ioslides WARNING: Undefined function 'Figure'

[ellie-ripley]

Checklist

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Issue

When knitting to ioslides, I am encountering "WARNING: Undefined function 'Figure'" in unexpected ways, and when I encounter it, the figure I expect to be produced is not produced. I have found two ways to generate the issue; both seem to have something to do with captions, so I believe they're related. The minimal example here contains both ways, along with explanation. (Note that you need some image.jpg around to make this example (not) work; it doesn't seem to matter what image it is, though.)

I've checked both output: ioslides (where the issue occurs) and output: html (where there are no warnings and the images display fine, but where I'm still confused about caption behaviour). It turns out that everything I've tried fits into one of two categories: either

	output:html	output:ioslides
warning	no	no
image	yes	yes
caption	no	no

or

	output:html	output:ioslides
warning	no	yes
image	yes	no
caption	yes	no

That is, the warning never occurs in output: html, and the image is always produced. But the caption only appears sometimes in output: html. (I don't know why.) And whenever the caption is displayed in output: html, the warning occurs and the image and caption both fail to appear in output: ioslides.

Session info

xfun::session_info("rmarkdown")
R version 4.5.2 (2025-10-31)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.7.1

Locale: en_AU.UTF-8 / en_AU.UTF-8 / en_AU.UTF-8 / C / en_AU.UTF-8 / en_AU.UTF-8

Package version:
  base64enc_0.1.3   bslib_0.9.0       cachem_1.1.0      cli_3.6.5         digest_0.6.39    
  evaluate_1.0.5    fastmap_1.2.0     fontawesome_0.5.3 fs_1.6.6          glue_1.8.0       
  graphics_4.5.2    grDevices_4.5.2   highr_0.11        htmltools_0.5.8.1 jquerylib_0.1.4  
  jsonlite_2.0.0    knitr_1.50        lifecycle_1.0.4   memoise_2.0.1     methods_4.5.2    
  mime_0.13         R6_2.6.1          rappdirs_0.3.3    rlang_1.1.6       rmarkdown_2.30   
  sass_0.4.10       stats_4.5.2       tinytex_0.58      tools_4.5.2       utils_4.5.2      
  xfun_0.54         yaml_2.3.11      

Pandoc version: 3.8.2.1

Example

---
title: example
author: example
output: ioslides
---

# First warning

## Warning 1
The following line generates the warning, and does not work to display an image 
in the rendered slide. With output: html, it generates no error and displays the image 
along with the caption. 

![caption](image.jpg)

# Suppressing the first warning

## Working options
This warning can be suppressed (and the image generated) by having some extra 
text in the markdown nearby. All of the following generate the image and produce 
no warning outputting to both html and ioslides; but none of them displays the caption 
in either output format.

## Text above 

Text on the line above
![caption](image.jpg)

## Text below

![caption](image.jpg)
Text on the line below

## Text before

Text preceding on the same line ![caption](image.jpg)

## Text after

![caption](image.jpg) Text following on the same line

# Second warning

## Warning 2
The code fence with options here is copied directly from 
https://bookdown.org/yihui/rmarkdown/ioslides-presentation.html. (The code inside 
is replaced with an image display rather than a plot.)

The image does not display and the warning is generated when outputting ioslides. 
When outputting html, there is no warning, and the image is displayed along with the caption.

```{r, cars, fig.cap="A scatterplot.", echo=FALSE}
knitr::include_graphics("image.jpg")
```

## Non-warning 2
This modified version of the code fence does not generate the warning and does 
display the image, outputting to either html or ioslides. No caption is displayed in 
either output format.

```{r, cars2, cars2.cap="A scatterplot.", echo=FALSE}
knitr::include_graphics("image.jpg")
```