ScrollBar.c

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/*
 * ObjectivelyMVC: Object oriented MVC framework for SDL3 and C.
 * Copyright (C) 2014 Jay Dolan <jay@jaydolan.com>
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software
 * in a product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 *
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 *
 * 3. This notice may not be removed or altered from any source distribution.
 */
 
#include <assert.h>
 
#include "ScrollBar.h"
#include "ScrollView.h"
 
#define _Class _ScrollBar
 
const EnumName ScrollBarVisibilityNames[] = MakeEnumNames(
  MakeEnumAlias(ScrollBarShow, show),
  MakeEnumAlias(ScrollBarHide, hide),
  MakeEnumAlias(ScrollBarAuto, auto)
);
 
#pragma mark - Delegate callbacks
 
static void didDragHandle(ScrollHandle *handle, float delta) {
 
  ScrollBar *self = handle->delegate.self;
 
  if (self->scrollView) {
 
    const SDL_Rect track = $((View *) self, bounds);
    const SDL_Size content = $((View *) self->scrollView->contentView, size);
    const SDL_Rect visible = $((View *) self->scrollView, bounds);
 
    const int scrollRange = content.h - visible.h;
    const int travel = track.h - ((View *) self->handle)->frame.h;
 
    if (scrollRange > 0 && travel > 0) {
 
      SDL_Point offset = self->scrollView->contentOffset;
      offset.y -= (int) (delta * ((float) scrollRange / travel));
 
      $(self->scrollView, scrollToOffset, &offset);
      $((View *) self, setNeedsLayout);
    }
  }
}
 
#pragma mark - Object
 
static void dealloc(Object *self) {
 
  ScrollBar *this = (ScrollBar *) self;
 
  release(this->handle);
 
  super(Object, self, dealloc);
}
 
#pragma mark - View
 
static View *init(View *self) {
  return (View *) $((ScrollBar *) self, initWithScrollView, NULL);
}
 
static void layoutSubviews(View *self) {
 
  ScrollBar *this = (ScrollBar *) self;
 
  super(View, self, layoutSubviews);
 
  if (this->scrollView == NULL || this->scrollView->contentView == NULL) {
    return;
  }
 
  const SDL_Rect track = $(self, bounds);
  const SDL_Size content = $(this->scrollView->contentView, size);
  const SDL_Rect visible = $((View *) this->scrollView, bounds);
 
  View *handle = (View *) this->handle;
 
  if (content.h <= visible.h || track.h <= 0) {
    handle->frame = (SDL_Rect) { 0, 0, track.w, track.h };
  } else {
 
    const int scrollRange = content.h - visible.h;
 
    int handleH = (int) ((float) track.h * visible.h / content.h);
    handleH = clamp(handleH, handle->minSize.h, track.h);
 
    const int travel = track.h - handleH;
    const float fraction = clamp((float) (-this->scrollView->contentOffset.y) / scrollRange, 0.f, 1.f);
 
    handle->frame = (SDL_Rect) { 0, (int) (fraction * travel), track.w, handleH };
  }
}
 
static void respondToEvent(View *self, const SDL_Event *event) {
 
  ScrollBar *this = (ScrollBar *) self;
 
  switch (event->type) {
 
    case SDL_EVENT_MOUSE_BUTTON_DOWN:
      if (this->scrollView) {
 
        const SDL_Point point = MakePoint(event->button.x, event->button.y);
        const SDL_Rect handleFrame = $((View *) this->handle, renderFrame);
        const SDL_Rect visible = $((View *) this->scrollView, bounds);
 
        SDL_Point offset = this->scrollView->contentOffset;
 
        if (point.y < handleFrame.y) {
          offset.y += visible.h;
        } else if (point.y > handleFrame.y + handleFrame.h) {
          offset.y -= visible.h;
        }
 
        $(this->scrollView, scrollToOffset, &offset);
        $(self, setNeedsLayout);
      }
      return;
 
    case SDL_EVENT_MOUSE_BUTTON_UP:
      $(self, resignTouchResponder);
      return;
 
    case SDL_EVENT_MOUSE_MOTION:
      return;
 
    default:
      break;
  }
 
  super(View, self, respondToEvent, event);
}
 
#pragma mark - ScrollBar
 
static ScrollBar *initWithScrollView(ScrollBar *self, ScrollView *scrollView) {
 
  self = (ScrollBar *) super(View, self, initWithFrame, NULL);
  if (self) {
 
    $((View *) self, addClassName, "scrollBar");
 
    self->handle = $(alloc(ScrollHandle), initWithFrame, NULL);
    assert(self->handle);
    self->handle->delegate.self = self;
    self->handle->delegate.didDrag = didDragHandle;
    $((View *) self, addSubview, (View *) self->handle);
 
    $(self, setScrollView, scrollView);
  }
 
  return self;
}
 
static void setScrollView(ScrollBar *self, ScrollView *scrollView) {
 
  self->scrollView = scrollView;
 
  $((View *) self, setNeedsLayout);
}
 
#pragma mark - Class lifecycle
 
static void initialize(Class *clazz) {
 
  ((ObjectInterface *) clazz->interface)->dealloc = dealloc;
 
  ((ViewInterface *) clazz->interface)->init = init;
  ((ViewInterface *) clazz->interface)->layoutSubviews = layoutSubviews;
  ((ViewInterface *) clazz->interface)->respondToEvent = respondToEvent;
 
  ((ScrollBarInterface *) clazz->interface)->initWithScrollView = initWithScrollView;
  ((ScrollBarInterface *) clazz->interface)->setScrollView = setScrollView;
}
 
Class *_ScrollBar(void) {
  static Class *clazz;
  static Once once;
 
  do_once(&once, {
    clazz = _initialize(&(const ClassDef) {
      .name = "ScrollBar",
      .superclass = _View(),
      .instanceSize = sizeof(ScrollBar),
      .interfaceSize = sizeof(ScrollBarInterface),
      .initialize = initialize,
    });
  });
 
  return clazz;
}
 
#undef _Class