fltk/src/Fl_Double_Window.cxx

//
// "$Id$"
//
// Double-buffered window code for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2009 by Bill Spitzak and others.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA.
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//

#include <config.h>
#include <FL/Fl.H>
#include <FL/Fl_Double_Window.H>
#include <FL/x.H>
#include <FL/fl_draw.H>

// On systems that support double buffering "naturally" the base
// Fl_Window class will probably do double-buffer and this subclass
// does nothing.

#if USE_XDBE

#include <X11/extensions/Xdbe.h>

static int use_xdbe;

static int can_xdbe() {
  static int tried;
  if (!tried) {
    tried = 1;
    int event_base, error_base;
    if (!XdbeQueryExtension(fl_display, &event_base, &error_base)) return 0;
    Drawable root = RootWindow(fl_display,fl_screen);
    int numscreens = 1;
    XdbeScreenVisualInfo *a = XdbeGetVisualInfo(fl_display,&root,&numscreens);
    if (!a) return 0;
    for (int j = 0; j < a->count; j++)
      if (a->visinfo[j].visual == fl_visual->visualid
	  /*&& a->visinfo[j].perflevel > 0*/) {use_xdbe = 1; break;}
    XdbeFreeVisualInfo(a);
  }
  return use_xdbe;
}
#endif

void Fl_Double_Window::show() {
  Fl_Window::show();
}

#if defined(USE_X11)

// maybe someone feels inclined to implement alpha blending on X11?
char fl_can_do_alpha_blending() {
  return 0;
}
#elif defined(WIN32)

// Code used to switch output to an off-screen window.  See macros in
// win32.H which save the old state in local variables.

typedef struct { BYTE a; BYTE b; BYTE c; BYTE d; } FL_BLENDFUNCTION;
typedef BOOL (WINAPI* fl_alpha_blend_func)
    (HDC,int,int,int,int,HDC,int,int,int,int,FL_BLENDFUNCTION);
static fl_alpha_blend_func fl_alpha_blend = NULL;
static FL_BLENDFUNCTION blendfunc = { 0, 0, 255, 1};

/*
 * This function checks if the version of MSWindows that we
 * curently run on supports alpha blending for bitmap transfers
 * and finds the required function if so.
 */
char fl_can_do_alpha_blending() {
  static char been_here = 0;
  static char can_do = 0;
  // do this test only once
  if (been_here) return can_do;
  been_here = 1;
  // load the library that implements alpha blending
  HMODULE hMod = LoadLibrary("MSIMG32.DLL");
  // give up if that doesn't exist (Win95?)
  if (!hMod) return 0;
  // now find the blending function inside that dll
  fl_alpha_blend = (fl_alpha_blend_func)GetProcAddress(hMod, "AlphaBlend");
  // give up if we can't find it (Win95)
  if (!fl_alpha_blend) return 0;
  // we have the call, but does our display support alpha blending?
  // get the desktop's device context
  HDC dc = GetDC(0L);
  if (!dc) return 0;
  // check the device capabilities flags. However GetDeviceCaps
  // does not return anything useful, so we have to do it manually:

  HBITMAP bm = CreateCompatibleBitmap(dc, 1, 1);
  HDC new_gc = CreateCompatibleDC(dc);
  int save = SaveDC(new_gc);
  SelectObject(new_gc, bm);
  /*COLORREF set = */ SetPixel(new_gc, 0, 0, 0x01010101);
  BOOL alpha_ok = fl_alpha_blend(dc, 0, 0, 1, 1, new_gc, 0, 0, 1, 1, blendfunc);
  RestoreDC(new_gc, save);
  DeleteDC(new_gc);
  DeleteObject(bm);
  ReleaseDC(0L, dc);

  if (alpha_ok) can_do = 1;
  return can_do;
}

HDC fl_makeDC(HBITMAP bitmap) {
  HDC new_gc = CreateCompatibleDC(fl_gc);
  SetTextAlign(new_gc, TA_BASELINE|TA_LEFT);
  SetBkMode(new_gc, TRANSPARENT);
#if USE_COLORMAP
  if (fl_palette) SelectPalette(new_gc, fl_palette, FALSE);
#endif
  SelectObject(new_gc, bitmap);
  return new_gc;
}

void fl_copy_offscreen(int x,int y,int w,int h,HBITMAP bitmap,int srcx,int srcy) {
  HDC new_gc = CreateCompatibleDC(fl_gc);
  int save = SaveDC(new_gc);
  SelectObject(new_gc, bitmap);
  BitBlt(fl_gc, x, y, w, h, new_gc, srcx, srcy, SRCCOPY);
  RestoreDC(new_gc, save);
  DeleteDC(new_gc);
}

