tikz: Can we set the corner coordinates of a rectangle?

Question

I already have

\tikzstyle{block} = [draw, fill=yellow!20, text centered, rectangle,
minimum height=0.8cm,minimum width=6em, align=right]

First, I can obtain a rectangle by

\node (rect) [block] at (0,0) {test};

Second, I can also obtain a rectangle by

\draw (0,0) rectangle (1,1);

Question: I want to use the first way to create a rectangle, whose properties have been predefined using \tikzstyle. If using the second way, I have to define the properties of the rectangle again. I know the coordinates of the corners of the rectangle can be obtained by

• rect.north east
• rect.north wast
• rect.south east
• rect.south west

Can I create a rectangle using the first way and specify the four corner coordinates of the rectangle?

Answer 1

Yes, you can.

Though, I limited your question to two corner coordinates, because unless you account for rotation, two coordinates suffice to specify a rectangle.

So many possibilities.

But before I divulge the actual solution to you let me give you some other ideas on positioning.

1. The anchor= key. It can be used as for example anchor=south west (see my example below) which set the south-west corner of the to-placed node at the at part.

2. With the positioning library you can even be more specific and could specify above right=<distance> of <coordinate> where <coordinate> can be an actual coordinate like 0,0 (enbrace the whole argument in { } when you use , in it!), a node or a node’s anchor.

   Unless <distance> is specified, none is used. This topic is a bit complex, it is best to read subsection 17.5.3 “Advanced Placement Options” of the PGF manual.

3. The fit library and its fit= key. The fit key takes a list of coordinates (or nodes, or anchors) and fits the to-be-fitted node so that those coordinates are enclosed by that node. But be aware of the inner sep key and the usual dimension-setting keys (height, width, etc.) as they can affect the placement; usually the corners do not lie at those coordinates.

4. My solution: the from=<coordinate 1> to <coordinate2> key. See the last point on the next list.

So many styles.

I have created four distinctive styles:

1. block filldraw contains
   • draw and
   • fill options. It is used in the other styles and on the rectangle path.
2. block rect contains
   • block filldraw (and inherits its option) and
   • the node-specific rectangle option (which is the default). This style can be applied to an path but doesn’t change much for the path unless it contains a node which would than inherit those node-specific styles (but not the draw and fill styles).
3. block contains
   • block rect,
   • minimum height and
   • minimum width. Again, it does not change much for paths but for nodes.

4. from style (that should be used on a node) takes its argument in the form

   from=<coordinate 1> to <coordinate 2>
   

   Now, those coordinates can be just arbitrary 0,0 but than the whole argument must be enclosed in { } (as I did in my example below). But they also can be nodes and their anchors. <coordinate 1> will be used as the lower left corner in the above right=of key.

   Both coordinates will be used to calculate the horizontal and vertical dimensions for the node. Note that I have used the minimum width and minimum height keys to set the needed dimensions. In this case, the node will grow with its content.

In the example I have set the opacity key to see the overlaying nodes and how they get positioned.

Code

\documentclass[tikz,border=2pt]{standalone}
\usetikzlibrary{positioning}
\makeatletter
\tikzset{
    block filldraw/.style={% only the fill and draw styles
        draw, fill=yellow!20},
    block rect/.style={% fill, draw + rectangle (without measurements)
        block filldraw, rectangle},
    block/.style={% fill, draw, rectangle + minimum measurements
        block rect, minimum height=0.8cm, minimum width=6em},
    from/.style args={#1 to #2}{% without transformations
        above right={0cm of #1},% needs positioning library
        /utils/exec=\pgfpointdiff
            {\tikz@scan@one@point\pgfutil@firstofone(#1)\relax}
            {\tikz@scan@one@point\pgfutil@firstofone(#2)\relax},
        minimum width/.expanded=\the\pgf@x,
        minimum height/.expanded=\the\pgf@y}}
\makeatother
\begin{document}
\begin{tikzpicture}[opacity=.4]
\draw[block filldraw]              (0,0) rectangle (1,1)       ;
\node[block] (rect)             at (0,0)                 {test};
\node[block, anchor=south west] at (0,0)                 {test};
\node[block rect, from={0,0 to 2,.5}]                 {from-to};

\foreach \x/\y/\pos in {0/0/below,1/1/above,2/.5/right}
  \fill[opacity=1] (\x,\y) circle (1pt) node [\pos] {$\x,\y$};
\end{tikzpicture}
\end{document}

Output

Code with fit and animation

\documentclass[tikz,border=2pt]{standalone}
\usetikzlibrary{positioning,fit}
\makeatletter
\tikzset{
    block filldraw/.style={% only the fill and draw styles
        draw, fill=yellow!20},
    block rect/.style={% fill, draw + rectangle (without measurements)
        block filldraw, rectangle},
    block/.style={% fill, draw, rectangle + minimum measurements
        block rect, minimum height=0.8cm, minimum width=6em},
    from/.style args={#1 to #2}{% without transformations
        above right={0cm of #1},% needs positioning library
        /utils/exec=\pgfpointdiff
            {\tikz@scan@one@point\pgfutil@firstofone(#1)\relax}
            {\tikz@scan@one@point\pgfutil@firstofone(#2)\relax},
        minimum width/.expanded=\the\pgf@x,
        minimum height/.expanded=\the\pgf@y}}
\makeatother
\newcommand*\hideme[1]{\ifnum\iCount<#1\relax\tikzset{every node/.style={opacity=0}}\fi}
\begin{document}
\foreach \iCount in {0,...,4}{
\begin{tikzpicture}[opacity=.6]
\draw[block filldraw]              (0,0) rectangle (1,1)       ; \hideme1
\node[block] (rect)             at (0,0)                 {test}; \hideme2
\node[block, anchor=south west] at (0,0)                 {test}; \hideme3
\node[block rect, from={0,0 to 2,.5}]                 {from-to}; \hideme4
\node[block rect, fit={(0,0)(1,1)}]                       {fit};  
\foreach \x/\y/\pos in {0/0/below,1/1/above,2/.5/right}
  \fill[opacity=1] (\x,\y) circle (1pt) node [opacity=1, \pos] {$\x,\y$};
\end{tikzpicture}}
\end{document}

Output with fit and animation