WALTER

https://www.reaper.fm/sdk/walter/
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WALTER is a Window Arrangement Logic Template Engine for REAPER that enables customization of the...
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### Sparse Coordinate List Examples

Source: https://www.reaper.fm/sdk/walter/walter.php

Examples showing equivalent assignments using sparse coordinate syntax.

```WALTER
set foo 1.0@w
  and
set foo [0 0 1.0 0]
...or
set foo recarm@w
  and
set foo [0 0 recarm 0]
```

--------------------------------

### Define a Mixer Mute Button Layout

Source: https://www.reaper.fm/sdk/walter/walter.php

Example of a basic layout definition for a mixer control panel element.

```WALTER
Layout "Mute button mixer"
  clear mcp.*
  set mcp.size [20 20]
  set mcp.mute [0 0 20 20 0 0 1 1]
EndLayout
```

--------------------------------

### Define user parameters

Source: https://www.reaper.fm/sdk/walter/walter.php

Creates ReaScript-accessible parameters for theme adjustment.

```WALTER
;                variable name     description for user   default  minimum maximum
define_parameter "hide_mute"       "Hide Mute Button"     0        0       1

; later in script, hide tcp.mute if hide_mute is set
set tcp.mute hide_mute==1 [0]

;  note that variable name is used to make the value persist for this theme
```

--------------------------------

### Set Z-order with front

Source: https://www.reaper.fm/sdk/walter/walter.php

Brings UI elements to the front of the Z order. Element ordering is static.

```WALTER
front tcp.solo
front tcp.mute
```

--------------------------------

### WALTER Expression Shorthand

Source: https://www.reaper.fm/sdk/walter/walter.php

Demonstrates equivalent ways to reference the current value of a destination variable using shorthand.

```text
  set var w<100 [0]
  set var w<100 [0] .
  set var w<100 [0] var
```

--------------------------------

### Accessing coordinate list components

Source: https://www.reaper.fm/sdk/walter/walter.php

Demonstrates how to extract specific scalar values from a coordinate list using curly brace indexing.

```WALTER
   set tmp [1 2 3 4 5 6 7 8]
   tmp{x} or tmp{0}  -- first item in coordinate_list (1)
   tmp{y} or tmp{1}
   tmp{w} or tmp{2}
   tmp{h} or tmp{3}
   tmp{ls} or tmp{4}
   tmp{ts} or tmp{5}
   tmp{rs} or tmp{6}
   tmp{bs} or tmp{7}  -- last item in coordinate_list (8)
```

--------------------------------

### Using coordinate list variables in expressions

Source: https://www.reaper.fm/sdk/walter/walter.php

Shows how to substitute scalar indices into conditional expressions and coordinate list definitions.

```WALTER
  set foo w>2 [1] [0 1 2 3 4 5 6 7]
```

```WALTER
  set foo w>tmp{y} [1] [0 1 tmp{y} 3 4 5 6 7]
```

--------------------------------

### Define WALTER macros

Source: https://www.reaper.fm/sdk/walter/walter.php

Creates reusable macros with parameters. Use ## for string concatenation.

```WALTER
macro setall dest src
   set dest [src src src src src src src src]
   set master.##dest dest
endmacro
setall tcp.mute 1  ; set tcp.mute [1 1 1 1 1 1 1], set master.tcp.mute tcp.mute
```

--------------------------------

### Coordinate List Structure

Source: https://www.reaper.fm/sdk/walter/walter.php

Visual breakdown of the 8-value coordinate list used for UI element positioning and scaling.

```WALTER
[0 0 20 20 0 0 1 1]
 ^ ^ ^  ^  ^ ^ ^ ^
 | | |  |  | | | |
 | | |  |  | | | \ bottom attach: scale the bottom edge of control with parent height by this factor
 | | |  |  | | \ right attach: scale the right edge of control with parent width by this factor
 | | |  |  \ top attach: scale the top edge of control with parent height by this factor
 | | |  \ left attach: scale the left edge of control with parent width by this factor
 | | \ height: height of control (before edge scaling, if any)
 | \ width: width of control (before edge scaling, if any)
 \ top: top edge of control (before edge scaling, if any)
 \ left: left edge of control (before edge scaling, if any)
```

--------------------------------

### Define custom elements

Source: https://www.reaper.fm/sdk/walter/walter.php

Registers a custom UI element. The name must contain 'custom.' and can function as a button or text label.

```WALTER
custom tcp.custom.xyz text_label command_id accessibility_description button_image
```

