build(deps): vendor libvterm at v0.3.3

Problem: Adding support for modern Nvim features (reflow, OSC 8, full
utf8/emoji support) requires coupling libvterm to Nvim internals
(e.g., utf8proc).

Solution: Vendor libvterm at v0.3.3.

33 files changed, 7126 insertions, 91 deletions

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 55319bb012..ef921cc3a4 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -248,7 +248,6 @@ jobs:
             luajit \
             lua-luv-dev
             # libtree-sitter-dev \
-            # libvterm-dev
 
             # Remove comments from packages once we start using these external
             # dependencies.
diff --git a/BUILD.md b/BUILD.md
index 895aec5fd1..710aa226d3 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -240,7 +240,7 @@ cmake --build build
 ### How to build without "bundled" dependencies
 
 1. Manually install the dependencies:
-    - libuv libluv libutf8proc libvterm luajit lua-lpeg tree-sitter tree-sitter-c tree-sitter-lua tree-sitter-markdown tree-sitter-query tree-sitter-vim tree-sitter-vimdoc unibilium
+    - libuv libluv libutf8proc luajit lua-lpeg tree-sitter tree-sitter-c tree-sitter-lua tree-sitter-markdown tree-sitter-query tree-sitter-vim tree-sitter-vimdoc unibilium
 2. Run CMake:
    ```sh
    cmake -B build -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo
@@ -248,7 +248,7 @@ cmake --build build
    ```
    If all the dependencies are not available in the package, you can use only some of the bundled dependencies as follows (example of using `ninja`):
    ```sh
-   cmake -S cmake.deps -B .deps -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo -DUSE_BUNDLED=OFF -DUSE_BUNDLED_LIBVTERM=ON -DUSE_BUNDLED_TS=ON
+   cmake -S cmake.deps -B .deps -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo -DUSE_BUNDLED=OFF -DUSE_BUNDLED_TS=ON
    cmake --build .deps
    cmake -B build -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo
    cmake --build build
@@ -261,7 +261,7 @@ cmake --build build
 
 ```sh
 sudo apt install luajit libluajit-5.1-dev lua-lpeg libunibilium-dev
-cmake -S cmake.deps -B .deps -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo -DUSE_BUNDLED=OFF -DUSE_BUNDLED_LIBUV=ON -DUSE_BUNDLED_LUV=ON -DUSE_BUNDLED_LIBVTERM=ON -DUSE_BUNDLED_TS=ON -DUSE_BUNDLED_UTF8PROC=ON
+cmake -S cmake.deps -B .deps -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo -DUSE_BUNDLED=OFF -DUSE_BUNDLED_LIBUV=ON -DUSE_BUNDLED_LUV=ON -DUSE_BUNDLED_TS=ON -DUSE_BUNDLED_UTF8PROC=ON
 cmake --build .deps
 cmake -B build -G Ninja -D CMAKE_BUILD_TYPE=RelWithDebInfo
 cmake --build build
@@ -275,7 +275,7 @@ cmake --build build
   ```
 - Example of using a package with some dependencies:
   ```
-  make BUNDLED_CMAKE_FLAG="-DUSE_BUNDLED=OFF -DUSE_BUNDLED_LUV=ON -DUSE_BUNDLED_TS=ON -DUSE_BUNDLED_LIBVTERM=ON -DUSE_BUNDLED_LIBUV=ON"
+  make BUNDLED_CMAKE_FLAG="-DUSE_BUNDLED=OFF -DUSE_BUNDLED_LUV=ON -DUSE_BUNDLED_TS=ON -DUSE_BUNDLED_LIBUV=ON"
   ```
 
