ScrollBar.c

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#include <stdlib.h>

#include <math.h>

#include "MEM_guardedalloc.h"

#include "Basic.h"
#include "ScrollBar.h"

struct _ScrollBar {
    int     rect[2][2];
    float   thumbpos, thumbpct;
    
    int     inset;
    int     minthumb;

    int     scrolling;
    float   scrolloffs;
};

static int scrollbar_get_thumbH(ScrollBar *sb) {
    int scrollable_h= rect_height(sb->rect) - 2*sb->inset;
    
    return clamp_i(sb->thumbpct*scrollable_h, sb->minthumb, scrollable_h);
}
static int scrollbar_get_thumbableH(ScrollBar *sb) {
    int scrollable_h= rect_height(sb->rect) - 2*sb->inset;
    int thumb_h= scrollbar_get_thumbH(sb);
    
    return scrollable_h - thumb_h;
}

static float scrollbar_co_to_pos(ScrollBar *sb, int yco) {
    int thumb_h= scrollbar_get_thumbH(sb);
    int thumbable_h= scrollbar_get_thumbableH(sb);
    int thumbable_y= (sb->rect[0][1]+sb->inset) + thumb_h/2;

    return (float) (yco-thumbable_y)/thumbable_h;
}



ScrollBar *scrollbar_new(int inset, int minthumb) {
    ScrollBar *sb= MEM_callocN(sizeof(*sb), "scrollbar_new");
    sb->inset= inset;
    sb->minthumb= minthumb;
    
    return sb;
}

void scrollbar_get_thumb(ScrollBar *sb, int thumb_r[2][2]) {
    int thumb_h= scrollbar_get_thumbH(sb);
    int thumbable_h= scrollbar_get_thumbableH(sb);

    thumb_r[0][0]= sb->rect[0][0]+sb->inset;
    thumb_r[1][0]= sb->rect[1][0]-sb->inset;

    thumb_r[0][1]= sb->rect[0][1]+sb->inset + sb->thumbpos*thumbable_h;
    thumb_r[1][1]= thumb_r[0][1] + thumb_h;
}

int scrollbar_is_scrolling(ScrollBar *sb) {
    return sb->scrolling;
}
int scrollbar_contains_pt(ScrollBar *sb, int pt[2]) {
    return rect_contains_pt(sb->rect, pt);
}

void scrollbar_start_scrolling(ScrollBar *sb, int yco) {
    int thumb_h_2= scrollbar_get_thumbH(sb)/2;
    int thumbable_h= scrollbar_get_thumbableH(sb);
    float npos= scrollbar_co_to_pos(sb, yco);

    sb->scrolloffs= sb->thumbpos - npos;
    if (fabs(sb->scrolloffs) >= (float) thumb_h_2/thumbable_h) {
        sb->scrolloffs= 0.0;
    }

    sb->scrolling= 1;
    sb->thumbpos= clamp_f(npos + sb->scrolloffs, 0.0, 1.0);
}
void scrollbar_keep_scrolling(ScrollBar *sb, int yco) {
    float npos= scrollbar_co_to_pos(sb, yco);

    sb->thumbpos= clamp_f(npos + sb->scrolloffs, 0.0, 1.0);
}
void scrollbar_stop_scrolling(ScrollBar *sb) {
    sb->scrolling= 0;
    sb->scrolloffs= 0.0;
}

void scrollbar_set_thumbpct(ScrollBar *sb, float pct) {
    sb->thumbpct= pct;
}
void scrollbar_set_thumbpos(ScrollBar *sb, float pos) {
    sb->thumbpos= clamp_f(pos, 0.0, 1.0);
}
void scrollbar_set_rect(ScrollBar *sb, int rect[2][2]) {
    rect_copy(sb->rect, rect);
}

float scrollbar_get_thumbpct(ScrollBar *sb) {
    return sb->thumbpct;
}
float scrollbar_get_thumbpos(ScrollBar *sb) {
    return sb->thumbpos;
}
void scrollbar_get_rect(ScrollBar *sb, int rect_r[2][2]) {
    rect_copy(rect_r, sb->rect);
}

void scrollbar_free(ScrollBar *sb) {
    MEM_freeN(sb);
}