fltk/src/fl_draw.cxx

//
// Label drawing code for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2020 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
//     https://www.fltk.org/bugs.php
//

// Implementation of fl_draw(const char*,int,int,int,int,Fl_Align)
// Used to draw all the labels and text, this routine:
// Word wraps the labels to fit into their bounding box.
// Breaks them into lines at the newlines.
// Expands all unprintable characters to ^X or \nnn notation
// Aligns them against the inside of the box.

#include <FL/fl_utf8.h>
#include <FL/Fl.H>
#include <FL/fl_draw.H>
#include <FL/Fl_Image.H>
#include <FL/platform.H>        // fl_open_display()

#include "flstring.h"
#include <ctype.h>
#include <math.h>
#include <stdlib.h>

char fl_draw_shortcut;  // set by fl_labeltypes.cxx

static char* underline_at;

/* If called with maxbuf==0, use an internally allocated buffer and enlarge it as needed.
 Otherwise, use buf as buffer but don't go beyond its length of maxbuf.
 */
static const char* expand_text_(const char* from, char*& buf, int maxbuf, double maxw, int& n,
               double &width, int wrap, int draw_symbols) {
  char* e = buf+(maxbuf-4);
  underline_at = 0;
  double w = 0;
  static int l_local_buff = 500;
  static char *local_buf = (char*)malloc(l_local_buff); // initial buffer allocation
  if (maxbuf == 0) {
    buf = local_buf;
    e = buf + l_local_buff - 4;
    }
  char* o = buf;
  char* word_end = o;
  const char* word_start = from;

  const char* p = from;
  for (;; p++) {

    int c = *p & 255;

    if (!c || c == ' ' || c == '\n') {
      // test for word-wrap:
      if (word_start < p && wrap) {
        double newwidth = w + fl_width(word_end, (int) (o-word_end) );
        if (word_end > buf && int(newwidth) > maxw) { // break before this word
          o = word_end;
          p = word_start;
          break;
        }
        word_end = o;
        w = newwidth;
      }
      if (!c) break;
      else if (c == '\n') {p++; break;}
      word_start = p+1;
    }

    if (o > e) {
      if (maxbuf) break; // don't overflow buffer
      l_local_buff += int(o - e) + 200; // enlarge buffer
      buf = (char*)realloc(local_buf, l_local_buff);
      e = buf + l_local_buff - 4; // update pointers to buffer content
      o = buf + (o - local_buf);
      word_end = buf + (word_end - local_buf);
      local_buf = buf;
    }

    if (c == '\t') {
      for (c = fl_utf_nb_char((uchar*)buf, (int) (o-buf) )%8; c<8 && o<e; c++)
           *o++ = ' ';
    } else if (c == '&' && fl_draw_shortcut && *(p+1)) {
      if (*(p+1) == '&') {p++; *o++ = '&';}
      else if (fl_draw_shortcut != 2) underline_at = o;
    } else if (c < ' ' || c == 127) { // ^X
      *o++ = '^';
      *o++ = c ^ 0x40;
    } else if (c == '@' && draw_symbols) { // Symbol???
      if (p[1] && p[1] != '@')  break;
      *o++ = c;
      if (p[1]) p++;
    } else {
      *o++ = c;
    }
  }

  width = w + fl_width(word_end, (int) (o-word_end));
  *o = 0;
  n = (int) (o-buf);
  return p;
}

/**
 Copy \p from to \p buf, replacing control characters with ^X.

 Stop at a newline or if \p maxbuf characters written to buffer.
 Also word-wrap if width exceeds maxw.
 Returns a pointer to the start of the next line of characters.
 Sets n to the number of characters put into the buffer.
 Sets width to the width of the string in the \ref drawing_fl_font "current font".
 */
const char*
fl_expand_text(const char* from, char* buf, int maxbuf, double maxw, int& n,
               double &width, int wrap, int draw_symbols) {
  return expand_text_(from,  buf, maxbuf, maxw,  n, width,  wrap,  draw_symbols);
}

/**
  The same as fl_draw(const char*,int,int,int,int,Fl_Align,Fl_Image*,int) with
  the addition of the \p callthis parameter, which is a pointer to a text drawing
  function such as fl_draw(const char*, int, int, int) to do the real work
*/
void fl_draw(
    const char* str,    // the (multi-line) string
    int x, int y, int w, int h, // bounding box
    Fl_Align align,
    void (*callthis)(const char*,int,int,int),
    Fl_Image* img, int draw_symbols)
{
  char *linebuf = NULL;
  const char* p;
  const char* e;
  int buflen;
  char symbol[2][255], *symptr;
  int symwidth[2], symoffset, symtotal, imgtotal;

