[Question]
  [
# Find X
I was inspired by math questions in which one is asked to "Find X" for a given shape. Originally, I was just going to have the challenge be to print the x and y location of the character 'x' in a String. But I supposed that would be too simple. So I considered the context they were normally in, and decided finding the length of a Line next to the x just seemed appropriate.
Given a string input containing a Diagram of ascii 'lines' as well as a single 'x' and potentially junk characters, print the length of the only line that has an 'x' directly adjecent to it.
## Examples
Input:
```
|
|
|x
|
|
```
Ouput:
```
5
```
Input:
```
|\
| \x
|  \
|___\
```
Output:
```
4
```
Input:
```
Diagram of a Wobbly Line:
IRRELEVANTTEXT____
____     ____/
    \___/ X ;)   
      x
```
Output:
```
3
```
Input:
```
  ______________
 / ____________ \
 |/ __________ \|
 ||/ ________ \||
 |||/ ______ \|||
 ||||/      \||||
 |||||/  x  |||||
 |||||\_____/||||
 ||||\_______/|||
 |||\_________/||
 ||\___________/|
  \_____________/
```
Output:
```
5
```
## Notes
* The Valid line characters are `\/_|`
* `\` connects the top left and bottom right of itself.
* `/` connects the top right and bottom left of itself.
* `_` connects the left and right of itself
* `|` connects the top and bottom of itself
* A line will always be straight, and only consist of one of the line characters repeated n times.
* The x will always be lowercase, and it will always be the only one in the diagram.
* Adjecent refers to the x being exactly one character above, below, or besides.
* The x will always be next to exactly one Line.
* Tabs will never appear in the input.
* Input and Output may be any acceptable format.
* This is Code Golf, so Shortest Code Wins!
* HAVE FUN. DO IT. ENJOY YOURSELF.
[Reference Implementation](https://repl.it/EQ0Z/2)
  
[Answer]
# Python 3, ~~428~~ ~~408~~ ~~385~~ 378 bytes
Working, but has a ton of potential to be golfed. I'm a bit rusty. 
Assumes input is padded with spaces to make a rectangle.
EDIT: Thanks to @Artyer for 23 byte savings!
EDIT2: Wow I completely missed a 6 byte savings. Saved 1 more by swapping sides of an equals check.
```
*i,=map(list,input().split('\n'))
r=c=s=q=e=w=0
o=lambda y,x:len(i[0])>x>=0<=y<len(i)
d='\/_|'
for l in i:
 if'x'in l:r=i.index(l);c=l.index('x')
for a,b in(1,0),(0,1),(-1,0),(0,-1):
 y,x=r+a,c+b;f=o(y,x)and i[y][x]
 if f in d:s=f;w=d.index(f);q,e=y,x
k=lambda y,x,g=[1,1,0,1][w],v=[1,-1,1,0][w]:o(y,x)and s==i[y][x]and(exec('i[y][x]=0')or 1+k(y+g,x+v)+k(y-g,x-v))
print(k(q,e))
```
Expanded version with explanation:
```
inputtt='''  ______________.
 / ____________ \
 |/ __________ \|
 ||/ ________ \||
 |||/ ______ \|||
 ||||/      \||||
 |||||/  x  |||||
 |||||\_____/||||
 ||||\_______/|||
 |||\_________/||
 ||\___________/|
  \_____________/'''
# First, we get the input from STDIN and make it
# into a doubly-nested array
*input_text,=map(list,inputtt.split('\n'))
# A pretty cool Python trick to assign 0 to
# mulitple variables at once.
row=col=line_letter=line_row=line_col=line_char_index=0
# A function to check if a certian row and col is
# in bounds or not. Uses python's comparator chaining
in_bounds=lambda y,x:len(input_text[0])>x>=0<=y<len(input_text)
# A string to store all the line characters.
chars='\/_|'
# Search for the x
for line in input_text:
 # If this line contains the x...
 if'x'in line:
     # Mark the row and column
     row=input_text.index(line);col=line.index('x')
# For each direction...
for down,right in(1,0),(0,1),(-1,0),(0,-1):
 # Move in that direction
 y,x=row+down,col+right
 # If the position is in bounds, mark the char at that position
 line_found=in_bounds(y,x)and input_text[y][x]
 # If the char is a line char, set all the variables saying we found it
 if line_found in chars:
  line_letter=line_found
  line_char_index=chars.index(line_found)
