Add examples/SVG_File_Surface.cxx and refer to it in the doc of class Fl_Surface_Device

This example code shows how to subclass Fl_Surface_Device and Fl_Graphics_Driver to
endow FLTK with a new kind of graphics output.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12980 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Fl_Device.H

@@ -51,6 +51,17 @@ class Fl_Widget;
  </ol>
  For back-compatibility, it is also possible to use the Fl_Surface_Device::set_current() member function
  to change the current drawing surface, once to the new surface, once to the previous one.
+ 
+ Class Fl_Surface_Device can also be derived to define new kinds of graphical output
+ usable with FLTK drawing functions.
+ An example would be to draw to an SVG file. This would require to create a new class,
+ say SVG_Surface, derived from class Fl_Surface_Device, and another new class,
+ say SVG_Graphics_Driver, derived from class Fl_Graphics_Driver.
+ Class SVG_Graphics_Driver should implement all virtual methods of the Fl_Graphics_Driver class
+ to support all FLTK drawing functions and have them draw into SVG files. Alternatively,
+ class SVG_Graphics_Driver could implement only some virtual methods, and only part of
+ the FLTK drawing API would be usable when drawing to SVG files
+ (see examples/SVG_File_Surface.cxx for a small, working implementation of this procedure).
  */
 class FL_EXPORT Fl_Surface_Device {
   /** The graphics driver in use by this surface. */

FL/Fl_Graphics_Driver.H

@@ -72,14 +72,6 @@ struct Fl_Fontdesc;
  drawing operations are directed to another drawing surface by Fl_Surface_Device::push_current() /
  Fl_Surface_Device::pop_current() / Fl_Surface_Device::set_current().
 
- The Fl_Graphics_Driver class is of interest if one wants to perform new kinds of drawing operations.
- An example would be to draw to an SVG file. This would require to create a new class,
- say SVG_Graphics_Driver, derived from class Fl_Graphics_Driver, and another new class,
- say SVG_Surface, derived from class Fl_Surface_Device. The new SVG_Graphics_Driver class should
- implement all virtual methods of the Fl_Graphics_Driver class to support all FLTK drawing functions
- and have them draw into SVG files. Alternatively, class SVG_Graphics_Driver could implement only some
- virtual methods, and only part of FLTK drawing functions would be usable when drawing to SVG files.
- 
  The Fl_Graphics_Driver class is essential for developers of the FLTK library.
  Each platform supported by FLTK requires to create a derived class of Fl_Graphics_Driver that
  implements all its virtual member functions according to the platform.

