Diff Viewer

The diff viewer widget displays file diffs in unified or side-by-side mode with syntax highlighting, hunk navigation, and intra-line change highlighting.

Basic Usage

import { ui } from "@rezi-ui/core";
import { defineWidget } from "@rezi-ui/core";
import type { DiffData } from "@rezi-ui/core";

const DiffViewer = defineWidget((ctx) => {
  const [scrollTop, setScrollTop] = ctx.useState(0);

  const diff: DiffData = {
    oldPath: "src/utils.ts",
    newPath: "src/utils.ts",
    status: "modified",
    hunks: [
      {
        oldStart: 1,
        oldCount: 3,
        newStart: 1,
        newCount: 4,
        header: "function hello()",
        lines: [
          { type: "context", content: "function hello() {" },
          { type: "delete", content: '  console.log("Hello");' },
          { type: "add", content: '  console.log("Hello, world!");' },
          { type: "add", content: '  console.log("Welcome");' },
          { type: "context", content: "}" },
        ],
      },
    ],
  };

  return ui.diffViewer({
    id: "my-diff",
    diff,
    mode: "unified",
    scrollTop,
    onScroll: setScrollTop,
  });
});

View Modes

Unified Mode

Traditional diff format with added/deleted lines interleaved:

ui.diffViewer({
  id: "unified-diff",
  diff,
  mode: "unified",
  scrollTop,
  onScroll: setScrollTop,
});

Output:

@@ -1,3 +1,4 @@ function hello()
  function hello() {
-   console.log("Hello");
+   console.log("Hello, world!");
+   console.log("Welcome");
  }

Side-by-Side Mode

Two-column layout showing old and new versions:

ui.diffViewer({
  id: "sidebyside-diff",
  diff,
  mode: "sideBySide",
  scrollTop,
  onScroll: setScrollTop,
});

Parsing Unified Diff

Parse standard unified diff output:

import { parseUnifiedDiff } from "@rezi-ui/core";

const diffText = `
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,3 +1,4 @@
 function hello() {
-  console.log("Hello");
+  console.log("Hello, world!");
+  console.log("Welcome");
 }
`;

const diff = parseUnifiedDiff(diffText);
// Returns: DiffData with oldPath, newPath, hunks, status

Intra-Line Highlighting

Highlight specific character ranges that changed within a line:

import { computeIntraLineHighlights } from "@rezi-ui/core";

const deletedLine = '  console.log("Hello");';
const addedLine = '  console.log("Hello, world!");';

const highlights = computeIntraLineHighlights(deletedLine, addedLine);
// Returns:
// {
//   deleted: [[18, 23]],  // "Hello" range
//   added: [[18, 31]],    // "Hello, world!" range
// }

const diff: DiffData = {
  oldPath: "file.ts",
  newPath: "file.ts",
  status: "modified",
  hunks: [
    {
      oldStart: 1,
      oldCount: 1,
      newStart: 1,
      newCount: 1,
      lines: [
        {
          type: "delete",
          content: deletedLine,
          highlights: highlights.deleted,
        },
        {
          type: "add",
          content: addedLine,
          highlights: highlights.added,
        },
      ],
    },
  ],
};

import { defineWidget } from "@rezi-ui/core";
import { navigateHunk, getHunkScrollPosition } from "@rezi-ui/core";

const DiffWithNav = defineWidget((ctx) => {
  const [focusedHunk, setFocusedHunk] = ctx.useState(0);
  const [scrollTop, setScrollTop] = ctx.useState(0);

  const goToNextHunk = () => {
    const nextHunk = navigateHunk(focusedHunk, "next", diff.hunks.length);
    setFocusedHunk(nextHunk);
    setScrollTop(getHunkScrollPosition(nextHunk, diff.hunks));
  };

  const goToPrevHunk = () => {
    const prevHunk = navigateHunk(focusedHunk, "prev", diff.hunks.length);
    setFocusedHunk(prevHunk);
    setScrollTop(getHunkScrollPosition(prevHunk, diff.hunks));
  };

  return ui.column({ gap: 1 }, [
    ui.row({ gap: 1 }, [
      ui.button({
        id: "prev-hunk",
        label: "← Previous Hunk",
        onPress: goToPrevHunk,
      }),
      ui.button({
        id: "next-hunk",
        label: "Next Hunk →",
        onPress: goToNextHunk,
      }),
      ui.text(`Hunk ${focusedHunk + 1} of ${diff.hunks.length}`),
    ]),
    ui.diffViewer({
      id: "nav-diff",
      diff,
      mode: "unified",
      scrollTop,
      focusedHunk,
      onScroll: setScrollTop,
    }),
  ]);
});

Hunk Actions

Stage/Unstage Hunks

ui.diffViewer({
  id: "git-diff",
  diff,
  mode: "unified",
  scrollTop,
  onScroll: setScrollTop,
  onStageHunk: (hunkIndex) => {
    console.log(`Stage hunk ${hunkIndex}`);
    // Call git add -p logic
  },
  onUnstageHunk: (hunkIndex) => {
    console.log(`Unstage hunk ${hunkIndex}`);
    // Call git reset -p logic
  },
});

