物件導向繪圖系統:引入使用者介面管理技術

Abstract

發展圖形應用程式通常包含三件事：產生一個圖形輸出模型，提供一些圖 形輸入機制，以及維持應用與圖形之間的相依或對應關係。現今有兩類系 統專門用以處理圖形的輸出與輸入：繪圖系統與使用者介面工具組。繪圖 系統通常提供表示圖形模型的強大能力，但只提供有限的圖形輸入機制， 並將應用與圖形之間的相依關係留給應用程式自行負責。另一方面，使用 者介面工具組通常提供強大且具彈性的輸入機制，有時並提供一個自動維 繫應用與使用者介面之間相依關係的機制，但表示圖形模型的能力卻相對 較弱。採用了使用者介面工具組中輸入處理與對應關係自動維繫機制的技 術，HAGI這一個物件導向繪圖系統提供下列特性： 1. 作為一個物件導 向繪圖系統，它除了提供一般結構化繪圖系統如GKS 的功能外，並提供表 示圖形模型的強大能力。 2. 提供了一個維繫應用與圖形相依關係的機 制。透過這個機制，圖形應用程式之應用部份與圖形部份的程式碼可以清 楚地分開。 3. 圖形輸入是利用邏輯交談器 (logical interactors)來 處理，而邏輯交談器是結合了邏輯輸入裝置 (logical input devices) 和使用者介面交談物件 (interaction objects) 的觀念，因此它提供更 大的適應性和擴充性來建立更高層次的交談式圖形使用者介面。 Graphics programming typically consists of three tasks: creating a graphical output model, providing graphical input mechanisms, and maintaining a dependency relationship between the graphics and the application. Today, there are two classes of systems addressing the same domain of managing graphical output and input: graphics systems and user interface tools. Graphics systems typically support a powerful graphics output modeling capability, but provide limited graphical input mechanisms and leave the application/graphics dependency maintenance to application programs. User interface tools, on the other hand, provide powerful and flexible input mechanisms and sometimes an application/user interface dependency maintenance mechanism, but have relatively weak graphics output modeling capability. By adopting the techniques of input handling and dependency maintenance from user interface tools, HAGI is an object-oriented graphics system being able to support the following features: 1. Being an object-oriented graphics system, it supports a powerful graphics modeling capability in addition to facilities that structured graphics systems such as GKS usually have. 2. A mechanism for maintaining the application/graphics dependency relationship is provided. With this mechanism, the application code and the graphics code of a graphics application are clearly separated. 3. Graphical input is handled by logical interactors, a blend of the concepts of logical input device and interaction object. Logical interactors provide great flexibility and extensibility for constructing highly interactive graphical user interfaces.