examples/SVG_File_Surface.cxx

@@ -0,0 +1,234 @@
+#include <FL/fl_draw.H>
+#include <stdio.h>
+#include <FL/Fl_Device.H>
+#include <FL/Fl_Graphics_Driver.H>
+#include <FL/Fl.H>
+#include <FL/Fl_Window.H>
+#include <FL/Fl_Box.H>
+
+class SVG_Graphics_Driver : public Fl_Graphics_Driver {
+  FILE *out_;
+  int width_;
+  const char *linecap_;
+  uchar red_, green_, blue_;
+public:
+  SVG_Graphics_Driver(FILE*);
+  ~SVG_Graphics_Driver();
+  FILE* file() {return out_;}
+protected:
+  const char *family_;
+  const char *bold_;
+  const char *style_;
+  void rect(int x, int y, int w, int h);
+  void rectf(int x, int y, int w, int h);
+  void line_style(int style, int width, char *dashes=0);
+  void line(int x1, int y1, int x2, int y2);
+  void font_(int f, int s);
+  void font(int f, int s);
+  void draw(const char *str, int n, int x, int y);
+  void draw(const char*, int, float, float) ;
+  void draw(int, const char*, int, int, int) ;
+  void rtl_draw(const char*, int, int, int) {}
+  void color(uchar r, uchar g, uchar b);
+  void color(Fl_Color c);
+  void draw_image(const uchar*, int, int, int, int, int, int) {}
+  void draw_image_mono(const uchar*, int, int, int, int, int, int) {}
+  void draw_image(void (*)(void*, int, int, int, uchar*), void*, int, int, int, int, int) {}
+  void draw_image_mono(void (*)(void*, int, int, int, uchar*), void*, int, int, int, int, int) {}
+  void draw(Fl_RGB_Image*, int, int, int, int, int, int) {}
+  void draw(Fl_Pixmap*, int, int, int, int, int, int) {}
+  void draw(Fl_Bitmap*, int, int, int, int, int, int) {}
+  double width(const char*, int) ;
+  int height() ;
+  int descent() ;
+  
+  void push_clip(int x, int y, int w, int h) {}
+  void pop_clip(){}
+  void xyline(int x, int y, int x1){}
+  void xyline(int x, int y, int x1, int y2){}
+  void yxline(int x, int y, int y1){}
+  void yxline(int x, int y, int y1, int x2){}
+  virtual void point(int x, int y) {}
+  virtual void line(int x, int y, int x1, int y1, int x2, int y2) {}
+  virtual void xyline(int x, int y, int x1, int y2, int x3) {}
+  virtual void yxline(int x, int y, int y1, int x2, int y3) {}
+  virtual void loop(int x0, int y0, int x1, int y1, int x2, int y2) {}
+  virtual void loop(int x0, int y0, int x1, int y1, int x2, int y2, int x3, int y3) {}
+  virtual void polygon(int x0, int y0, int x1, int y1, int x2, int y2) {}
+  virtual void polygon(int x0, int y0, int x1, int y1, int x2, int y2, int x3, int y3) {}
+  virtual int clip_box(int x, int y, int w, int h, int &X, int &Y, int &W, int &H) {return 0;}
+  virtual int not_clipped(int x, int y, int w, int h) {return 0;}
+  virtual void push_no_clip() {}
+  virtual void begin_complex_polygon() {}
+  virtual void transformed_vertex(double xf, double yf) {}
+  virtual void vertex(double x, double y) {}
+  virtual void end_points() {}
+  virtual void end_line() {}
+  virtual void end_loop() {}
+  virtual void end_polygon() {}
+  virtual void end_complex_polygon() {}
+  virtual void gap() {}
+  virtual void circle(double x, double y, double r) {}
+  virtual void arc(int x, int y, int w, int h, double a1, double a2) {}
+  virtual void pie(int x, int y, int w, int h, double a1, double a2) {}
+  virtual Fl_Bitmask create_bitmask(int w, int h, const uchar *array) {return 0;}
+  virtual void delete_bitmask(Fl_Bitmask bm) {}
+};
+
+class SVG_File_Surface : public Fl_Surface_Device {
+  int width_, height_;
+public:
+  SVG_File_Surface(int width, int height, FILE*);
+  int width() { return width_; }
+  int height() { return height_; }
+  ~SVG_File_Surface();
+};
+
+
+SVG_Graphics_Driver::SVG_Graphics_Driver(FILE *f) {
+  out_ = f;
+  width_ = 1;
+  linecap_ = "butt";
+  family_ = "";
+  bold_ = "";
+  style_ = "";
+  red_ = green_ = blue_ = 0;
+}
+
+SVG_Graphics_Driver::~SVG_Graphics_Driver()
+{
+}
+
+void SVG_Graphics_Driver::rect(int x, int y, int w, int h) {
+  fprintf(out_, "<rect x=\"%d\" y=\"%d\" width=\"%d\" height=\"%d\" "
+	  "fill=\"none\" stroke=\"rgb(%u,%u,%u)\" stroke-width=\"%d\"/>\n", x, y, w, h, red_, green_, blue_, width_);
+}
+
+void SVG_Graphics_Driver::rectf(int x, int y, int w, int h) {
+  fprintf(out_, "<rect x=\"%d\" y=\"%d\" width=\"%d\" height=\"%d\" "
