From 910fe47b2ed1284d93ff4d274f5c2341cb0d2d0b Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Mon, 18 May 2026 22:46:53 +0530
Subject: feat: add on-screen keyboard with layout/hit detection tests

---
 main/keyboard.c | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 main/keyboard.c

(limited to 'main/keyboard.c')

diff --git a/main/keyboard.c b/main/keyboard.c
new file mode 100644
index 0000000..741bd08
--- /dev/null
+++ b/main/keyboard.c
@@ -0,0 +1,162 @@
+#include "keyboard.h"
+#include <string.h>
+
+static const char *s_alpha_lower[] = {
+    "qwertyuiop",
+    "asdfghjkl",
+    "\001zxcvbnm\b",
+    "\002\003 \004"
+};
+
+static const char *s_alpha_upper[] = {
+    "QWERTYUIOP",
+    "ASDFGHJKL",
+    "\001ZXCVBNM\b",
+    "\002\003 \004"
+};
+
+static const char *s_numsym[] = {
+    "1234567890",
+    "-/:;()$&@\"",
+    "\001.,?!'\\b",
+    "\002\003 \004"
+};
+
+#define CTRL_SHIFT  '\001'
+#define CTRL_LAYER  '\002'
+#define CTRL_SPACE  '\003'
+#define CTRL_DONE   '\004'
+#define CTRL_BS     '\b'
+
+void kb_state_init(kb_state_t *st) {
+    if (!st) return;
+    memset(st, 0, sizeof(*st));
+    st->layer = KB_ALPHA_LOWER;
+    st->reveal = false;
+}
+
+static const char **get_layer(kb_layer_t layer) {
+    switch (layer) {
+        case KB_ALPHA_UPPER: return s_alpha_upper;
+        case KB_NUMSYM:      return s_numsym;
+        default:             return s_alpha_lower;
+    }
+}
+
+static int key_is_ctrl(char c) {
+    return c == CTRL_SHIFT || c == CTRL_LAYER || c == CTRL_SPACE || c == CTRL_DONE || c == CTRL_BS;
+}
+
+int kb_get_row_keys(int row, kb_layer_t layer, const char **keys_out) {
+    if (row < 0 || row >= KB_ROW_COUNT) {
+        *keys_out = NULL;
+        return 0;
+    }
+    const char **layer_rows = get_layer(layer);
+    const char *row_str = layer_rows[row];
+    *keys_out = row_str;
+    return (int)strlen(row_str);
+}
+
+static int row_x_offset(int row) {
+    switch (row) {
+        case 0: return 5;
+        case 1: return 14;
+        case 2: return 23;
+        case 3: return 5;
+        default: return 0;
+    }
+}
+
+static int key_width_at(int row, int col, int total_keys) {
+    (void)col;
+    if (row == 3) {
+        if (col == 0) return 42;
+        if (col == total_keys - 1) return 50;
+        if (total_keys == 3 && col == 1) return 168;
+        if (total_keys == 4 && col == 1) return 168;
+        if (total_keys == 4 && col == 2) return 42;
+    }
+    return KB_KEY_W;
+}
+
+kb_result_t kb_hit_test(int tx, int ty, kb_layer_t layer) {
+    kb_result_t result = {KB_ACTION_NONE, 0};
+
+    if (ty < KB_START_Y || ty >= KB_START_Y + KB_ROW_COUNT * (KB_KEY_H + KB_KEY_GAP)) {
+        return result;
+    }
+
+    int row = (ty - KB_START_Y) / (KB_KEY_H + KB_KEY_GAP);
+    if (row < 0 || row >= KB_ROW_COUNT) return result;
+
+    const char *row_str;
+    int total_keys = kb_get_row_keys(row, layer, &row_str);
+    if (total_keys == 0) return result;
+
+    int x_off = row_x_offset(row);
+    int cx = x_off;
+
+    for (int col = 0; col < total_keys; col++) {
+        int kw = key_width_at(row, col, total_keys);
+        if (tx >= cx && tx < cx + kw) {
+            char c = row_str[col];
+            if (c == CTRL_SHIFT) {
+                result.action = KB_ACTION_SHIFT;
+            } else if (c == CTRL_LAYER) {
+                result.action = KB_ACTION_LAYER;
+            } else if (c == CTRL_SPACE) {
+                result.action = KB_ACTION_SPACE;
+                result.ch = ' ';
+            } else if (c == CTRL_DONE) {
+                result.action = KB_ACTION_DONE;
+            } else if (c == CTRL_BS) {
+                result.action = KB_ACTION_BACKSPACE;
+            } else {
+                result.action = KB_ACTION_CHAR;
+                result.ch = c;
+            }
+            return result;
+        }
+        cx += kw + KB_KEY_GAP;
+    }
+
+    return result;
+}
+
+void kb_apply(kb_state_t *st, kb_result_t result) {
+    if (!st || result.action == KB_ACTION_NONE) return;
+
+    switch (result.action) {
+        case KB_ACTION_CHAR:
+            if (st->cursor < KB_INPUT_MAX) {
+                st->input[st->cursor++] = result.ch;
+                st->input[st->cursor] = '\0';
+            }
+            break;
+        case KB_ACTION_BACKSPACE:
+            if (st->cursor > 0) {
+                st->cursor--;
+                st->input[st->cursor] = '\0';
+            }
+            break;
+        case KB_ACTION_SHIFT:
+            if (st->layer == KB_ALPHA_LOWER) st->layer = KB_ALPHA_UPPER;
+            else if (st->layer == KB_ALPHA_UPPER) st->layer = KB_ALPHA_LOWER;
+            break;
+        case KB_ACTION_LAYER:
+            if (st->layer == KB_NUMSYM) st->layer = KB_ALPHA_LOWER;
+            else st->layer = KB_NUMSYM;
+            break;
+        case KB_ACTION_SPACE:
+            if (st->cursor < KB_INPUT_MAX) {
+                st->input[st->cursor++] = ' ';
+                st->input[st->cursor] = '\0';
+            }
+            break;
+        case KB_ACTION_DONE:
+            break;
+        default:
+            break;
+    }
+}
-- 
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