  line_row,line_col=y,x
recur=lambda y,x,\
       # Find which directions we are supposed to recur in based on the line char
       g=[1,1,0,1][line_char_index],v=[1,-1,1,0][line_char_index]:\
       # If the char is in bounds and we are still on the line...
       in_bounds(y,x)and input_text[y][x]==line_letter and\
       # Set the spot to a 0, so we won't go back, increment,
       # and recur in both directions
       (exec('i[y][x]=0')or 1+recur(y+g,x+v)+recur(y-g,x-v))
# Finally, print the answer
print(recur(line_row,line_col))
```
[Answer]
# JavaScript (ES6), ~~165~~, 155 bytes
EDIT: Inlined *x* and *w*, to save some more bytes.
**Golfed**
(assumes input is padded with spaces to make a rectangle)
```
t=>([k=e=o=1,v=t.search`\n`+2,-1,-v].some(h=>i=({"|":v-1,"_":1,"/":v,"\\":v})[d=t[r=l=t.search`x`+h]]),[...t].map(_=>o+=(k&=t[l-=i]==d)+(e&=t[r+=i]==d)),o)
```
**Expanded**
```
/*
   G(<input string,space padded>) => line length
*/
G=t=> {
    /*
     ! Note that these two are inlined, in the "golfed" version !
     "w" - line "width"
     "x" - index of "x"
    */
    x=t.search`x`;
    w=t.search`\n`+1;
    /*
    Locate the "line"    
     l,r - left cursor, right cursor (for navigating along the line)
     k - left stop flag, e - right stop flag
     i - increment
     d - direction (char)
    */
    [k=e=o=1,v=w+1,-1,-w-1].some(h=>i=({"|":w,"_":1,"/":v,"\\":v})[d=t[r=l=x+h]]);
    /* 
     Travel along the line axis in both directions
    
     Note, the stop condition should rather be: while(k|e), 
     but we iterate over all the chars with map instead (as o is guaranteed to be < # chars),
     to save some space
    */
    [...t].map(_=>o+=(k&=t[l-=i]==d)+(e&=t[r+=i]==d));
    /* 
      Resulting line length
    */
    return o;
};
```
**Test**
```
G= 
t=>([k=e=o=1,v=t.search`\n`+2,-1,-v].some(h=>i=({"|":v-1,"_":1,"/":v,"\\":v})[d=t[r=l=t.search`x`+h]]),[...t].map(_=>o+=(k&=t[l-=i]==d)+(e&=t[r+=i]==d)),o);
[
G( 
 "| \n" +
 "| \n" +
 "|x\n" +
 "| \n" +
 "| \n"
),
G(
"|\\   \n" +
"| \\x \n" +
"|  \\ \n" +
"|___\\\n"
),
G(
"Diagram of a Wobbly Line:\n" +
"IRRELEVANTTEXT____       \n" +
"____     ____\/           \n" +
"    \___\/ X ;)           \n" +    
"      x                  \n"
),
G(
" ______________ \n"  +
"/ ____________ \\\n" +
"|/ __________ \\|\n" +
"||/ ________ \\||\n" + 
"|||/ ______ \\|||\n" +
"||||/      \\||||\n" +
"|||||/  x  |||||\n"  +
"|||||\_____\/||||\n" +
"||||\_______\/|||\n" +
"|||\_________\/||\n" +
"||\___________\/|\n" +
" \_____________\/\n"
)
]
```
Sample output (if you run this in Google Chrome Developer Tools console)
> 
> [5, 4, 3, 5]
> 
> 
> 
[Answer]
# Lua, 480 Bytes
Lua, Being the Verbose Language it is, doesn't beat the Python Answer. But it doesn't need to.
```
a=...s={}for _ in a:gmatch"[^\n]*"do s[#s+1]={}for S in _:gmatch"."do if S=="x"then x=#s[#s]+1y=#s end s[#s][#s[#s]+1]=S end end c="\\/_|"X={-1,1,1,0}Y={-1,-1,0,-1}for _,d in pairs({{x-1,y},{x,y-1},{x+1,y},{x,y+1}})do K=d[2]k=d[1]h=s[K]w=h and h[k]C=w and c:find(w)if C then n=1 j=k J=K while true do j=j+X[C]J=J+Y[C]if s[J]and s[J][j]==w then n=n+1 else break end end j=k J=K while true do j=j-X[C]J=J-Y[C]if s[J]and s[J][j]==w then n=n+1 else break end end print(n)break end end
```
Similar to my reference implementation, but takes an actual shot at golfing, and does some things a bit more smartly than before. Still could probably be golfed a bit better though.
