src/jexer/TVScroller.java

   1 /**
   2  * Jexer - Java Text User Interface
   3  *
   4  * License: LGPLv3 or later
   5  *
   6  * This module is licensed under the GNU Lesser General Public License
   7  * Version 3.  Please see the file "COPYING" in this directory for more
   8  * information about the GNU Lesser General Public License Version 3.
   9  *
  10  *     Copyright (C) 2015  Kevin Lamonte
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public License
  14  * as published by the Free Software Foundation; either version 3 of
  15  * the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this program; if not, see
  24  * http://www.gnu.org/licenses/, or write to the Free Software
  25  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  26  * 02110-1301 USA
  27  *
  28  * @author Kevin Lamonte [kevin.lamonte@gmail.com]
  29  * @version 1
  30  */
  31 package jexer;
  32
  33 import jexer.bits.CellAttributes;
  34 import jexer.bits.GraphicsChars;
  35 import jexer.event.TMouseEvent;
  36
  37 /**
  38  * TVScroller implements a simple vertical scroll bar.
  39  */
  40 public final class TVScroller extends TWidget {
  41
  42     /**
  43      * Value that corresponds to being on the top edge of the scroll bar.
  44      */
  45     private int topValue = 0;
  46
  47     /**
  48      * Get the value that corresponds to being on the top edge of the scroll
  49      * bar.
  50      *
  51      * @return the scroll value
  52      */
  53     public int getTopValue() {
  54         return topValue;
  55     }
  56
  57     /**
  58      * Set the value that corresponds to being on the top edge of the scroll
  59      * bar.
  60      *
  61      * @param topValue the new scroll value
  62      */
  63     public void setTopValue(final int topValue) {
  64         this.topValue = topValue;
  65     }
  66
  67     /**
  68      * Value that corresponds to being on the bottom edge of the scroll bar.
  69      */
  70     private int bottomValue = 100;
  71
  72     /**
  73      * Get the value that corresponds to being on the bottom edge of the
  74      * scroll bar.
  75      *
  76      * @return the scroll value
  77      */
  78     public int getBottomValue() {
  79         return bottomValue;
  80     }
  81
  82     /**
  83      * Set the value that corresponds to being on the bottom edge of the
  84      * scroll bar.
  85      *
  86      * @param bottomValue the new scroll value
  87      */
  88     public void setBottomValue(final int bottomValue) {
  89         this.bottomValue = bottomValue;
  90     }
  91
  92     /**
  93      * Current value of the scroll.
  94      */
  95     private int value = 0;
  96
  97     /**
  98      * Get current value of the scroll.
  99      *
 100      * @return the scroll value
 101      */
 102     public int getValue() {
 103         return value;
 104     }
 105
 106     /**
 107      * Set current value of the scroll.
 108      *
 109      * @param value the new scroll value
 110      */
 111     public void setValue(final int value) {
 112         this.value = value;
 113     }
 114
 115     /**
 116      * The increment for clicking on an arrow.
 117      */
 118     private int smallChange = 1;
 119
 120     /**
 121      * Set the increment for clicking on an arrow.
 122      *
 123      * @param smallChange the new increment value
 124      */
 125     public void setSmallChange(final int smallChange) {
 126         this.smallChange = smallChange;
 127     }
 128
 129     /**
 130      * The increment for clicking in the bar between the box and an arrow.
 131      */
 132     private int bigChange = 20;
 133
 134     /**
 135      * Set the increment for clicking in the bar between the box and an
 136      * arrow.
 137      *
 138      * @param bigChange the new increment value
 139      */
 140     public void setBigChange(final int bigChange) {
 141         this.bigChange = bigChange;
 142     }
 143
 144     /**
 145      * When true, the user is dragging the scroll box.
 146      */
 147     private boolean inScroll = false;
 148
 149     /**
 150      * Public constructor.
 151      *
 152      * @param parent parent widget
 153      * @param x column relative to parent
 154      * @param y row relative to parent
 155      * @param height height of scroll bar
 156      */
 157     public TVScroller(final TWidget parent, final int x, final int y,
 158         final int height) {
 159
 160         // Set parent and window
 161         super(parent);
 162
 163         setX(x);
 164         setY(y);
 165         setHeight(height);
 166         setWidth(1);
 167     }
 168
 169     /**
 170      * Compute the position of the scroll box (a.k.a. grip, thumb).
 171      *
 172      * @return Y position of the box, between 1 and height - 2
 173      */
 174     private int boxPosition() {
 175         return (getHeight() - 3) * (value - topValue) / (bottomValue - topValue) + 1;
 176     }
 177
 178     /**
 179      * Draw a vertical scroll bar.