  // count how many lines and put the last one into the buffer:
  int lines;
  double width;

  // if the image is set as a backdrop, ignore it here
  if (img && (align & FL_ALIGN_IMAGE_BACKDROP)) img = 0;

  symbol[0][0] = '\0';
  symwidth[0]  = 0;

  symbol[1][0] = '\0';
  symwidth[1]  = 0;

  if (draw_symbols) {
    if (str && str[0] == '@' && str[1] && str[1] != '@') {
      // Start with a symbol...
      for (symptr = symbol[0];
           *str && !isspace(*str) && symptr < (symbol[0] + sizeof(symbol[0]) - 1);
           *symptr++ = *str++) {/*empty*/}
      *symptr = '\0';
      if (isspace(*str)) str++;
      symwidth[0] = (w < h ? w : h);
    }

    if (str && (p = strrchr(str, '@')) != NULL && p > (str + 1) && p[-1] != '@') {
      strlcpy(symbol[1], p, sizeof(symbol[1]));
      symwidth[1] = (w < h ? w : h);
    }
  }

  symtotal = symwidth[0] + symwidth[1];
  imgtotal = (img && (align&FL_ALIGN_IMAGE_NEXT_TO_TEXT)) ? img->w() : 0;

  int strw = 0;
  int strh;

  if (str) {
    for (p = str, lines=0; p;) {
      e = expand_text_(p, linebuf, 0, w - symtotal - imgtotal, buflen, width,
                         align&FL_ALIGN_WRAP, draw_symbols);
      if (strw<width) strw = (int)width;
      lines++;
      if (!*e || (*e == '@' && e[1] != '@' && draw_symbols)) break;
      p = e;
    }
  } else lines = 0;

  if ((symwidth[0] || symwidth[1]) && lines) {
    if (symwidth[0]) symwidth[0] = lines * fl_height();
    if (symwidth[1]) symwidth[1] = lines * fl_height();
  }

  symtotal = symwidth[0] + symwidth[1];
  strh = lines * fl_height();

  // figure out vertical position of the first line:
  int xpos;
  int ypos;
  int height = fl_height();
  int imgvert = ((align&FL_ALIGN_IMAGE_NEXT_TO_TEXT)==0);
  int imgh = img && imgvert ? img->h() : 0;
  int imgw[2] = {0, 0};

  symoffset = 0;

  if (align & FL_ALIGN_BOTTOM) ypos = y+h-(lines-1)*height-imgh;
  else if (align & FL_ALIGN_TOP) ypos = y+height;
  else ypos = y+(h-lines*height-imgh)/2+height;

  // draw the image unless the "text over image" alignment flag is set...
  if (img && imgvert && !(align & FL_ALIGN_TEXT_OVER_IMAGE)) {
    if (img->w() > symoffset) symoffset = img->w();

    if (align & FL_ALIGN_LEFT) xpos = x + symwidth[0];
    else if (align & FL_ALIGN_RIGHT) xpos = x + w - img->w() - symwidth[1];
    else xpos = x + (w - img->w() - symtotal) / 2 + symwidth[0];

    img->draw(xpos, ypos - height);
    ypos += img->h();
  }

  // draw the image to the side of the text
  if (img && !imgvert /* && (align & !FL_ALIGN_TEXT_NEXT_TO_IMAGE)*/ ) {
    if (align & FL_ALIGN_TEXT_OVER_IMAGE) { // image is right of text
      imgw[1] = img->w();
      if (align & FL_ALIGN_LEFT) xpos = x + symwidth[0] + strw + 1;
      else if (align & FL_ALIGN_RIGHT) xpos = x + w - symwidth[1] - imgw[1] + 1;
      else xpos = x + (w - strw - symtotal - imgw[1]) / 2 + symwidth[0] + strw + 1;
    } else { // image is to the left of the text
      imgw[0] = img->w();
      if (align & FL_ALIGN_LEFT) xpos = x + symwidth[0] - 1;
      else if (align & FL_ALIGN_RIGHT) xpos = x + w - symwidth[1] - strw - imgw[0] - 1;
      else xpos = x + (w - strw - symtotal - imgw[0]) / 2 - 1;
    }
    int yimg = ypos - height;
    if (align & FL_ALIGN_TOP) ;
    else if (align & FL_ALIGN_BOTTOM) yimg += strh - img->h() - 1;
    else yimg += (strh - img->h() - 1) / 2;
    img->draw(xpos, yimg);
  }