## With comments.
```
a=... -- Take the input from the command line.
s={}  -- Store the string as a 2D Table, instead of a multiline string.
for _ in a:gmatch"[^\n]*"do -- For each new row.
    s[#s+1] = {}            -- Make a new sub-table. This is our line.
    for S in _:gmatch"."do  -- For every character.
        if S=="x"then x=#s[#s]+1y=#s end -- If it's an x, mark down the X and Y position of it.
        s[#s][#s[#s]+1]=S                -- Push the character. This could probably be better golfed.
    end
end
c="\\/_|"   -- The ascii line characters.
X={-1,1,1,0}    -- Their X Directionals.
Y={-1,-1,0,-1}  -- Their Y Directionals.
                -- These are inversed to get their opposite direction.
for _,d in pairs({{x-1,y},{x,y-1},{x+1,y},{x,y+1}}) do -- For each up down left and right.
    K=d[2]  -- K = y
    k=d[1]  -- k = x
    h=s[K]  -- h = the yth row
    w=h and h[k]    -- w = the xth character of the yth row, if the yth row exists.
    C=w and c:find(w) -- C = the id of the ascii line character, if w existed.
    if C then
        n=1 -- n = the length of the line.
        j=k -- Temp x
        J=K -- Temp y
        while true do
            j=j+X[C] -- Increment j by the directional of the ascii.
            J=J+Y[C] -- Ditto. for J
            if s[J]and s[J][j]==w then -- if it's still the same.
                n=n+1 -- Add 1 to the length.
            else
                break -- Or stop.
            end
        end
        j=k -- Re-assign the temps as their original.
        J=K
        while true do
            j=j-X[C] -- Search in the other direction.
            J=J-Y[C]
            if s[J]and s[J][j]==w then
                n=n+1
            else
                break
            end
        end
        print(n) -- Print the length.
        break
    end
end
```
[Answer]
# JavaScript (ES6), 175
Assuming input is padded with spaces to make a rectangle.
```
s=>(o=>{s.replace(/[_|\\/]/g,(c,p)=>[o,-o,1,-1].map(d=>s[p+d]=='x'?[q,k]=[p,c]:c));for(n=z=k>'_'?o:k>'\\'?-1:k>'/'?o-1:o+1;s[q+=z]==k||z<0&&(n=-1,z=-z);)n++})(~s.search`
`)||n
```
*Less golfed*
```
s=>{
  o = ~s.search`\n`; // offset between rows (negated)
  // look for a line character near an 'x'
  s.replace(/[_|\\/]/g, 
     (c,p)=> // for each line char 'c' in position 'p'
     [o,-o,1,-1].map(d=>s[p+d]=='x' // found a near 'x' ?
                        ?[q,k]=[p,c] // remember char and position
                        :c)
  );
  n=0;
  z=k>'_'?o:k>'\\'?-1:k>'/'?o-1:o+1; // offset to prev char of line
  while (s[q+=z]==k // move to left/top first
         || z<0 && (n=0,z=-z) // at left/top, go back and start counting
        )
    n++;
  return n-1;
}
```
**Test** Dots instead of spaces for clarity
```
f=
s=>(o=>{s.replace(/[_|\\/]/g,(c,p)=>[o,-o,1,-1].map(d=>s[p+d]=='x'?[q,k]=[p,c]:c));for(n=z=k>'_'?o:k>'\\'?-1:k>'/'?o-1:o+1;s[q+=z]==k||z<0&&(n=-1,z=-z);)n++})(~s.search`
`)||n
out=x=>O.textContent+=x
;["|.\n|.\n|x\n|.\n|.\n", "|\\...\n|.\\x.\n|..\\.\n|___\\\n"
,"Diagram of a Wobbly Line:\nIRRELEVANTTEXT...........\n____.....____/...........\n....\\___/.X.;)...........\n......x..................\n"
,"./ ____________ \\\n.|/ __________ \|\n.||/ ________ \\||\n.|||/ ______ \\|||\n.||||/      \\||||\n.|||||/  x  |||||\n.|||||\\_____/||||\n.||||\\_______/|||\n.|||\\_________/||\n.||\\___________/|\n. \\_____________/\n"].forEach(s=>out(s+f(s)+'\n\n'))
```
```
<pre id=O></pre>
```
]