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// fl_scroll_area.C
// 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 <FL/x.H>
// scroll a rectangle and redraw the newly exposed portions:
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;
}
#ifdef WIN32
BitBlt(fl_gc, dest_x, dest_y, src_w, src_h, fl_gc, src_x, src_y,SRCCOPY);
// NYI: need to redraw areas that the source of BitBlt was bad due to
// overlapped windows, probably similar to X version:
#else
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 assumme 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;
}
#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);
}
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