 ## Build prerequisites
diff --git a/MAINTAIN.md b/MAINTAIN.md
index f7f0c5769c..442fd996a6 100644
--- a/MAINTAIN.md
+++ b/MAINTAIN.md
@@ -129,8 +129,6 @@ Some can be auto-bumped by `scripts/bump_deps.lua`.
 * [gettext](https://ftp.gnu.org/pub/gnu/gettext/)
 * [libiconv](https://ftp.gnu.org/pub/gnu/libiconv)
 * [libuv](https://github.com/libuv/libuv)
-* [libvterm](https://www.leonerd.org.uk/code/libvterm/)
-    * Downloading from the original source is unreliable, so we use our [mirror](https://github.com/neovim/libvterm) instead.
 * [lua-compat](https://github.com/keplerproject/lua-compat-5.3)
 * [tree-sitter](https://github.com/tree-sitter/tree-sitter)
 * [unibilium](https://github.com/neovim/unibilium)
@@ -146,6 +144,8 @@ These dependencies are "vendored" (inlined), we must update the sources manually
 * `src/xdiff/`: [xdiff](https://github.com/git/git/tree/master/xdiff)
 * `src/cjson/`: [lua-cjson](https://github.com/openresty/lua-cjson)
 * `src/klib/`: [Klib](https://github.com/attractivechaos/klib)
+* `src/vterm/`: [libvterm](https://www.leonerd.org.uk/code/libvterm/),
+    [mirror](https://github.com/neovim/libvterm)
 * `runtime/lua/vim/inspect.lua`: [inspect.lua](https://github.com/kikito/inspect.lua)
 * `src/nvim/tui/terminfo_defs.h`: terminfo definitions
     * Run `scripts/update_terminfo.sh` to update these definitions.
diff --git a/cmake.deps/CMakeLists.txt b/cmake.deps/CMakeLists.txt
index 05db090765..43f50b4485 100644
--- a/cmake.deps/CMakeLists.txt
+++ b/cmake.deps/CMakeLists.txt
@@ -27,7 +27,6 @@ set(DEPS_IGNORE_SHA FALSE)
 option(USE_BUNDLED "Use bundled dependencies." ON)
 
 option(USE_BUNDLED_LIBUV "Use the bundled libuv." ${USE_BUNDLED})
-option(USE_BUNDLED_LIBVTERM "Use the bundled libvterm." ${USE_BUNDLED})
 option(USE_BUNDLED_LPEG "Use the bundled lpeg." ${USE_BUNDLED})
 # PUC Lua is only used for tests, unless explicitly requested.
 option(USE_BUNDLED_LUA "Use the bundled version of lua." OFF)
@@ -96,10 +95,6 @@ if(USE_BUNDLED_UNIBILIUM)
   include(BuildUnibilium)
 endif()
 
-if(USE_BUNDLED_LIBVTERM)
-  include(BuildLibvterm)
-endif()
-
 if(USE_BUNDLED_LIBUV)
   include(BuildLibuv)
 endif()
diff --git a/cmake.deps/CMakePresets.json b/cmake.deps/CMakePresets.json
index 7d9f473581..043124c29c 100644
--- a/cmake.deps/CMakePresets.json
+++ b/cmake.deps/CMakePresets.json
@@ -16,7 +16,6 @@
       "description": "Build neovim with external deps on ubuntu",
       "cacheVariables": {
         "USE_BUNDLED":"OFF",
-        "USE_BUNDLED_LIBVTERM":"ON",
         "USE_BUNDLED_TS":"ON",
         "USE_BUNDLED_UTF8PROC":"ON"
       },
diff --git a/cmake.deps/cmake/BuildLibvterm.cmake b/cmake.deps/cmake/BuildLibvterm.cmake
deleted file mode 100644
index 3415d8debe..0000000000
--- a/cmake.deps/cmake/BuildLibvterm.cmake
+++ /dev/null
@@ -1,8 +0,0 @@
-get_externalproject_options(libvterm ${DEPS_IGNORE_SHA})
-ExternalProject_Add(libvterm
-  DOWNLOAD_DIR ${DEPS_DOWNLOAD_DIR}/libvterm
-  PATCH_COMMAND ${CMAKE_COMMAND} -E copy
-    ${CMAKE_CURRENT_SOURCE_DIR}/cmake/LibvtermCMakeLists.txt
-    ${DEPS_BUILD_DIR}/src/libvterm/CMakeLists.txt
-  CMAKE_ARGS ${DEPS_CMAKE_ARGS}
-  ${EXTERNALPROJECT_OPTIONS})
diff --git a/cmake.deps/cmake/LibvtermCMakeLists.txt b/cmake.deps/cmake/LibvtermCMakeLists.txt
deleted file mode 100644
index c197523786..0000000000
--- a/cmake.deps/cmake/LibvtermCMakeLists.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-cmake_minimum_required(VERSION 3.13)
-project(libvterm C)
-
-add_compile_options(-w)
-
-include(GNUInstallDirs)
-
-include_directories(${CMAKE_SOURCE_DIR}/include)
-include_directories(${CMAKE_BINARY_DIR})
-
-file(GLOB VTERM_SOURCES ${CMAKE_SOURCE_DIR}/src/*.c)
-add_library(vterm ${VTERM_SOURCES})
-install(TARGETS vterm ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
-
-install(FILES include/vterm.h include/vterm_keycodes.h
-  DESTINATION include)
-
-if(NOT WIN32)
-  file(GLOB BIN_SOURCES ${CMAKE_SOURCE_DIR}/bin/*.c)
-  foreach(EXE_C ${BIN_SOURCES})
-    get_filename_component(target_name ${EXE_C} NAME_WE)
-    add_executable(${target_name} ${EXE_C})
-    target_link_libraries(${target_name} vterm)
-    install(TARGETS ${target_name} RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
-  endforeach()
-endif()
-
-# vim: set ft=cmake:
diff --git a/cmake.deps/deps.txt b/cmake.deps/deps.txt
index 63ec369f76..03e10f2026 100644
--- a/cmake.deps/deps.txt
+++ b/cmake.deps/deps.txt
@@ -10,9 +10,6 @@ LUA_SHA256 2640fc56a795f29d28ef15e13c34a47e223960b0240e8cb0a82d9b0738695333
 UNIBILIUM_URL https://github.com/neovim/unibilium/archive/d72c3598e7ac5d1ebf86ee268b8b4ed95c0fa628.tar.gz
 UNIBILIUM_SHA256 9c4747c862ab5e3076dcf8fa8f0ea7a6b50f20ec5905618b9536655596797487
 
