search: wip: re-direct input while searching, and build a search buffer

This adds a new state, 'is_searching'. While active, input is
re-directed, and stored in a search buffer. In the future, we'll use
this buffer and search for its content in the scrollback buffer, and
move the view and create a selection on matches.

When rendering in 'is_searching', everything is dimmed. In the future,
we'll render the current search buffer on-top of the dimmed "regular"
terminal output.

search.c

@@ -0,0 +1,107 @@
+#include "search.h"
+
+#include <wchar.h>
+#include <xkbcommon/xkbcommon-compose.h>
+
+#define LOG_MODULE "search"
+#define LOG_ENABLE_DBG 1
+#include "log.h"
+#include "render.h"
+
+void
+search_begin(struct terminal *term)
+{
+    LOG_DBG("search: begin");
+
+    free(term->search.buf);
+    term->search.buf = NULL;
+    term->search.len = 0;
+    term->search.sz = 0;
+    term->is_searching = true;
+
+    render_refresh(term);
+}
+
+void
+search_cancel(struct terminal *term)
+{
+    LOG_DBG("search: cancel");
+
+    free(term->search.buf);
+    term->search.buf = NULL;
+    term->search.len = 0;
+    term->search.sz = 0;
+    term->is_searching = false;
+
+    render_refresh(term);
+}
+
+void
+search_input(struct terminal *term, uint32_t key, xkb_keysym_t sym, xkb_mod_mask_t mods)
+{
+    LOG_DBG("search: input: sym=%d/0x%x, mods=0x%08x", sym, sym, mods);
+
+    const xkb_mod_mask_t ctrl = 1 << term->kbd.mod_ctrl;
+    //const xkb_mod_mask_t alt = 1 << term->kbd.mod_alt;
+    //const xkb_mod_mask_t shift = 1 << term->kbd.mod_shift;
+    //const xkb_mod_mask_t meta = 1 << term->kbd.mod_meta;
+
+    enum xkb_compose_status compose_status = xkb_compose_state_get_status(
+        term->kbd.xkb_compose_state);
+
+    if ((mods == 0 && sym == XKB_KEY_Escape) || (mods == ctrl && sym == XKB_KEY_g))
+        search_cancel(term);
+
+    else if (mods == 0 && sym == XKB_KEY_BackSpace) {
+        if (term->search.len > 0)
+            term->search.buf[--term->search.len] = L'\0';
+    }
+
+    else {
+        uint8_t buf[64] = {0};
+        int count = 0;
+
+        if (compose_status == XKB_COMPOSE_COMPOSED) {
+            count = xkb_compose_state_get_utf8(
+                term->kbd.xkb_compose_state, (char *)buf, sizeof(buf));
+            xkb_compose_state_reset(term->kbd.xkb_compose_state);
+        } else {
+            count = xkb_state_key_get_utf8(
+                term->kbd.xkb_state, key, (char *)buf, sizeof(buf));
+        }
+
+        const char *src = (const char *)buf;
+        mbstate_t ps = {0};
+        size_t wchars = mbsnrtowcs(NULL, &src, count, 0, &ps);
+
+        if (wchars == -1) {
+            LOG_ERRNO("failed to convert %.*s to wchars", count, buf);
+            return;
+        }
+
+        while (term->search.len + wchars >= term->search.sz) {
+            size_t new_sz = term->search.sz == 0 ? 64 : term->search.sz * 2;
+            wchar_t *new_buf = realloc(term->search.buf, new_sz * sizeof(term->search.buf[0]));
+
+            if (new_buf == NULL) {
+                LOG_ERRNO("failed to resize search buffer");
+                return;
+            }
+
+            term->search.buf = new_buf;
+            term->search.sz = new_sz;
+        }
+
+        assert(term->search.len + wchars < term->search.sz);
+
+        memset(&ps, 0, sizeof(ps));
+        mbsnrtowcs(&term->search.buf[term->search.len], &src, count,
+                   term->search.sz - term->search.len - 1, &ps);
+
+        term->search.len += wchars;
+        term->search.buf[term->search.len] = L'\0';
+    }
+
+    LOG_DBG("search: buffer: %S", term->search.buf);
+    render_refresh(term);
+}