feat: native clipboard image sync (Linux, opt-in sync_images)

internal/clipboard/clipboard.go

@@ -8,6 +8,12 @@
 // Each platform file defines its own New() constructor using //go:build tags.
 package clipboard
 
+import "errors"
+
+// ErrNoImage is returned by ImageClipboard.ReadImage when the clipboard holds
+// no image data. It is a normal condition, not an error.
+var ErrNoImage = errors.New("clipboard: no image")
+
 // Clipboard is the cross-platform clipboard interface.
 type Clipboard interface {
 	// Read returns the current text content of the clipboard.
@@ -17,3 +23,15 @@ type Clipboard interface {
 	// Write sets the clipboard text content.
 	Write(text string) error
 }
+
+// ImageClipboard is an optional interface implemented by platforms that can
+// read and write image data from the clipboard. Use a type assertion to detect
+// support: `if ic, ok := cb.(clipboard.ImageClipboard); ok { ... }`.
+type ImageClipboard interface {
+	// ReadImage returns the MIME type and raw bytes of the clipboard image.
+	// It returns ErrNoImage if the clipboard holds no image.
+	ReadImage() (mime string, data []byte, err error)
+
+	// WriteImage sets the clipboard image content.
+	WriteImage(mime string, data []byte) error
+}

internal/clipboard/clipboard_linux.go

@@ -3,6 +3,7 @@
 package clipboard
 
 import (
+	"bytes"
 	"fmt"
 	"os"
 	"os/exec"
@@ -70,3 +71,37 @@ func (c *linuxClipboard) Write(text string) error {
 	}
 	return nil
 }
+
+// ReadImage returns the PNG image from the clipboard, if any.
+func (c *linuxClipboard) ReadImage() (string, []byte, error) {
+	var args []string
+	if c.pasteCmd == "wl-paste" {
+		args = []string{"--type", "image/png"}
+	} else {
+		args = []string{"-selection", "clipboard", "-t", "image/png", "-o"}
+	}
+
+	cmd := exec.Command(c.pasteCmd, args...)
+	out, err := cmd.Output()
+	if err != nil || len(out) == 0 {
+		return "", nil, ErrNoImage
+	}
+	return "image/png", out, nil
+}
+
+// WriteImage writes image bytes to the clipboard using the given MIME type.
+func (c *linuxClipboard) WriteImage(mime string, data []byte) error {
+	var args []string
+	if c.copyCmd == "wl-copy" {
+		args = []string{"--type", mime}
+	} else {
+		args = []string{"-selection", "clipboard", "-t", mime}
+	}
+
+	cmd := exec.Command(c.copyCmd, args...)
+	cmd.Stdin = bytes.NewReader(data)
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("clipboard write image (%s): %w", c.copyCmd, err)
+	}
+	return nil
+}