image: preserve fractional cell extents

image-kitty.c

@@ -76,6 +76,8 @@ struct kitty_state {
 	u_int	 height;
 	u_int	 source_x;
 	u_int	 source_y;
+	u_int	 x_offset;
+	u_int	 y_offset;
 	u_int	 source_width;
 	u_int	 source_height;
 	u_int	 columns;
@@ -526,6 +528,8 @@ kitty_control(struct kitty_state *ks, const u_char *buf, size_t len)
 		case 'S':
 		case 'C':
 		case 'U':
+		case 'X':
+		case 'Y':
 			if (kitty_number((const char *)value, valuelen,
 			    &number) != 0)
 				return (-1);
@@ -546,6 +550,8 @@ kitty_control(struct kitty_state *ks, const u_char *buf, size_t len)
 			case 'S': ks->data_size = number; break;
 			case 'C': ks->no_cursor = (number != 0); break;
 			case 'U': ks->virtual = (number != 0); break;
+			case 'X': ks->x_offset = number; break;
+			case 'Y': ks->y_offset = number; break;
 			}
 			break;
 		}
@@ -855,7 +861,7 @@ kitty_place_image(struct image *source, struct kitty_state *ks, u_int xpixel,
 	uint64_t	 numerator, denominator, value;
 	u_int		 x, y, width, height, sx, sy, canvas_width;
 	u_int		 canvas_height, cell_width, cell_height, source_width;
-	u_int		 source_height;
+	u_int		 source_height, display_width, display_height;
 	struct image	*im;
 
 	x = ks->source_x;
@@ -869,11 +875,17 @@ kitty_place_image(struct image *source, struct kitty_state *ks, u_int xpixel,
 	height = ks->source_height;
 	if (height == 0 || height > source_height - y)
 		height = source_height - y;
+	if (ks->x_offset > UINT_MAX - width ||
+	    ks->y_offset > UINT_MAX - height)
+		return (NULL);
+	display_width = width + ks->x_offset;
+	display_height = height + ks->y_offset;
 
 	cell_width = (xpixel == 0 ? 8 : xpixel);
 	cell_height = (ypixel == 0 ? 16 : ypixel);
 	if (ks->columns == 0 && ks->rows == 0) {
-		image_size_in_cells(width, height, cell_width, cell_height,
+		image_size_in_cells(display_width, display_height, cell_width,
+		    cell_height,
 		    &sx, &sy);
 		value = (uint64_t)sx * cell_width;
 		if (value > UINT_MAX)
@@ -886,46 +898,46 @@ kitty_place_image(struct image *source, struct kitty_state *ks, u_int xpixel,
 	} else if (ks->columns != 0 && ks->rows != 0) {
 		sx = ks->columns;
 		sy = ks->rows;
-		canvas_width = width;
-		canvas_height = height;
+		canvas_width = display_width;
+		canvas_height = display_height;
 	} else if (ks->columns != 0) {
 		sx = ks->columns;
-		numerator = (uint64_t)height * sx * cell_width;
-		denominator = (uint64_t)width * cell_height;
+		numerator = (uint64_t)display_height * sx * cell_width;
+		denominator = (uint64_t)display_width * cell_height;
 		value = (numerator + denominator - 1) / denominator;
 		if (value == 0 || value > UINT_MAX)
 			return (NULL);
 		sy = value;
-		canvas_width = width;
-		numerator = (uint64_t)sy * cell_height * width;
+		canvas_width = display_width;
+		numerator = (uint64_t)sy * cell_height * display_width;
 		denominator = (uint64_t)sx * cell_width;
 		value = (numerator + denominator - 1) / denominator;
-		if (value < height)
-			value = height;
+		if (value < display_height)
+			value = display_height;
 		if (value > UINT_MAX)
 			return (NULL);
 		canvas_height = value;
 	} else {
 		sy = ks->rows;
-		numerator = (uint64_t)width * sy * cell_height;
-		denominator = (uint64_t)height * cell_width;
+		numerator = (uint64_t)display_width * sy * cell_height;
+		denominator = (uint64_t)display_height * cell_width;
 		value = (numerator + denominator - 1) / denominator;
 		if (value == 0 || value > UINT_MAX)
 			return (NULL);
 		sx = value;
-		canvas_height = height;
-		numerator = (uint64_t)sx * cell_width * height;
+		canvas_height = display_height;
+		numerator = (uint64_t)sx * cell_width * display_height;
 		denominator = (uint64_t)sy * cell_height;
 		value = (numerator + denominator - 1) / denominator;
-		if (value < width)
-			value = width;
+		if (value < display_width)
+			value = display_width;
 		if (value > UINT_MAX)
 			return (NULL);
 		canvas_width = value;
 	}
 