-LIBVTERM_URL https://github.com/neovim/libvterm/archive/0a15c6e983b0db7ef8276e0792414a805d01bdaf.tar.gz
-LIBVTERM_SHA256 c4683e7a2d71c04781fd0ab7719a94202800e97a9e091514c16983bb732b0fa7
-
 LUV_URL https://github.com/luvit/luv/releases/download/1.48.0-2/luv-1.48.0-2.tar.gz
 LUV_SHA256 2c3a1ddfebb4f6550293a40ee789f7122e97647eede51511f57203de48c03b7a
 
diff --git a/cmake/FindLibvterm.cmake b/cmake/FindLibvterm.cmake
deleted file mode 100644
index 68c2646d47..0000000000
--- a/cmake/FindLibvterm.cmake
+++ /dev/null
@@ -1,31 +0,0 @@
-find_path2(LIBVTERM_INCLUDE_DIR vterm.h)
-find_library2(LIBVTERM_LIBRARY vterm)
-
-if(LIBVTERM_INCLUDE_DIR AND EXISTS "${LIBVTERM_INCLUDE_DIR}/vterm.h")
-  file(STRINGS ${LIBVTERM_INCLUDE_DIR}/vterm.h VTERM_VERSION_MAJOR REGEX "#define VTERM_VERSION_MAJOR")
-  string(REGEX MATCH "[0-9]+" VTERM_VERSION_MAJOR ${VTERM_VERSION_MAJOR})
-
-  file(STRINGS ${LIBVTERM_INCLUDE_DIR}/vterm.h VTERM_VERSION_MINOR REGEX "#define VTERM_VERSION_MINOR")
-  string(REGEX MATCH "[0-9]+" VTERM_VERSION_MINOR ${VTERM_VERSION_MINOR})
-
-  file(STRINGS ${LIBVTERM_INCLUDE_DIR}/vterm.h VTERM_VERSION_PATCH REGEX "#define VTERM_VERSION_PATCH")
-
-  # The following is needed to give a coherent error for versions 0.3.2 and
-  # smaller.
-  if(VTERM_VERSION_PATCH)
-    string(REGEX MATCH "[0-9]+" VTERM_VERSION_PATCH ${VTERM_VERSION_PATCH})
-    string(PREPEND VTERM_VERSION_PATCH ".")
-  endif()
-
-  set(VTERM_VERSION ${VTERM_VERSION_MAJOR}.${VTERM_VERSION_MINOR}${VTERM_VERSION_PATCH})
-endif()
-
-find_package_handle_standard_args(Libvterm
-  REQUIRED_VARS LIBVTERM_INCLUDE_DIR LIBVTERM_LIBRARY
-  VERSION_VAR VTERM_VERSION)
-
-add_library(libvterm INTERFACE)
-target_include_directories(libvterm SYSTEM BEFORE INTERFACE ${LIBVTERM_INCLUDE_DIR})
-target_link_libraries(libvterm INTERFACE ${LIBVTERM_LIBRARY})
-
-mark_as_advanced(LIBVTERM_INCLUDE_DIR LIBVTERM_LIBRARY)
diff --git a/contrib/local.mk.example b/contrib/local.mk.example
index 61fc0b95b8..bdb889dfcd 100644
--- a/contrib/local.mk.example
+++ b/contrib/local.mk.example
@@ -45,7 +45,6 @@
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_GETTEXT=OFF
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_LIBICONV=OFF
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_LIBUV=OFF
-# DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_LIBVTERM=OFF
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_LUAJIT=OFF
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_LUV=OFF
 # DEPS_CMAKE_FLAGS += -DUSE_BUNDLED_TS=OFF
diff --git a/runtime/doc/dev_vimpatch.txt b/runtime/doc/dev_vimpatch.txt
index 9a2380b162..5119613b55 100644
--- a/runtime/doc/dev_vimpatch.txt
+++ b/runtime/doc/dev_vimpatch.txt
@@ -139,7 +139,6 @@ TYPES OF "NOT APPLICABLE" VIM PATCHES ~
     - NA files: `src/gui_*`, `src/gvim_*`, `src/GvimExt/*`, `src/testdir/test_gui*`
 - `balloon` changes: Nvim does not support balloon feature
     - NA files: `src/beval_*`, `src/testdir/test_balloon_*`
-- libvterm changes: Nvim does not vendor libvterm in `src/`.
 - Screendump tests from `test_popupwin.vim`, `test_popupwin_textprop.vim`:
   https://github.com/neovim/neovim/pull/12741#issuecomment-704677141
 - json changes: incompatible API https://github.com/neovim/neovim/pull/4131
diff --git a/src/clint.py b/src/clint.py
index 67185a7340..cc144543a0 100755
--- a/src/clint.py
+++ b/src/clint.py
@@ -880,6 +880,7 @@ def CheckIncludes(filename, lines, error):
             "mpack/object.h",
             "nvim/func_attr.h",
             "termkey/termkey.h",
+            "vterm/vterm.h",
             ]
 