+	  "fill=\"rgb(%u,%u,%u)\" />\n", x, y, w, h, red_, green_, blue_);
+}
+
+void SVG_Graphics_Driver::line(int x1, int y1, int x2, int y2) {
+  fprintf(out_, 
+	  "<line x1=\"%d\" y1=\"%d\" x2=\"%d\" y2=\"%d\" "
+	  "style=\"stroke:rgb(%u,%u,%u);stroke-width:%d;stroke-linecap:%s\" />\n", 
+	  x1,y1,x2,y2, red_, green_, blue_, width_, linecap_);
+}
+
+void SVG_Graphics_Driver::font_(int ft, int s) {
+  Fl_Graphics_Driver::font(ft, s);
+  int famnum = ft/4;
+  if (famnum == 0) family_ = "Helvetica";
+  else if (famnum == 1) family_ = "Courier";
+  else family_ = "Times";
+  int modulo = ft % 4;
+  int use_bold = modulo == 1 || modulo == 3;
+  int use_italic = modulo >= 2;  
+  bold_ =  ( use_bold ? " font-weight=\"bold\"" : "" );
+  style_ =  ( use_italic ? " font-style=\"italic\"" : "" );
+  if (use_italic && famnum != 2) style_ = " font-style=\"oblique\"";
+}
+
+void SVG_Graphics_Driver::font(int ft, int s) {
+  Fl_Display_Device::display_device()->driver()->font(ft, s);
+  font_(ft, s);
+}
+
+void SVG_Graphics_Driver::line_style(int style, int width, char *dashes) {
+  if (width == 0) width = 1;
+  width_ = width;
+  if (style & FL_CAP_SQUARE) linecap_ = "square";
+  if (style & FL_CAP_ROUND) linecap_ = "round";
+  else linecap_ = "butt";
+}
+
+void SVG_Graphics_Driver::draw(const char *str, int n, int x, int y) {
+  // Caution: Internet Explorer ignores the xml:space="preserve" attribute
+  // work-around: replace all spaces by no-break space = U+00A0 = 0xC2-0xA0 (UTF-8) before sending to IE
+  fprintf(out_, "<text x=\"%d\" y=\"%d\" font-family=\"%s\"%s%s font-size=\"%d\" "
+          "xml:space=\"preserve\" "
+          " fill=\"rgb(%u,%u,%u)\" textLength=\"%d\">%.*s</text>\n",x, y, family_, bold_, style_, size(), red_, green_, blue_, (int)width(str, n), n, str);
+
+}
+
+void SVG_Graphics_Driver::draw(const char* str, int n, float fx, float fy) {
+  return draw(str, n, (int)fx, (int)fy);
+}
+
+void SVG_Graphics_Driver::draw(int angle, const char* str, int n, int x, int y) {
+  fprintf(out_, "<g transform=\"translate(%d,%d) rotate(%d)\">", x, y, -angle);
+  draw(str, n, 0, 0);
+  fputs("</g>\n", out_);
+}
+
+void SVG_Graphics_Driver::color(Fl_Color c) {
+  Fl_Graphics_Driver::color(c);
+  Fl::get_color(c, red_, green_, blue_);
+}
+
+void SVG_Graphics_Driver::color(uchar r, uchar g, uchar b) {
+  red_ = r;
+  green_ = g;
+  blue_ = b;
+}
+
+double SVG_Graphics_Driver::width(const char* str, int l) {
+ return Fl_Display_Device::display_device()->driver()->width(str, l);
+}
+
+int SVG_Graphics_Driver::height() {
+  return Fl_Display_Device::display_device()->driver()->height();
+}
+
+int SVG_Graphics_Driver::descent() {
+  return Fl_Display_Device::display_device()->driver()->descent();
+}
+
+SVG_File_Surface::SVG_File_Surface(int w, int h, FILE *f) : Fl_Surface_Device(NULL) {
+  fprintf(f,
+	  "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n"
+	  "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \n"
+	  "\"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n"
+	  "<svg width=\"%dpx\" height=\"%dpx\" viewBox=\"0 0 %d %d\"\n"
+	  "xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\">\n", w, h, w, h);
+  width_ = w; height_ = h;
+  driver(new SVG_Graphics_Driver(f));
+}
+
+SVG_File_Surface::~SVG_File_Surface() {
+  SVG_Graphics_Driver *driver = (SVG_Graphics_Driver*)this->driver();
+  fputs("</svg>\n", driver->file());
+  fflush(driver->file());
+  delete driver;
+}
+
+
+int main(int argc, char **argv) {
+  Fl_Window *window = new Fl_Window(340,180);
+  Fl_Box *box = new Fl_Box(20,40,300,100,"Hello, World!");
+  box->box(FL_UP_BOX);
+  box->labelfont(FL_BOLD+FL_ITALIC);
+  box->labelsize(36);
+  box->labeltype(FL_SHADOW_LABEL);
+  window->end();
+  window->show(argc, argv);
+  
+  FILE *out = fl_fopen("hello.svg", "w");
+  if (out) {
+    SVG_File_Surface *svg = new SVG_File_Surface(box->w(), box->h(), out);
+    Fl_Surface_Device::push_current(svg);
+    fl_color(box->color());
+    fl_rectf(0, 0, box->w(), box->h());
+    fl_font(box->labelfont(), 36);
+    fl_color(box->labelcolor());
+    fl_draw(box->label(), 5, 50);
+    Fl_Surface_Device::pop_current();
+    delete svg;
+    fclose(out);
+  }
+
+  return Fl::run();
+}
+
+