void fl_copy_offscreen_with_alpha(int x,int y,int w,int h,HBITMAP bitmap,int srcx,int srcy) {
  HDC new_gc = CreateCompatibleDC(fl_gc);
  int save = SaveDC(new_gc);
  SelectObject(new_gc, bitmap);
  BOOL alpha_ok = 0;
  // first try to alpha blend
  int to_display = Fl_Device::current()->type() < 256; // true iff display output
  if ( (!to_display) || fl_can_do_alpha_blending()) // if not on display, always try alpha_blend
    alpha_ok = fl_alpha_blend(fl_gc, x, y, w, h, new_gc, srcx, srcy, w, h, blendfunc);
  // if that failed (it shouldn't), still copy the bitmap over, but now alpha is 1
  if (!alpha_ok)
    BitBlt(fl_gc, x, y, w, h, new_gc, srcx, srcy, SRCCOPY);
  RestoreDC(new_gc, save);
  DeleteDC(new_gc);
}

extern void fl_restore_clip();

#elif defined(__APPLE_QUARTZ__)

char fl_can_do_alpha_blending() {
  return 1;
}

Fl_Offscreen fl_create_offscreen(int w, int h) {
  void *data = calloc(w*h,4);
  CGColorSpaceRef lut = CGColorSpaceCreateDeviceRGB();
  CGContextRef ctx = CGBitmapContextCreate(
    data, w, h, 8, w*4, lut, kCGImageAlphaNoneSkipLast);
  CGColorSpaceRelease(lut);
  return (Fl_Offscreen)ctx;
}

Fl_Offscreen fl_create_offscreen_with_alpha(int w, int h) {
  void *data = calloc(w*h,4);
  CGColorSpaceRef lut = CGColorSpaceCreateDeviceRGB();
  CGContextRef ctx = CGBitmapContextCreate(
    data, w, h, 8, w*4, lut, kCGImageAlphaPremultipliedLast);
  CGColorSpaceRelease(lut);
  return (Fl_Offscreen)ctx;
}

void fl_copy_offscreen(int x,int y,int w,int h,Fl_Offscreen osrc,int srcx,int srcy) {
  CGContextRef src = (CGContextRef)osrc;
  void *data = CGBitmapContextGetData(src);
  int sw = CGBitmapContextGetWidth(src);
  int sh = CGBitmapContextGetHeight(src);
  CGImageAlphaInfo alpha = CGBitmapContextGetAlphaInfo(src);
  CGColorSpaceRef lut = CGColorSpaceCreateDeviceRGB();
  CGDataProviderRef src_bytes = CGDataProviderCreateWithData( 0L, data, sw*sh*4, 0L);
  CGImageRef img = CGImageCreate( sw, sh, 8, 4*8, 4*sw, lut, alpha,
    src_bytes, 0L, false, kCGRenderingIntentDefault);
  // fl_push_clip();
  CGRect rect = { { x, y }, { w, h } };
  Fl_X::q_begin_image(rect, srcx, srcy, sw, sh);
  CGContextDrawImage(fl_gc, rect, img);
  Fl_X::q_end_image();
  CGImageRelease(img);
  CGColorSpaceRelease(lut);
  CGDataProviderRelease(src_bytes);
}

void fl_delete_offscreen(Fl_Offscreen ctx) {
  if (!ctx) return;
  void *data = CGBitmapContextGetData((CGContextRef)ctx);
  CGContextRelease((CGContextRef)ctx);
  if (!data) return;
  free(data);
}

const int stack_max = 16;
static int stack_ix = 0;
static CGContextRef stack_gc[stack_max];
static Window stack_window[stack_max];

void fl_begin_offscreen(Fl_Offscreen ctx) {
  if (stack_ix<stack_max) {
    stack_gc[stack_ix] = fl_gc;
    stack_window[stack_ix] = fl_window;
  } else 
    fprintf(stderr, "FLTK CGContext Stack overflow error\n");
  stack_ix++;

  fl_gc = (CGContextRef)ctx;
  fl_window = 0;
  //fl_push_no_clip();
  CGContextSaveGState(fl_gc);
  Fl_X::q_fill_context();
}

void fl_end_offscreen() {
  Fl_X::q_release_context();
  //fl_pop_clip();
  if (stack_ix>0)
    stack_ix--;
  else
    fprintf(stderr, "FLTK CGContext Stack underflow error\n");
  if (stack_ix<stack_max) {
    fl_gc = stack_gc[stack_ix];
    fl_window = stack_window[stack_ix];
  }
}

extern void fl_restore_clip();