     for i in check_includes_ignore:
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index d153c9e3ef..87c9506709 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -30,7 +30,6 @@ target_link_libraries(main_lib INTERFACE ${LUV_LIBRARY})
 
 find_package(Iconv REQUIRED)
 find_package(Libuv 1.28.0 REQUIRED)
-find_package(Libvterm 0.3.3 REQUIRED)
 find_package(Lpeg REQUIRED)
 find_package(Treesitter 0.22.6 REQUIRED)
 find_package(Unibilium 2.0 REQUIRED)
@@ -38,7 +37,6 @@ find_package(UTF8proc REQUIRED)
 
 target_link_libraries(main_lib INTERFACE
   iconv
-  libvterm
   lpeg
   treesitter
   unibilium
@@ -366,8 +364,8 @@ file(MAKE_DIRECTORY ${TOUCHES_DIR} ${GENERATED_DIR} ${GENERATED_INCLUDES_DIR})
 
 file(GLOB NVIM_SOURCES CONFIGURE_DEPENDS *.c)
 file(GLOB NVIM_HEADERS CONFIGURE_DEPENDS *.h)
-file(GLOB EXTERNAL_SOURCES CONFIGURE_DEPENDS ../xdiff/*.c ../mpack/*.c ../cjson/*.c ../klib/*.c ../termkey/*.c)
-file(GLOB EXTERNAL_HEADERS CONFIGURE_DEPENDS ../xdiff/*.h ../mpack/*.h ../cjson/*.h ../klib/*.h ../termkey/*.h)
+file(GLOB EXTERNAL_SOURCES CONFIGURE_DEPENDS ../xdiff/*.c ../mpack/*.c ../cjson/*.c ../klib/*.c ../termkey/*.c ../vterm/*.c)
+file(GLOB EXTERNAL_HEADERS CONFIGURE_DEPENDS ../xdiff/*.h ../mpack/*.h ../cjson/*.h ../klib/*.h ../termkey/*.h ../vterm/*.h)
 
 file(GLOB NLUA0_SOURCES CONFIGURE_DEPENDS ../mpack/*.c)
 
diff --git a/src/nvim/os/win_defs.h b/src/nvim/os/win_defs.h
index 852059f78b..024719806c 100644
--- a/src/nvim/os/win_defs.h
+++ b/src/nvim/os/win_defs.h
@@ -16,6 +16,9 @@
 #include <sys/stat.h>
 #include <windows.h>
 
+// vterm.h defines an `unsigned int small` in a struct, triggering error C2632
+#undef small
+
 // Windows does not have S_IFLNK but libuv defines it
 // and sets the flag for us when calling uv_fs_stat.
 #include <uv.h>
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index 507a9e3a2a..abc9b3534b 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -40,8 +40,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <vterm.h>
-#include <vterm_keycodes.h>
 