 	im = image_create_view(source, x, y, width, height, canvas_width,
-	    canvas_height, sx, sy);
+	    canvas_height, sx, sy, ks->x_offset, ks->y_offset);
 	if (im != NULL && ks->no_cursor)
 		image_set_no_cursor(im);
 	return (im);

image-sixel.c

@@ -603,7 +603,7 @@ sixel_scale(struct sixel_image *si, u_int cell_w, u_int cell_h, u_int ox,
 {
 	struct sixel_image	*new;
 	u_int			 cx, cy, pox, poy, psx, psy, tsx, tsy, px, py;
-	uint64_t	 x0, x1, y0, y1;
+	uint64_t	 x0, x1, y0, y1, tx0, tx1, ty0, ty1;
 	u_int			 x, y, i;
 
 	/*
@@ -640,8 +640,27 @@ sixel_scale(struct sixel_image *si, u_int cell_w, u_int cell_h, u_int ox,
 	psx = x1 - x0;
 	psy = y1 - y0;
 
-	tsx = sx * cell_w;
-	tsy = sy * cell_h;
+	/*
+	 * Preserve any partial final source cell. The grid still covers whole
+	 * cells, but the SIXEL raster must end at the corresponding pixel offset
+	 * rather than stretching to the cell boundary.
+	 */
+	tx1 = ((uint64_t)si->sx * cell_w + si->cell_w - 1) / si->cell_w;
+	ty1 = ((uint64_t)si->sy * cell_h + si->cell_h - 1) / si->cell_h;
+	if (tx1 > UINT_MAX || ty1 > UINT_MAX)
+		return (NULL);
+	tx0 = (uint64_t)ox * cell_w;
+	ty0 = (uint64_t)oy * cell_h;
+	if (tx0 >= tx1 || ty0 >= ty1)
+		return (NULL);
+	if ((uint64_t)(ox + sx) * cell_w < tx1)
+		tx1 = (uint64_t)(ox + sx) * cell_w;
+	if ((uint64_t)(oy + sy) * cell_h < ty1)
+		ty1 = (uint64_t)(oy + sy) * cell_h;
+	tsx = tx1 - tx0;
+	tsy = ty1 - ty0;
+	if (tsx == 0 || tsy == 0)
+		return (NULL);
 
 	new = xcalloc (1, sizeof *si);
 	new->cell_w = cell_w;

image.c

@@ -971,13 +971,15 @@ image_create(u_int width, u_int height, u_int canvas_width,
 	return (im);
 }
 
-/* Create an immutable rectangular view without copying its source pixels. */
-/* Create a cell-aligned view of an existing image. */
+/* Create a cell-aligned view of an existing image with an optional offset. */
 struct image *
 image_create_view(struct image *source, u_int x, u_int y, u_int width,
-    u_int height, u_int canvas_width, u_int canvas_height, u_int sx, u_int sy)
+    u_int height, u_int canvas_width, u_int canvas_height, u_int sx, u_int sy,
+    u_int x_offset, u_int y_offset)
 {
 	struct image	*im;
+	u_char		*pixels;
+	u_int		padded_width, padded_height, yy;
 
 	if (source == NULL || x >= source->width || y >= source->height ||
 	    width == 0 || width > source->width - x || height == 0 ||
@@ -988,9 +990,28 @@ image_create_view(struct image *source, u_int x, u_int y, u_int width,
 	    sx > USHRT_MAX || sy > USHRT_MAX)
 		return (NULL);
 
