fltk/src/fl_scroll_area.cxx

//
// "$Id$"
//
// Scrolling routines for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2010 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:
//
//     http://www.fltk.org/COPYING.php
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//

// Drawing function to move the contents of a rectangle.  This is passed
// a "callback" which is called to draw rectangular areas that are moved
// into the drawing area.

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

// scroll a rectangle and redraw the newly exposed portions:
/**
  Scroll a rectangle and draw the newly exposed portions.
  \param[in] X,Y       position of top-left of rectangle
  \param[in] W,H       size of rectangle
  \param[in] dx,dy     pixel offsets for shifting rectangle
  \param[in] draw_area callback function to draw rectangular areas
  \param[in] data      pointer to user data for callback
  The contents of the rectangular area is first shifted by \p dx
  and \p dy pixels. The \p draw_area callback is then called for
  every newly exposed rectangular area.
  */
void fl_scroll(int X, int Y, int W, int H, int dx, int dy,
               void (*draw_area)(void*, int,int,int,int), void* data)
{
  if (!dx && !dy) return;
  if (dx <= -W || dx >= W || dy <= -H || dy >= H) {
    // no intersection of old an new scroll
    draw_area(data,X,Y,W,H);
    return;
  }
  int src_x, src_w, dest_x, clip_x, clip_w;
  if (dx > 0) {
    src_x = X;
    dest_x = X+dx;
    src_w = W-dx;
    clip_x = X;
    clip_w = dx;
  } else {
    src_x = X-dx;
    dest_x = X;
    src_w = W+dx;
    clip_x = X+src_w;
    clip_w = W-src_w;
  }
  int src_y, src_h, dest_y, clip_y, clip_h;
  if (dy > 0) {
    src_y = Y;
    dest_y = Y+dy;
    src_h = H-dy;
    clip_y = Y;
    clip_h = dy;
  } else {
    src_y = Y-dy;
    dest_y = Y;
    src_h = H+dy;
    clip_y = Y+src_h;
    clip_h = H-src_h;
  }

#if defined(USE_X11)
  XCopyArea(fl_display, fl_window, fl_window, fl_gc,
	    src_x, src_y, src_w, src_h, dest_x, dest_y);
  // we have to sync the display and get the GraphicsExpose events! (sigh)
  for (;;) {
    XEvent e; XWindowEvent(fl_display, fl_window, ExposureMask, &e);
    if (e.type == NoExpose) break;
    // otherwise assume it is a GraphicsExpose event:
    draw_area(data, e.xexpose.x, e.xexpose.y,
	      e.xexpose.width, e.xexpose.height);
    if (!e.xgraphicsexpose.count) break;
  }
#elif defined(WIN32)
  typedef int (WINAPI* fl_GetRandomRgn_func)(HDC, HRGN, INT);
  static fl_GetRandomRgn_func fl_GetRandomRgn = 0L;
  static char first_time = 1;

  // We will have to do some Region magic now, so let's see if the 
  // required function is available (and it should be staring w/Win95)
  if (first_time) {
    HMODULE hMod = GetModuleHandle("GDI32.DLL");
    if (hMod) {
      fl_GetRandomRgn = (fl_GetRandomRgn_func)GetProcAddress(hMod, "GetRandomRgn");
    }
    first_time = 0;
  }

  // Now check if the source scrolling area is fully visible.
  // If it is, we will do a quick scroll and just update the 
  // newly exposed area. If it is not, we go the safe route and 
  // re-render the full area instead.
  // Note 1: we could go and find the areas that are actually
  // obscured and recursively call fl_scroll for the newly found
  // rectangles. However, this practice would rely on the 
  // elements of the undocumented Rgn structure.
  // Note 2: although this method should take care of most 
  // multi-screen solutions, it will not solve issues scrolling
  // from a different resolution screen onto another.
  // Note 3: this has been tested with image maps, too.
  if (fl_GetRandomRgn) {
    // get the DC region minus all overlapping windows
    HRGN sys_rgn = CreateRectRgn(0, 0, 0, 0);
    fl_GetRandomRgn(fl_gc, sys_rgn, 4);
    // now get the source scrolling rectangle 
    HRGN src_rgn = CreateRectRgn(src_x, src_y, src_x+src_w, src_y+src_h);
    POINT offset = { 0, 0 };
    if (GetDCOrgEx(fl_gc, &offset)) {
      OffsetRgn(src_rgn, offset.x, offset.y);
    }
    // see if all source pixels are available in the system region
    // Note: we could be a bit more merciful and subtract the 
    // scroll destination region as well.
    HRGN dst_rgn = CreateRectRgn(0, 0, 0, 0);
    int r = CombineRgn(dst_rgn, src_rgn, sys_rgn, RGN_DIFF);
    DeleteObject(dst_rgn);
    DeleteObject(src_rgn);
    DeleteObject(sys_rgn);
    if (r!=NULLREGION) {
      draw_area(data,X,Y,W,H);
      return;
    }
  }

  // Great, we can do an accelerated scroll instead of re-rendering
  BitBlt(fl_gc, dest_x, dest_y, src_w, src_h, fl_gc, src_x, src_y,SRCCOPY);

#elif defined(__APPLE_QUARTZ__)
  CGImageRef img = Fl_X::CGImage_from_window_rect(Fl_Window::current(), src_x, src_y, src_w, src_h);
  if (img) {
    CGRect rect = { { dest_x, dest_y }, { src_w, src_h } };
    Fl_X::q_begin_image(rect, 0, 0, src_w, src_h);
    CGContextDrawImage(fl_gc, rect, img);
    Fl_X::q_end_image();
    CFRelease(img);
    }
#else
# error unsupported platform
#endif
  if (dx) draw_area(data, clip_x, dest_y, clip_w, src_h);
  if (dy) draw_area(data, X, clip_y, W, clip_h);
}

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