---
title: "custom-aesthetics-glue-strings"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{custom-aesthetics-glue-strings}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.width = 6,
  fig.height = 4
)
```

```{r setup}
library(ggsvg)
library(ggplot2)
```


# Introduction

Using custom `glue` strings within SVG allow for customised control 
of SVG rendering.

Rendering is not limited to CSS Selector properties.  You can insert text 
dynamically for parameters such as animation parameters, class names or 
really anything within an SVG.

## Test data

```{r}
test_df <- data.frame(
  x = runif(10), 
  y = runif(10), 
  count = sample(3:5, 10, T),
  type  = sample(c('a', 'b', 'c'), 10, T))

test_df
```



## Mapping  Aesthetics with `{glue}` strings

Here is a simple SVG consisting of 2 stacked circles - a big circle on the 
bottom and a small circle resting on top.

```{r fig.height=1}
snowman_txt <- '
  <svg viewBox="0 0 100 100 ">
    <circle id="top" cx="50" cy="20" r="20" fill="brown" stroke="black" />
    <circle id="bot" cx="50" cy="70" r="30" fill="brown" stroke="black" />
  </svg>
  '

grid::grid.draw( svg_to_rasterGrob(snowman_txt, width=800, height=800) )
```



In this example, I want to be able to map values to the fill colour for 
the top and bottom circles.

To do this I insert formatting strings as used in the `glue` package i.e.
insert new mapped variables `{{bot_fill}}` and `{{top_fill}}`.

When creating the plot, `ggsvg` will fill in these locations with appropriately
mapped variables dependend on what `scale_svg*()` are applied to tplot

```{r}
snowman_txt <- '
  <svg viewBox="0 0 100 100 ">
    <circle id="top"  cx="50" cy="20" r="20" fill="{{top_fill}}" stroke="black" />
    <circle id="bot"  cx="50" cy="70" r="30" fill="{{bot_fill}}" stroke="black" />
  </svg>
  '

ggplot(test_df) + 
  geom_point_svg(aes(x, y, top_fill = count), 
                 svg = snowman_txt, size = 20,
                 bot_fill='#aaaaaa') + 
  theme_bw() + 
  scale_svg_default() 
```



```{r}
ggplot(test_df) + 
  geom_point_svg(aes(x, y, top_fill = count), 
                 svg = snowman_txt, size = 20,
                 bot_fill='#aaaaaa') + 
  theme_bw() + 
  scale_svg_fill_viridis_c(aesthetics = "top_fill")
```






```{r}
ggplot(test_df) + 
  geom_point_svg(aes(x, y, 
                     top_fill = count, bot_fill = x), 
                 svg = snowman_txt, size = 20) + 
  theme_bw() + 
  scale_svg_fill_viridis_c(aesthetics = "top_fill") +
  scale_svg_fill_viridis_c(aesthetics = "bot_fill", option = 'A')
```



### <a name="preferred"></a> Preferred naming for custom aesthetics 

Custom aesthetics should be named with a `_[type]` suffix in order to
keep `{ggsvg}` working well with `{ggplot2}`.  E.g: 

* Use **`shade_fill`**. Not `shade` or `fill_shade`
* Use **`rect_size`**.  Not `size_rect` or `rect_bigness`
* Use **`path_alpha`**. Not `transparency`

The `type` suffix should be any of the standard ggplot aesthetics (fill, colour, size etc).

The `prefix` can be any name that makes sense to you.

Naming in this way will allow multiple fill aesthetics as long as they have a 
unique name.