icat: Report panics in the render function correctly

Also, only fallback to imagemagick on error when the engine is not
specified as builtin

kittens/icat/magick.go

@@ -5,6 +5,7 @@ package icat
 import (
 	"fmt"
 
+	"github.com/kovidgoyal/go-parallel"
 	"github.com/kovidgoyal/kitty/tools/tui/graphics"
 	"github.com/kovidgoyal/kitty/tools/utils/images"
 )
@@ -31,6 +32,11 @@ func Render(path string, ro *images.RenderOptions, frames []images.IdentifyRecor
 }
 
 func render_image_with_magick(imgd *image_data, src *opened_input) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = parallel.Format_stacktrace_on_panic(r, 1)
+		}
+	}()
 	err = src.PutOnFilesystem()
 	if err != nil {
 		return err

kittens/icat/native.go

@@ -4,13 +4,15 @@ package icat
 
 import (
 	"fmt"
+	"image"
+	"image/gif"
+
+	"github.com/kovidgoyal/go-parallel"
 	"github.com/kovidgoyal/kitty/tools/tty"
 	"github.com/kovidgoyal/kitty/tools/tui/graphics"
 	"github.com/kovidgoyal/kitty/tools/utils"
 	"github.com/kovidgoyal/kitty/tools/utils/images"
 	"github.com/kovidgoyal/kitty/tools/utils/shm"
-	"image"
-	"image/gif"
 
 	"github.com/kovidgoyal/exiffix"
 	"github.com/kovidgoyal/imaging"
@@ -151,6 +153,11 @@ func add_gif_frames(ctx *images.Context, imgd *image_data, gf *gif.GIF) error {
 }
 
 func render_image_with_go(imgd *image_data, src *opened_input) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = parallel.Format_stacktrace_on_panic(r, 1)
+		}
+	}()
 	ctx := images.Context{}
 	switch {
 	case imgd.format_uppercase == "GIF" && opts.Loop != 0:

kittens/icat/process_images.go

@@ -279,7 +279,7 @@ func process_arg(arg input_arg) {
 	var format string
 	var err error
 	imgd := image_data{source_name: arg.value}
-	if opts.Engine == "auto" || opts.Engine == "native" {
+	if opts.Engine == "auto" || opts.Engine == "builtin" {
 		c, format, err = image.DecodeConfig(f.file)
 		f.Rewind()
 		can_use_go = err == nil
@@ -299,12 +299,16 @@ func process_arg(arg input_arg) {
 		}
 		err = render_image_with_go(&imgd, &f)
 		if err != nil {
-			merr := render_image_with_magick(&imgd, &f)
+			if opts.Engine != "builtin" {
-			if merr != nil {
+				merr := render_image_with_magick(&imgd, &f)
-				report_error(arg.value, "Could not render image to RGB", err)
+				if merr != nil {
-				return
+					report_error(arg.value, "Could not render image to RGB", err)
+					return
+				}
+				err = nil
 			}
-			err = nil
+			report_error(arg.value, "could not render", err)
+			return
 		}
 	} else {
 		err = render_image_with_magick(&imgd, &f)

tools/utils/images/to_rgba.go

@@ -24,16 +24,17 @@ func (self *Context) run_paste(src imaging.Scanner, background image.Image, pos
 	var pix []uint8
 	switch v := background.(type) {
 	case *image.NRGBA:
-		i := background.(*image.NRGBA)
+		stride = v.Stride
-		stride = i.Stride
+		pix = v.Pix
-		pix = i.Pix
 	case *imaging.NRGB:
-		i := background.(*imaging.NRGB)
+		stride = v.Stride
-		stride = i.Stride
+		pix = v.Pix
-		pix = i.Pix
 	default:
 		panic(fmt.Sprintf("Unsupported image type: %v", v))
 	}
+	if len(pix) != background.Bounds().Dy()*stride {
+		panic(fmt.Sprintf("background image has insufficient pixel data. Bounds: %v Stride: %d", background.Bounds(), stride))
+	}
 	if err := self.SafeParallel(interRect.Min.Y, interRect.Max.Y, func(ys <-chan int) {
 		for y := range ys {
 			x1 := interRect.Min.X - pasteRect.Min.X