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//
// Scrolling routines 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
//
// 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_Window_Driver.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.
\warning With FLTK 1.4 and above, it's recommended to put graphical elements in an Fl_Scroll
widget rather than use function fl_scroll() to update those elements. That's because fl_scroll()
may not produce a pixel-accurate result when the GUI scaling factor value is not a multiple of 100%.
Alternatively, use fl_scroll() when the scaling factor value is a multiple of 100% and perform a
full redraw of the graphical elements otherwise. Statement <tt>float s = Fl::screen_scale(win->screen_num());</tt>
gives the current scaling factor value given Fl_Window *win.
*/
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;
}
int retval = Fl_Window_Driver::driver(Fl_Window::current())->scroll(src_x, src_y, src_w, src_h,
dest_x, dest_y, draw_area, data);
if (retval) {
draw_area(data,X,Y,W,H);
return;
}
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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