  // now draw all the lines:
  if (str) {
    int desc = fl_descent();
    for (p=str; ; ypos += height) {
      if (lines>1) e = expand_text_(p, linebuf, 0, w - symtotal - imgtotal, buflen,
                                width, align&FL_ALIGN_WRAP, draw_symbols);
      else e = "";

      if (width > symoffset) symoffset = (int)(width + 0.5);

      if (align & FL_ALIGN_LEFT) xpos = x + symwidth[0] + imgw[0];
      else if (align & FL_ALIGN_RIGHT) xpos = x + w - (int)(width + .5) - symwidth[1] - imgw[1];
      else xpos = x + (w - (int)(width + .5) - symtotal - imgw[0] - imgw[1]) / 2 + symwidth[0] + imgw[0];

      callthis(linebuf,buflen,xpos,ypos-desc);

      if (underline_at && underline_at >= linebuf && underline_at < (linebuf + buflen))
        callthis("_",1,xpos+int(fl_width(linebuf,(int) (underline_at-linebuf))),ypos-desc);

      if (!*e || (*e == '@' && e[1] != '@')) break;
      p = e;
    }
  }

  // draw the image if the "text over image" alignment flag is set...
  if (img && imgvert && (align & FL_ALIGN_TEXT_OVER_IMAGE)) {
    if (img->w() > symoffset) symoffset = img->w();

    if (align & FL_ALIGN_LEFT) xpos = x + symwidth[0];
    else if (align & FL_ALIGN_RIGHT) xpos = x + w - img->w() - symwidth[1];
    else xpos = x + (w - img->w() - symtotal) / 2 + symwidth[0];

    img->draw(xpos, ypos);
  }

  // draw the symbols, if any...
  if (symwidth[0]) {
    // draw to the left
    if (align & FL_ALIGN_LEFT) xpos = x;
    else if (align & FL_ALIGN_RIGHT) xpos = x + w - symtotal - symoffset;
    else xpos = x + (w - symoffset - symtotal) / 2;

    if (align & FL_ALIGN_BOTTOM) ypos = y + h - symwidth[0];
    else if (align & FL_ALIGN_TOP) ypos = y;
    else ypos = y + (h - symwidth[0]) / 2;

    fl_draw_symbol(symbol[0], xpos, ypos, symwidth[0], symwidth[0], fl_color());
  }

  if (symwidth[1]) {
    // draw to the right
    if (align & FL_ALIGN_LEFT) xpos = x + symoffset + symwidth[0];
    else if (align & FL_ALIGN_RIGHT) xpos = x + w - symwidth[1];
    else xpos = x + (w - symoffset - symtotal) / 2 + symoffset + symwidth[0];

    if (align & FL_ALIGN_BOTTOM) ypos = y + h - symwidth[1];
    else if (align & FL_ALIGN_TOP) ypos = y;
    else ypos = y + (h - symwidth[1]) / 2;

    fl_draw_symbol(symbol[1], xpos, ypos, symwidth[1], symwidth[1], fl_color());
  }
}

/**
  Fancy string drawing function which is used to draw all the labels.

  The string is formatted and aligned inside the passed box.
  Handles '\\t' and '\\n', expands all other control characters to '^X',
  and aligns inside or against the edges of the box.
  See Fl_Widget::align() for values of \p align. The value FL_ALIGN_INSIDE
  is ignored, as this function always prints inside the box.
  If \p img is provided and is not \p NULL, the image is drawn above or
  below the text as specified by the \p align value.
  The \p draw_symbols argument specifies whether or not to look for symbol
  names starting with the '\@' character'
*/
void fl_draw(
  const char* str,
  int x, int y, int w, int h,
  Fl_Align align,
  Fl_Image* img,
  int draw_symbols)
{
  if ((!str || !*str) && !img) return;
  if (w && h && !fl_not_clipped(x, y, w, h) && (align & FL_ALIGN_INSIDE)) return;
  if (align & FL_ALIGN_CLIP)
    fl_push_clip(x, y, w, h);
  fl_draw(str, x, y, w, h, align, fl_draw, img, draw_symbols);
  if (align & FL_ALIGN_CLIP)
    fl_pop_clip();
}

/**
  Measure how wide and tall the string will be when printed by the
  fl_draw() function with \p align parameter. If the incoming \p w
  is non-zero it will wrap to that width.

