grid: don't pre-allocate the entire grid (with all scrollback lines)

The row array may now contain NULL pointers. This means the
corresponding row hasn't yet been allocated and initialized.

On a resize, we explicitly allocate the visible rows.

Uninitialized rows are then allocated the first time they are
referenced.

commands.c

@@ -26,7 +26,7 @@ cmd_scrollback_up(struct terminal *term, int rows)
     assert(new_view < term->grid->num_rows);
 
     /* Avoid scrolling in uninitialized rows */
-    while (!term->grid->rows[new_view]->initialized)
+    while (term->grid->rows[new_view] == NULL)
         new_view = (new_view + 1) % term->grid->num_rows;
 
     if (new_view == term->grid->view) {
@@ -87,7 +87,7 @@ cmd_scrollback_down(struct terminal *term, int rows)
 
         for (int i = 0; i < term->rows; i++) {
             int row_no = (new_view + i) % term->grid->num_rows;
-            if (!term->grid->rows[row_no]->initialized) {
+            if (term->grid->rows[row_no] == NULL) {
                 all_initialized = false;
                 new_view--;
                 break;

grid.c

@@ -25,3 +25,22 @@ grid_swap_row(struct grid *grid, int row_a, int row_b)
     grid->rows[real_a]->dirty = true;
     grid->rows[real_b]->dirty = true;
 }
+
+struct row *
+grid_row_alloc(int cols)
+{
+    struct row *row = malloc(sizeof(*row));
+    row->cells = calloc(cols, sizeof(row->cells[0]));
+    row->dirty = false;  /* TODO: parameter? */
+    return row;
+}
+
+void
+grid_row_free(struct row *row)
+{
+    if (row == NULL)
+        return;
+
+    free(row->cells);
+    free(row);
+}

grid.h

@@ -3,18 +3,34 @@
 #include <stddef.h>
 #include "terminal.h"
 
+void grid_swap_row(struct grid *grid, int row_a, int row_b);
+struct row *grid_row_alloc(int cols);
+void grid_row_free(struct row *row);
+
 static inline struct row *
-grid_row(struct grid *grid, int row)
+grid_row(struct grid *grid, int row_no)
 {
     assert(grid->offset >= 0);
-    return grid->rows[(grid->offset + row + grid->num_rows) % grid->num_rows];
+
+    int real_row = (grid->offset + row_no + grid->num_rows) % grid->num_rows;
+    struct row *row = grid->rows[real_row];
+
+    if (row == NULL) {
+        row = grid_row_alloc(grid->num_cols);
+        grid->rows[real_row] = row;
+    }
+
+    return row;
 }
 
 static inline struct row *
-grid_row_in_view(struct grid *grid, int row)
+grid_row_in_view(struct grid *grid, int row_no)
 {
     assert(grid->view >= 0);
-    return grid->rows[(grid->view + row + grid->num_rows) % grid->num_rows];
-}
 
-void grid_swap_row(struct grid *grid, int row_a, int row_b);
+    int real_row = (grid->offset + row_no + grid->num_rows) % grid->num_rows;
+    struct row *row = grid->rows[real_row];
+
+    assert(row != NULL);
+    return row;
+}

main.c

@@ -624,15 +624,11 @@ out:
     if (term.kbd.xkb != NULL)
         xkb_context_unref(term.kbd.xkb);
 
-    for (int row = 0; row < term.normal.num_rows; row++) {
-        free(term.normal.rows[row]->cells);
-        free(term.normal.rows[row]);
-    }
+    for (int row = 0; row < term.normal.num_rows; row++)
+        grid_row_free(term.normal.rows[row]);
     free(term.normal.rows);
-    for (int row = 0; row < term.alt.num_rows; row++) {
-        free(term.alt.rows[row]->cells);
-        free(term.alt.rows[row]);
-    }
+    for (int row = 0; row < term.alt.num_rows; row++)
+        grid_row_free(term.alt.rows[row]);
     free(term.alt.rows);
 
     for (size_t i = 0; i < sizeof(term.fonts) / sizeof(term.fonts[0]); i++) {

render.c

@@ -346,21 +346,27 @@ reflow(struct row **new_grid, int new_cols, int new_rows,
         size_t copy_cols = min(new_cols, old_cols);
         size_t clear_cols = new_cols - copy_cols;
 
+        if (old_grid[r] == NULL)
+            continue;
+
+        if (new_grid[r] == NULL)
+            new_grid[r] = grid_row_alloc(new_cols);
+
         struct cell *new_cells = new_grid[r]->cells;
         const struct cell *old_cells = old_grid[r]->cells;
 
-        new_grid[r]->initialized = old_grid[r]->initialized;
         new_grid[r]->dirty = old_grid[r]->dirty;
-
         memcpy(new_cells, old_cells, copy_cols * sizeof(new_cells[0]));
         memset(&new_cells[copy_cols], 0, clear_cols * sizeof(new_cells[0]));
     }
 
+#if 0
     for (int r = min(new_rows, old_rows); r < new_rows; r++) {
         new_grid[r]->initialized = false;
         new_grid[r]->dirty = false;
         memset(new_grid[r]->cells, 0, new_cols * sizeof(new_grid[r]->cells[0]));
     }
+#endif
 }
 
 /* Move to terminal.c? */
@@ -386,20 +392,14 @@ render_resize(struct terminal *term, int width, int height)
     const int new_alt_grid_rows = new_rows;
 
     /* Allocate new 'normal' grid */
-    struct row **normal = malloc(new_normal_grid_rows * sizeof(normal[0]));
-    for (int r = 0; r < new_normal_grid_rows; r++) {
-        struct row *row = malloc(sizeof(*row));
-        row->cells = malloc(new_cols * sizeof(row->cells[0]));
-        normal[r] = row;
-    }
+    struct row **normal = calloc(new_normal_grid_rows, sizeof(normal[0]));
+    for (int r = 0; r < new_rows; r++)
+        normal[r] = grid_row_alloc(new_cols);
 
     /* Allocate new 'alt' grid */
-    struct row **alt = malloc(new_alt_grid_rows * sizeof(alt[0]));
-    for (int r = 0; r < new_alt_grid_rows; r++) {
-        struct row *row = malloc(sizeof(*row));
-        row->cells = malloc(new_cols * sizeof(row->cells[0]));
-        alt[r] = row;
-    }
+    struct row **alt = calloc(new_alt_grid_rows, sizeof(alt[0]));
+    for (int r = 0; r < new_rows; r++)
+        alt[r] = grid_row_alloc(new_cols);
 
     /* Reflow content */
     reflow(normal, new_cols, new_normal_grid_rows,
@@ -407,23 +407,14 @@ render_resize(struct terminal *term, int width, int height)
     reflow(alt, new_cols, new_alt_grid_rows,
            term->alt.rows, old_cols, old_alt_grid_rows);
 
-    for (int r = 0; r < new_rows; r++) {
-        normal[r]->initialized = true;
-        alt[r]->initialized = true;
-    }
-
     /* Free old 'normal' grid */
-    for (int r = 0; r < term->normal.num_rows; r++) {
-        free(term->normal.rows[r]->cells);
-        free(term->normal.rows[r]);
-    }
+    for (int r = 0; r < term->normal.num_rows; r++)
+        grid_row_free(term->normal.rows[r]);
     free(term->normal.rows);
 
     /* Free old 'alt' grid */
-    for (int r = 0; r < term->alt.num_rows; r++) {
-        free(term->alt.rows[r]->cells);
-        free(term->alt.rows[r]);
-    }
+    for (int r = 0; r < term->alt.num_rows; r++)
+        grid_row_free(term->alt.rows[r]);
     free(term->alt.rows);
 
     term->cols = new_cols;
@@ -431,8 +422,10 @@ render_resize(struct terminal *term, int width, int height)
 
     term->normal.rows = normal;
     term->normal.num_rows = new_normal_grid_rows;
+    term->normal.num_cols = new_cols;
     term->alt.rows = alt;
     term->alt.num_rows = new_alt_grid_rows;
+    term->alt.num_cols = new_cols;
 
     LOG_INFO("resize: %dx%d, grid: cols=%d, rows=%d",
              term->width, term->height, term->cols, term->rows);

terminal.c

@@ -169,7 +169,6 @@ term_scroll_partial(struct terminal *term, struct scroll_region region, int rows
     for (int r = max(region.end - rows, 0); r < region.end; r++) {
         struct row *row = grid_row(term->grid, r);
         erase_line(term, row);
-        row->initialized = true;
     }
 
     term_damage_scroll(term, DAMAGE_SCROLL, region, rows);

terminal.h

@@ -94,11 +94,11 @@ struct damage {
 struct row {
     struct cell *cells;
     bool dirty;
-    bool initialized;
 };
 
 struct grid {
     int num_rows;
+    int num_cols;
     int offset;
     int view;