CommonPIC32

Annotated lib/viewport.c

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137:ea0474d34182
2021-12-14 Paul Boddie file changeset files shortlog Fixed pin labels: RB10/PGEC3 should be RB10/PGED2.
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/*
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 * Common viewport-related functions.
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 *
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 * Copyright (C) 2018 Paul Boddie <paul@boddie.org.uk>
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 *
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 * This program is free software: you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation, either version 3 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
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 */
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#include "viewport.h"
 
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/* Initialise the origin for a viewport. */
 
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void viewport_set_origin(viewport_t *v, int xorigin, int yorigin)
 
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{
 
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    int frame;
 
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    /* Set the origin for every frame. */
 
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    v->xorigin = xorigin;
 
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    v->yorigin = yorigin;
 
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    for (frame = 0; frame < v->cfg->frames; frame++)
 
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    {
 
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        v->xorigins[frame] = xorigin;
 
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        v->yorigins[frame] = yorigin;
 
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    }
 
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}
 
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/* Update the origin by the given changes in origin coordinates. */
 
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void viewport_update_origin(viewport_t *v, int dx, int dy)
 
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{
 
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    int xstep, ystep;
 
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    int frame = v->cfg->frame;
 
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    /* Change the origin coordinates. */
 
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    v->xorigin += dx;
 
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    v->yorigin += dy;
 
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    /* Determine the magnitude of the scrolling required from this frame to the
 
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       current origin. */
 
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    xstep = v->xorigin - v->xorigins[frame];
 
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    ystep = v->yorigin - v->yorigins[frame];
 
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    /* Scroll the frame, converting to columns and rows. */
 
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    display_scroll(v->cfg, xstep / v->xscale, ystep / v->yscale);
 
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    /* For horizontal scrolling, plot the exposed column at the left (if
 
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       scrolling left) or at the right (if scrolling right). */
 
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    if (v->update)
 
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        v->update(v->xorigin, v->yorigin, xstep, ystep);
 
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    /* Record the origin for this frame. */
 
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    v->xorigins[frame] = v->xorigin;
 
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    v->yorigins[frame] = v->yorigin;
 
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}
 
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/* Update the display, unplotting a sprite and replotting the background. */
 
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void viewport_unplot_sprite_from_image(viewport_t *v, sprite_t *s, sprite_t *bg)
 
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{
 
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    int frame = v->cfg->frame;
 
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    image_unplot_sprite_from_image(s, bg, v->xorigins[frame], v->yorigins[frame]);
 
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}