  The \ref drawing_fl_font "current font" is used to do the width/height
  calculations, so unless its value is known at the time fl_measure() is
  called, it is advised to first set the current font with fl_font().
  With event-driven GUI programming you can never be sure which
  widget was exposed and redrawn last, nor which font it used.
  If you have not called fl_font() explicitly in your own code,
  the width and height may be set to unexpected values, even zero!

  \b Note: In the general use case, it's a common error to forget to set
  \p w to 0 before calling fl_measure() when wrap behavior isn't needed.

  \param[in] str nul-terminated string
  \param[out] w,h width and height of string in current font
  \param[in] draw_symbols non-zero to enable @@symbol handling [default=1]

  \code
  // Example: Common use case for fl_measure()
  const char *s = "This is a test";
  int wi=0, hi=0;              // initialize to zero before calling fl_measure()
  fl_font(FL_HELVETICA, 14);   // set current font face/size to be used for measuring
  fl_measure(s, wi, hi);       // returns pixel width/height of string in current font
  \endcode
*/
void fl_measure(const char* str, int& w, int& h, int draw_symbols) {
  if (!str || !*str) {w = 0; h = 0; return;}
  h = fl_height();
  char *linebuf = NULL;
  const char* p;
  const char* e;
  int buflen;
  int lines;
  double width=0;
  int W = 0;
  int symwidth[2], symtotal;

  symwidth[0] = 0;      // size of symbol at beginning of string (if any)
  symwidth[1] = 0;      // size of symbol at end of string (if any)

  if (draw_symbols) {
    // Symbol at beginning of string?
    const char *sym2 = (str[0]=='@' && str[1]=='@') ? str+2 : str;      // sym2 check will skip leading @@
    if (str[0] == '@' && str[1] != '@') {
      while (*str && !isspace(*str)) { ++str; }         // skip over symbol
      if (isspace(*str)) ++str;                         // skip over trailing space
      sym2 = str;                                       // sym2 check will skip leading symbol
      symwidth[0] = h;
    }
    // Symbol at end of string?
    if ((p=strchr(sym2,'@')) != NULL && p[1] != '@') {
      symwidth[1] = h;
    }
  }

  symtotal = symwidth[0] + symwidth[1];

  for (p = str, lines=0; p;) {
//    e = expand(p, linebuf, w - symtotal, buflen, width, w != 0, draw_symbols);
    e = expand_text_(p, linebuf, 0, w - symtotal, buflen, width,
                        w != 0, draw_symbols);
    if ((int)ceil(width) > W) W = (int)ceil(width);
    lines++;
    if (!*e || (*e == '@' && e[1] != '@' && draw_symbols)) break;
    p = e;
  }

  if ((symwidth[0] || symwidth[1]) && lines) {
    if (symwidth[0]) symwidth[0] = lines * fl_height();
    if (symwidth[1]) symwidth[1] = lines * fl_height();
  }

  symtotal = symwidth[0] + symwidth[1];

  w = W + symtotal;
  h = lines*h;
}

/**
  Sets the current font, which is then used in various drawing routines.
  You may call this outside a draw context if necessary to measure text,
  for instance by calling fl_width(), fl_measure(), or fl_text_extents(),
  but on X this will open the display.

  The font is identified by a \p face and a \p size.
  The size of the font is measured in pixels and not "points".
  Lines should be spaced \p size pixels apart or more.
*/
void fl_font(Fl_Font face, Fl_Fontsize fsize) {
  if (!fl_graphics_driver)
    fl_open_display();
  fl_graphics_driver->font(face, fsize);
}

/**
  This function returns the actual height of the specified \p font
  and \p size. Normally the font height should always be 'size',
  but with the advent of XFT, there are (currently) complexities
  that seem to only be solved by asking the font what its actual
  font height is. (See STR#2115)

  This function was originally undocumented in 1.1.x, and was used
  only by Fl_Text_Display. We're now documenting it in 1.3.x so that
  apps that need precise height info can get it with this function.

  \returns the height of the font in pixels.

