dlib C++ Library - fonts_abstract.h

// Copyright (C) 2005 Davis E. King (davis@dlib.net), Nils Labugt, Keita Mochizuki
// License: Boost Software License See LICENSE.txt for the full license.
#undef DLIB_FONTs_ABSTRACT_
#ifdef DLIB_FONTs_ABSTRACT_
#include <string>
#include "../serialize.h"
#include "../unicode.h"
#include <iostream>
namespace dlib
{
// ----------------------------------------------------------------------------------------
 class letter 
 { 
 /*!
 WHAT THIS OBJECT REPRESENTS
 This object represents a letter in a font. It tells you the nominal 
 width of the letter and which pixels form the letter.
 THREAD SAFETY
 const versions of this object are thread safe but if you are going to
 be modifying it then you must serialize access to it.
 !*/
 public:
 struct point 
 {
 /*!
 WHAT THIS OBJECT REPRESENTS
 This object represents one of the pixels of a letter. 
 
 The origin (i.e. (0,0)) of the coordinate plane is at the left 
 side of the letter's baseline. Also note that y is negative when 
 above the baseline and positive below (it is zero on the baseline 
 itself).
 The x value is positive going to the right and negative to the left.
 The meaning of a negative x value is that any points with a negative
 x value will overlap with the preceding letter.
 !*/
 point (
 );
 /*!
 ensures
 - This constructor does nothing. The value of x and y 
 are undefined after its execution.
 !*/
 point (
 signed char x_,
 signed char y_
 );
 /*!
 ensures
 - #x == x_
 - #y == y_
 !*/
 signed char x;
 signed char y;
 };
 // ---------------------------------
 letter (
 );
 /*!
 ensures
 - #width() == 0 
 - #num_of_points() == 0 
 !*/
 letter (
 unsigned short width_,
 unsigned short point_count
 );
 /*!
 ensures
 - #width() == width_
 - #num_of_points() == point_count
 !*/
 ~letter(
 );
 /*!
 ensures
 - any resources used by *this have been freed
 !*/
 
 const unsigned short width (
 ) const;
 /*!
 ensures
 - returns the width reserved for this letter in pixels. This is the 
 number of pixels that are reserved for this letter between adjoining 
 letters. It isn't necessarily the width of the actual letter itself. 
 (for example, you can make a letter with a width less than how wide it 
 actually is so that it overlaps with its neighbor letters.)
 !*/
 const unsigned short num_of_points (
 ) const;
 /*!
 ensures
 - returns the number of pixels that make up this letter.
 !*/
 point& operator[] (
 unsigned short i
 );
 /*!
 requires
 - i < num_of_points()
 ensures
 - returns a non-const reference to the ith point in this letter.
 !*/
 const point& operator[] (
 unsigned short i
 ) const;
 /*!
 requires
 - i < num_of_points()
 ensures
 - returns a const reference to the ith point in this letter.
 !*/
 void swap (
 letter& item
 );
 /*!
 ensures
 - swaps *this with item
 !*/
 
