Plot Viewer

Raven shows plots from its managed R terminal directly in VS Code via a built-in viewer panel. The viewer is backed by httpgd, a headless graphics device for R that exposes plots over a local HTTP/WebSocket server. Each R session gets its own plot panel with independent history, theme-aware backgrounds, and export to PNG, SVG, or PDF.

Prerequisites

Install the httpgd R package, version 2.0.2 or newer:

install.packages("httpgd")

No other R packages are required. Standard R, arf, and radian all work because Raven loads its bootstrap profile via R_PROFILE_USER.

Behavior

• Run any plotting code in the Raven R terminal (e.g., plot(1:10), ggplot(...) + geom_point()).
• The first plot from each R session opens its own "Raven Plot Viewer" panel in the column configured by raven.plot.viewerColumn (default: beside). The second session's panel is "Raven Plot Viewer 2", the third "Raven Plot Viewer 3", and so on (numbered per VS Code window). Each R terminal therefore gets a separate viewer with its own plot history.
• Subsequent plots from the same session update that session's panel without stealing focus from your editor.
• The viewer toolbar provides previous/next history navigation, remove the current plot, and three icon-only controls on the right: a share icon that opens a popover with Copy / PNG / SVG / PDF export actions, an Open in browser button, and an Apply VS Code theme toggle (a color-palette icon; the button background fills with the accent color when on). Hover any icon for a descriptive tooltip; the three right-side controls additionally expose aria-labels for assistive technologies, while the navigation/remove buttons rely on their title text. Right-clicking a plot copies it to the clipboard as PNG.
• If your terminal exits (R session ends), the last rendered plot stays visible with an "R session ended" indicator and must be closed manually.
• When a new R session is started or the panel is reopened, a subsequent plot from that new session will recreate the plot panel.

Color theme

The toolbar's Apply VS Code theme button recolors the live plot to match your active editor theme. When on, the plot's canvas background is hidden by a CSS overlay (the webview's editor background shows through), axis labels and tick text use --vscode-editor-foreground, and the strokes of other shape elements (axes, gridlines, and the outlines of shapes such as bars) use the same foreground color. When off, plots render with their R-supplied colors against a white canvas (the default — matches what plot() and ggplot() produce in any other R environment).

The setting is off by default, persists globally via VS Code's Memento, and applies to every open plot panel — toggling in one panel updates the others. There is no command-palette entry or keybinding; the toolbar button is the only control. (Parity with REditorSupport.R's r.plot.toggleStyle.)

Known limitations

• User-supplied colors are clobbered. Aesthetic mappings like aes(color = species) or plot(..., col = "red") are overridden by the CSS overlay's stroke: var(--vscode-editor-foreground) rule. If you want to see your palette, turn the toggle off.
• Text positions may shift. httpgd computes text widths at render time using R's chosen font; the CSS overlay forces --vscode-editor-font-family, which can produce different glyph widths and cause rotated tick labels or dense legends to overlap. For publication-quality output use Export PNG / SVG with the toggle off.
• Exported images aren't retinted. Copy, Save (PNG/SVG/PDF), and Open in browser always use httpgd's default (white) background so shared images stay portable across themes. The toggle is webview-only.
• Light themes change less. On a light theme the editor's background is near-white and the foreground is near-black, so the visible difference vs. the default plot is subtle.

Substrate (for the curious)

The toggle works by rendering the plot as inline SVG inside the webview's document (not as <img src=>). This lets CSS variables and selectors reach into the SVG nodes. The SVG is sanitized by DOMPurify before insertion (script tags, event handlers, external references, and inline style="..." attributes are stripped). Safe presentation properties (fill, stroke, font, etc.) are first migrated from style="..." to SVG presentation attributes, so plot colors survive the sanitizer.

Settings

Setting	Default	Description
raven.plot.viewerColumn	beside	Initial column when a new viewer opens.

The viewer's overall enable/disable is controlled by raven.rConsole.activation — there is no separate raven.plot.enabled toggle.

Troubleshooting

• No viewer appears. Confirm httpgd is installed (packageVersion("httpgd")) and that you're running R inside a terminal launched via Raven (the terminal profile dropdown's "R" entry, or any of Raven's send-to-R commands). Plots from terminals you opened manually outside Raven won't trigger the viewer.
• httpgd console message about installing or upgrading. Follow the printed install.packages("httpgd") instructions. Plots fall back to R's default graphics device until httpgd is available.
• The plot viewer doesn't activate at all. Check raven.rConsole.activation. If you have the REditorSupport extension enabled or you're using Positron, the default auto value leaves Raven's R-session features off. Set it to "enabled" to turn them on.