ruby-****@sourc*****
ruby-****@sourc*****
2013年 3月 19日 (火) 04:32:58 JST
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URL = http://ruby-gnome2.sourceforge.jp/hiki.cgi?tut-gtk2-dancr-intro
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== Sorry this article is still under construction
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== Introduction
(12.1){{br}}
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+Though, the emphasis in this chapter is going to be on Ruby Cairo graphics library, in order to gain sufficient command of Ruby graphics and GUI programming, we should really look at both the pure GTK as well as Cairo graphics features as they overlap in any serious GUI program. But to even begin to talk about the Cairo library functionality where it overlaps with the regular GUI programming, for instance such as, mixing user input within Cairo graphic context, i.e. drawing dots, lines, and other geometric shapes, undoing and redoing earlier drawing actions, as well as, dragging and dropping drawn graphic objects, we need to be sufficiently knowledgeable about both of these two graphic environments (libraries) before user starts interfering with them.
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+Up to this chapter, in this tutorial, we have become reasonably familiar with our Ruby GUI based on pure GTK. However, even in the area of pure GTK without the Cairo library, many things are still shrouded in mystery. Most noticeably, we are considerably inexperienced and lacking most of the details, of how any kind of drawing is stored in the memory, when only different parts of it should be removed and redone, and most importantly, how it changes with time, as a user draws or deletes parts of the larger drawing, graphic piece or image. Not surprisingly, we are also very poorly acquainted with the backgrounds onto which one draws or paints, as well as with understanding of what a drawing or an image is. For instance, is it an object on its own, or does the drawn item become a part of the background when finally drawn, painted, or rendered onto the 'drawable'? Therefor, when GTK was augmented with Cairo graphics library, which itself contains its own drawable backgrounds, it
becomes necessary to learn what are the relationships between these drawable areas and drawn/painted images in either of these two environments.
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+The best way to get introduced to these issues is by trying to tackle the real life graphic programming issues related to background surfaces to which or from which a user should be able to draw, paint or programmatically generate geometric shapes, as well copy miscellaneous images, rendering them to the drawing area, and most importantly also remove her art after it was drawn, painted or copied to electronic surfaces and/or devices, most often, but not exclusively, the computer screen. This latest functionality in most GUI environments is dubbed "undoing" and/or "redoing".