 #include "klib/kvec.h"
 #include "nvim/api/private/helpers.h"
@@ -94,6 +92,8 @@
 #include "nvim/ui.h"
 #include "nvim/vim_defs.h"
 #include "nvim/window.h"
+#include "vterm/vterm.h"
+#include "vterm/vterm_keycodes.h"
 
 typedef struct {
   VimState state;
diff --git a/src/vterm/LICENSE b/src/vterm/LICENSE
new file mode 100644
index 0000000000..0d051634b2
--- /dev/null
+++ b/src/vterm/LICENSE
@@ -0,0 +1,23 @@
+
+
+The MIT License
+
+Copyright (c) 2008 Paul Evans <leonerd@leonerd.org.uk>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/src/vterm/encoding.c b/src/vterm/encoding.c
new file mode 100644
index 0000000000..434ac3f99b
--- /dev/null
+++ b/src/vterm/encoding.c
@@ -0,0 +1,230 @@
+#include "vterm_internal.h"
+
+#define UNICODE_INVALID 0xFFFD
+
+#if defined(DEBUG) && DEBUG > 1
+# define DEBUG_PRINT_UTF8
+#endif
+
+struct UTF8DecoderData {
+  // number of bytes remaining in this codepoint
+  int bytes_remaining;
+
+  // number of bytes total in this codepoint once it's finished
+  // (for detecting overlongs)
+  int bytes_total;
+
+  int this_cp;
+};
+
+static void init_utf8(VTermEncoding *enc, void *data_)
+{
+  struct UTF8DecoderData *data = data_;
+
+  data->bytes_remaining = 0;
+  data->bytes_total     = 0;
+}
+
+static void decode_utf8(VTermEncoding *enc, void *data_,
+                        uint32_t cp[], int *cpi, int cplen,
+                        const char bytes[], size_t *pos, size_t bytelen)
+{
+  struct UTF8DecoderData *data = data_;
+
+#ifdef DEBUG_PRINT_UTF8
+  printf("BEGIN UTF-8\n");
+#endif
+
+  for(; *pos < bytelen && *cpi < cplen; (*pos)++) {
+    unsigned char c = bytes[*pos];
+
+#ifdef DEBUG_PRINT_UTF8
+    printf(" pos=%zd c=%02x rem=%d\n", *pos, c, data->bytes_remaining);
+#endif
+
+    if(c < 0x20) // C0
+      return;
+
+    else if(c >= 0x20 && c < 0x7f) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      cp[(*cpi)++] = c;
+#ifdef DEBUG_PRINT_UTF8
+      printf(" UTF-8 char: U+%04x\n", c);
+#endif
+      data->bytes_remaining = 0;
+    }
+
+    else if(c == 0x7f) // DEL
+      return;
+
+    else if(c >= 0x80 && c < 0xc0) {
+      if(!data->bytes_remaining) {
+        cp[(*cpi)++] = UNICODE_INVALID;
+        continue;
+      }
+
+      data->this_cp <<= 6;
+      data->this_cp |= c & 0x3f;
+      data->bytes_remaining--;
+
+      if(!data->bytes_remaining) {
+#ifdef DEBUG_PRINT_UTF8
+        printf(" UTF-8 raw char U+%04x bytelen=%d ", data->this_cp, data->bytes_total);
+#endif
+        // Check for overlong sequences
+        switch(data->bytes_total) {
+        case 2:
+          if(data->this_cp <  0x0080) data->this_cp = UNICODE_INVALID;
+          break;
+        case 3:
+          if(data->this_cp <  0x0800) data->this_cp = UNICODE_INVALID;
+          break;
+        case 4:
+          if(data->this_cp < 0x10000) data->this_cp = UNICODE_INVALID;
+          break;
+        case 5:
+          if(data->this_cp < 0x200000) data->this_cp = UNICODE_INVALID;
+          break;
+        case 6:
