os: add Text_painter::Font::height method

Issue #2716

repos/gems/include/gems/cached_font.h

@@ -263,7 +263,7 @@ class Genode::Cached_font : public Text_painter::Font
 		}
 
 		unsigned baseline() const override { return _font.baseline(); }
-
+		unsigned height()   const override { return _font.height(); }
 		Area bounding_box() const override { return _font.bounding_box(); }
 };
 

repos/gems/include/gems/ttf_font.h

@@ -36,6 +36,7 @@ class Ttf_font : public Text_painter::Font
 
 		float    const _scale;
 		unsigned const _baseline;
+		unsigned const _height;
 		Area     const _bounding_box;
 
 		struct Glyph_buffer;
@@ -67,7 +68,7 @@ class Ttf_font : public Text_painter::Font
 		Advance_info advance_info(Codepoint) const override;
 
 		unsigned baseline() const override { return _baseline; }
-
+		unsigned   height() const override { return _height; }
 		Area bounding_box() const override { return _bounding_box; }
 };
 

repos/gems/include/gems/vfs_font.h

@@ -77,6 +77,7 @@ class Genode::Vfs_font : public Text_painter::Font
 		Directory const _font_dir;
 		unsigned  const _baseline;
 		Area      const _bounding_box;
+		unsigned  const _height;
 
 		struct Glyph_buffer
 		{
@@ -141,6 +142,7 @@ class Genode::Vfs_font : public Text_painter::Font
 			_baseline(_value_from_file(_font_dir, "baseline", 0U)),
 			_bounding_box(_value_from_file(_font_dir, "max_width",  0U),
 			              _value_from_file(_font_dir, "max_height", 0U)),
+			_height(_value_from_file(_font_dir, "height", 0U)),
 			_buffer(alloc, _bounding_box),
 			_glyphs_file(_font_dir, "glyphs")
 		{ }
@@ -162,7 +164,7 @@ class Genode::Vfs_font : public Text_painter::Font
 		}
 
 		unsigned baseline() const override { return _baseline; }
-
+		unsigned   height() const override { return _height; }
 		Area bounding_box() const override { return _bounding_box; }
 };
 

repos/gems/src/lib/ttf_font/ttf_font.cc

@@ -247,6 +247,7 @@ Ttf_font::Ttf_font(Allocator &alloc, void const *ttf, float px)
 	_stbtt_font_info(_create_stbtt_font_info(alloc, ttf)),
 	_scale(stbtt_ScaleForPixelHeight(&_stbtt_font_info, px)),
 	_baseline(obtain_baseline(_stbtt_font_info, _scale)),
+	_height(px + 0.5 /* round to integer */),
 	_bounding_box(obtain_bounding_box(_stbtt_font_info, _scale)),
 	_glyph_buffer(*new (alloc) Glyph_buffer(alloc, _bounding_box))
 { }

repos/gems/src/lib/vfs/ttf/vfs.cc

@@ -94,12 +94,14 @@ struct Vfs_ttf::Local_factory : File_system_factory
 	Glyphs_file_system _glyphs_fs { _font->cached_font };
 
 	Readonly_value_file_system<unsigned> _baseline_fs   { "baseline",   0 };
+	Readonly_value_file_system<unsigned> _height_fs     { "height",     0 };
 	Readonly_value_file_system<unsigned> _max_width_fs  { "max_width",  0 };
 	Readonly_value_file_system<unsigned> _max_height_fs { "max_height", 0 };
 
 	void _update_attributes()
 	{
 		_baseline_fs  .value(_font->font.font().baseline());
+		_height_fs    .value(_font->font.font().height());
 		_max_width_fs .value(_font->font.font().bounding_box().w());
 		_max_height_fs.value(_font->font.font().bounding_box().h());
 	}
@@ -118,6 +120,7 @@ struct Vfs_ttf::Local_factory : File_system_factory
 
 		if (node.has_type(Readonly_value_file_system<unsigned>::type_name()))
 			return _baseline_fs.matches(node)   ? &_baseline_fs
+			     : _height_fs.matches(node)     ? &_height_fs
 			     : _max_width_fs.matches(node)  ? &_max_width_fs
 			     : _max_height_fs.matches(node) ? &_max_height_fs
 			     : nullptr;
@@ -149,6 +152,7 @@ class Vfs_ttf::File_system : private Local_factory,
 				xml.attribute("name", node.attribute_value("name", Name()));
 				xml.node("glyphs", [&] () { });
 				xml.node("readonly_value", [&] () { xml.attribute("name", "baseline");   });
+				xml.node("readonly_value", [&] () { xml.attribute("name", "height");     });
 				xml.node("readonly_value", [&] () { xml.attribute("name", "max_width");  });
 				xml.node("readonly_value", [&] () { xml.attribute("name", "max_height"); });
 			});

repos/os/include/nitpicker_gfx/text_painter.h

@@ -75,6 +75,11 @@ struct Text_painter
 			 */
 			virtual unsigned baseline() const = 0;
 
+			/**
+			 * Return height of text in pixels when rendered with the font
+			 */
+			virtual unsigned height() const = 0;
+
 			/**
 			 * Return the bounding box that fits each single glyph of the font
 			 */

repos/os/include/nitpicker_gfx/tff_font.h

@@ -231,6 +231,11 @@ class Tff_font : public Text_painter::Font
 			return m.vpos + m.height;
 		}
 
+		unsigned height() const override
+		{
+			return _bounding_box.h();
+		}
+
 		Area bounding_box() const override { return _bounding_box; }
 };