#else
# error unsupported platform
#endif

/**
  Forces the window to be redrawn.
*/
void Fl_Double_Window::flush() {flush(0);}

/**
  Forces the window to be redrawn.
  \param[in] eraseoverlay non-zero to erase overlay, zero to ignore

  Fl_Overlay_Window relies on flush(1) copying the back buffer to the
  front everywhere, even if damage() == 0, thus erasing the overlay,
  and leaving the clip region set to the entire window.
*/
void Fl_Double_Window::flush(int eraseoverlay) {
  make_current(); // make sure fl_gc is non-zero
  Fl_X *myi = Fl_X::i(this);
  if (!myi->other_xid) {
#if USE_XDBE
    if (can_xdbe()) {
      myi->other_xid =
        XdbeAllocateBackBufferName(fl_display, fl_xid(this), XdbeCopied);
      myi->backbuffer_bad = 1;
    } else
#endif
#if defined(USE_X11) || defined(WIN32)
    myi->other_xid = fl_create_offscreen(w(), h());
    clear_damage(FL_DAMAGE_ALL);
#elif defined(__APPLE_QUARTZ__)
    if (force_doublebuffering_) {
      myi->other_xid = fl_create_offscreen(w(), h());
      clear_damage(FL_DAMAGE_ALL);
    }
#else
# error unsupported platform
#endif
  }
#if USE_XDBE
  if (use_xdbe) {
    if (myi->backbuffer_bad) {
      // Make sure we do a complete redraw...
      if (myi->region) {XDestroyRegion(myi->region); myi->region = 0;}
      clear_damage(FL_DAMAGE_ALL);
      myi->backbuffer_bad = 0;
    }

    // Redraw as needed...
    if (damage()) {
      fl_clip_region(myi->region); myi->region = 0;
      fl_window = myi->other_xid;
      draw();
      fl_window = myi->xid;
    }

    // Copy contents of back buffer to window...
    XdbeSwapInfo s;
    s.swap_window = fl_xid(this);
    s.swap_action = XdbeCopied;
    XdbeSwapBuffers(fl_display, &s, 1);
    return;
  } else
#endif
  if (damage() & ~FL_DAMAGE_EXPOSE) {
    fl_clip_region(myi->region); myi->region = 0;
#ifdef WIN32
    HDC _sgc = fl_gc;
    fl_gc = fl_makeDC(myi->other_xid);
    int save = SaveDC(fl_gc);
    fl_restore_clip(); // duplicate region into new gc
    draw();
    RestoreDC(fl_gc, save);
    DeleteDC(fl_gc);
    fl_gc = _sgc;
    //# if defined(USE_CAIRO)
    //if Fl::cairo_autolink_context() Fl::cairo_make_current(this); // capture gc changes automatically to update the cairo context adequately
    //# endif
#elif defined(__APPLE__)
    if ( myi->other_xid ) {
      fl_begin_offscreen( myi->other_xid );
      fl_clip_region( 0 );   
      draw();
      fl_end_offscreen();
    } else {
      draw();
    }
#else // X:
    fl_window = myi->other_xid;
    draw();
    fl_window = myi->xid;
#endif
  }
  if (eraseoverlay) fl_clip_region(0);
  // on Irix (at least) it is faster to reduce the area copied to
  // the current clip region:
  int X,Y,W,H; fl_clip_box(0,0,w(),h(),X,Y,W,H);
  if (myi->other_xid) fl_copy_offscreen(X, Y, W, H, myi->other_xid, X, Y);
}

void Fl_Double_Window::resize(int X,int Y,int W,int H) {
  int ow = w();
  int oh = h();
  Fl_Window::resize(X,Y,W,H);
#if USE_XDBE
  if (use_xdbe) return;
#endif
  Fl_X* myi = Fl_X::i(this);
  if (myi && myi->other_xid && (ow != w() || oh != h())) {
    fl_delete_offscreen(myi->other_xid);
    myi->other_xid = 0;
  }
}

void Fl_Double_Window::hide() {
  Fl_X* myi = Fl_X::i(this);
  if (myi && myi->other_xid) {
#if USE_XDBE
    if (!use_xdbe)
#endif
      fl_delete_offscreen(myi->other_xid);
  }
  Fl_Window::hide();
}

/**
  The destructor <I>also deletes all the children</I>. This allows a
  whole tree to be deleted at once, without having to keep a pointer to
  all the children in the user code.
*/
Fl_Double_Window::~Fl_Double_Window() {
  hide();
}

//
// End of "$Id$".
//