vt: wip: implement scrolling region

This is largely untested, but existing scrolling code has been
converted to using a terminal-global scrolling region that is defined
as start-end of the scrollable region.

This is compared to the old code where the scrolling region where
defined in terms of marginals, counted in lines from top and from
bottom.

csi.c

@@ -380,6 +380,21 @@ csi_dispatch(struct terminal *term, uint8_t final)
             break;
         }
 
+        case 'r': {
+            int start = term->vt.params.idx > 0 ? term->vt.params.v[0].value : 1;
+            int end = term->vt.params.idx > 1
+                ? term->vt.params.v[1].value : term->grid.rows;
+
+            /* 1-based */
+            term->grid.scrolling_region.start = start - 1;
+            term->grid.scrolling_region.end = end - 1;
+
+            tll_free(term->grid.damage);
+            grid_damage_update(&term->grid, 0, term->grid.rows * term->grid.cols);
+            grid_cursor_to(&term->grid, 0, 0);
+            break;
+        }
+
         case 't':
             /*
              * TODO: xterm's terminfo specifies *both* \e[?1049h *and*

grid.c

@@ -87,8 +87,11 @@ grid_damage_erase(struct grid *grid, int start, int length)
 
 static void
 damage_adjust_after_scroll(struct grid *grid, enum damage_type damage_type,
-                           int top_margin, int bottom_margin, int lines)
+                           int lines)
 {
+    int top_margin = grid->scrolling_region.start;
+    int bottom_margin = grid->rows - grid->scrolling_region.end;
+
     const int adjustment
         = lines * grid->cols * (damage_type == DAMAGE_SCROLL_REVERSE ? -1 : 1);
     top_margin *= grid->cols;
@@ -131,8 +134,7 @@ damage_adjust_after_scroll(struct grid *grid, enum damage_type damage_type,
 }
 
 void
-grid_damage_scroll(struct grid *grid, enum damage_type damage_type,
+grid_damage_scroll(struct grid *grid, enum damage_type damage_type, int lines)
-                   int top_margin, int bottom_margin, int lines)
 {
     if (tll_length(grid->damage) > 0 &&
         tll_front(grid->damage).type == damage_type)
@@ -140,33 +142,26 @@ grid_damage_scroll(struct grid *grid, enum damage_type damage_type,
         /* Merge with existing scroll damage */
 
         struct damage *dmg = &tll_front(grid->damage);
-
-        assert(dmg->scroll.top_margin == top_margin);
-        assert(dmg->scroll.bottom_margin == bottom_margin);
-
         dmg->scroll.lines += lines;
 
+        const int scrolling_region =
+            grid->scrolling_region.end - grid->scrolling_region.start;
+
         /* If we've scrolled away the entire screen, replace with an erase */
-        if (dmg->scroll.lines >= (grid->rows - (dmg->scroll.top_margin +
+        if (dmg->scroll.lines >= scrolling_region) {
-                                                dmg->scroll.bottom_margin))) {
             dmg->type = DAMAGE_ERASE;
-            dmg->range.start = dmg->scroll.top_margin * grid->cols;
+            dmg->range.start = grid->scrolling_region.start * grid->cols;
-            dmg->range.length = (grid->rows - top_margin - bottom_margin) * grid->cols;
+            dmg->range.length = scrolling_region * grid->cols;
         }
     } else {
         struct damage dmg = {
             .type = damage_type,
-            .scroll = {
+            .scroll = {.lines = lines},
-                .top_margin = top_margin,
-                .bottom_margin = bottom_margin,
-                .lines = lines
-            },
         };
         tll_push_front(grid->damage, dmg);
     }
 
-    damage_adjust_after_scroll(
+    damage_adjust_after_scroll(grid, damage_type, lines);
-        grid, damage_type, top_margin, bottom_margin, lines);
 }
 
 void
@@ -243,15 +238,12 @@ grid_cursor_down(struct grid *grid, int count)
 void
 grid_scroll(struct grid *grid, int rows)
 {
-    const int top_margin = 0;
+    const int grid_rows = grid->scrolling_region.end - grid->scrolling_region.start;
-    const int bottom_margin = 0;
+    const int top_margin = grid->scrolling_region.start;
-    const int grid_rows = grid->rows - top_margin - bottom_margin;
+    const int bottom_margin = grid->rows - grid->scrolling_region.end;
 
     if (rows >= grid_rows) {
         assert(false && "untested");
-        grid_erase(grid,
-                   top_margin * grid->cols,
-                   (grid->rows - bottom_margin) * grid->cols);
         return;
     }
 