 private:
 // restricted functions
 letter(letter&); // copy constructor
 letter& operator=(letter&); // assignment operator
 };
 inline void swap (
 letter& a,
 letter& b
 ) { a.swap(b); }
 /*!
 provides a global swap
 !*/
// ----------------------------------------------------------------------------------------
 void serialize (
 const letter& item, 
 std::ostream& out 
 ); 
 /*!
 provides serialization support for letter objects
 !*/
 void deserialize (
 letter& item, 
 std::istream& in
 ); 
 /*!
 provides deserialization support for letter objects
 !*/
// ----------------------------------------------------------------------------------------
 class font
 {
 /*!
 WHAT THIS OBJECT REPRESENTS
 This object defines an interface for a font type. It provides metrics
 for the font and functions to help you draw strings on a canvas object.
 THREAD SAFETY
 All the functions in this class are thread safe.
 !*/
 public:
 virtual bool has_character (
 unichar ch
 )const=0;
 /*!
 ensures
 - if (this font has a glyph for the given character) then
 - returns true
 - else
 - returns false
 !*/
 bool has_character(char ch) const { return this->has_character(zero_extend_cast<unichar>(ch)); }
 bool has_character(wchar_t ch) const { return this->has_character(zero_extend_cast<unichar>(ch)); }
 /* Cast char and wchar_t to unichar correctly when char or wchar_t is a signed type */
 virtual const letter& operator[] (
 unichar ch
 )const=0;
 /*!
 ensures
 - if (has_character(ch) == true) then
 - returns a letter object that tells you how to draw this character.
 - else
 - returns some default glyph for characters that aren't in this font.
 !*/
 const letter& operator[] (char ch) const { return (*this)[zero_extend_cast<unichar>(ch)]; };
 const letter& operator[] (wchar_t ch) const { return (*this)[zero_extend_cast<unichar>(ch)]; };
 /* Cast char and wchar_t to unichar correctly when char or wchar_t is a signed type */
 virtual const unsigned long height (
 ) const = 0;
 /*!
 ensures
 - returns the height in pixels of the tallest letter in the font 
 !*/
 virtual const unsigned long ascender (
 ) const = 0;
 /*!
 ensures
 - returns the height() minus the number of pixels below the baseline used
 by the letter that hangs the lowest below the baseline.
 !*/
 virtual const unsigned long left_overflow (
 ) const = 0;
 /*! 
 ensures
 - returns how far outside and to the left of its width a letter
 from this font may set pixels. (i.e. how many extra pixels to its
 left may a font use)
 !*/
 virtual const unsigned long right_overflow (
 ) const = 0;
 /*! 
 ensures
 - returns how far outside and to the right of its width a letter
 from this font may set pixels. (i.e. how many extra pixels to its
 right may a font use)
 !*/
 template <typename T, typename traits, typename alloc>
 void compute_size (
 const std::basic_string<T,traits,alloc>& str,
 unsigned long& width,
 unsigned long& height,
 typename std::basic_string<T,traits,alloc>::size_type first = 0,
 typename std::basic_string<T,traits,alloc>::size_type last = std::basic_string<T,traits,alloc>::npos
 ) const;
 /*!
 requires
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - first <= last
 - last < str.size()
 ensures
 - all characters in str with an index < first are ignored by this
 function.
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - all characters in str with an index > last are ignored by 
 this function.
 - if (str.size() == 0) then
 - #width == 0
 - #height == 0
 - else
 - #width == sum of the widths of the characters in the widest 
 line in str + left_overflow() + right_overflow(). 
 - #height == (count(str.begin(),str.end(),'\n')+1)*height()
 !*/
 template <typename C, typename T, typename traits, typename alloc, typename pixel_type>
 void draw_string (
 const C& c,
 const rectangle& rect,
 const std::basic_string<T,traits,alloc>& str,
 const pixel_type& color = rgb_pixel(0,0,0),
 typename std::basic_string<T,traits,alloc>::size_type first = 0,
 typename std::basic_string<T,traits,alloc>::size_type last = std::basic_string<T,traits,alloc>::npos,
 const rectangle area = rectangle(-infinity,-infinity,infinity,infinity)
 ) const;
 /*!
 requires
 - C is a dlib::canvas or an object with a compatible interface.
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - first <= last
 - last < str.size()
 ensures
 - all characters in str with an index < first are ignored by this
 function.
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - all characters in str with an index > last are ignored by 
 this function.
 - if (str.size() == 0) then
 - does nothing
 - else
 - draws str on the given canvas at the position defined by rect. 
 Also uses the given pixel colors for the font color.
 - If the string is too big to fit in rect then the right and
 bottom sides of it will be clipped to make it fit. 
 - only the part of the string that is contained inside the area
 rectangle will be drawn
 !*/
 template <typename T, typename traits, typename alloc>
 const rectangle compute_cursor_rect (
 const rectangle& rect,
 const std::basic_string<T,traits,alloc>& str,
 unsigned long index,
 typename std::basic_string<T,traits,alloc>::size_type first = 0,
 typename std::basic_string<T,traits,alloc>::size_type last = std::basic_string<T,traits,alloc>::npos
 ) const;
 /*!
 requires
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - first <= last
 - last < str.size()
 ensures
 - the returned rectangle has a width of 1 and a 
 height of this->height().
 - computes the location of the cursor that would sit just before
 the character str[index] if str were drawn on the screen by
 draw_string(rect,str,...,first,last). The cursor location is
 returned in the form of a rectangle.
 - if (index < first) then
 - the returned cursor will be just before the character str[first].
 - if (last != std::basic_string<T,traits,alloc>::npos && index > last) then
 - the returned cursor will be just after the character str[last]
 - if (str.size() == 0) then
 - the returned cursor will be just at the start of the rectangle where
 str would be drawn if it wasn't empty.
 - if (index > str.size()-1) then
 - the returned cursor will be just after the character str[str.size()-1]
 !*/
 template <typename T, typename traits, typename alloc>
 const unsigned long compute_cursor_pos (
 const rectangle& rect,
 const std::basic_string<T,traits,alloc>& str,
 long x,
 long y,
 typename std::basic_string<T,traits,alloc>::size_type first = 0,
 typename std::basic_string<T,traits,alloc>::size_type last = std::basic_string<T,traits,alloc>::npos
 ) const;
 /*!
 requires
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - first <= last
 - last < str.size()
 ensures
 - returns a number idx that has the following properties:
 - if (first < str.size()) then
 - first <= idx
 - else
 - idx == str.size()
 - if (last != std::basic_string<T,traits,alloc>::npos) then
 - idx <= last + 1
 - compute_cursor_rect(rect,str,idx,first,last) == the cursor
 position that is closest to the pixel (x,y)
 !*/
 private:
 // restricted functions
 font(font&); // copy constructor
 font& operator=(font&); // assignment operator
 };
// ----------------------------------------------------------------------------------------
 class default_font : public font
 {
 /*!
 WHAT THIS OBJECT REPRESENTS
 This is an implementation of the Helvetica 12 point font.
 THREAD SAFETY
 It is safe to call get_font() and access the returned font from any 
 thread and no synchronization is needed as long as it is called 
 after the main() function has been entered.
 !*/
 public:
 static const shared_ptr_thread_safe<font> get_font(
 );
 /*!
 ensures
 - returns an instance of this font.
 throws
 - std::bad_alloc
 This exception is thrown if there is a problem gathering the needed
 memory for the font object.
 !*/
 private:
 // restricted functions
 default_font(); // normal constructor
 default_font(default_font&); // copy constructor
 default_font& operator=(default_font&); // assignment operator 
 };
// ----------------------------------------------------------------------------------------
 class bdf_font : public font
 {
 
