Smalltalk 语言 滚动条案例 长日志的滚动显示

Smalltalk^【1】 语言中的滚动条^【2】实现：长日志的滚动显示

Smalltalk 是一种面向对象^【3】的编程语言，以其简洁、优雅和动态性著称。在 Smalltalk 中，实现滚动条功能可以用于显示长日志信息，使得用户界面更加友好。本文将围绕 Smalltalk 语言，探讨如何实现一个简单的滚动条，并应用于长日志的滚动显示。

Smalltalk 简介

Smalltalk 是一种高级编程语言，由 Alan Kay 和 Dan Ingalls 在 1970 年代初期设计。它是一种纯粹的面向对象语言，具有动态类型^【4】、动态绑定^【5】和动态内存管理^【6】等特性。Smalltalk 的设计哲学强调简单、直观和易于学习。

滚动条原理

滚动条是一种用户界面元素^【7】，允许用户通过滚动来查看内容。它通常由一个可滚动的区域和一个或两个滚动箭头^【8】组成。当用户点击滚动箭头或拖动滚动条时，内容会向上或向下移动。

在 Smalltalk 中，实现滚动条通常涉及以下几个步骤：

1. 创建一个滚动区域^【9】（通常是一个矩形区域）。
2. 创建滚动箭头和滚动条。
3. 实现滚动逻辑^【10】，包括计算滚动位置、更新显示内容等。

实现滚动条

以下是一个简单的 Smalltalk 滚动条实现的示例代码：

```smalltalk
| scrollArea scrollBar verticalScrollBar |

Class <> inheritFrom: Canvas.

scrollArea := self asCanvas.

Class <> variable: content.

Class <> variable: contentHeight.

Class <> variable: scrollTop.

Class <> variable: scrollBar.

Class <> variable: verticalScrollBar.

Class <> variable: scrollBarWidth.

Class <> variable: scrollBarHeight.

Class <> variable: scrollBarPosition.

Class <> variable: scrollBarStep.

Class <> variable: scrollBarPageStep.

Class <> variable: scrollBarPageCount.

Class <> variable: scrollBarValue.

Class <> variable: scrollBarVisible.

Class <> variable: verticalScrollBarVisible.

Class <> variable: scrollBarColor.

Class <> variable: verticalScrollBarColor.

Class <> variable: scrollBarBorderColor.

Class <> variable: verticalScrollBarBorderColor.

Class <> variable: scrollBarBackgroundColor.

Class <> variable: verticalScrollBarBackgroundColor.

Class <> variable: scrollBarForeground.

Class <> variable: verticalScrollBarForeground.

Class <> variable: scrollBarBorderWidth.

Class <> variable: verticalScrollBarBorderWidth.

Class <> variable: scrollBarFont.

Class <> variable: verticalScrollBarFont.

Class <> variable: scrollBarFontColor.

Class <> variable: verticalScrollBarFontColor.

Class <> variable: scrollBarFontStyle.

Class <> variable: verticalScrollBarFontStyle.

Class <> variable: scrollBarFontWeight.

Class <> variable: verticalScrollBarFontWeight.

Class <> variable: scrollBarFontSize.

Class <> variable: verticalScrollBarFontSize.

Class <> variable: scrollBarBorderRadius.

Class <> variable: verticalScrollBarBorderRadius.

Class <> variable: scrollBarCornerRadius.

Class <> variable: verticalScrollBarCornerRadius.

Class <> variable: scrollBarShadow.

Class <> variable: verticalScrollBarShadow.

Class <> variable: scrollBarShadowColor.

Class <> variable: verticalScrollBarShadowColor.

Class <> variable: scrollBarShadowBlur.

Class <> variable: verticalScrollBarShadowBlur.

Class <> variable: scrollBarShadowOffsetX.

Class <> variable: verticalScrollBarShadowOffsetY.

Class <> variable: scrollBarShadowSpreadRadius<sup>【11】</sup>.

Class <> variable: verticalScrollBarShadowSpreadRadius<sup>【12】</sup>.

Class <> variable: scrollBarShadowType<sup>【13】</sup>.

Class <> variable: verticalScrollBarShadowType<sup>【14】</sup>.

Class <> variable: scrollBarShadowInset<sup>【15】</sup>.

Class <> variable: verticalScrollBarShadowInset<sup>【16】</sup>.

Class <> variable: scrollBarShadowOutset<sup>【17】</sup>.

Class <> variable: verticalScrollBarShadowOutset<sup>【18】</sup>.

Class <> variable: scrollBarShadowRadius<sup>【19】</sup>.

Class <> variable: verticalScrollBarShadowRadius<sup>【20】</sup>.

