
+
 	frame->geometry_dirty = 0;
 }
 
@@ -938,7 +945,8 @@ frame_repaint(struct frame *frame, cairo_t *cr)
 
 	cairo_save(cr);
 	theme_render_frame(frame->theme, cr, frame->width, frame->height,
-			   frame->title, &frame->buttons, flags);
+			   frame->title, &frame->title_rect,
+			   &frame->buttons, flags);
 	cairo_restore(cr);
 
 	wl_list_for_each(button, &frame->buttons, link)