dd basic drag thumbnail support to dnd kitten

kittens/dnd/drag.go

@@ -3,6 +3,7 @@ package dnd
 import (
 	"errors"
 	"fmt"
+	"image"
 	"io"
 	"maps"
 	"os"
@@ -11,6 +12,7 @@ import (
 	"strings"
 
 	"github.com/emmansun/base64"
+	"github.com/kovidgoyal/imaging"
 	"github.com/kovidgoyal/kitty/tools/tui/loop"
 	"github.com/kovidgoyal/kitty/tools/utils"
 	"github.com/kovidgoyal/kitty/tools/utils/streaming_base64"
@@ -50,6 +52,72 @@ type drag_status struct {
 	remote_item_write_id   loop.IdType
 }
 
+func find_drag_image(drag_sources map[string]*drag_source) image.Image {
+	for mime, ds := range drag_sources {
+		if strings.HasPrefix(mime, "image/") && ds.path != "" {
+			q, err := imaging.Open(ds.path)
+			if err == nil {
+				return q
+			}
+		}
+	}
+	var uri_list []string
+	if ds := drag_sources["text/uri-list"]; ds != nil && len(ds.data) > 0 {
+		if q, err := parse_uri_list(string(ds.data)); err == nil {
+			for _, path := range q {
+				if path != "" {
+					uri_list = append(uri_list, path)
+				}
+			}
+		}
+	}
+	for _, path := range uri_list {
+		q, err := imaging.Open(path)
+		if err == nil {
+			return q
+		}
+	}
+	// TODO: Try to generate an image based preview using the machinery from the choose-files kitten
+	return nil
+}
+
+func (dnd *dnd) set_drag_image() (err error) {
+	img := dnd.drag_thumbnail
+	if img == nil {
+		img = find_drag_image(dnd.drag_sources)
+	}
+	if img == nil {
+		return
+	}
+	num_channels := utils.IfElse(imaging.IsOpaque(img), 3, 4)
+	sz := dnd.opts.DragThumbnailSize
+	if max(img.Bounds().Dx(), img.Bounds().Dy()) > sz {
+		w, h := 0, 0
+		if img.Bounds().Dx() >= img.Bounds().Dy() {
+			w = sz
+		} else {
+			h = sz
+		}
+		img = imaging.ResizeWithOpacity(img, w, h, imaging.Lanczos, num_channels == 3)
+		if dnd.drag_thumbnail != nil {
+			dnd.drag_thumbnail = img
+		}
+	}
+	var pix []byte
+	if imaging.IsOpaque(img) {
+		_, pix = 3, imaging.AsRGBData8(img)
+	} else {
+		pix = imaging.AsRGBAData8(img)
+	}
+	cmd := DC{
+		Type: 'p', X: -1, Y: utils.IfElse(num_channels == 3, 24, 32), Xp: img.Bounds().Dx(), Yp: img.Bounds().Dy(),
+		Payload: pix}
+	dnd.lp.QueueDnDData(cmd)
+	cmd.Payload = nil
+	dnd.lp.QueueDnDData(cmd)
+	return nil
+}
+
 func (dnd *dnd) on_potential_drag_start(cell_x, cell_y int) (err error) {
 	if !dnd.allow_drags || dnd.drag_status.active {
 		return
@@ -72,7 +140,11 @@ func (dnd *dnd) on_potential_drag_start(cell_x, cell_y int) (err error) {
 		}
 	}
 	dnd.drag_status.offered_mimes = mimes
-	// TODO: set the drag image
+	err = dnd.set_drag_image()
+	if err != nil {
+		dnd.finish_drag("EIO")
+		return err
+	}
 	dnd.lp.QueueDnDData(DC{Type: 'P', X: -1}) // start drag
 	dnd.drag_status.active = true
 

kittens/dnd/main.go

@@ -5,6 +5,7 @@ package dnd
 import (
 	"bytes"
 	"fmt"
+	"image"
 	"io"
 	"maps"
 	"net/url"
@@ -15,6 +16,7 @@ import (
 	"strings"
 	"sync/atomic"
 
+	"github.com/kovidgoyal/imaging"
 	"github.com/kovidgoyal/kitty/tools/cli"
 	"github.com/kovidgoyal/kitty/tools/tty"
 	"github.com/kovidgoyal/kitty/tools/tui/loop"
@@ -78,6 +80,7 @@ type dnd struct {
 	opts                     *Options
 	drop_dests               map[string]*drop_dest
 	drag_sources             map[string]*drag_source
+	drag_thumbnail           image.Image
 	allow_drops, allow_drags bool
 
 	lp                                     *loop.Loop
@@ -382,6 +385,12 @@ func dnd_main(cmd *cli.Command, opts *Options, args []string) (rc int, err error
 		}
 	}
 	dnd := dnd{opts: opts, drop_dests: drop_dests, drag_sources: drag_sources}
+	if opts.DragThumbnail != "" {
+		if dnd.drag_thumbnail, err = imaging.Open(opts.DragThumbnail); err != nil {
+			return 1, err
+		}
+	}
+
 	defer func() {
 		dnd.end_drop(false)
 		if dnd.confirm_drop.staging_dir != nil {

kittens/dnd/main.py

@@ -33,6 +33,19 @@ default=disallowed
 type=choices
 Allow dropping anywhere, not just on the Copy or Move drop regions. Dropping anywhere will perform
 the specified action.
+
+
+--drag-thumbnail
+Path to an image to use as the drag icon when starting a drag. Must be in PNG/JPEG/GIF/WEBP formats.
+Other formats will require the presence of ImageMagick on the system to load the image.
+If not specified, an image is derived based on the data being dragged.
+
+
+--drag-thumbnail-size
+default=512
+type=int
+The thumbnail size for the image used as the drag icon. Images larger than this size are downscaled.
+Note that the terminal may reject the drag if the image is too large.
 '''.format