  \todo  In the future, when the XFT issues are resolved, this function
         should simply return the 'size' value.
*/
int fl_height(int font, int size) {
    if ( font == fl_font() && size == fl_size() ) return(fl_height());
    int tf = fl_font(), ts = fl_size();   // save
    fl_font(font,size);
    int height = fl_height();
    fl_font(tf,ts);                       // restore
    return(height);
}

/** Removes any GUI scaling factor in subsequent drawing operations.
 This must be matched by a later call to fl_restore_scale().
 This function can be used to transiently perform drawing operations
 that are not rescaled by the current value of the GUI scaling factor.
 The resulting drawing context has no clipping region.
 \return The GUI scaling factor value that was in place when the function started.
 */
float fl_override_scale() {
  return fl_graphics_driver->override_scale();
}

/** Restores the GUI scaling factor and the clipping region in subsequent drawing operations.
 \param s Value returned by a previous call to fl_override_scale(). */
void fl_restore_scale(float s) {
  fl_graphics_driver->restore_scale(s);
}

/**
  Draw a check mark inside the given bounding box.

  The check mark is allowed to fill the entire box but the algorithm used
  makes sure that a 1-pixel border is kept free if the box is large enough.
  You need to calculate margins for box borders etc. yourself.

  The check mark size is limited (minimum and maximum size) and the check
  mark is always centered in the given box.

  \note If the box is too small (bad GUI design) the check mark will be drawn
    over the box borders. This is intentional for better user experience.
    Otherwise users might not be able to recognize if a box is checked.

  The size limits are implementation details and may be changed at any time.

  \param[in]  bb   rectangle that defines the bounding box
  \param[in]  col  Fl_Color to draw the check mark

  \since 1.4.0
*/

void fl_draw_check(Fl_Rect bb, Fl_Color col) {

  const int md = 6; // max. d1 value: 3 * md + 1 pixels wide
  int tx = bb.x();
  int ty = bb.y();
  int tw = bb.w();
  int th = bb.h();
  int lh = 3;       // line height 3 means 4 pixels
  int d1, d2;

  Fl_Color saved_color = fl_color();

  // make sure there's a free 1-pixel border if the area is large enough
  if (tw > 10) {
    tx++;
    tw -= 2;
  }
  if (th > 10) {
    ty++;
    th -= 2;
  }
  // calculate d1, the width and height of the left part of the check mark
  d1 = tw / 3;
  d2 = 2 * d1;
  if (d1 > md) {
    d1 = md;
    d2 = 2 * d1;
  }
  // make sure the height fits
  if (d2 + lh + 1 > th) {
    d2 = th - lh - 1;
    d1 = (d2+1) / 2;
  }
  // check minimal size (box too small)
  if (d1 < 2) {
    d1 = 2;
    d2 = 4;
  }
  // reduce line height (width) for small sizes
  if (d1 < 3)
    lh = 2;

  tw = d1 + d2 + 1; // total width
  th = d2 + lh + 1; // total height

  tx = bb.x() + (bb.w() - tw + 1) / 2;  // x position (centered)
  ty = bb.y() + (bb.h() - th + 1) / 2;  // y position (centered)

  // Set DEBUG_FRAME to 1 - 3 for debugging (0 otherwise)
  // Bit 1 set: draws a green background (the entire given box)
  // Bit 2 set: draws a red frame around the check mark (the bounding box)
  // The background (1) can be used to test correct positioning by the widget code

#define DEBUG_FRAME (0)
#if (DEBUG_FRAME)
  if (DEBUG_FRAME & 1) {    // 1 = background
    fl_color(0x88dd8800);
    fl_rectf(bb.x(), bb.y(), bb.w(), bb.h());
  }
  if (DEBUG_FRAME & 2) {    // 2 = bounding box
    fl_color(0xff000000);
    fl_rect(tx, ty, tw, th);
  }
#endif

  // draw the check mark

  fl_color(col);

  fl_begin_complex_polygon();

    ty += d2 - d1;            // upper border of check mark: left to right
    fl_vertex(tx, ty);
    fl_vertex(tx + d1, ty + d1);
    fl_vertex(tx + d1 + d2, ty + d1 - d2);
    ty += lh;                 // lower border of check mark: right to left
    fl_vertex(tx + d1 + d2, ty + d1 - d2);
    fl_vertex(tx + d1, ty + d1);
    fl_vertex(tx, ty);

  fl_end_complex_polygon();

  fl_color(saved_color);

} // fl_draw_check()