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sixel: size provided by DECGRA does *not* limit the sixel size

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Foot has, up until now, used a fixed image size when the application
used DECGRA (Raster Attributes) to “configure” the image size.

This was based on a misunderstanding, that this was how you emitted
sixels where the height was *not* a multiple of 6.

This isn’t the case. The VT340 documentation is actually pretty clear
about this:

  Ph and Pv do not limit the size of the image defined by the sixel
  data. However, Ph and Pv let you omit background sixel data from the
  image definition and still have a color background. They also
  provide a concise way for the application or terminal to encode the
  size of an image.

This is also how XTerm behaves. Test image:

  \EPq
  "1;1;1;1
  #0;2;0;0;0#1;2;100;100;0#2;2;0;100;0
  #1~~@@vv@@~~@@~~$
  #2??}}GG}}??}}??-
  #1!14@
  \E\

This uses DECGRA to set the image size to 1x1. The sixel however
is *not* clipped to 1x1, but is resized to 14x12
This commit is contained in:
Daniel Eklöf 2021-03-06 15:03:47 +01:00
parent be980a6282
commit c95c663989
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GPG key ID: 5BBD4992C116573F
2 changed files with 1 additions and 7 deletions
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7
sixel.c
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@ -45,7 +45,6 @@ sixel_init(struct terminal *term)
term->sixel.image.data = xmalloc(1 * 6 * sizeof(term->sixel.image.data[0]));
term->sixel.image.width = 1;
term->sixel.image.height = 6;
term->sixel.image.autosize = true;
/* TODO: default palette */
@ -841,9 +840,6 @@ sixel_unhook(struct terminal *term)
static bool
resize(struct terminal *term, int new_width, int new_height)
{
if (!term->sixel.image.autosize)
return false;
LOG_DBG("resizing image: %dx%d -> %dx%d",
term->sixel.image.width, term->sixel.image.height,
new_width, new_height);
@ -1034,8 +1030,7 @@ decgra(struct terminal *term, uint8_t c)
if (ph >= term->sixel.image.height && pv >= term->sixel.image.width &&
ph <= term->sixel.max_height && pv <= term->sixel.max_width)
{
if (resize(term, ph, pv))
term->sixel.image.autosize = false;
resize(term, ph, pv);
}
term->sixel.state = SIXEL_DECSIXEL;

1
terminal.h
View file

@ -531,7 +531,6 @@ struct terminal {
uint32_t *data; /* Raw image data, in ARGB */
int width; /* Image width, in pixels */
int height; /* Image height, in pixels */
bool autosize;
} image;
bool scrolling:1; /* Private mode 80 */