--------------------------------

### Implicit coordinate list indexing

Source: https://www.reaper.fm/sdk/walter/walter.php

Illustrates how omitting the index in a coordinate list reference defaults to the current index.

```WALTER
  set tmp [1 2 3 4]
  set foo [0 0 tmp tmp]
    and
  set foo [0 0 tmp{2} tmp{3}]
```

--------------------------------

### Scalar Value Assignment

Source: https://www.reaper.fm/sdk/walter/walter.php

Demonstrates how scalar values are applied across coordinate lists.

```WALTER
set foo 1.0
  and
set foo [1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0]
...or
set foo h
  and
set foo [h h h h h h h h]
```

--------------------------------

### Sparse Coordinate List Syntax

Source: https://www.reaper.fm/sdk/walter/walter.php

Syntax for assigning a scalar value to a specific coordinate index.

```WALTER
scalar@x or scalar@0
scalar@y or scalar@1
scalar@w or scalar@2
scalar@h or scalar@3
scalar@ls or scalar@4
scalar@ts or scalar@5
scalar@rs or scalar@6
scalar@bs or scalar@7
```

--------------------------------

### Set WALTER attributes

Source: https://www.reaper.fm/sdk/walter/walter.php

Assigns expressions to attributes or user variables. Avoid using '.' in user variable names as they are reserved.

```WALTER
set tcp.mute [0 0 10 10]
set myvar w<100 [0 0 10 10] [20 20 10 10]
set myvar w<100 [0 0 10 10] w<200 [20 20 10 10] [40 40 10 10]
```

--------------------------------

### Define WALTER values

Source: https://www.reaper.fm/sdk/walter/walter.php

Acts as a preprocessor to define values or coordinate sets for reuse.

```WALTER
def square10 10 10
set tcp.mute [0 0 square10] ; sets tcp.mute to [0 0 10 10]
def two_coords [10 10 0 0] [0 0 10 10]
set tcp.mute + two_coords   ; sets tcp.mute to [10 10 10 10]
set tcp.mute w<100 two_coords ; like set.tcp.mute w<100 [10 10 0 0] [0 0 10 10]
```

--------------------------------

### Predefined Scalar Variables

Source: https://www.reaper.fm/sdk/walter/walter.php

Lists the available read-only scalar variables for use in WALTER expressions.

```text
        w                 -- width of parent, pixels
        h                 -- height of parent, pixels
        reaper_version    -- REAPER version (i.e. 4.25)_(requires v4.15+)_
        os_type           -- (REAPER 5.972+) - set to 0 on Windows, 1 on macOS (pre v7.70)
                             2 on Linux (pre v7.70). Note on v7.71+, os_type will be 0 for
                             all platforms, unless the theme specifies "want_os_type 1" in 
                             rtconfig.txt, in which case macOS will be 3, on Linux will be 4.
                             (v7.70 will always report 3/4 for macOS/Linux)
```

--------------------------------

### WALTER Operator String Syntax

Source: https://www.reaper.fm/sdk/walter/walter.php

Defines the available comparison and combinator operators for use in WALTER expressions.

```text
Comparisons:
        val1<val2     --   if val1 is less than val2, use first expression, otherwise second
        val1>val2     --   if val1 is greater than val2 ...
        val1<=val2     --   if val1 is less than or equal to val2, use first expression, otherwise second
        val1>=val2     --   if val1 is greater than or equal to val2 ...
        val1==val2    --   if val1 equals val2 ...
        val1!=val2    --   if val1 does not equal val2 ...
        ?val1         --   if val1 is nonzero ...
        !val1         --   if val1 is zero ...
        val1&val2     --   bitwise AND (if any bit is set in both val1 and val2)

Combinators:
        +             --   sum first expression and second expression
        -             --   subtract second expression from first expression  _(REAPER 5.0+)_
        *             --   multiply first expression and second expression
        /             --   divide first expression by second expression _(REAPER 5.0+)_
        +:val1:val2   --   val1*(first expression) + val2*(second expression)
        *:val1:val2   --   ((first expression)+[val1 val1...])*((second expression)+[val2 val2...])
```

--------------------------------

### Clear WALTER attributes

Source: https://www.reaper.fm/sdk/walter/walter.php

Clears specific attributes or wildcard lists of attributes to empty.

```WALTER
clear tcp.mute
clear tcp.*
```

--------------------------------

### Reset WALTER attributes

Source: https://www.reaper.fm/sdk/walter/walter.php

Resets attributes or wildcard lists of attributes to their default settings.

```WALTER
reset tcp.mute
reset tcp.*
```
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