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shm: shm_scroll(): initial implementation of reverse scrolling

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Implemented by truncating the file size and moving the offset
backwards. This means we can only reverse scroll when we've previously
scrolled forward.

TODO: figure out if we can somehow do fast reverse scrolling even
though offset is 0 (or well, less than required for scrolling).
This commit is contained in:
Daniel Eklöf 2020-03-23 21:14:51 +01:00
parent 0de3701984
commit 759fd572e9
No known key found for this signature in database
GPG key ID: 5BBD4992C116573F
2 changed files with 143 additions and 28 deletions
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100
shm.c
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@ -64,8 +64,6 @@ instantiate_offset(struct wl_shm *shm, struct buffer *buf, size_t new_offset)
assert(buf->wl_buf == NULL);
assert(buf->pix == NULL);
assert(new_offset >= buf->offset);
static size_t page_size = 0;
if (page_size == 0) {
page_size = sysconf(_SC_PAGE_SIZE);
@ -286,10 +284,10 @@ shm_can_scroll(void)
return can_punch_hole;
}
bool
shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
static bool
shm_scroll_forward(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
assert(can_punch_hole);
assert(buf->busy);
@ -365,7 +363,6 @@ shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows,
LOG_INFO("PUNCH HOLE: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
bool ret = instantiate_offset(shm, buf, new_offset);
if (ret && bottom_keep_rows > 0) {
@ -387,7 +384,94 @@ shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows,
return ret;
}
void
static bool
shm_scroll_reverse(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
assert(rows > 0);
size_t diff = rows * buf->stride;
if (diff > buf->offset)
return false;
const size_t new_offset = buf->offset - rows * buf->stride;
assert(new_offset < buf->offset);
#if TIME_SCROLL
struct timeval time0;
gettimeofday(&time0, NULL);
struct timeval tot;
struct timeval time1 = time0;
#endif
if (bottom_keep_rows > 0) {
/* Copy 'bottom' region to its new location */
memmove(
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + rows + bottom_keep_rows) * buf->stride,
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + bottom_keep_rows) * buf->stride,
bottom_keep_rows * buf->stride);
#if TIME_SCROLL
gettimeofday(&time1, NULL);
timersub(&time1, &time0, &tot);
LOG_INFO("memmove (bottom region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
/* Destroy old objects (they point to the old offset) */
pixman_image_unref(buf->pix);
wl_buffer_destroy(buf->wl_buf);
munmap(buf->real_mmapped, buf->mmap_size);
buf->pix = NULL;
buf->wl_buf = NULL;
buf->real_mmapped = buf->mmapped = NULL;
if (ftruncate(buf->fd, new_offset + buf->size) < 0) {
abort();
}
#if TIME_SCROLL
struct timeval time2;
gettimeofday(&time2, NULL);
timersub(&time2, &time1, &tot);
LOG_INFO("ftruncate: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
bool ret = instantiate_offset(shm, buf, new_offset);
if (ret && top_keep_rows > 0) {
/* Copy current 'top' region to its new location */
memmove(
(uint8_t *)buf->mmapped + (top_margin + 0) * buf->stride,
(uint8_t *)buf->mmapped + (top_margin + rows) * buf->stride,
top_keep_rows * buf->stride);
#if TIME_SCROLL
struct timeval time3;
gettimeofday(&time3, NULL);
timersub(&time3, &time2, &tot);
LOG_INFO("memmove (top region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
return ret;
}
bool
shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
assert(rows != 0);
return rows > 0
? shm_scroll_forward(shm, buf, rows, top_margin, top_keep_rows, bottom_margin, bottom_keep_rows)
: shm_scroll_reverse(shm, buf, -rows, top_margin, top_keep_rows, bottom_margin, bottom_keep_rows);
}
void
shm_purge(struct wl_shm *shm, unsigned long cookie)
{
LOG_DBG("cookie=%lx: purging all buffers", cookie);