-	im = image_create1(width, height, canvas_width, canvas_height, sx, sy,
-	    source->stride, source->pixels + (size_t)y * source->stride +
-	    (size_t)x * 4);
+	if (x_offset == 0 && y_offset == 0) {
+		im = image_create1(width, height, canvas_width, canvas_height,
+		    sx, sy, source->stride, source->pixels +
+		    (size_t)y * source->stride + (size_t)x * 4);
+	} else {
+		if (x_offset > UINT_MAX - width ||
+		    y_offset > UINT_MAX - height)
+			return (NULL);
+		padded_width = width + x_offset;
+		padded_height = height + y_offset;
+		if ((uint64_t)padded_width * padded_height * 4 > SIZE_MAX)
+			return (NULL);
+		pixels = xcalloc((size_t)padded_width * padded_height, 4);
+		for (yy = 0; yy < height; yy++) {
+			memcpy(pixels + (size_t)(yy + y_offset) * padded_width * 4 +
+			    (size_t)x_offset * 4,
+			    source->pixels + (size_t)(y + yy) * source->stride +
+			    (size_t)x * 4, (size_t)width * 4);
+		}
+		im = image_create1(padded_width, padded_height, canvas_width,
+		    canvas_height, sx, sy, (size_t)padded_width * 4, pixels);
+	}
 	if (im == NULL)
 		return (NULL);
 	im->parent_id = source->id;

regress/image-support.sh

@@ -79,14 +79,24 @@ $TMUX2 new-session -d -x 10 -y 4 "
 	printf '\033Pq\"1;1;26;26#0;2;100;100;100#0!26~-!26~-!26~-!26~-!26B\033\\'
 	sleep 10" || exit 1
 $TMUX2 set -g status off || exit 1
+$TMUX2 set -as terminal-features ',*:sixel' || exit 1
 $TMUX new-session -d -x 10 -y 4 || exit 1
 $TMUX set -g status off || exit 1
+$TMUX pipe-pane -O "cat >$TMP" || exit 1
 $TMUX send-keys -l "$TMUX2 attach-session" || exit 1
 $TMUX send-keys Enter || exit 1
 sleep 1
 $TMUX capture-pane -pS0 -E0 >$TMP || exit 1
 grep -q '^#=' $TMP || exit 1
 
+# Re-emitting the image preserves the 26-pixel raster rather than expanding
+# it to the two complete 16-pixel grid cells occupied by the image.
+$TMUX pipe-pane || exit 1
+$TMUX pipe-pane -O "cat >$TMP" || exit 1
+$TMUX2 refresh-client -R || exit 1
+sleep 1
+grep -a '"1;1;26;26' $TMP >/dev/null || exit 1
+
 # A selection redraw uses the single-cell path. It must leave ASCII image
 # cells visible (graphical clients skip these cells to avoid erasing pixels).
 $TMUX2 copy-mode || exit 1

tmux.h

@@ -4237,7 +4237,7 @@ char		*regsub(const char *, const char *, const char *, int);
 struct image	*image_create(u_int, u_int, u_int, u_int, u_int, u_int,
 		     u_char *);
 struct image	*image_create_view(struct image *, u_int, u_int, u_int,
-		     u_int, u_int, u_int, u_int, u_int);
+		     u_int, u_int, u_int, u_int, u_int, u_int, u_int);
 struct image	*image_find(u_int);
 u_int		 image_get_id(const struct image *);
 void		 image_get_size(const struct image *, u_int *, u_int *);