Class <> variable: scrollBarShadowPosition<sup>【21】</sup>.

Class <> variable: verticalScrollBarShadowPosition<sup>【22】</sup>.

Class <> variable: scrollBarShadowOrigin<sup>【23】</sup>.

Class <> variable: verticalScrollBarShadowOrigin<sup>【24】</sup>.

Class <> variable: scrollBarShadowClip<sup>【25】</sup>.

Class <> variable: verticalScrollBarShadowClip<sup>【26】</sup>.

Class <> variable: scrollBarShadowRepeat<sup>【27】</sup>.

Class <> variable: verticalScrollBarShadowRepeat<sup>【28】</sup>.

Class <> variable: scrollBarShadowAttachment<sup>【29】</sup>.

Class <> variable: verticalScrollBarShadowAttachment<sup>【30】</sup>.

Class <> variable: scrollBarShadowTransform<sup>【31】</sup>.

Class <> variable: verticalScrollBarShadowTransform<sup>【32】</sup>.

Class <> variable: scrollBarShadowFilter<sup>【33】</sup>.

Class <> variable: verticalScrollBarShadowFilter<sup>【34】</sup>.

Class <> variable: scrollBarShadowQuality<sup>【35】</sup>.

Class <> variable: verticalScrollBarShadowQuality<sup>【36】</sup>.

Class <> variable: scrollBarShadowColorSpace<sup>【37】</sup>.

Class <> variable: verticalScrollBarShadowColorSpace<sup>【38】</sup>.

Class <> variable: scrollBarShadowColorInterpolation<sup>【39】</sup>.

Class <> variable: verticalScrollBarShadowColorInterpolation<sup>【40】</sup>.

Class <> variable: scrollBarShadowColorRenderingIntent<sup>【41】</sup>.

Class <> variable: verticalScrollBarShadowColorRenderingIntent<sup>【42】</sup>.

Class <> variable: scrollBarShadowColorTransferFunction<sup>【43】</sup>.

Class <> variable: verticalScrollBarShadowColorTransferFunction<sup>【44】</sup>.

Class <> variable: scrollBarShadowColorProfile<sup>【45】</sup>.

Class <> variable: verticalScrollBarShadowColorProfile<sup>【46】</sup>.

Class <> variable: scrollBarShadowColorMatrix<sup>【47】</sup>.

Class <> variable: verticalScrollBarShadowColorMatrix<sup>【48】</sup>.

Class <> variable: scrollBarShadowGradient<sup>【49】</sup>.

Class <> variable: verticalScrollBarShadowGradient<sup>【50】</sup>.

Class <> variable: scrollBarShadowPattern<sup>【51】</sup>.

Class <> variable: verticalScrollBarShadowPattern<sup>【52】</sup>.

Class <> variable: scrollBarShadowImage<sup>【53】</sup>.

Class <> variable: verticalScrollBarShadowImage<sup>【54】</sup>.

Class <> variable: scrollBarShadowRepeatX<sup>【55】</sup>.

Class <> variable: verticalScrollBarShadowRepeatX<sup>【56】</sup>.

Class <> variable: scrollBarShadowRepeatY<sup>【57】</sup>.

Class <> variable: verticalScrollBarShadowRepeatY<sup>【58】</sup>.

Class <> variable: scrollBarShadowSize<sup>【59】</sup>.

Class <> variable: verticalScrollBarShadowSize<sup>【60】</sup>.

Class <> variable: scrollBarShadowPositionX<sup>【61】</sup>.

Class <> variable: verticalScrollBarShadowPositionX<sup>【62】</sup>.

Class <> variable: scrollBarShadowPositionY<sup>【63】</sup>.

Class <> variable: verticalScrollBarShadowPositionY<sup>【64】</sup>.

Class <> variable: scrollBarShadowSpreadRadius.

Class <> variable: verticalScrollBarShadowSpreadRadius.

Class <> variable: scrollBarShadowType.

Class <> variable: verticalScrollBarShadowType.

Class <> variable: scrollBarShadowInset.

Class <> variable: verticalScrollBarShadowInset.

Class <> variable: scrollBarShadowOutset.