 180      */
 181     @Override
 182     public void draw() {
 183         CellAttributes arrowColor = getTheme().getColor("tscroller.arrows");
 184         CellAttributes barColor = getTheme().getColor("tscroller.bar");
 185         getScreen().putCharXY(0, 0, GraphicsChars.CP437[0x1E], arrowColor);
 186         getScreen().putCharXY(0, getHeight() - 1, GraphicsChars.CP437[0x1F],
 187             arrowColor);
 188
 189         // Place the box
 190         if (bottomValue > topValue) {
 191             getScreen().vLineXY(0, 1, getHeight() - 2,
 192                 GraphicsChars.CP437[0xB1], barColor);
 193             getScreen().putCharXY(0, boxPosition(), GraphicsChars.BOX,
 194                 arrowColor);
 195         } else {
 196             getScreen().vLineXY(0, 1, getHeight() - 2, GraphicsChars.HATCH,
 197                 barColor);
 198         }
 199
 200     }
 201
 202     /**
 203      * Perform a small step change up.
 204      */
 205     public void decrement() {
 206         if (bottomValue == topValue) {
 207             return;
 208         }
 209         value -= smallChange;
 210         if (value < topValue) {
 211             value = topValue;
 212         }
 213     }
 214
 215     /**
 216      * Perform a small step change down.
 217      */
 218     public void increment() {
 219         if (bottomValue == topValue) {
 220             return;
 221         }
 222         value += smallChange;
 223         if (value > bottomValue) {
 224             value = bottomValue;
 225         }
 226     }
 227
 228     /**
 229      * Perform a big step change up.
 230      */
 231     public void bigDecrement() {
 232         if (bottomValue == topValue) {
 233             return;
 234         }
 235         value -= bigChange;
 236         if (value < topValue) {
 237             value = topValue;
 238         }
 239     }
 240
 241     /**
 242      * Perform a big step change down.
 243      */
 244     public void bigIncrement() {
 245         if (bottomValue == topValue) {
 246             return;
 247         }
 248         value += bigChange;
 249         if (value > bottomValue) {
 250             value = bottomValue;
 251         }
 252     }
 253
 254     /**
 255      * Go to the top edge of the scroller.
 256      */
 257     public void toTop() {
 258         value = topValue;
 259     }
 260
 261     /**
 262      * Go to the bottom edge of the scroller.
 263      */
 264     public void toBottom() {
 265         value = bottomValue;
 266     }
 267
 268     /**
 269      * Handle mouse button releases.
 270      *
 271      * @param mouse mouse button release event
 272      */
 273     @Override
 274     public void onMouseUp(final TMouseEvent mouse) {
 275         if (bottomValue == topValue) {
 276             return;
 277         }
 278
 279         if (inScroll) {
 280             inScroll = false;
 281             return;
 282         }
 283
 284         if ((mouse.getX() == 0)
 285             && (mouse.getY() == 0)
 286         ) {
 287             // Clicked on the top arrow
 288             decrement();
 289             return;
 290         }
 291
 292         if ((mouse.getX() == 0)
 293             && (mouse.getY() == getHeight() - 1)
 294         ) {
 295             // Clicked on the bottom arrow
 296             increment();
 297             return;
 298         }
 299
 300         if ((mouse.getX() == 0)
 301             && (mouse.getY() > 0)
 302             && (mouse.getY() < boxPosition())
 303         ) {
 304             // Clicked between the top arrow and the box
 305             value -= bigChange;
 306             if (value < topValue) {
 307                 value = topValue;
 308             }
 309             return;
 310         }
 311
 312         if ((mouse.getX() == 0)
 313             && (mouse.getY() > boxPosition())
 314             && (mouse.getY() < getHeight() - 1)
 315         ) {
 316             // Clicked between the box and the bottom arrow
 317             value += bigChange;
 318             if (value > bottomValue) {
 319                 value = bottomValue;
 320             }
 321             return;
 322         }
 323     }
 324
 325     /**
 326      * Handle mouse movement events.
 327      *
 328      * @param mouse mouse motion event
 329      */
 330     @Override
 331     public void onMouseMotion(final TMouseEvent mouse) {
 332         if (bottomValue == topValue) {
 333             return;
 334         }
 335
 336         if ((mouse.getMouse1()) &&
 337             (inScroll) &&
 338             (mouse.getY() > 0) &&
 339             (mouse.getY() < getHeight() - 1)
 340         ) {
 341             // Recompute value based on new box position
 342             value = (bottomValue - topValue) * (mouse.getY()) / (getHeight() - 3) + topValue;
 343             return;
 344         }
 345
 346         inScroll = false;
 347     }
 348
 349     /**
 350      * Handle mouse press events.
 351      *
 352      * @param mouse mouse button press event
 353      */
 354     @Override
 355     public void onMouseDown(final TMouseEvent mouse) {
 356         if (bottomValue == topValue) {
 357             return;
 358         }
 359
 360         if ((mouse.getX() == 0)
 361             && (mouse.getY() == boxPosition())
 362         ) {
 363             inScroll = true;
 364             return;
 365         }
 366     }
 367
 368 }