3 files changed, 29 insertions, 19 deletions
diff --git a/src/local/container.nim b/src/local/container.nim
index 6bdfe64b..5632bd88 100644
--- a/src/local/container.nim
+++ b/src/local/container.nim
@@ -122,6 +122,8 @@ type
     offx*: int # same as CanvasImage.offx
     dispw*: int # same as CanvasImage.dispw
     erry*: int # same as CanvasImage.offy % 6
+    # whether the image has transparency, *disregarding the last row*
+    transparent*: bool
 
   Container* = ref object of RootObj
     # note: this is not the same as source.request.url (but should be synced
diff --git a/src/local/pager.nim b/src/local/pager.nim
index ec242472..e8034af7 100644
--- a/src/local/pager.nim
+++ b/src/local/pager.nim
@@ -586,7 +586,6 @@ proc loadCachedImage(pager: Pager; container: Container; image: PosBitmap;
       url = newURL("img-codec+x-sixel:encode").get
       headers.add("Cha-Image-Sixel-Halfdump", "1")
       headers.add("Cha-Image-Sixel-Palette", $pager.term.sixelRegisterNum)
-      headers.add("Cha-Image-Background-Color", $image.bgcolor)
       headers.add("Cha-Image-Offset", $offx & 'x' & $erry)
       headers.add("Cha-Image-Crop-Width", $dispw)
     of imKitty:
@@ -630,6 +629,11 @@ proc loadCachedImage(pager: Pager; container: Container; image: PosBitmap;
       cachedImage.data = blob
       cachedImage.state = cisLoaded
       cachedImage.cacheId = cacheId
+      if imageMode == imSixel and 4 < blob.size:
+        #TODO this should be a response header, but loader can't send us
+        # those yet...
+        let u = cast[ptr UncheckedArray[uint8]](blob.buffer)[4]
+        cachedImage.transparent = u == 1
     )
   )
   container.cachedImages.add(cachedImage)
@@ -660,7 +664,7 @@ proc initImages(pager: Pager; container: Container) =
     let canvasImage = pager.term.loadImage(cached.data, container.process,
       imageId, image.x - container.fromx, image.y - container.fromy,
       image.width, image.height, image.x, image.y, pager.bufWidth,
-      pager.bufHeight, erry, offx, dispw)
+      pager.bufHeight, erry, offx, dispw, cached.transparent)
     if canvasImage != nil:
       newImages.add(canvasImage)
   pager.term.clearImages(pager.bufHeight)
diff --git a/src/local/term.nim b/src/local/term.nim
index 0e245256..3f38193b 100644
--- a/src/local/term.nim
+++ b/src/local/term.nim
@@ -73,6 +73,7 @@ type
     damaged: bool
     marked*: bool
     dead: bool
+    transparent: bool # note: this is only set in outputSixelImage
     kittyId: int
     # 0 if kitty
     erry: int
@@ -735,7 +736,12 @@ proc checkImageDamage*(term: Terminal; maxh: int) =
       let mx = image.x + (image.dispw - image.offx) div term.attrs.ppc
       for y in max(image.y, 0) ..< ey0:
         let od = term.lineDamage[y]
-        if od < mx:
+        if image.transparent and od > image.x:
+          image.damaged = true
+          if od < mx:
+            # damage starts inside this image; move it to its beginning.
+            term.lineDamage[y] = image.x
+        elif not image.transparent and od < mx:
           image.damaged = true
           if y >= ey1:
             break
@@ -752,7 +758,8 @@ proc checkImageDamage*(term: Terminal; maxh: int) =
               term.lineDamage[y] = mx
 
 proc loadImage*(term: Terminal; data: Blob; pid, imageId, x, y, width, height,
-    rx, ry, maxw, maxh, erry, offx, dispw: int): CanvasImage =
+    rx, ry, maxw, maxh, erry, offx, dispw: int; transparent: bool):
+    CanvasImage =
   if (let image = term.findImage(pid, imageId, rx, ry, width, height, erry,
         offx, dispw); image != nil):
     # reuse image on screen
@@ -777,7 +784,8 @@ proc loadImage*(term: Terminal; data: Blob; pid, imageId, x, y, width, height,
     ry: ry,
     width: width,
     height: height,
-    erry: erry
+    erry: erry,
+    transparent: transparent
   )
   if term.positionImage(image, x, y, maxw, maxh):
     return image
@@ -796,26 +804,22 @@ proc outputSixelImage(term: Terminal; x, y: int; image: CanvasImage;
   let offy = image.offy
   let dispw = image.dispw
   let disph = image.disph
-  var outs = term.cursorGoto(x, y)
   let realw = dispw - offx
   let realh = disph - offy
-  # set transparency if we want to draw a non-6-divisible number
-  # of rows; omit it otherwise, for then some terminals (e.g. foot)
-  # handle the image more efficiently
-  let trans = realh mod 6 != 0
-  outs &= DCS & "0;" & $int(trans) & 'q'
-  # set raster attributes
-  outs &= "\"1;1;" & $realw & ';' & $realh
-  if data.len < 4: # bounds check
-    outs &= ST
-    term.write(outs)
+  if data.len < 5: # bounds check
     return
   let sraLen = int(data.getU32BE(0))
-  let preludeLen = sraLen + 4
+  let preludeLen = sraLen + 5
   if preludeLen > data.len:
-    outs &= ST
-    term.write(outs)
     return
+  var outs = term.cursorGoto(x, y)
+  # set transparency if we want to draw a non-6-divisible number
+  # of rows *or* the image is transparent; omit it otherwise, for then
+  # some terminals (e.g. foot) handle the image more efficiently
+  let trans = realh mod 6 != 0 or image.transparent
+  outs &= DCS & "0;" & $int(trans) & "q"
+  # set raster attributes
+  outs &= "\"1;1;" & $realw & ';' & $realh
   term.write(outs)
   term.write(data.toOpenArray(4, preludeLen - 1))
   let lookupTableLen = int(data.getU32BE(data.len - 4))