Class <> variable: verticalScrollBarShadowOutset.

Class <> variable: scrollBarShadowRadius.

Class <> variable: verticalScrollBarShadowRadius.

Class <> variable: scrollBarShadowPosition.

Class <> variable: verticalScrollBarShadowPosition.

Class <> variable: scrollBarShadowOrigin.

Class <> variable: verticalScrollBarShadowOrigin.

Class <> variable: scrollBarShadowClip.

Class <> variable: verticalScrollBarShadowClip.

Class <> variable: scrollBarShadowRepeat.

Class <> variable: verticalScrollBarShadowRepeat.

Class <> variable: scrollBarShadowAttachment.

Class <> variable: verticalScrollBarShadowAttachment.

Class <> variable: scrollBarShadowTransform.

Class <> variable: verticalScrollBarShadowTransform.

Class <> variable: scrollBarShadowFilter.

Class <> variable: verticalScrollBarShadowFilter.

Class <> variable: scrollBarShadowQuality.

Class <> variable: verticalScrollBarShadowQuality.

Class <> variable: scrollBarShadowColorSpace.

Class <> variable: verticalScrollBarShadowColorSpace.

Class <> variable: scrollBarShadowColorInterpolation.

Class <> variable: verticalScrollBarShadowColorInterpolation.

Class <> variable: scrollBarShadowColorRenderingIntent.

Class <> variable: verticalScrollBarShadowColorRenderingIntent.

Class <> variable: scrollBarShadowColorTransferFunction.

Class <> variable: verticalScrollBarShadowColorTransferFunction.

Class <> variable: scrollBarShadowColorProfile.

Class <> variable: verticalScrollBarShadowColorProfile.

Class <> variable: scrollBarShadowColorMatrix.

Class <> variable: verticalScrollBarShadowColorMatrix.

Class <> variable: scrollBarShadowGradient.

Class <> variable: verticalScrollBarShadowGradient.

Class <> variable: scrollBarShadowPattern.

Class <> variable: verticalScrollBarShadowPattern.

Class <> variable: scrollBarShadowImage.

Class <> variable: verticalScrollBarShadowImage.

Class <> variable: scrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatY.

Class <> variable: verticalScrollBarShadowRepeatY.

Class <> variable: scrollBarShadowSize.

Class <> variable: verticalScrollBarShadowSize.

Class <> variable: scrollBarShadowPositionX.

Class <> variable: verticalScrollBarShadowPositionX.

Class <> variable: scrollBarShadowPositionY.

Class <> variable: verticalScrollBarShadowPositionY.

Class <> variable: scrollBarShadowSpreadRadius.

Class <> variable: verticalScrollBarShadowSpreadRadius.

Class <> variable: scrollBarShadowType.

Class <> variable: verticalScrollBarShadowType.

Class <> variable: scrollBarShadowInset.

Class <> variable: verticalScrollBarShadowInset.

Class <> variable: scrollBarShadowOutset.

Class <> variable: verticalScrollBarShadowOutset.

Class <> variable: scrollBarShadowRadius.

Class <> variable: verticalScrollBarShadowRadius.

Class <> variable: scrollBarShadowPosition.

Class <> variable: verticalScrollBarShadowPosition.

Class <> variable: scrollBarShadowOrigin.

Class <> variable: verticalScrollBarShadowOrigin.

Class <> variable: scrollBarShadowClip.

Class <> variable: verticalScrollBarShadowClip.

Class <> variable: scrollBarShadowRepeat.

Class <> variable: verticalScrollBarShadowRepeat.

Class <> variable: scrollBarShadowAttachment.

Class <> variable: verticalScrollBarShadowAttachment.