 /*!
 WHAT THIS OBJECT REPRESENTS
 This is a font object that is capable of loading of loading BDF (Glyph 
 Bitmap Distribution Format) font files.
 THREAD SAFETY
 If you only access this object via the functions in the parent class font 
 then this object is thread safe. But if you need to call any of the
 functions introduced in this derived class then you need to serialize 
 access to this object while you call these functions.
 !*/
 public:
 bdf_font( 
 long default_char = -1 
 );
 /*!
 ensures
 - for all x:
 - #has_character(x) == false
 (i.e. this font starts out empty. You have to call read_bdf_file()
 to load it with data)
 - if (default_char == -1) then
 - the letter returned by (*this)[ch] for values of
 ch where has_character(ch) == false will be the
 default glyph defined in the bdf file.
 - else
 - the letter returned by (*this)[ch] for values of
 ch where has_character(ch) == false will be the
 letter (*this)[default_char].
 !*/
 
 long read_bdf_file( 
 std::istream& in, 
 unichar max_enc, 
 unichar min_enc = 0 
 );
 /*!
 ensures
 - attempts to read the font data from the given input stream into
 *this. The input stream is expected to contain a valid BDF file.
 - reads in characters with encodings in the range min_enc to max_enc
 into this font. All characters in the font file outside this range
 are ignored.
 - returns the number of characters loaded into this font from the
 given input stream.
 !*/
 void adjust_metrics();
 /*!
 ensures
 - Computes metrics based on actual glyphs loaded, instead of using 
 the values in the bdf file header. (May be useful if loading glyphs 
 from more than one file or a small part of a file.)
 !*/
 private:
 
 bdf_font( bdf_font& ); // copy constructor
 bdf_font& operator=( bdf_font& ); // assignment operator
 
 };
// ----------------------------------------------------------------------------------------
 const shared_ptr_thread_safe<font> get_native_font(
 );
 /*!
 requires
 - DLIB_NO_GUI_SUPPORT is not defined
 ensures
 - returns a font object that uses the local font
 !*/
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_FONTs_ABSTRACT_