wip: initial scroll back support

Can scroll up and down, and stops when the beginning/end of history is
reached.

However, it probably breaks when the entire scrollback buffer has been
filled - we need to detect when the view has wrapped around to the
current terminal offset.

The detection of when we've reached the bottom of the history is also
flawed, and only works when we overshoot the bottom with at least a
page.

Resizing the windows while in a view most likely doesn't work.

The view will not detect a wrapped around scrollback buffer. I.e. if
the user has scrolled back, and is stationary at a view, but there is
still output being produced. Then eventually the scrollback buffer
will wrap around. In this case, the correct thing to do is make the
view start following the beginning of the history. Right now it
doesn't, meaning once the scrollback buffer wraps around, you'll start
seeing command output...

commands.c

@@ -0,0 +1,61 @@
+#include "commands.h"
+
+#define LOG_MODULE "commands"
+#define LOG_ENABLE_DBG 1
+#include "log.h"
+#include "terminal.h"
+#include "render.h"
+#include "grid.h"
+
+#define max(x, y) ((x) > (y) ? (x) : (y))
+
+void
+cmd_scrollback_up(struct terminal *term)
+{
+    assert(term->grid->offset >= 0);
+    int new_view = (term->grid->view + term->grid->num_rows - term->rows) % term->grid->num_rows;
+
+    LOG_WARN("%d" ,new_view);
+    assert(new_view >= 0);
+    assert(new_view < term->grid->num_rows);
+
+    while (!term->grid->rows[new_view]->initialized)
+        new_view = (new_view + 1) % term->grid->num_rows;
+
+    LOG_DBG("scrollback UP: %d -> %d (offset = %d, rows = %d)",
+            term->grid->view, new_view, term->grid->offset, term->grid->num_rows);
+    term->grid->view = new_view;
+
+    for (int i = 0; i < term->rows; i++)
+        grid_row_in_view(term->grid, i)->dirty = true;
+
+    if (term->frame_callback == NULL)
+        grid_render(term);
+}
+
+void
+cmd_scrollback_down(struct terminal *term)
+{
+    assert(term->grid->offset >= 0);
+    int new_view = (term->grid->view + term->rows) % term->grid->num_rows;
+
+    LOG_WARN("%d" ,new_view);
+    assert(new_view >= 0);
+    assert(new_view < term->grid->num_rows);
+
+    if (!term->grid->rows[new_view]->initialized) {
+        while (!term->grid->rows[new_view]->initialized)
+            new_view = (new_view + term->grid->num_rows - 1) % term->grid->num_rows;
+        new_view = (new_view + term->grid->num_rows - term->rows + 1) % term->grid->num_rows;
+    }
+
+    LOG_DBG("scrollback DOWN: %d -> %d (offset = %d, rows = %d)",
+            term->grid->view, new_view, term->grid->offset, term->grid->num_rows);
+    term->grid->view = new_view;
+
+    for (int i = 0; i < term->rows; i++)
+        grid_row_in_view(term->grid, i)->dirty = true;
+
+    if (term->frame_callback == NULL)
+        grid_render(term);
+}

commands.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include "terminal.h"
+
+void cmd_scrollback_up(struct terminal *term);
+void cmd_scrollback_down(struct terminal *term);

grid.h

@@ -10,6 +10,13 @@ grid_row(struct grid *grid, int row)
     return grid->rows[(grid->offset + row + grid->num_rows) % grid->num_rows];
 }
 
+static inline struct row *
+grid_row_in_view(struct grid *grid, int row)
+{
+    assert(grid->view >= 0);
+    return grid->rows[(grid->view + row + grid->num_rows) % grid->num_rows];
+}
+
 static inline void
 grid_swap_row(struct grid *grid, int row_a, int row_b)
 {

input.c

@@ -17,6 +17,7 @@
 #include "terminal.h"
 #include "render.h"
 #include "keymap.h"
+#include "commands.h"
 
 static void
 keyboard_keymap(void *data, struct wl_keyboard *wl_keyboard,
@@ -140,6 +141,18 @@ keyboard_key(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial,
     keymap_mods |= term->kbd.alt ? MOD_ALT : MOD_NONE;
     keymap_mods |= term->kbd.ctrl ? MOD_CTRL : MOD_NONE;
 
+    if (effective_mods == shift) {
+        if (sym == XKB_KEY_Page_Up) {
+            cmd_scrollback_up(term);
+            found_map = true;
+        }
+
+        else if (sym == XKB_KEY_Page_Down) {
+            cmd_scrollback_down(term);
+            found_map = true;
+        }
+    }
+
     for (size_t i = 0; i < sizeof(key_map) / sizeof(key_map[0]) && !found_map; i++) {
         const struct key_map *k = &key_map[i];
         if (k->sym != sym)
@@ -160,6 +173,13 @@ keyboard_key(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial,
 
             write(term->ptmx, info->seq, strlen(info->seq));
             found_map = true;
+
+            if (term->grid->view != term->grid->offset) {
+                term->grid->view = term->grid->offset;
+                /* TODO: damage view */
+                term_damage_all(term);
+            }
+
             break;
         }
     }
@@ -182,6 +202,13 @@ keyboard_key(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial,
                 write(term->ptmx, "\x1b", 1);
 
             write(term->ptmx, buf, count);
+
+            if (term->grid->view != term->grid->offset) {
+                term->grid->view = term->grid->offset;
+                /* TODO: damage view */
+                term_damage_all(term);
+            }
+
         }
     }
 

