fltk/cairo/Fl_Cairo.cxx

//
// Main header file for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2021 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
//

#include <config.h>

#ifdef FLTK_HAVE_CAIRO
#include <FL/Fl.H>
#include <FL/platform.H>
#include <FL/Fl_Window.H>

// Cairo is currently supported for the following platforms:
// Win32, Apple Quartz, X11

#if defined(USE_X11) // X11
#  include <cairo-xlib.h>
#elif defined(_WIN32)
#  include <cairo-win32.h>
#elif defined(__APPLE_QUARTZ__) // PORTME: Cairo Support
#  include <cairo-quartz.h>
#else
#  error Cairo is not supported on this platform.
#endif

// static Fl module initialization :
Fl_Cairo_State Fl::cairo_state_;        ///< contains all necessary info for current cairo context mapping


// Fl cairo features implementation

// Fl_Cairo_State class impl

void  Fl_Cairo_State::autolink(bool b)  {
#ifdef FLTK_USE_CAIRO
  autolink_ = b;
#else
  Fl::fatal("In Fl::autolink(bool) : Cairo autolink() feature is only "
            "available with the enable-cairoext configure option, now quitting.");
#endif
}

/**
    Provides a corresponding cairo context for window \a wi.
    This is needed in a draw() override if Fl::cairo_autolink_context()
    returns false, which is the default.
    The cairo_context() does not need to be freed as it is freed every time
    a new cairo context is created. When the program terminates,
    a call to Fl::cairo_make_current(0) will destroy any residual context.
    \note A new cairo context is not always re-created when this method
    is used. In particular, if the current graphical context and the current
    window didn't change between two calls, the previous gc is internally kept,
    thus optimizing the drawing performances.
    Also, after this call, Fl::cairo_cc() is adequately updated with this
    cairo  context.
    \note Only available when configure has the --enable-cairo option
    \return the valid cairo_t* cairo context associated to this window.
*/
cairo_t * Fl::cairo_make_current(Fl_Window* wi) {
    if (!wi) return NULL; // Precondition

    if (fl_gc==0) { // means remove current cc
        Fl::cairo_cc(0); // destroy any previous cc
        cairo_state_.window(0);
        return 0;
    }

    // don't re-create a context if it's the same gc/window couple
    if (fl_gc==Fl::cairo_state_.gc() && fl_xid(wi) == (Window) Fl::cairo_state_.window())
        return Fl::cairo_cc();

    cairo_state_.window(wi);

  cairo_t * cairo_ctxt;
#ifndef __APPLE__
  float scale = Fl::screen_scale(wi->screen_num()); // get the screen scaling factor
#endif
#if defined(USE_X11)
  cairo_ctxt = Fl::cairo_make_current(0, wi->w() * scale, wi->h() * scale);
#else
  // on macOS, scaling is done before by Fl_Window::make_current(), on Windows, the size is not used
  cairo_ctxt = Fl::cairo_make_current(fl_gc, wi->w(), wi->h());
#endif
#ifndef __APPLE__
  cairo_scale(cairo_ctxt, scale, scale);
#endif
  return cairo_ctxt;
}

/*
    Creates transparently a cairo_surface_t object.
    gc is an HDC context in Windows, a CGContext* in Quartz, and
    a display on X11 (not used on this platform)
 */

static cairo_surface_t * cairo_create_surface(void * gc, int W, int H) {
# if defined(USE_X11)
    return cairo_xlib_surface_create(fl_display, fl_window, fl_visual->visual, W, H);
# elif   defined(_WIN32)
    return cairo_win32_surface_create((HDC) gc);
# elif defined(__APPLE_QUARTZ__)
  return cairo_quartz_surface_create_for_cg_context((CGContextRef) gc, W, H);
# else
#  error Cairo is not supported under this platform.
# endif
}

/**
  Creates a cairo context from a \a gc only, gets its window size or
  offscreen size if fl_window is null.
  \note Only available when configure has the --enable-cairo option
*/
cairo_t * Fl::cairo_make_current(void *gc) {
    int W=0,H=0;
#if defined(USE_X11)
  // FIXME X11 get W,H
  // gc will be the window handle here
  // # warning FIXME get W,H for cairo_make_current(void*)
#elif defined(__APPLE_QUARTZ__)
    if (fl_window) {
      W = Fl_Window::current()->w();
      H = Fl_Window::current()->h();
    }
    else {
      W = CGBitmapContextGetWidth(fl_gc);
      H = CGBitmapContextGetHeight(fl_gc);
    }
#elif defined(_WIN32)
    // we don't need any W,H for Windows
#else
# error Cairo is not supported on this platform.
#endif
    if (!gc) {
        Fl::cairo_cc(0);
        cairo_state_.gc(0); // keep track for next time
        return 0;
    }
    if (gc==Fl::cairo_state_.gc() &&
        fl_window== (Window) Fl::cairo_state_.window() &&
        cairo_state_.cc()!=0)
        return Fl::cairo_cc();
    cairo_state_.gc(fl_gc); // keep track for next time
    cairo_surface_t * s = cairo_create_surface(gc, W, H);
    cairo_t * c = cairo_create(s);
    cairo_surface_destroy(s);
    cairo_state_.cc(c);
    return c;
}

/**
   Creates a cairo context from a \a gc and its size
   \note Only available when configure has the --enable-cairo option
*/
cairo_t * Fl::cairo_make_current(void *gc, int W, int H) {
    if (gc==Fl::cairo_state_.gc() &&
        fl_window== (Window) Fl::cairo_state_.window() &&
        cairo_state_.cc()!=0) // no need to create a cc, just return that one
        return cairo_state_.cc();

    // we need to (re-)create a fresh cc ...
    cairo_state_.gc(gc); // keep track for next time
    cairo_surface_t * s = cairo_create_surface(gc, W, H);
    cairo_t * c = cairo_create(s);
    cairo_state_.cc(c); //  and purge any previously owned context
    cairo_surface_destroy(s);
    return c;
}
#else
// just don't leave the libfltk_cairo lib empty to avoid warnings
#include <FL/Fl_Export.H>
FL_EXPORT int fltk_cairo_dummy() { return 1;}
#endif // FLTK_HAVE_CAIRO