[[layout]]
== Managing Layout

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TODO The intro text below is now completely hidden, as this text is
not visible in web edition and all the text is web-conditional.
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ifdef::web[]
Ever since the ancient xeroxians invented graphical user interfaces, programmers
have wanted to make GUI programming ever easier for themselves. Solutions
started simple. When GUIs appeared on PC desktops, practically all screens were
of the VGA type and fixed into 640x480 size. Mac or X Window System on UNIX were
not much different. Everyone was so happy with such awesome graphics resolutions
that they never thought that an application would have to work on a radically
different screen size. At worst, screens could only grow, they thought, giving
more space for more windows. In the 80s, the idea of having a computer screen in
your pocket was simply not realistic. Hence, the GUI APIs allowed placing UI
components using screen coordinates. Visual Basic and some other systems
provided an easy way for the designer to drag and drop components on a
fixed-sized window. One would have thought that at least translators would have
complained about the awkwardness of such a solution, but apparently they were
not, as non-engineers, heard or at least cared about. At best, engineers could
throw at them a resource editor that would allow them to resize the UI
components by hand. Such was the spirit back then.
endif::web[]

ifdef::web[]
After the web was born, layout design was doomed to change for ever. At first,
layout didn't matter much, as everyone was happy with plain headings,
paragraphs, and a few hyperlinks here and there. Designers of HTML wanted the
pages to run on any screen size. The screen size was actually not pixels but
rows and columns of characters, as the baby web was really just hyper __text__,
not graphics. That was soon to be changed. The first GUI-based browser, NCSA
Mosaic, launched a revolution that culminated in Netscape Navigator. Suddenly,
people who had previously been doing advertisement brochures started writing
HTML. This meant that layout design had to be easy not just for programmers, but
also allow the graphics designer to do his or her job without having to know a
thing about programming. The W3C committee designing web standards came up with
the CSS (Cascading Style Sheet) specification, which allowed trivial separation
of appearance from content. Later versions of HTML followed, XHTML and HTML 5
appeared, as did countless other standards.
endif::web[]

ifdef::web[]
Page description and markup languages are a wonderful solution for static
presentations, such as books and most web pages. Real applications, however,
need to have more control. They need to be able to change the state of user
interface components and even their layout on the run. This creates a need to
separate the presentation from content on exactly the right
level.

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Vaadin provides a solution for this, using themes and CSS, but let us first look
at what Java did for UI programming.
////

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Changing the layout steps right on the feet of the graphics designers, so we
have a conflict. We will discuss this conflict later, but let us first look at
what Java did for UI programming.
////
endif::web[]

ifdef::web[]
Thanks to the attack of graphics designers, desktop applications were, when it
comes to appearance, far behind web design. Sun Microsystems had come in 1995
with a new programming language, Java, for writing cross-platform desktop
applications. Java's original graphical user interface toolkit, AWT (Abstract
Windowing Toolkit), was designed to work on multiple operating systems as well
as embedded in web browsers. One of the special aspects of AWT was the layout
manager, which allowed user interface components to be flexible, growing and
shrinking as needed. This made it possible for the user to resize the windows of
an application flexibly and also served the needs of localization, as text
strings were not limited to some fixed size in pixels. It became even possible
to resize the pixel size of fonts, and the rest of the layout adapted to the new
size.
endif::web[]

Layout management of Vaadin is a direct successor of the web-based concept for
separation of content and appearance and of the Java AWT solution for binding
the layout and user interface components into objects in programs. Vaadin layout
components allow you to position your UI components on the screen in a
hierarchical fashion, much like in conventional Java UI toolkits such as AWT,
Swing, or SWT. In addition, you can approach the layout from the direction of
the web with the [classname]#CustomLayout# component, which you can use to write
your layout as a template in HTML that provides locations of any contained
components. The [classname]#AbsoluteLayout# allows the old-style pixel-position
based layouting, but it also supports percentual values, which makes it usable
for scalable layouts. It is also useful as an area on which the user can
position items with drag and drop.

ifdef::web[]
The moral of the story is that, because Vaadin is intended for web applications,
appearance is of high importance. The solutions have to be the best of both
worlds and satisfy artists of both kind: code and graphics. On the API side, the
layout is controlled by UI components, particularly the layout components. On
the visual side, it is controlled by themes. Themes can contain any HTML, Sass,
CSS, and JavaScript that you or your web artists create to make people feel good
about your software.
endif::web[]


include::layout-overview.asciidoc[leveloffset=+2]

include::layout-root-layout.asciidoc[leveloffset=+2]

include::layout-orderedlayout.asciidoc[leveloffset=+2]

include::layout-gridlayout.asciidoc[leveloffset=+2]

include::layout-formlayout.asciidoc[leveloffset=+2]

include::layout-panel.asciidoc[leveloffset=+2]

include::layout-sub-window.asciidoc[leveloffset=+2]

include::layout-splitpanel.asciidoc[leveloffset=+2]

include::layout-tabsheet.asciidoc[leveloffset=+2]

include::layout-accordion.asciidoc[leveloffset=+2]

include::layout-absolutelayout.asciidoc[leveloffset=+2]

include::layout-csslayout.asciidoc[leveloffset=+2]

include::layout-settings.asciidoc[leveloffset=+2]

include::layout-customlayout.asciidoc[leveloffset=+2]