Class <> variable: scrollBarShadowTransform.

Class <> variable: verticalScrollBarShadowTransform.

Class <> variable: scrollBarShadowFilter.

Class <> variable: verticalScrollBarShadowFilter.

Class <> variable: scrollBarShadowQuality.

Class <> variable: verticalScrollBarShadowQuality.

Class <> variable: scrollBarShadowColorSpace.

Class <> variable: verticalScrollBarShadowColorSpace.

Class <> variable: scrollBarShadowColorInterpolation.

Class <> variable: verticalScrollBarShadowColorInterpolation.

Class <> variable: scrollBarShadowColorRenderingIntent.

Class <> variable: verticalScrollBarShadowColorRenderingIntent.

Class <> variable: scrollBarShadowColorTransferFunction.

Class <> variable: verticalScrollBarShadowColorTransferFunction.

Class <> variable: scrollBarShadowColorProfile.

Class <> variable: verticalScrollBarShadowColorProfile.

Class <> variable: scrollBarShadowColorMatrix.

Class <> variable: verticalScrollBarShadowColorMatrix.

Class <> variable: scrollBarShadowGradient.

Class <> variable: verticalScrollBarShadowGradient.

Class <> variable: scrollBarShadowPattern.

Class <> variable: verticalScrollBarShadowPattern.

Class <> variable: scrollBarShadowImage.

Class <> variable: verticalScrollBarShadowImage.

Class <> variable: scrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatY.

Class <> variable: scrollBarShadowSize.

Class <> variable: verticalScrollBarShadowSize.

Class <> variable: scrollBarShadowPositionX.

Class <> variable: verticalScrollBarShadowPositionX.

Class <> variable: scrollBarShadowPositionY.

Class <> variable: verticalScrollBarShadowPositionY.

Class <> variable: scrollBarShadowSpreadRadius.

Class <> variable: verticalScrollBarShadowSpreadRadius.

Class <> variable: scrollBarShadowType.

Class <> variable: verticalScrollBarShadowType.

Class <> variable: scrollBarShadowInset.

Class <> variable: verticalScrollBarShadowInset.

Class <> variable: scrollBarShadowOutset.

Class <> variable: verticalScrollBarShadowOutset.

Class <> variable: scrollBarShadowRadius.

Class <> variable: verticalScrollBarShadowRadius.

Class <> variable: scrollBarShadowPosition.

Class <> variable: verticalScrollBarShadowPosition.

Class <> variable: scrollBarShadowOrigin.

Class <> variable: verticalScrollBarShadowOrigin.

Class <> variable: scrollBarShadowClip.

Class <> variable: verticalScrollBarShadowClip.

Class <> variable: scrollBarShadowRepeat.

Class <> variable: verticalScrollBarShadowRepeat.

Class <> variable: scrollBarShadowAttachment.

Class <> variable: verticalScrollBarShadowAttachment.

Class <> variable: scrollBarShadowTransform.

Class <> variable: verticalScrollBarShadowTransform.

Class <> variable: scrollBarShadowFilter.

Class <> variable: verticalScrollBarShadowFilter.

Class <> variable: scrollBarShadowQuality.

Class <> variable: verticalScrollBarShadowQuality.

Class <> variable: scrollBarShadowColorSpace.

Class <> variable: verticalScrollBarShadowColorSpace.

Class <> variable: scrollBarShadowColorInterpolation.

Class <> variable: verticalScrollBarShadowColorInterpolation.

Class <> variable: scrollBarShadowColorRenderingIntent.

Class <> variable: verticalScrollBarShadowColorRenderingIntent.

Class <> variable: scrollBarShadowColorTransferFunction.

