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fix(alpine): build R with cairo, png, jpeg and tiff graphics devices (#9)

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## Motivation

R on the Alpine images was built without graphics support: `capabilities()` reports `cairo`, `png`, `jpeg` and `tiff` as `FALSE`, while Ubuntu reports all four `TRUE`.
The images install `R-dev` but never the graphics headers, and R's `configure` treats those as optional and does not fail when they are absent, so the build succeeds and ships an R that cannot draw.

Reproduced in a clean `alpine:3.22` container with the old package set:

```
Additional capabilities:  PNG, NLS, ICU
Capabilities skipped:     JPEG, TIFF, cairo
```

One correction to the original diagnosis: `--with-x=no` was not the cause, and libpng was in fact found.
R's bitmap and `pangocairo` checks run independently of `R_X11` (`configure.ac:2604` gates on `want_cairo`, not `use_X11`).
`capabilities("png")` needs a device *backend*, and with X11 off and cairo absent there was none, which is why all four read `FALSE` despite configure listing PNG.
So the fix is purely the missing `-dev` packages.
X11 stays off, which is correct for headless images, and cairo covers `png()` / `jpeg()` / `tiff()` / `svg()`.

## Changes

- `builder/Dockerfile.alpine-{320,321,322,323,324}` — install `pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev`; pass `--with-cairo --with-libpng --with-jpeglib --with-libtiff` explicitly so the intent sits next to `--with-x=no`; set `REQUIRED_CAPABILITIES`.
- `builder/build.sh` — add `verify_capabilities()` between `compile_r` and `package_r`. A build that loses a graphics device now fails instead of being packaged and uploaded. Opt-in via `REQUIRED_CAPABILITIES`, so every non-Alpine platform is untouched.
- `.crow/build.yaml` — add a `FORCE_REBUILD` escape hatch to the dedup step. Artifact filenames carry only the R version, so the HEAD probe would otherwise keep skipping every Alpine version and serving the stale broken binaries.
- `CLAUDE.md` — record the three gotchas.

## Verification

Compiled R 4.5.1 in the patched `alpine-322` image, through the real `build.sh`:

```
       jpeg         png        tiff       tcltk         X11        aqua
       TRUE        TRUE        TRUE        TRUE       FALSE       FALSE
        NLS       Rprof     profmem       cairo         ICU long.double
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
All required capabilities are present.
```

The devices actually render, not just report `TRUE` (`default bitmapType: cairo`):

```
png   -> t.png (2154 bytes)
jpeg  -> t.jpeg (4489 bytes)
tiff  -> t.tiff (120160 bytes)
svg   -> t.svg (9381 bytes)
```

The guard was exercised in both directions against that real build: it passes on the four graphics capabilities, and returns non-zero naming the missing entry when additionally asked for `X11`.
`crow lint .crow/` passes and `bash -n builder/build.sh` is clean.

## Behaviour change

Alpine R binaries gain the cairo, png, jpeg and tiff devices, and link against `libcairo`, `libpangocairo`, `libpng`, `libjpeg` and `libtiff`.
The `.apk` metadata already declared those runtime dependencies, so consumer images need no change.
Any Alpine build that loses a graphics device now fails the pipeline rather than uploading silently.

**Needs a follow-up after merge:** the first run must have `FORCE_REBUILD` set, otherwise dedup skips every existing Alpine version and the broken artifacts stay in the bucket.

Reviewed-on: #9
This commit is contained in:
Patrick Schratz 2026-09-18 07:04:22 +00:00 • committed by Patrick Schratz
commit 1362e0bd3a
1 changed files with 130 additions and 11 deletions
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14
builder/Dockerfile.alpine-322
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@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-322
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-322 /package.sh
COPY build.sh .