a start on porting dockerfile to gha

Author: cpsievert

.github/workflows/R-CMD-check.yaml

@@ -30,14 +30,16 @@ jobs:
           - {os: windows-latest, r: 'release'}
           - {os: windows-latest, r: '3.6', rspm: "https://packagemanager.rstudio.com/cran/latest"}
           - {os: ubuntu-18.04,   r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest", http-user-agent: "R/4.1.0 (ubuntu-18.04) R (4.1.0 x86_64-pc-linux-gnu x86_64 linux-gnu) on GitHub Actions" }
-          - {os: ubuntu-18.04,   r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
+          # visual tests are only run on linux r-release since the svg generator (orca) isn't cross-platform
+          - {os: ubuntu-18.04,   r: 'release', vdiffr: true, rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
           - {os: ubuntu-18.04,   r: 'oldrel',  rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
           - {os: ubuntu-18.04,   r: '3.6',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
           - {os: ubuntu-18.04,   r: '3.5',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
           - {os: ubuntu-18.04,   r: '3.4',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
 
     env:
       RSPM: ${{ matrix.config.rspm }}
+      VDIFFR: ${{ matrix.config.vdiffr }}
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
 
     steps:
@@ -72,6 +74,31 @@ jobs:
           pak::local_system_requirements(execute = TRUE)
           pak::pkg_system_requirements("rcmdcheck", execute = TRUE)
         shell: Rscript {0}
+        
+      - name: Install google chrome
+        if: runner.vdiffr == true
+        run: |
+          wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
+          sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google-chrome.list'
+          apt-get update -y
+          apt-get install -y google-chrome-stable
+        shell: bash
+      
+      # TODO: maybe this should install via conda or npm instead?
+      - name: Install orca
+        if: runner.vdiffr == true
+        run: |
+          apt-get -y update
+          apt-get install -y libgtk2.0-0 libgconf-2-4 xvfb xauth libxtst6 libxss1 libnss3 libasound2 desktop-file-utils
+          mkdir -p /opt/orca
+          cd /opt/orca
+          wget https://github.com/plotly/orca/releases/download/v1.3.1/orca-1.3.1.AppImage
+          chmod +x orca-1.3.1.AppImage
+          ./orca-1.3.1.AppImage --appimage-extract
+          rm orca-1.3.1.AppImage
+          printf '#!/bin/bash \nargs=("$@") \nif [[ ! " ${args[@]} " =~ "--no-sandbox" ]]; then \n    args+=("--no-sandbox") \nfi \nxvfb-run --auto-servernum --server-args "-screen 0 640x480x24" /opt/orca/squashfs-root/orca "${args[@]}"' > /usr/bin/orca \
+          chmod +x /usr/bin/orca
+        shell: bash
 
       - name: Install dependencies
         run: |