+          if(data->this_cp < 0x4000000) data->this_cp = UNICODE_INVALID;
+          break;
+        }
+        // Now look for plain invalid ones
+        if((data->this_cp >= 0xD800 && data->this_cp <= 0xDFFF) ||
+           data->this_cp == 0xFFFE ||
+           data->this_cp == 0xFFFF)
+          data->this_cp = UNICODE_INVALID;
+#ifdef DEBUG_PRINT_UTF8
+        printf(" char: U+%04x\n", data->this_cp);
+#endif
+        cp[(*cpi)++] = data->this_cp;
+      }
+    }
+
+    else if(c >= 0xc0 && c < 0xe0) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      data->this_cp = c & 0x1f;
+      data->bytes_total = 2;
+      data->bytes_remaining = 1;
+    }
+
+    else if(c >= 0xe0 && c < 0xf0) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      data->this_cp = c & 0x0f;
+      data->bytes_total = 3;
+      data->bytes_remaining = 2;
+    }
+
+    else if(c >= 0xf0 && c < 0xf8) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      data->this_cp = c & 0x07;
+      data->bytes_total = 4;
+      data->bytes_remaining = 3;
+    }
+
+    else if(c >= 0xf8 && c < 0xfc) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      data->this_cp = c & 0x03;
+      data->bytes_total = 5;
+      data->bytes_remaining = 4;
+    }
+
+    else if(c >= 0xfc && c < 0xfe) {
+      if(data->bytes_remaining)
+        cp[(*cpi)++] = UNICODE_INVALID;
+
+      data->this_cp = c & 0x01;
+      data->bytes_total = 6;
+      data->bytes_remaining = 5;
+    }
+
+    else {
+      cp[(*cpi)++] = UNICODE_INVALID;
+    }
+  }
+}
+
+static VTermEncoding encoding_utf8 = {
+  .init   = &init_utf8,
+  .decode = &decode_utf8,
+};
+
+static void decode_usascii(VTermEncoding *enc, void *data,
+                           uint32_t cp[], int *cpi, int cplen,
+                           const char bytes[], size_t *pos, size_t bytelen)
+{
+  int is_gr = bytes[*pos] & 0x80;
+
+  for(; *pos < bytelen && *cpi < cplen; (*pos)++) {
+    unsigned char c = bytes[*pos] ^ is_gr;
+
+    if(c < 0x20 || c == 0x7f || c >= 0x80)
+      return;
+
+    cp[(*cpi)++] = c;
+  }
+}
+
+static VTermEncoding encoding_usascii = {
+  .decode = &decode_usascii,
+};
+
+struct StaticTableEncoding {
+  const VTermEncoding enc;
+  const uint32_t chars[128];
+};
+
+static void decode_table(VTermEncoding *enc, void *data,
+                         uint32_t cp[], int *cpi, int cplen,
+                         const char bytes[], size_t *pos, size_t bytelen)
+{
+  struct StaticTableEncoding *table = (struct StaticTableEncoding *)enc;
+  int is_gr = bytes[*pos] & 0x80;
+
+  for(; *pos < bytelen && *cpi < cplen; (*pos)++) {
+    unsigned char c = bytes[*pos] ^ is_gr;
+
+    if(c < 0x20 || c == 0x7f || c >= 0x80)
+      return;
+
+    if(table->chars[c])
+      cp[(*cpi)++] = table->chars[c];
+    else
+      cp[(*cpi)++] = c;
+  }
+}
+
+#include "encoding/DECdrawing.inc"
+#include "encoding/uk.inc"
+
+static struct {
+  VTermEncodingType type;
+  char designation;
+  VTermEncoding *enc;
+}
+encodings[] = {