Apply/Revert Hunks

ui.diffViewer({
  id: "patch-diff",
  diff,
  mode: "unified",
  scrollTop,
  onScroll: setScrollTop,
  onApplyHunk: (hunkIndex) => {
    console.log(`Apply hunk ${hunkIndex}`);
    // Apply this hunk to working copy
  },
  onRevertHunk: (hunkIndex) => {
    console.log(`Revert hunk ${hunkIndex}`);
    // Revert this hunk from working copy
  },
});

Expand/Collapse Hunks

import { defineWidget } from "@rezi-ui/core";

const CollapsibleDiff = defineWidget((ctx) => {
  const [expandedHunks, setExpandedHunks] = ctx.useState<readonly number[]>([]);

  return ui.diffViewer({
    id: "collapsible-diff",
    diff,
    mode: "unified",
    scrollTop: 0,
    expandedHunks,
    onScroll: () => {},
    onHunkToggle: (hunkIndex, expanded) => {
      if (expanded) {
        setExpandedHunks([...expandedHunks, hunkIndex]);
      } else {
        setExpandedHunks(expandedHunks.filter((i) => i !== hunkIndex));
      }
    },
  });
});

File Status

The status field indicates the type of change:

const addedFile: DiffData = {
  oldPath: "/dev/null",
  newPath: "src/new-file.ts",
  status: "added",
  hunks: [...],
};

const deletedFile: DiffData = {
  oldPath: "src/old-file.ts",
  newPath: "/dev/null",
  status: "deleted",
  hunks: [...],
};

const renamedFile: DiffData = {
  oldPath: "src/old-name.ts",
  newPath: "src/new-name.ts",
  status: "renamed",
  hunks: [...],
};

const modifiedFile: DiffData = {
  oldPath: "src/file.ts",
  newPath: "src/file.ts",
  status: "modified",
  hunks: [...],
};

Context Lines

Control how many context lines to show around changes:

ui.diffViewer({
  id: "context-diff",
  diff,
  mode: "unified",
  scrollTop,
  onScroll: setScrollTop,
  contextLines: 5, // Default: 3
});

Line Numbers

ui.diffViewer({
  id: "numbered-diff",
  diff,
  mode: "unified",
  scrollTop,
  onScroll: setScrollTop,
  lineNumbers: true, // Default: true
});

Git Workflow Example

import { defineWidget } from "@rezi-ui/core";
import { parseUnifiedDiff } from "@rezi-ui/core";

const GitDiffViewer = defineWidget((ctx) => {
  const [diffText, setDiffText] = ctx.useState("");
  const [scrollTop, setScrollTop] = ctx.useState(0);

  // Load diff from git
  ctx.useEffect(() => {
    const loadDiff = async () => {
      // Example: git diff HEAD~1 HEAD
      const result = await runGitCommand("git", ["diff", "HEAD~1", "HEAD"]);
      setDiffText(result.stdout);
    };
    loadDiff();
  }, []);

  const diff = parseUnifiedDiff(diffText);

  return ui.column({ gap: 1 }, [
    ui.row({ gap: 1 }, [
      ui.text(`${diff.oldPath} → ${diff.newPath}`, { variant: "heading" }),
      ui.spacer({ flex: 1 }),
      ui.badge({
        text: diff.status,
        variant:
          diff.status === "added"
            ? "success"
            : diff.status === "deleted"
              ? "error"
              : "default",
      }),
    ]),
    ui.diffViewer({
      id: "git-diff",
      diff,
      mode: "unified",
      scrollTop,
      onScroll: setScrollTop,
      onStageHunk: async (hunkIndex) => {
        // Stage this hunk
        await runGitCommand("git", ["add", "-p", diff.newPath]);
      },
    }),
  ]);
});

Diff Colors

Default color scheme (customizable via theme):

import { DIFF_COLORS } from "@rezi-ui/core";

// Default colors:
// {
//   addBg: { r: 35, g: 65, b: 35 },      // Added line background
//   deleteBg: { r: 65, g: 35, b: 35 },   // Deleted line background
//   addFg: { r: 150, g: 255, b: 150 },   // Added text
//   deleteFg: { r: 255, g: 150, b: 150 }, // Deleted text
//   hunkHeader: { r: 100, g: 149, b: 237 }, // Hunk header
//   lineNumber: { r: 100, g: 100, b: 100 }, // Line numbers
//   border: { r: 80, g: 80, b: 80 },     // Borders
// }

Flatten Hunks for Rendering

import { flattenHunks } from "@rezi-ui/core";
import type { FlattenedDiffLine } from "@rezi-ui/core";

const flattened: readonly FlattenedDiffLine[] = flattenHunks(diff.hunks);
// Returns array of:
// {
//   hunkIndex: number,
//   lineIndex: number,
//   line: DiffLine,
//   oldLineNum: number | null,
//   newLineNum: number | null,
// }

