Fix label bounding box calculation to include glyph descenders [WIP] (ref #4308)

include/mapnik/text/harfbuzz_shaper.hpp

@@ -360,7 +360,8 @@ struct harfbuzz_shaper
                     // Try next font in fontset
                     continue;
                 }
-                double max_glyph_height = 0;
+                double ymin = 0;
+                double ymax = 0;
                 for (auto const& c_id : clusters)
                 {
                     auto const& c = glyphinfos[c_id];
@@ -382,19 +383,18 @@ struct harfbuzz_shaper
                             // Overwrite default advance with better value provided by HarfBuzz
                             g.unscaled_advance = gpos.x_advance;
                             g.offset.set(gpos.x_offset * g.scale_multiplier, gpos.y_offset * g.scale_multiplier);
-                            double tmp_height = g.height();
+                            ymin = std::min(ymin, g.ymin());
+                            ymax = std::max(ymax, g.ymax());
                             if (g.face->is_color())
                             {
-                                tmp_height = g.ymax();
+                                ymin = 0.0;
                             }
-                            if (tmp_height > max_glyph_height)
-                                max_glyph_height = tmp_height;
                             width_map[char_index] += g.advance();
                             line.add_glyph(std::move(g), scale_factor);
                         }
                     }
                 }
-                line.update_max_char_height(max_glyph_height);
+                line.update_max_char_height(ymin, ymax);
                 break; // When we reach this point the current font had all glyphs.
             }
         }

include/mapnik/text/icu_shaper.hpp

@@ -93,7 +93,8 @@ struct icu_shaper
                 std::size_t num_chars = static_cast<std::size_t>(num_char);
                 shaped.releaseBuffer(length);
                 bool shaped_status = true;
-                double max_glyph_height = 0;
+                double ymin = 0;
+                double ymax = 0;
                 if (U_SUCCESS(err) && (num_chars == length))
                 {
                     unsigned char_index = 0;
@@ -113,9 +114,8 @@ struct icu_shaper
                         {
                             g.face = face;
                             g.scale_multiplier = size / face->get_face()->units_per_EM;
-                            double tmp_height = g.height();
+                            ymin = std::min(ymin, g.ymin());
-                            if (tmp_height > max_glyph_height)
+                            ymax = std::max(ymax, g.ymax());
-                                max_glyph_height = tmp_height;
                             width_map[char_index++] += g.advance();
                             line.add_glyph(std::move(g), scale_factor);
                         }
@@ -123,7 +123,7 @@ struct icu_shaper
                 }
                 if (!shaped_status)
                     continue;
-                line.update_max_char_height(max_glyph_height);
+                line.update_max_char_height(ymin, ymax);
                 return;
             }
         }

include/mapnik/text/text_layout.hpp

@@ -117,6 +117,7 @@ class text_layout
 
     inline rotation const& orientation() const { return orientation_; }
     inline pixel_position const& displacement() const { return displacement_; }
+    inline double base_ajustment() const { return baseline_adjustment_; }
     inline box2d<double> const& bounds() const { return bounds_; }
     inline horizontal_alignment_e horizontal_alignment() const { return halign_; }
     pixel_position alignment_offset() const;
@@ -173,6 +174,7 @@ class text_layout
     bool repeat_wrap_char_ = false;
     bool rotate_displacement_ = false;
     double text_ratio_ = 0.0;
+    double baseline_adjustment_ = 0.0;
     pixel_position displacement_ = {0, 0};
     box2d<double> bounds_ = {0, 0, 0, 0};
 

include/mapnik/text/text_line.hpp

@@ -65,7 +65,11 @@ class MAPNIK_DECL text_line : util::noncopyable
     double max_char_height() const { return max_char_height_; }
 
     // Called for each font/style to update the maximum height of this line.
-    void update_max_char_height(double max_char_height);
+    void update_max_char_height(double ymin, double ymax);
+
+    // Verticall adjustment
+
+    double baseline_adjustment() const { return baseline_adjustment_;}
 
     // Line height including line spacing.
     double line_height() const { return line_height_; }
@@ -88,6 +92,7 @@ class MAPNIK_DECL text_line : util::noncopyable
     glyph_vector glyphs_;
     double line_height_;     // Includes line spacing (returned by freetype)
     double max_char_height_; // Max height of any glyphs in line - calculated by shaper
+    double baseline_adjustment_; // Adjustment to (0,0) origin
     double width_;
     double glyphs_width_;
     unsigned first_char_;

src/text/placement_finder.cpp

@@ -172,7 +172,6 @@ bool placement_finder::find_point_placement(pixel_position const& pos)
 
         // Find text origin.
         pixel_position layout_center = pos + layout.displacement();
-
         if (!base_point_set)
         {
             glyphs->set_base_point(layout_center);
@@ -180,9 +179,10 @@ bool placement_finder::find_point_placement(pixel_position const& pos)
         }
 
         box2d<double> bbox = layout.bounds();
-        bbox.re_center(layout_center.x, layout_center.y);
 
-        /* For point placements it is faster to just check the bounding box. */
+        bbox.re_center(layout_center.x, layout_center.y - layout.base_ajustment());
+
+        // For point placements it is faster to just check the bounding box.
         if (collision(bbox, layouts_.text(), false))
             return false;
 

src/text/text_layout.cpp

@@ -210,6 +210,7 @@ void text_layout::layout()
     displacement_ = scale_factor_ * displacement_ + alignment_offset();
     if (rotate_displacement_)
         displacement_ = displacement_.rotate(!orientation_);
+
     // Find layout bounds, expanded for rotation
     rotated_box2d(bounds_, orientation_, displacement_, width_, height_);
 }
@@ -436,6 +437,7 @@ void text_layout::add_line(text_line&& line)
         line.set_first_line(true);
     }
     height_ += line.height();
+    baseline_adjustment_ = line.baseline_adjustment();
     glyphs_count_ += line.size();
     width_ = std::max(width_, line.width());
     lines_.emplace_back(std::move(line));

src/text/text_line.cpp

@@ -30,6 +30,7 @@ text_line::text_line(unsigned first_char, unsigned last_char)
     : glyphs_()
     , line_height_(0.0)
     , max_char_height_(0.0)
+    , baseline_adjustment_(0.0)
     , width_(0.0)
     , glyphs_width_(0.0)
     , first_char_(first_char)
@@ -42,6 +43,7 @@ text_line::text_line(text_line&& rhs)
     : glyphs_(std::move(rhs.glyphs_))
     , line_height_(std::move(rhs.line_height_))
     , max_char_height_(std::move(rhs.max_char_height_))
+    , baseline_adjustment_(std::move(baseline_adjustment_))
     , width_(std::move(rhs.width_))
     , glyphs_width_(std::move(rhs.glyphs_width_))
     , first_char_(std::move(rhs.first_char_))
@@ -92,9 +94,10 @@ double text_line::height() const
     return line_height_;
 }
 
-void text_line::update_max_char_height(double max_char_height)
+void text_line::update_max_char_height(double ymin, double ymax)
 {
-    max_char_height_ = std::max(max_char_height_, max_char_height);
+    max_char_height_ = std::max(max_char_height_, ymax - ymin);
+    baseline_adjustment_ = ymin;
 }
 
 void text_line::set_first_line(bool first_line)