+  { ENC_UTF8,      'u', &encoding_utf8 },
+  { ENC_SINGLE_94, '0', (VTermEncoding*)&encoding_DECdrawing },
+  { ENC_SINGLE_94, 'A', (VTermEncoding*)&encoding_uk },
+  { ENC_SINGLE_94, 'B', &encoding_usascii },
+  { 0 },
+};
+
+/* This ought to be INTERNAL but isn't because it's used by unit testing */
+VTermEncoding *vterm_lookup_encoding(VTermEncodingType type, char designation)
+{
+  for(int i = 0; encodings[i].designation; i++)
+    if(encodings[i].type == type && encodings[i].designation == designation)
+      return encodings[i].enc;
+  return NULL;
+}
diff --git a/src/vterm/encoding/DECdrawing.inc b/src/vterm/encoding/DECdrawing.inc
new file mode 100644
index 0000000000..627397bcc2
--- /dev/null
+++ b/src/vterm/encoding/DECdrawing.inc
@@ -0,0 +1,36 @@
+static const struct StaticTableEncoding encoding_DECdrawing = {
+  { .decode = &decode_table },
+  {
+    [0x60] = 0x25C6,  // BLACK DIAMOND
+    [0x61] = 0x2592,  // MEDIUM SHADE (checkerboard)
+    [0x62] = 0x2409,  // SYMBOL FOR HORIZONTAL TAB
+    [0x63] = 0x240C,  // SYMBOL FOR FORM FEED
+    [0x64] = 0x240D,  // SYMBOL FOR CARRIAGE RETURN
+    [0x65] = 0x240A,  // SYMBOL FOR LINE FEED
+    [0x66] = 0x00B0,  // DEGREE SIGN
+    [0x67] = 0x00B1,  // PLUS-MINUS SIGN (plus or minus)
+    [0x68] = 0x2424,  // SYMBOL FOR NEW LINE
+    [0x69] = 0x240B,  // SYMBOL FOR VERTICAL TAB
+    [0x6a] = 0x2518,  // BOX DRAWINGS LIGHT UP AND LEFT (bottom-right corner)
+    [0x6b] = 0x2510,  // BOX DRAWINGS LIGHT DOWN AND LEFT (top-right corner)
+    [0x6c] = 0x250C,  // BOX DRAWINGS LIGHT DOWN AND RIGHT (top-left corner)
+    [0x6d] = 0x2514,  // BOX DRAWINGS LIGHT UP AND RIGHT (bottom-left corner)
+    [0x6e] = 0x253C,  // BOX DRAWINGS LIGHT VERTICAL AND HORIZONTAL (crossing lines)
+    [0x6f] = 0x23BA,  // HORIZONTAL SCAN LINE-1
+    [0x70] = 0x23BB,  // HORIZONTAL SCAN LINE-3
+    [0x71] = 0x2500,  // BOX DRAWINGS LIGHT HORIZONTAL
+    [0x72] = 0x23BC,  // HORIZONTAL SCAN LINE-7
+    [0x73] = 0x23BD,  // HORIZONTAL SCAN LINE-9
+    [0x74] = 0x251C,  // BOX DRAWINGS LIGHT VERTICAL AND RIGHT
+    [0x75] = 0x2524,  // BOX DRAWINGS LIGHT VERTICAL AND LEFT
+    [0x76] = 0x2534,  // BOX DRAWINGS LIGHT UP AND HORIZONTAL
+    [0x77] = 0x252C,  // BOX DRAWINGS LIGHT DOWN AND HORIZONTAL
+    [0x78] = 0x2502,  // BOX DRAWINGS LIGHT VERTICAL
+    [0x79] = 0x2A7D,  // LESS-THAN OR SLANTED EQUAL-TO
+    [0x7a] = 0x2A7E,  // GREATER-THAN OR SLANTED EQUAL-TO
+    [0x7b] = 0x03C0,  // GREEK SMALL LETTER PI
+    [0x7c] = 0x2260,  // NOT EQUAL TO
+    [0x7d] = 0x00A3,  // POUND SIGN
+    [0x7e] = 0x00B7,  // MIDDLE DOT
+  }
+};
diff --git a/src/vterm/encoding/uk.inc b/src/vterm/encoding/uk.inc
new file mode 100644
index 0000000000..5c7700226b
--- /dev/null
+++ b/src/vterm/encoding/uk.inc
@@ -0,0 +1,6 @@
+static const struct StaticTableEncoding encoding_uk = {
+  { .decode = &decode_table },
+  {
+    [0x23] = 0x00a3,  // £
+  }
+};
diff --git a/src/vterm/fullwidth.inc b/src/vterm/fullwidth.inc
new file mode 100644