meson.build

@@ -58,6 +58,7 @@ endforeach
 
 executable(
   'f00ter',
+  'commands.c', 'commands.h',
   'csi.c', 'csi.h',
   'font.c', 'font.h',
   'grid.c', 'grid.h',

render.c

@@ -243,7 +243,7 @@ grid_render(struct terminal *term)
     gseq.count = 0;
 
     for (int r = 0; r < term->rows; r++) {
-        struct row *row = grid_row(term->grid, r);
+        struct row *row = grid_row_in_view(term->grid, r);
 
         if (!row->dirty)
             continue;
@@ -266,10 +266,10 @@ grid_render(struct terminal *term)
         = (term->grid->offset + term->cursor.row) * term->cols + term->cursor.col;
 
     if (last_cursor != cursor_as_linear) {
-        int row = last_cursor / term->cols - term->grid->offset;
+        int row = last_cursor / term->cols - term->grid->view;
         int col = last_cursor % term->cols;
         if (row >= 0 && row < term->rows) {
-            render_cell(term, buf, &grid_row(term->grid, row)->cells[col], col, row);
+            render_cell(term, buf, &grid_row_in_view(term->grid, row)->cells[col], col, row);
             all_clean = false;
 
             wl_surface_damage_buffer(
@@ -286,7 +286,7 @@ grid_render(struct terminal *term)
 
     render_cell(
         term, buf,
-        &grid_row(term->grid, term->cursor.row)->cells[term->cursor.col],
+        &grid_row_in_view(term->grid, term->cursor.row)->cells[term->cursor.col],
         term->cursor.col, term->cursor.row);
 
     wl_surface_damage_buffer(
@@ -304,6 +304,7 @@ grid_render(struct terminal *term)
     }
 
     assert(term->grid->offset >= 0 && term->grid->offset < term->grid->num_rows);
+    assert(term->grid->view >= 0 && term->grid->view < term->grid->num_rows);
 
     cairo_surface_flush(buf->cairo_surface);
     wl_surface_attach(term->wl.surface, buf->wl_buf, 0, 0);
@@ -338,12 +339,18 @@ reflow(struct row **new_grid, int new_cols, int new_rows,
         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]));
     }
 
-    for (int r = min(new_rows, old_rows); r < new_rows; r++)
+    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]));
+    }
 }
 
 /* Move to terminal.c? */
@@ -356,6 +363,8 @@ render_resize(struct terminal *term, int width, int height)
     term->width = width;
     term->height = height;
 
+    const int scrollback_lines = 10000;
+
     const int old_cols = term->cols;
     const int old_rows = term->rows;
     const int old_normal_grid_rows = term->normal.num_rows;
@@ -363,7 +372,7 @@ render_resize(struct terminal *term, int width, int height)
 
     const int new_cols = term->width / term->cell_width;
     const int new_rows = term->height / term->cell_height;
-    const int new_normal_grid_rows = new_rows;
+    const int new_normal_grid_rows = new_rows + scrollback_lines;
     const int new_alt_grid_rows = new_rows;
 
     /* Allocate new 'normal' grid */
@@ -388,6 +397,11 @@ 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);
@@ -430,10 +444,18 @@ render_resize(struct terminal *term, int width, int height)
     if (term->scroll_region.end >= old_rows)
         term->scroll_region.end = term->rows;
 
+    term->normal.offset %= term->normal.num_rows;
+    term->normal.view %= term->alt.num_rows;
+
+    term->alt.offset %= term->alt.num_rows;
+    term->alt.view %= term->alt.num_rows;
+
     term_cursor_to(
         term,
         min(term->cursor.row, term->rows - 1),
         min(term->cursor.col, term->cols - 1));
+
+    /* TODO: damage view */
     term_damage_all(term);
 
     if (term->frame_callback == NULL)

terminal.c

@@ -152,11 +152,18 @@ term_scroll_partial(struct terminal *term, struct scroll_region region, int rows
         grid_swap_row(term->grid, i, i + rows);
 
     /* Offset grid origin */
+    bool view_follows = term->grid->view == term->grid->offset;
     term->grid->offset += rows;
     term->grid->offset %= term->grid->num_rows;
 
-    for (int r = max(region.end - rows, 0); r < region.end; r++)
-        erase_line(term, grid_row(term->grid, r));
+    if (view_follows)
+        term->grid->view = term->grid->offset;
+
+    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);
     term->grid->cur_row = grid_row(term->grid, term->cursor.row);
@@ -174,9 +181,14 @@ term_scroll_reverse_partial(struct terminal *term,
 {
     assert(rows < term->rows && "unimplemented");
 
+    bool view_follows = term->grid->view == term->grid->offset;
+
     term->grid->offset += term->grid->num_rows - rows;
     term->grid->offset %= term->grid->num_rows;
 
+    if (view_follows)
+        term->grid->view = term->grid->offset;
+
     /* Bottom non-scrolling region */
     for (int i = region.end + rows; i < term->rows + rows; i++)
         grid_swap_row(term->grid, i, i - rows);

terminal.h

@@ -94,11 +94,13 @@ struct damage {
 struct row {
     struct cell *cells;
     bool dirty;
+    bool initialized;
 };
 
 struct grid {
     int num_rows;
     int offset;
+    int view;
 
     struct row **rows;
     struct row *cur_row;