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5.4 Lecture Browser Visualizations

The Lecture Browser provides three to four visualization frames, depending on the version. These frames include the Key Frame View Frame, the Information Mural, the Box View, and the Image Frame. The Image Frame is used to view single slides, whereas the other three frames present the data from the entire lecture class in different styles.

5.4.1 Key Frame View

The Key Frame View displays all slides as thumbnail images ordered by Sections over time. Slides within a Section form a vertical chain of images, similar to a film strip. Film strips are horizontally placed next to each other, ordered by time of appearance.

Figure 1.9: Key Frame View in versions 0, 1, and 2
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Figure 1.10: Key Frame View with highlighted Slide and transparent Magnifying Glass, Version 1
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Figure 1.11: Key Frame View with highlighted Slide, Version 2
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Moving the mouse over a thumbnail enlarges the image in the interface and provides a fast browsing experience of the contents. In versions 0 and 1, the enlarged image is placed in a semi-transparent panel on top of the interface. In this view, enlarged images are seamlessly stitched vertically similar to the thumbnail film strip, and mouse cursor movement over the thumbnail images translates into the position in the enlarged image series, similar to a magnifying glass. In version 2, after feedback about the disorienting occlusion of the thumbnail images, this functionality was replaced by enlarging images in the Image Frame instead.

Technical Note for Java Swing development: The transparent magnifying glass is implemented on a GlassPane. The underlying interface uses JInternalFrame. In practice, the combination of JInternalFrame and GlassPane causes some documented side effects. When resizing or moving a JInternalFrame while a custom GlassPane is used, the custom GlassPane disappears (is set invisible), because the resizing and moving effects are rendered in a GlassPane of its own. After resizing or moving are complete, the custom GlassPane is not returned to visibility automatically. The Lecture Browser circumvents this issue with a constantly running thread (sleeps every 250 ms), which tests the visibility of the custom GlassPane and, if necessary, returns its visibility. Practically speaking, the four method calls per second do not impact speed, and the calls are frequent enough to provide smooth visibility of the GlassPane.

The thumbnail slide under the mouse cursor is marked with transparent horizontal and vertical bars as guides. While working in the Key Frame View, this guide is also triggered momentarily in the Information Mural (versions 0 and 1).

A colored rectangle is placed above each film strip, indicating the media type for each Section. Clicking once on the colored area for a Section selects all of the Slides for that Section. A selected Section is marked with a transparent vertical bar. Once a Section is selected, its Slides can be played back as a slide show. This is particularly helpful for the Slides in a Section, because the playback quickly demonstrates the evolution of the content in the Section. A selected section is marked with a transparent vertical bar. In order to distinguish a selected section from a marked slide, the transparent color has slightly different color values.

Figure 1.12: Key Frame View with selected Section
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If a Section is part of a Topic (Topic = several Sections separated by temporal breaks), the entire Topic to which a Section belongs can be selected with a second click on the Section's colored rectangle. Slides from a selected Topic can be played back in a slide show similar to those of a Section.

Figure 1.13: Key Frame View with selected Topic
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