index 0000000000..a703529a76
--- /dev/null
+++ b/src/vterm/fullwidth.inc
@@ -0,0 +1,111 @@
+  { 0x1100, 0x115f },
+  { 0x231a, 0x231b },
+  { 0x2329, 0x232a },
+  { 0x23e9, 0x23ec },
+  { 0x23f0, 0x23f0 },
+  { 0x23f3, 0x23f3 },
+  { 0x25fd, 0x25fe },
+  { 0x2614, 0x2615 },
+  { 0x2648, 0x2653 },
+  { 0x267f, 0x267f },
+  { 0x2693, 0x2693 },
+  { 0x26a1, 0x26a1 },
+  { 0x26aa, 0x26ab },
+  { 0x26bd, 0x26be },
+  { 0x26c4, 0x26c5 },
+  { 0x26ce, 0x26ce },
+  { 0x26d4, 0x26d4 },
+  { 0x26ea, 0x26ea },
+  { 0x26f2, 0x26f3 },
+  { 0x26f5, 0x26f5 },
+  { 0x26fa, 0x26fa },
+  { 0x26fd, 0x26fd },
+  { 0x2705, 0x2705 },
+  { 0x270a, 0x270b },
+  { 0x2728, 0x2728 },
+  { 0x274c, 0x274c },
+  { 0x274e, 0x274e },
+  { 0x2753, 0x2755 },
+  { 0x2757, 0x2757 },
+  { 0x2795, 0x2797 },
+  { 0x27b0, 0x27b0 },
+  { 0x27bf, 0x27bf },
+  { 0x2b1b, 0x2b1c },
+  { 0x2b50, 0x2b50 },
+  { 0x2b55, 0x2b55 },
+  { 0x2e80, 0x2e99 },
+  { 0x2e9b, 0x2ef3 },
+  { 0x2f00, 0x2fd5 },
+  { 0x2ff0, 0x2ffb },
+  { 0x3000, 0x303e },
+  { 0x3041, 0x3096 },
+  { 0x3099, 0x30ff },
+  { 0x3105, 0x312f },
+  { 0x3131, 0x318e },
+  { 0x3190, 0x31ba },
+  { 0x31c0, 0x31e3 },
+  { 0x31f0, 0x321e },
+  { 0x3220, 0x3247 },
+  { 0x3250, 0x4dbf },
+  { 0x4e00, 0xa48c },
+  { 0xa490, 0xa4c6 },
+  { 0xa960, 0xa97c },
+  { 0xac00, 0xd7a3 },
+  { 0xf900, 0xfaff },
+  { 0xfe10, 0xfe19 },
+  { 0xfe30, 0xfe52 },
+  { 0xfe54, 0xfe66 },
+  { 0xfe68, 0xfe6b },
+  { 0xff01, 0xff60 },
+  { 0xffe0, 0xffe6 },
+  { 0x16fe0, 0x16fe3 },
+  { 0x17000, 0x187f7 },
+  { 0x18800, 0x18af2 },
+  { 0x1b000, 0x1b11e },
+  { 0x1b150, 0x1b152 },
+  { 0x1b164, 0x1b167 },
+  { 0x1b170, 0x1b2fb },
+  { 0x1f004, 0x1f004 },
+  { 0x1f0cf, 0x1f0cf },
+  { 0x1f18e, 0x1f18e },
+  { 0x1f191, 0x1f19a },
+  { 0x1f200, 0x1f202 },
+  { 0x1f210, 0x1f23b },
+  { 0x1f240, 0x1f248 },
+  { 0x1f250, 0x1f251 },
+  { 0x1f260, 0x1f265 },
+  { 0x1f300, 0x1f320 },
+  { 0x1f32d, 0x1f335 },
+  { 0x1f337, 0x1f37c },
+  { 0x1f37e, 0x1f393 },
+  { 0x1f3a0, 0x1f3ca },
+  { 0x1f3cf, 0x1f3d3 },
+  { 0x1f3e0, 0x1f3f0 },
+  { 0x1f3f4, 0x1f3f4 },
+  { 0x1f3f8, 0x1f43e },
+  { 0x1f440, 0x1f440 },
+  { 0x1f442, 0x1f4fc },
+  { 0x1f4ff, 0x1f53d },
+  { 0x1f54b, 0x1f54e },
+  { 0x1f550, 0x1f567 },
+  { 0x1f57a, 0x1f57a },
+  { 0x1f595, 0x1f596 },
+  { 0x1f5a4, 0x1f5a4 },
+  { 0x1f5fb, 0x1f64f },
+  { 0x1f680, 0x1f6c5 },
+  { 0x1f6cc, 0x1f6cc },
+  { 0x1f6d0, 0x1f6d2 },
+  { 0x1f6d5, 0x1f6d5 },
+  { 0x1f6eb, 0x1f6ec },
+  { 0x1f6f4, 0x1f6fa },
+  { 0x1f7e0, 0x1f7eb },
+  { 0x1f90d, 0x1f971 },
+  { 0x1f973, 0x1f976 },
+  { 0x1f97a, 0x1f9a2 },
+  { 0x1f9a5, 0x1f9aa },
+  { 0x1f9ae, 0x1f9ca },
+  { 0x1f9cd, 0x1f9ff },
+  { 0x1fa70, 0x1fa73 },
+  { 0x1fa78, 0x1fa7a },
+  { 0x1fa80, 0x1fa82 },
+  { 0x1fa90, 0x1fa95 },
diff --git a/src/vterm/keyboard.c b/src/vterm/keyboard.c
new file mode 100644
index 0000000000..d31c8be12d
--- /dev/null
+++ b/src/vterm/keyboard.c
@@ -0,0 +1,226 @@
+#include "vterm_internal.h"
+
+#include <stdio.h>
+
+#include "utf8.h"
+