Direct Manipulation

What is direct manipulation? In computer science, direct manipulation is a human– computer interaction style which involves continuous representation of objects of interest and rapid, reversible, and incremental actions and feedback. An example of direct manipulation is resizing a graphical shape, such as a rectangle, by dragging its corners or edges with a mouse.

The API The Direct Manipulation APIs let you create great pan, zoom, and drag user experiences. To do this, it processes touch input on a region or object, generates output transforms, and applies the transforms to UI elements

Developer Audience The Direct Manipulation API is for experienced developers who know C/C++, have a solid understanding of the Component Object Model (COM), and are familiar with Windows programming concepts.

Run-time requirements Direct Manipulation was introduced in Windows 8. It is included in both 32-bit and 64-bit versions.

Why use DirectManipulation Handles interactions in a straightforward and consistent manner. Direct Manipulation works by pre-declaring the behaviors and interactions for a region or object. For example, a web page is often configured for pan and zoom. At runtime, input is then associated with this region/object through a simple API call. From this point forward Direct Manipulation does all the heavy lifting of processing the input, applying constraints and personality, and generating the output transforms.

Why use DirectManipulation Build responsive touch applications. To optimize responsiveness and minimize latency, Direct Manipulation processing occurs on a separate, independent thread from the UI thread. As a result, output transforms can run in parallel to activity on the UI thread. The UI thread activity may include application logic, rendering, layout, and anything else that consumes cycles on the processor.

Disadvantages May require graphics displays and pointing devices May be hard to code

Basic concepts The most basic Direct Manipulation implementation consists of a viewport, content, and interactions. The viewport is a region that is able to receive and process input from user interactions. It is also the region of the content that is visible to the end-user. The content is the actual object that end-users can see and is what moves or scales in response to a user interaction. The primary user interactions (also known as manipulations) supported by Direct Manipulation are panning and zooming.

Processing keyboard and mouse input Direct Manipulation allows keyboard and mouse messages to be forwarded manually from the application UI thread via the ProcessInput API such that they can be handled appropriately by Direct Manipulation.

Sources https://dl.acm.org/citation.cfm?doid=1978942.1979033 https://msdn.microsoft.com/zh-cn/ie/hh446969(v=vs.80) https://web.cs.dal.ca/~jamie/teach/MatthewDean/dialog_st yles/tsld012.htm

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