Re: Dynamic Control of Graphics

• To: mathgroup at smc.vnet.net
• Subject: [mg105124] Re: Dynamic Control of Graphics
• From: Albert Retey <awnl at gmx-topmail.de>
• Date: Sat, 21 Nov 2009 03:36:59 -0500 (EST)
• References: <he0oae\$4ov\$1@smc.vnet.net>

```PeterSF schrieb:
> I am new to the dynamic features of the Mathematica fron end.  Having spent a
> considerable amount of time, I am still strufggling with the following
> problem: how to control dynamically individual elements of a combined graphics?
> Specifically, we are given
> Show[ Plot[ Sin[x], {x,0,Pi} ], Graphics[ { textColor, Text
> ["Test"] } ],
>                                                 Graphics[ { lineWidth,
> Line[{ {0,0}, {0,2}] } ] ]
> The objective is to change:
>     * the color of text (the 2nd element) if and only if a mouse is
>       over that text;
>     * the thickness of the line (the 3rd element) if and only if a
> mouse is
>       over that line.
> I can see how to handle these simultaneously:
>
> DynamicModule[ { lineWidth = Thin, textColor = Blue},
>    Dynamic @ EventHandler[ Show[ Plot[Sin[x], {x, 0, \[Pi]} ],
>        Graphics[{ textColor, Text["XXX", {1, 1}]}],
>        Graphics[{ lineWidth, Line[{{0, 0}, {2, 1}}]}]],
>   "MouseClicked" :> (textColor  = Red, lineWidth )]]
>
> The question is, how can one control the wdth and the color
> individually?
>
> More broadly, I need to perform the following tasks: upon mouseover to
> change the appearance of a single graphics element (line, text, etc.);
> then, upon mouse click, to store in a variable which elements was
> selected (clicked over); and, upon pressing of the Delete key, to
> remove that element from the combined graphics.
>
> I would be most greatful for any and all of the help you could give
> me.

I think the following is doing what you described, except that I am
using the "d" key instead of the delete key. Unfortunatly there seems to
be no documented way to get ahold of the Delete key pressed events, or
am I missing something? I am using a combination of Mouseover, Dynamic
and Eventhandler:

DynamicModule[{
selected = None, highlighted = None,
lineWidth = Thin, textColor = Blue,
curve, text, line
},
curve = Plot[Sin[x], {x, 0, \[Pi]}] /. Line[points_] :> Mouseover[
Dynamic[highlighted = None; Line[points]],
Dynamic[highlighted = Hold[curve]; Line[points]]
];
text = Graphics[Mouseover[
Dynamic[{highlighted = None; Blue, Text["XXX", {1, 1}]}],
Dynamic[{highlighted = Hold[text]; Red, Text["XXX", {1, 1}]}]
]];
line = Graphics[Mouseover[
Dynamic[{highlighted = None; Thin, Line[{{0, 0}, {2, 1}}]}],
Dynamic[{highlighted = Hold[line]; Thick, Line[{{0, 0}, {2, 1}}]}]
]];
EventHandler[
Column[{
Dynamic[Show[curve, text, line]],
Dynamic[highlighted],
Dynamic[selected]
}],
{
"MouseClicked" :> (selected = highlighted),
{"KeyDown", "d"} :> (
Print["deleting: " <> ToString[selected]];
Set @@ Append[selected, Graphics[]]
)
},
PassEventsDown -> True
]]

hth,

albert

```

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