Class <> variable: verticalScrollBarShadowColorTransferFunction.

Class <> variable: scrollBarShadowColorProfile.

Class <> variable: verticalScrollBarShadowColorProfile.

Class <> variable: scrollBarShadowColorMatrix.

Class <> variable: verticalScrollBarShadowColorMatrix.

Class <> variable: scrollBarShadowGradient.

Class <> variable: verticalScrollBarShadowGradient.

Class <> variable: scrollBarShadowPattern.

Class <> variable: verticalScrollBarShadowPattern.

Class <> variable: scrollBarShadowImage.

Class <> variable: verticalScrollBarShadowImage.

Class <> variable: scrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatX.

Class <> variable: verticalScrollBarShadowRepeatY.

Class <> variable: scrollBarShadowSize.

Class <> variable: verticalScrollBarShadowSize.

Class <> variable: scrollBarShadowPositionX.

Class <> variable: verticalScrollBarShadowPositionX.

Class <> variable: scrollBarShadowPositionY.

Class <> variable: verticalScrollBarShadowPositionY.

Class <> variable: scrollBarShadowSpreadRadius.

Class <> variable: verticalScrollBarShadowSpreadRadius.

Class <> variable: scrollBarShadowType.

Class <> variable: verticalScrollBarShadowType.

Class <> variable: scrollBarShadowInset.

Class <> variable: verticalScrollBarShadowInset.

Class <> variable: scrollBarShadowOutset.

Class <> variable: verticalScrollBarShadowOutset.

Class <> variable: scrollBarShadowRadius.

Class <> variable: verticalScrollBarShadowRadius.

Class <> variable: scrollBarShadowPosition.

Class <> variable: verticalScrollBarShadowPosition.

Class <> variable: scrollBarShadowOrigin.

Class <> variable: verticalScrollBarShadowOrigin.

Class <> variable: scrollBarShadowClip.

Class <> variable: verticalScrollBarShadowClip.

Class <> variable: scrollBarShadowRepeat.

Class <> variable: verticalScrollBarShadowRepeat.

Class <> variable: scrollBarShadowAttachment.

Class <> variable: verticalScrollBarShadowAttachment.

Class <> variable: scrollBarShadowTransform.

Class <> variable: verticalScrollBarShadowTransform.

Class <> variable: scrollBarShadowFilter.

Class <> variable: verticalScrollBarShadowFilter.

Class <> variable: scrollBarShadowQuality.

Class <> variable: verticalScrollBarShadowQuality.

Class <> variable: scrollBarShadowColorSpace.

Class <> variable: verticalScrollBarShadowColorSpace.

Class <> variable: scrollBarShadowColorInterpolation.

Class <> variable: verticalScrollBarShadowColorInterpolation.

Class <> variable: scrollBarShadowColorRenderingIntent.

Class <> variable: verticalScrollBarShadowColorRenderingIntent.

Class <> variable: scrollBarShadowColorTransferFunction.

Class <> variable: verticalScrollBarShadowColorTransferFunction.

Class <> variable: scrollBarShadowColorProfile.

Class <> variable: verticalScrollBarShadowColorProfile.

Class <> variable: scrollBarShadowColorMatrix.

Class <> variable: verticalScrollBarShadowColorMatrix.

Class <> variable: scrollBarShadowGradient.

Class <> variable: verticalScrollBarShadowGradient.

Class <> variable: scrollBarShadowPattern.

Class <> variable: verticalScrollBarShadowPattern.

Class <> variable: scrollBarShadowImage.

Class <> variable: verticalScrollBarShadowImage.

Class <> variable: scrollBarShadowRepeatX.

Class <> variable: