render/grid: move grid reflow code to grid.c

grid.c

@@ -1,12 +1,14 @@
 #include "grid.h"
 
-//#include <string.h>
+#include <string.h>
 #include <assert.h>
 
 #define LOG_MODULE "grid"
 #define LOG_ENABLE_DBG 0
 #include "log.h"
 
+#define max(x, y) ((x) > (y) ? (x) : (y))
+
 void
 grid_swap_row(struct grid *grid, int row_a, int row_b, bool initialize)
 {
@@ -49,3 +51,145 @@ grid_row_free(struct row *row)
     free(row->cells);
     free(row);
 }
+
+int
+grid_reflow(struct grid *grid, int new_rows, int new_cols,
+            int old_screen_rows, int new_screen_rows)
+{
+    struct row *const *old_grid = grid->rows;
+    const int old_rows = grid->num_rows;
+    const int old_cols = grid->num_cols;
+
+    assert(old_rows != new_rows || old_cols != new_cols);
+
+    int new_col_idx = 0;
+    int new_row_idx = 0;
+
+    struct row **new_grid = calloc(new_rows, sizeof(new_grid[0]));
+    struct row *new_row = new_grid[new_row_idx];
+
+    assert(new_row == NULL);
+    new_row = grid_row_alloc(new_cols, true);
+    new_grid[new_row_idx] = new_row;
+
+    /* Start at the beginning of the old grid's scrollback. That is,
+     * at the output that is *oldest* */
+    int offset = grid->offset + old_screen_rows;
+
+    /*
+     * Walk the old grid
+     */
+    for (int r = 0; r < old_rows; r++) {
+
+        /* Unallocated (empty) rows we can simply skip */
+        const struct row *old_row = old_grid[(offset + r) & (old_rows - 1)];
+        if (old_row == NULL)
+            continue;
+
+        /*
+         * Keep track of empty cells. If the old line ends with a
+         * string of empty cells, we don't need to, nor do we want to,
+         * add those to the new line. However, if there are non-empty
+         * cells *after* the string of empty cells, we need to emit
+         * the empty cells too. And that may trigger linebreaks
+         */
+        int empty_count = 0;
+
+        /* Walk current line of the old grid */
+        for (int c = 0; c < old_cols; c++) {
+            if (old_row->cells[c].wc == 0) {
+                empty_count++;
+                continue;
+            }
+
+            int old_cols_left = old_cols - c;
+            int cols_needed = empty_count + old_cols_left;
+            int new_cols_left = new_cols - new_col_idx;
+            if (new_cols_left < cols_needed && new_cols_left >= old_cols_left)
+                empty_count = max(0, empty_count - (cols_needed - new_cols_left));
+
+            for (int i = 0; i < empty_count + 1; i++) {
+                const struct cell *old_cell = &old_row->cells[c - empty_count + i];
+
+                /* Out of columns on current row in new grid? */
+                if (new_col_idx >= new_cols) {
+                    /*
+                     * If last cell on last row and first cell on new
+                     * row are non-empty, wrap the line, otherwise
+                     * insert a hard line break.
+                     */
+                    if (new_row->cells[new_cols - 1].wc == 0 ||
+                        old_cell->wc == 0)
+                    {
+                        new_row->linebreak = true;
+                    }
+
+                    new_col_idx = 0;
+                    new_row_idx = (new_row_idx + 1) & (new_rows - 1);
+
+                    new_row = new_grid[new_row_idx];
+                    if (new_row == NULL) {
+                        new_row = grid_row_alloc(new_cols, true);
+                        new_grid[new_row_idx] = new_row;
+                    } else {
+                        memset(new_row->cells, 0, new_cols * sizeof(new_row->cells[0]));
+                        new_row->linebreak = false;
+                    }
+                }
+
+                assert(new_row != NULL);
+                assert(new_col_idx >= 0);
+                assert(new_col_idx < new_cols);
+
+                new_row->cells[new_col_idx] = *old_cell;
+                new_row->cells[new_col_idx].attrs.clean = 1;
+                new_col_idx++;
+            }
+
+            empty_count = 0;
+        }
+
+        if (old_row->linebreak) {
+            new_row->linebreak = true;
+
+            new_col_idx = 0;
+            new_row_idx = (new_row_idx + 1) & (new_rows - 1);
+
+            new_row = new_grid[new_row_idx];
+            if (new_row == NULL) {
+                new_row = grid_row_alloc(new_cols, true);
+                new_grid[new_row_idx] = new_row;
+            } else {
+                memset(new_row->cells, 0, new_cols * sizeof(new_row->cells[0]));
+                new_row->linebreak = false;
+            }
+        }
+    }
+
+    /* Set offset such that the last reflowed row is at the bottom */
+    grid->offset = new_row_idx - new_screen_rows + 1;
+    while (grid->offset < 0)
+        grid->offset += new_rows;
+    while (new_grid[grid->offset] == NULL)
+        grid->offset = (grid->offset + 1) & (new_rows - 1);
+    grid->view = grid->offset;
+
+    /* Ensure all visible rows have been allocated */
+    for (int r = 0; r < new_screen_rows; r++) {
+        int idx = (grid->offset + r) & (new_rows - 1);
+        if (new_grid[idx] == NULL)
+            new_grid[idx] = grid_row_alloc(new_cols, true);
+    }
+
+    /* Free old grid */
+    for (int r = 0; r < grid->num_rows; r++)
+        grid_row_free(old_grid[r]);
+    free(grid->rows);
+
+    grid->cur_row = new_grid[new_row_idx];
+    grid->rows = new_grid;
+    grid->num_rows = new_rows;
+    grid->num_cols = new_cols;
+
+    return new_row_idx;
+}