msgviewer: implement inline image viewing

Implement inline image viewing for jpeg, png, bmp, tiff, and webp
formats. When a user has no configured image filter and the image is
supported and the terminal has either sixel or kitty image protocol
support, the image will be displayed in the message viewer.

Always clear the screen before each draw. This call is necessary in
vaxis to allow for images to be cleared properly between renders. There
is no performance impact: the call only resets each cell to a blank
cell, and aerc will redraw each one already.

Changelog-added: Inline image previews when no filter is defined for
 `image/*` and the terminal supports it.
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 99 insertions, 2 deletions

diff --git a/app/msgviewer.go b/app/msgviewer.go
index e45a6d3e..8d2e380a 100644
--- a/app/msgviewer.go
+++ b/app/msgviewer.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"image"
 	"io"
 	"os"
 	"os/exec"
@@ -24,8 +25,28 @@ import (
 	"git.sr.ht/~rjarry/aerc/log"
 	"git.sr.ht/~rjarry/aerc/models"
 	"git.sr.ht/~rjarry/go-opt"
+	"git.sr.ht/~rockorager/vaxis"
+	"git.sr.ht/~rockorager/vaxis/widgets/align"
+
+	// Image support
+	_ "image/jpeg"
+	_ "image/png"
+
+	_ "golang.org/x/image/bmp"
+	_ "golang.org/x/image/tiff"
+	_ "golang.org/x/image/webp"
 )
 
+// All imported image types need to be explicitly stated here. We want to check
+// if we _can_ display something before we download it
+var supportedImageTypes = []string{
+	"image/jpeg",
+	"image/png",
+	"image/bmp",
+	"image/tiff",
+	"image/webp",
+}
+
 var _ ProvidesMessages = (*MessageViewer)(nil)
 
 type MessageViewer struct {
@@ -405,6 +426,11 @@ type PartViewer struct {
 	noFilter   *ui.Grid
 	uiConfig   *config.UIConfig
 	copying    int32
+	inlineImg  bool
+	image      image.Image
+	graphic    vaxis.Image
+	width      int
+	height     int
 
 	links []string
 }
@@ -535,7 +561,27 @@ func NewPartViewer(
 
 func (pv *PartViewer) SetSource(reader io.Reader) {
 	pv.source = reader
-	pv.attemptCopy()
+	switch pv.inlineImg {
+	case true:
+		pv.decodeImage()
+	default:
+		pv.attemptCopy()
+	}
+}
+
+func (pv *PartViewer) decodeImage() {
+	atomic.StoreInt32(&pv.copying, copying)
+	go func() {
+		defer log.PanicHandler()
+		defer pv.Invalidate()
+		defer atomic.StoreInt32(&pv.copying, 0)
+		img, _, err := image.Decode(pv.source)
+		if err != nil {
+			log.Errorf("error decoding image: %v", err)
+			return
+		}
+		pv.image = img
+	}()
 }
 
 func (pv *PartViewer) attemptCopy() {
@@ -711,7 +757,13 @@ func (pv *PartViewer) Invalidate() {
 
 func (pv *PartViewer) Draw(ctx *ui.Context) {
 	style := pv.uiConfig.GetStyle(config.STYLE_DEFAULT)
-	if pv.filter == nil {
+	switch {
+	case pv.filter == nil && canInline(pv.part.FullMIMEType()) && pv.err == nil:
+		pv.inlineImg = true
+	case pv.filter == nil:
+		// No filter, can't inline, and/or we attempted to inline an image
+		// and resulted in an error (maybe because of a bad encoding or
+		// the terminal doesn't support any graphics protocol).
 		ctx.Fill(0, 0, ctx.Width(), ctx.Height(), ' ', style)
 		pv.noFilter.Draw(ctx)
 		return
@@ -728,12 +780,48 @@ func (pv *PartViewer) Draw(ctx *ui.Context) {
 	if pv.term != nil {
 		pv.term.Draw(ctx)
 	}
+	if pv.image != nil && (pv.resized(ctx) || pv.graphic == nil) {
+		// This path should only occur on resizes or the first pass
+		// after the image is downloaded and could be slow due to
+		// encoding the image to either sixel or uploading via the kitty
+		// protocol. Generally it's pretty fast since we will only ever
+		// be downsizing images
+		vx := ctx.Window().Vx
+		if pv.graphic == nil {
+			var err error
+			pv.graphic, err = vx.NewImage(pv.image)
+			if err != nil {
+				log.Errorf("Couldn't create image: %v", err)
+				return
+			}
+		}
+		pv.graphic.Resize(pv.width, pv.height)
+	}
+	if pv.graphic != nil {
+		w, h := pv.graphic.CellSize()
+		win := align.Center(ctx.Window(), w, h)
+		pv.graphic.Draw(win)
+	}
 }
 
 func (pv *PartViewer) Cleanup() {
 	if pv.term != nil {
 		pv.term.Close()
 	}
+	if pv.graphic != nil {
+		pv.graphic.Destroy()
+	}
+}
+
+func (pv *PartViewer) resized(ctx *ui.Context) bool {
+	w := ctx.Width()
+	h := ctx.Height()
+	if pv.width != w || pv.height != h {
+		pv.width = w
+		pv.height = h
+		return true
+	}
+	return false
 }
 
 func (pv *PartViewer) Event(event tcell.Event) bool {
@@ -779,3 +867,12 @@ func (hv *HeaderView) Draw(ctx *ui.Context) {
 func (hv *HeaderView) Invalidate() {
 	ui.Invalidate()
 }
+
+func canInline(mime string) bool {
+	for _, ext := range supportedImageTypes {
+		if mime == ext {
+			return true
+		}
+	}
+	return false
+}