Props Reference

DiffViewerProps

Prop	Type	Default	Description
`id`	`string`	Required	Widget identifier
`diff`	`DiffData`	Required	Diff data to display
`mode`	`"unified" \| "sideBySide"`	Required	View mode
`scrollTop`	`number`	Required	Vertical scroll position
`onScroll`	`(scrollTop: number) => void`	Required	Scroll callback
`expandedHunks`	`readonly number[]`	—	Expanded hunk indices
`focusedHunk`	`number`	—	Currently focused hunk
`lineNumbers`	`boolean`	`true`	Show line numbers
`contextLines`	`number`	`3`	Context lines around changes
`focusedHunkStyle`	`TextStyle`	—	Focused hunk header style
`onHunkToggle`	`(hunkIndex: number, expanded: boolean) => void`	—	Hunk expand callback
`onStageHunk`	`(hunkIndex: number) => void`	—	Stage hunk callback
`onUnstageHunk`	`(hunkIndex: number) => void`	—	Unstage hunk callback
`onApplyHunk`	`(hunkIndex: number) => void`	—	Apply hunk callback
`onRevertHunk`	`(hunkIndex: number) => void`	—	Revert hunk callback
`focusable`	`boolean`	`true`	Include in tab order
`accessibleLabel`	`string`	—	Accessibility label
`focusConfig`	`FocusConfig`	—	Focus appearance
`scrollbarVariant`	`"minimal" \| "classic" \| "modern" \| "dots" \| "thin"`	`"minimal"`	Scrollbar style
`scrollbarStyle`	`TextStyle`	—	Scrollbar color

DiffData

Field	Type	Description
`oldPath`	`string`	Original file path
`newPath`	`string`	New file path
`hunks`	`readonly DiffHunk[]`	Diff hunks
`isBinary`	`boolean`	Binary file flag
`status`	`"added" \| "deleted" \| "modified" \| "renamed" \| "copied"`	File change status

DiffHunk

Field	Type	Description
`oldStart`	`number`	Original line range start
`oldCount`	`number`	Original line count
`newStart`	`number`	New line range start
`newCount`	`number`	New line count
`header`	`string`	Optional header text
`lines`	`readonly DiffLine[]`	Hunk lines

DiffLine

Field	Type	Description
`type`	`"context" \| "add" \| "delete"`	Line type
`content`	`string`	Line content
`oldLineNumber`	`number`	Original line number
`newLineNumber`	`number`	New line number
`highlights`	`readonly [number, number][]`	Intra-line change ranges

Code Editor - Multi-line code editing
Logs Console - Streaming output display

Location in Source

Implementation: packages/core/src/widgets/diffViewer.ts
Types: packages/core/src/widgets/types.ts:2014-2103
Factory: packages/core/src/widgets/ui.ts:diffViewer()

Primitives

Inputs

Data Display

Navigation

Overlays

Visualization

Layout

Feedback

Diff Viewer

Diff Viewer Widget

Basic Usage

View Modes

Unified Mode

Side-by-Side Mode

Parsing Unified Diff

Intra-Line Highlighting

Hunk Navigation

Hunk Actions

Stage/Unstage Hunks

Apply/Revert Hunks

Expand/Collapse Hunks

File Status

Context Lines

Line Numbers

Git Workflow Example

Diff Colors

Flatten Hunks for Rendering

Props Reference

DiffViewerProps

DiffData

DiffHunk

DiffLine

Location in Source

Build docs developers (and LLMs) love

Primitives

Inputs

Data Display

Navigation

Overlays

Visualization

Layout

Feedback

Documentation Index

​Diff Viewer Widget

​Basic Usage

​View Modes

​Unified Mode

​Side-by-Side Mode

​Parsing Unified Diff

​Intra-Line Highlighting

​Hunk Navigation

​Hunk Actions

​Stage/Unstage Hunks

​Apply/Revert Hunks

​Expand/Collapse Hunks

​File Status

​Context Lines

​Line Numbers

​Git Workflow Example

​Diff Colors

​Flatten Hunks for Rendering

​Props Reference

​DiffViewerProps

​DiffData

​DiffHunk

​DiffLine

​Related Widgets

​Location in Source

Build docs developers (and LLMs) love

Diff Viewer Widget

Basic Usage

View Modes

Unified Mode

Side-by-Side Mode

Parsing Unified Diff

Intra-Line Highlighting

Hunk Navigation

Hunk Actions

Stage/Unstage Hunks

Apply/Revert Hunks

Expand/Collapse Hunks

File Status

Context Lines

Line Numbers

Git Workflow Example

Diff Colors

Flatten Hunks for Rendering

Props Reference

DiffViewerProps

DiffData

DiffHunk

DiffLine

Related Widgets

Location in Source