@@ -266,7 +258,7 @@ grid_scroll(struct grid *grid, int rows)
         &grid->cells[cell_dst], &grid->cells[cell_src],
         bytes);
 
-    grid_damage_scroll(grid, DAMAGE_SCROLL, top_margin, bottom_margin, rows);
+    grid_damage_scroll(grid, DAMAGE_SCROLL, rows);
     grid_erase(
         grid,
         (grid_rows - bottom_margin - rows) * grid->cols,
@@ -276,9 +268,9 @@ grid_scroll(struct grid *grid, int rows)
 void
 grid_scroll_reverse(struct grid *grid, int rows)
 {
-    const int top_margin = 0;
+    const int grid_rows = grid->scrolling_region.end - grid->scrolling_region.start;
-    const int bottom_margin = 0;
+    const int top_margin = grid->scrolling_region.start;
-    const int grid_rows = grid->rows - top_margin - bottom_margin;
+    const int bottom_margin = grid->rows - grid->scrolling_region.end;
 
     if (rows >= grid_rows) {
         assert(false && "todo");
@@ -296,7 +288,7 @@ grid_scroll_reverse(struct grid *grid, int rows)
         &grid->cells[cell_dst], &grid->cells[cell_src],
         bytes);
 
-    grid_damage_scroll(grid, DAMAGE_SCROLL_REVERSE, top_margin, bottom_margin, rows);
+    grid_damage_scroll(grid, DAMAGE_SCROLL_REVERSE, rows);
     grid_erase(
         grid,
         top_margin * grid->cols,

grid.h

@@ -5,8 +5,7 @@
 void grid_damage_update(struct grid *grid, int start, int length);
 void grid_damage_erase(struct grid *grid, int start, int length);
 void grid_damage_scroll(
-    struct grid *grid, enum damage_type damage_type,
+    struct grid *grid, enum damage_type damage_type, int lines);
-    int top_margin, int bottom_margin, int lines);
 
 void grid_erase(struct grid *grid, int start, int end);
 

main.c

@@ -256,20 +256,19 @@ grid_render_scroll(struct context *c, struct buffer *buf,
                    const struct damage *dmg)
 {
     //int x = 0;
-    int dst_y = (dmg->scroll.top_margin + 0) * c->term.grid.cell_height;
+    const int scrolling_region
-    int src_y = (dmg->scroll.top_margin + dmg->scroll.lines) * c->term.grid.cell_height;
+        = c->term.grid.scrolling_region.end - c->term.grid.scrolling_region.start;
+
+    int dst_y = (c->term.grid.scrolling_region.start + 0) * c->term.grid.cell_height;
+    int src_y = (c->term.grid.scrolling_region.start + dmg->scroll.lines) * c->term.grid.cell_height;
     int width = buf->width;
-    int height = (c->term.grid.rows -
+    int height = (scrolling_region - dmg->scroll.lines) * c->term.grid.cell_height;
-                  dmg->scroll.top_margin -
-                  dmg->scroll.bottom_margin -
-                  dmg->scroll.lines) * c->term.grid.cell_height;
 
