tweak multiline hover text to have proper interline spacing

* grapher/CairoWidget.cxx (CairoTextBox::draw): Use font information
  to caculate legible spacing. Also change the font to something more
  readable.
* testsuite/systemtap.examples/general/grapher.stp: Put carriage
  returns in the right spots.

1 files changed, 13 insertions, 7 deletions

diff --git a/grapher/CairoWidget.cxx b/grapher/CairoWidget.cxx
index db0e464e..eefe3d28 100644
--- a/grapher/CairoWidget.cxx
+++ b/grapher/CairoWidget.cxx
@@ -50,6 +50,15 @@ namespace systemtap
   {
     if (!_visible)
       return;
+    cr->save();
+    cr->select_font_face("Sans", Cairo::FONT_SLANT_NORMAL,
+                         Cairo::FONT_WEIGHT_BOLD);
+    cr->set_font_size(10.0);
+    Cairo::FontExtents fontExtent;
+    cr->get_font_extents(fontExtent);
+    // Some naughty fonts have a height less than ascent + descent
+    double fontHeight = max(fontExtent.ascent + fontExtent.descent + 1.0,
+                            fontExtent.height);
     vector<string> lines;
     split(lines, contents, is_any_of("\n"));
     vector<Cairo::TextExtents> extents;
@@ -62,10 +71,8 @@ namespace systemtap
         cr->get_text_extents(*itr, extent);
         extents.push_back(extent);
         width = max(width, extent.width);
-        height += extent.height;
+        height += fontHeight;
       }
-    
-    cr->save();
     cr->move_to(_x0 - 2, _y0 - 2);
     cr->line_to(_x0 + width + 2, _y0 - 2);
     cr->line_to(_x0 + width + 2, _y0 + height + 2);
@@ -74,15 +81,14 @@ namespace systemtap
     cr->set_source_rgba(1.0, 1.0, 1.0, .8);
     cr->fill();
     cr->set_source_rgba(0.0, 0.0, 0.0, 1.0);
-    vector<Cairo::TextExtents>::iterator titr = extents.begin();
     double texty = _y0;
     for (vector<string>::iterator itr = lines.begin(), end = lines.end();
          itr != end;
-         ++itr,++titr)
+         ++itr)
       {
-        cr->move_to(_x0, texty + titr->height);
+        cr->move_to(_x0, texty + fontExtent.ascent);
         cr->show_text(*itr);
-        texty += titr->height;
+        texty += fontHeight;
       }
     cr->restore();
   }