     const uint32_t stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
 
     LOG_DBG("damage: SCROLL: %d-%d by %d lines (dst-y: %d, src-y: %d, "
             "height: %d, stride: %d, mmap-size: %zu)",
-            dmg->scroll.top_margin,
+            c->term.grid.scrolling_region.start, c->term.grid.scrolling_region.end,
-            c->term.grid.rows - dmg->scroll.bottom_margin,
             dmg->scroll.lines,
             dst_y, src_y, height, stride,
             buf->size);
@@ -286,8 +285,7 @@ grid_render_scroll(struct context *c, struct buffer *buf,
     struct damage erase = {
         .type = DAMAGE_ERASE,
         .range = {
-            .start = (c->term.grid.rows -
+            .start = (c->term.grid.scrolling_region.end -
-                      dmg->scroll.bottom_margin -
                       dmg->scroll.lines) * cols,
             .length = dmg->scroll.lines * cols
         },
@@ -300,20 +298,19 @@ grid_render_scroll_reverse(struct context *c, struct buffer *buf,
                            const struct damage *dmg)
 {
     //int x = 0;
-    int src_y = (dmg->scroll.top_margin + 0) * c->term.grid.cell_height;
+    const int scrolling_region =
-    int dst_y = (dmg->scroll.top_margin + dmg->scroll.lines) * c->term.grid.cell_height;
+        c->term.grid.scrolling_region.end - c->term.grid.scrolling_region.start;
+
+    int src_y = (c->term.grid.scrolling_region.start + 0) * c->term.grid.cell_height;
+    int dst_y = (c->term.grid.scrolling_region.start + dmg->scroll.lines) * c->term.grid.cell_height;
     int width = buf->width;
-    int height = (c->term.grid.rows -
+    int height = (scrolling_region - dmg->scroll.lines) * c->term.grid.cell_height;
-                  dmg->scroll.top_margin -
-                  dmg->scroll.bottom_margin -
-                  dmg->scroll.lines) * c->term.grid.cell_height;
 
     const uint32_t stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
 
     LOG_DBG("damage: SCROLL REVERSE: %d-%d by %d lines (dst-y: %d, src-y: %d, "
             "height: %d, stride: %d, mmap-size: %zu)",
-            dmg->scroll.top_margin,
+            c->term.grid.scrolling_region.start, c->term.grid.scrolling_region.end,
-            c->term.grid.rows - dmg->scroll.bottom_margin,
             dmg->scroll.lines,
             dst_y, src_y, height, stride,
             buf->size);
@@ -330,7 +327,7 @@ grid_render_scroll_reverse(struct context *c, struct buffer *buf,
     struct damage erase = {
         .type = DAMAGE_ERASE,
         .range = {
-            .start = dmg->scroll.top_margin * cols,
+            .start = c->term.grid.scrolling_region.start * cols,
             .length = dmg->scroll.lines * cols
         },
     };
@@ -405,7 +402,9 @@ resize(struct context *c, int width, int height)
     c->width = width;
     c->height = height;
 
-    size_t old_cells_len = c->term.grid.cols * c->term.grid.rows;
+    const size_t old_rows = c->term.grid.rows;
+    const size_t old_cols = c->term.grid.cols;
+    const size_t old_cells_len = old_rows * old_cols;
 
     c->term.grid.cell_width = (int)ceil(c->fextents.max_x_advance);
     c->term.grid.cell_height = (int)ceil(c->fextents.height);
@@ -455,6 +454,9 @@ resize(struct context *c, int width, int height)
         LOG_ERRNO("TIOCSWINSZ");
     }
 
+    if (c->term.grid.scrolling_region.end == old_rows)
+        c->term.grid.scrolling_region.end = c->term.grid.rows;
+
     tll_free(c->term.grid.damage);
     assert(tll_length(c->term.grid.damage) == 0);
     grid_damage_update(&c->term.grid, 0, c->term.grid.rows * c->term.grid.cols);

terminal.h

@@ -40,8 +40,6 @@ struct damage {
 
         /* DAMAGE_SCROLL, DAMAGE_SCROLL_REVERSE */
         struct {
-            int top_margin;
-            int bottom_margin;
             int lines;
         } scroll;
     };
@@ -53,6 +51,13 @@ struct grid {
     int cell_width;
     int cell_height;
 
+    /* Scrolling region - counted as lines excluded from scrolling,
+     * from top and from bottom */
+    struct {
+        int start;
+        int end;
+    } scrolling_region;
+
     int linear_cursor;
     struct {
         int row;

vt.c

@@ -574,12 +574,12 @@ esc_dispatch(struct terminal *term, uint8_t final)
 
     case '=':
         /* Other half of xterm's smkx */
-        LOG_WARN("ignoring ESC with final %c", final);
+        LOG_WARN("unimplemented: keypad mode change");
         break;
 
     case '>':
         /* Other half of xterm's rmkx */
-        LOG_WARN("ignoring ESC with final %c", final);
+        LOG_WARN("unimplemented: keypad mode change");
         break;
 
     default: